ALS Amyotrophic Lateral Sclerosis MGUS polyneuropathy
Anterior Interosseous Syndrome MMN
Arthrogryposis Multiplex Mononeuropathy
Axillary neuropathy Multifocal Motor Neuropathy with Conduction Blocks
Botulism Muscular Dystrophy
Brachial plexopathy Musculocutaneous neuropathy
Carpal Tunnel Syndrome Myasthenia Gravis
Cervical radiculopathy Myopathy
Chronic Immune Demyelinating Polyneuropathy CIDP Neuropathy
Cubital Tunnel Syndrome Obturator neuropathy
Dermatomyosits Pelvic girdle neuropathy
Dorsal Scapular neuropathy Peroneal neuropathy
Entrapment syndromes Plantar neuropathy
Facio-scapulo-peroneal SMA Plexopathy
Fazio-Lande SMA Polymyositis
Femoral neuropathy Polyneuropathy
GBS Posterior Interosseous Syndrome
Gluteal neuropathy Pronator Teres Syndrome
Guillain-Barre Syndrome Radial neuropathy
Guyon’s canal entrapment Radiculopathy
Handcuff neuropathy Scapulo-peroneal SMA
Inclusion Body Myositis Sciatic neuropathy
Infantile SMA Shoulder girdle mononeuropathy
Juvenile bulbar SMA SMA
Juvenile SMA Spinal Muscular Atrophy
Kugelberg-Wellander SMA Stiff Person Syndrome
Lambert-Eaton Syndrome Suprascapular neuropathy
Lateral Femoral Cutaneous neuropathy Tarsal Tunnel Syndrome
Long Thoracic neuropathy Tibial neuropathy
Lumbar plexopthy Ulnar neuropathy
Lumbar radiculopathy Ulnar palmar branch neuropathy
Median neuropathy Werding-Hoffman SMA

Amyotrophic Lateral Sclerosis

Muscle wasting in ALS is a result of anterior horn cell degeneration, thus the essential electrophysiologic features include sparing of the sensory fibers with a widespread affliction of motor neurons. EMG showed active denervation (axonal loss) with evidence of chronic reinnervation crossing the individual myotomes.

Median neuropathy

Median mononeuropathy at the wrist (CTS) is the most common mononeuropathy in clinical practice. In addition to evaluating for presence and severity of CTS, the role o the EMG is to exclude a neurogenic co-morbidity. Furthermore, as a pre-operative workup it establishes a very useful electrophysiologic baseline. In a situation where an unwanted post-operative outcome is seen, the absence of preoperative values precludes an assessment of the interval change. When available, a meaningful comparison can be made (electrophysiologic worsening, improvement or no change) which in turn can assist in a decision making process about a possible re-exploration of the carpal tunnel.

Possible sites of lesion for the median nerve include:

  • Pronator Teres Syndrome (pain over the PT muscle; mimics CTS, weakness of APB and Flexor Pollicis; Normal distal NCS; EMG of PT normal while distal muscles abnormal)
  • Interosseous Syndrome (pain in the forearm; no sensory deficits; inability to make OK sign; Normal NCS and EMG of FPL, FDP I and Pronator Quadratus)
  • CTS (10% of population affected; frequently neglected in clinical practice; distal NCS abnormal; EMG of APB abnormal)
  • Digital nerve lesion

Pronator Teres Syndrome:

From: www.wheelessonline.com


- Differential Dx:
- lacertus fibrosus:
- draws tightly across the median nerve when the forearm is held in resisted supination and flexion;
- independent flexion of the middle finger flexion (FDS) localizes the level of entrapment to the fibrous arcade of the FDS;
- flexor superficialis crossover syndrome:
- resisted flexion of flexor superficialis of long finger combined w/ parasthesias in forearm & hand while pronating wrist, clinical test for median nerve entrapment at pronator teres & flexor superficialis cross over;
- C6 / C7 radiculopathy:
- involvment of these levels will cause numbeness of thumb, index, and long fingers, and the median nerve innervated muscles of the forearm;
- the correct diagnosis is made by establishing the function of the muscles innervated by the C6-C7 portions of the radial nerve (ie the function of the wrist entensors and the triceps);
- Exam:
- see: exam for carpal tunnel;
- Phalen and tunnel test are negative;
- pain in wrist and forearm;
- weakness of thenar muscles;
- thenar muscles are weak but muscles of ain (fpl, fdp, quad) are spared;
- dysesthesia in "palmar triangle;"
- pronator teres can be implicated when arm is held in resisted pronation and flexion and then gradually extended while in pronated position;
- EMG:
- when EMG does not confirm pronator teres syndrome but clinical evidence is suggestive, then wait 4-6 wks and repeat the EMG;
- Treatment:
- realease of humeral head of pronator teres and the superficialis bridge as well as associated compressing structures;

Myopathy

Myopathic conditions can be acquired or genetic. Most frequent clinical presentation includes proximal weakness. EMG shows small, polyphasic motor units with an “early” recruitment pattern. EMG diagnosis is anatomic, thus specific etiology must be determined:

Spinal Muscular Atrophy

Various types of Spinal Muscular Atrophy show the same or similar electrophysiologic findings consisting of fibrillations, positive sharp waves, large motor units and a reduced recruitment pattern.

Shoulder girdle mononeuropathies

Isolated lesion of the individual nerves of the brachial plexus can occur due to fractures, intramuscular injections, shoulder dislocation or an infectious process. Supraspinatus nerve entrapment can be related to a ganglion or rheumatoid disease. EMG can differentiate if an entrapment is present at the spinoglenoid notch, affecting only the Infraspinatus muscle. These mononeuropathies clinically present as pain and weakness of the individual muscles thus the electrophysiology relies and the needle EMG examination


Shoulder girdle mononeuropathies include:

Lambert – Eaton Syndrome

Lambert – Eaton Myasthenic Syndrome (LEMS), in which a pre-synaptic release of acetyl-choline is blocked, a marked increment is seen on the repetitive stimulation test (RST). This feature can differentiate this condition from Myasthenia Gravis in which a decrement is seen on the RST. Botulism cam also cause an incremental response on RST, but the increment is usually lesser then in LEMS.

Plexopathies

Brachial and Lumbar plexopathies represent a complex anatomical diagnostic challenge. Differential diagnosis most frequently includes: Root lesion vs. Plexus lesion vs. “Double Crush Syndrome”. The EMG abnormalities in motor AND sensory NCS are seen, as the lesion is distal to the Dorsal Root Ganglion. EMG changes on needle examination are seen in the appropriate brachial truck or cord distribution without paraspinal muscle involvement.

                

Radiculopathies

Radiculopathies are very frequently encountered in clinical practice. The most common deferential diagnosis includes:

Non-Neuromuscular (orthopedic) Lesions:

  • Muscle strain/sprain
  • Rotator cuff tendonitis/tear
  • Subacromial/trochanteric bursitis
  • Epicondylitis
  • Degenerative joint disease

Neuromuscular Lesions:

  • Motor neuron disease
  • Brachial and Lumbosacral Plexopathy
  • Mononeuropathy
  • Polyneuropathy

Cervical Radiculopathies:

  • C5: 2 - 14%
  • C6: 19 - 25%
  • C7: 56 - 70%
  • C8: 4 - 12%

Lumbar Radiculopathies:

  • L2/3
  • L4
  • L5 : most common
  • S1: second to L5

The goal of the EMG is to localize the compressed, and to establish the presence or absence of active axonal loss and/or chronic reinnervation changes. A very important role of the NCS/EMG is to evaluate for presence of a “Double Crush Syndrome”, in which a distal mononeuropathy is superimposed. The electrophysiologic abnormalities in radiculopathies include:

Possible abnormalities in motor NCS:

  • Normal sensory NCS (lesion is proximal to DRG)
  • Possible active denervation in appropriate myotome and paraspinals
  • Very important limitations of EMG in radiculopathies are:
  • Absence of abnormalities in acute lesions (< 2 weeks)
  • “Normal” EMG in purely demyelinating lesions (no denervation)
  • “Normal” EMG in lesions limited to the sensory nerve root

Polyneuropathies

The role of the NCS/EMG is to establish the presence of a polyneuropathy, define the fiber type affliction (i.e. pure sensory, pure motor, sensory-motor), determine the possible pathological process (axonal vs. demyelinating), and to exclude other conditions which could clinically present in a similar fashion. The ultimate goal of a polyneuropathy workup is to establish the etiology, and potentially offer treatment. NCS/EMG testing is a very powerful tool in reaching such goal. Relatively recent scientific advances in the field of immune mediated neuromuscular disease have established a very important role of NCS/EMG in diagnosing conditions such as Chronic Immune Demyelinating Polyneuropathy, Multifocal Motor Neuropathy with Conduction Blocks, Guillain-Barre Syndrome and MGUS associated polyneuropathy.

Ulnar neuropathy

The EMG in ulnar nerve lesions can establish the location of the pathological process, document the severity and evaluate for common differential diagnosis which includes lower trunk brachial plexopathy and C8 radiculopathy.

Possible sites of lesion for the ulnar nerve include:

  • Cubital tunnel syndrome (sensory symptoms in the 4th and 5th digit; weakness of FDI and ADM; abnormal NCS and EMG of FDI and ADM with sparing of FCU)
  • At Guyon’s canal (sensory deficit spares dorsum of the hand; weakness of the FDI and ADM; abnormal ulnar sensory NCS with normal dorsal ulnar cutaneous NCS)
  • Palmar branch (pure motor affliction of the FDI; NCS to the FDI abnormal and normal to the ADM; EMG of the FDI abnormal)
  • Digital nerve lesion

Mononeuropathies

NCS/EMG is very helpful to pinpoint the exact location of the lesion and to exclude a polyneuropathy, radiculopathy or plexopathy. Varieties of techniques are available for evaluation of individual nerves.

The mononeuropathies which could be seen in the upper extremities and shoulder girdle are:

  • Long Thoracic neuropathy
  • Suprascapular neuropathy
  • Dorsal Scapular neuropathy
  • Axillary neuropathy
  • Musculocutaneous neuropathy
  • Radial nerve
    • Posterior Interosseous neuropathy

      Posterior Interosseous Syndrome:

      From: www.wheelessonline.com


      - Inciting causes:
           - radiocapitellar joint ganglions and synovitis
           - congenital tightness of ligamentous arcade of Frohse;
           - include poorly placed screws for fracture fixation
                  - PIN is vulnerable during ORIF of proximal radius;
                  - in 25% of pts, PIN lies in direct contact w/ periosteum of radius just dorsal to the biciptial tuberosity;
                  - fixation device applied to radius, which might have its proximal screw at level of the bicipital tuberosity, could cause
                          PIN syndrome by entrapment beneath the plate;
                  - to avoid this complication, the nerve should be directly exposed;
           - idiopathic compression syndrome:
                  - sites of compression:
                         - fibrous bands anterior to the radial head at the entrance of radial tunnel (uncommon cause of compression);
                         - radial recurrent vessels (leash of Henry);
                         - tendinous origin of ECRB: the ECRL is more superficial and is not a source of compression;
                         - arcade of Froshe:
                               - this is the most common location of nerve compression in radial tunnel syndrome;
                               - lies deep to the extensor carpi radialis brevis
                               - tendinous proximal border of supinator (arcade of Frohse):
                         - distal edge of the supinator at exit: this is the least common site of compression;
                  - reference:
                         - Radial nerve entrapment at the elbow: surgical anatomy.
                         - Peripheral nerve compression.  RH Gelberman et al. JBJS. Vol 75-A. 1993. p 1854-1878.
      
      - Diff Dx: of Post Interosseous Nerve Syndrome:
           - C7 radiculopathy:
                 - unlike PIN, there will be weakness of triceps and wrist flexors;
           - lateral epicondylitis (ECRB)
                 - it is often misdiagnosed as resistant tennis elbow or PIN Syndrome;
                 - unlike tennis elbow, there is tenderness about 4 cm distal to the lateral humeral epicondyle;
           - distal PIN syndrome:
                 - pts w/ distal posterior interosseous nerve syndrome have pain with repetitive dorsiflexion & tenderness centered 
                   over the 4th extensor compartment;
           - trigger finger (no passive movement possible);
           - extensor tendon rupture:
                 - may be differentiated by tenodesis effect of passive flexion of wrist: if the tendons are intact, the digits will 
                   extend (ie., tenodesis effect is lost);
           - failure of digit extension from chronic dislocation of MCP (see MP joint in RA)
                 - pt can maintain extension achieved passively
                 - Bouvier's Test
      
      

      - Exam:
           - following muscles are intact with PIN syndrome:
                - BR, ECRL , often ECRB, & supinator;
           - pts commonly have tenderness over lateral epicondyle & almost always have tenderness more distally over the arcade of Froshe;
           - pain is almost always experienced w/ resisted supination of the forearm and frequently w/ resisted pronation;
                 - full pronation of forearm produces pressure on PIN by sharp tendinous edge of the origin of ECRB  muscle;
                 - PIN may be compressed by the tendinous origin of the ECRB;
                 - active supination from a pronated position (tightening supinator) along w/ wrist flexion (which tighens the ECRB) 
                   may reproduce the patient's symptoms;
           - most will have pain w/ resisted extension of extension of middle finger;
           - pt will unable to extend thumb or other digits at MCP joints;
                 - w/ complete palsy, pts will continue to have wrist extension (ECU) but they are unable to extend wrist at neutral or in ulnar deviation;
                 - they can extend the digits at the interphalangeal joints, but not at MP joints;
           - pain is relieved by blocking the posterior interosseous nerve 3 cm proximal to the wrist joint;
                 - performed by injecting approx 1 cm ulnar to Lister's tubercle;
      
      
  • Median nerve
    • Pronator Teres Syndrome

      Pronator Teres Syndrome:

      From: www.wheelessonline.com


      - Differential Dx:
           - lacertus fibrosus:
                - draws tightly across the median nerve when the forearm is held in resisted supination and flexion;
                - independent flexion of the middle finger flexion (FDS) localizes the level of entrapment to the fibrous arcade of the FDS;
           - flexor superficialis crossover syndrome:
                - resisted flexion of flexor superficialis of long finger combined w/ parasthesias in forearm & hand while pronating wrist, clinical test for
                      median nerve entrapment at pronator teres & flexor superficialis cross over;
           - C6 / C7 radiculopathy:
                - involvment of these levels will cause numbeness of thumb, index, and long fingers, and the median nerve innervated muscles of the forearm;
                - the correct diagnosis is made by establishing the function of the muscles innervated by the C6-C7 portions of the radial nerve (ie the
                      function of the wrist entensors and the triceps);
      
      - Exam:
           - see: exam for carpal tunnel;
           - Phalen and tunnel test are negative;
           - pain in wrist and forearm;
           - weakness of thenar muscles;
           - thenar muscles are weak but muscles of ain (fpl, fdp, quad) are spared;
           - dysesthesia in "palmar triangle;"
                - pronator teres can be implicated when arm is held in resisted pronation and flexion and then gradually extended while in pronated position;
      
      - EMG:
           - when EMG does not confirm pronator teres syndrome but clinical evidence is suggestive, then wait 4-6 wks and repeat the EMG;
      
      - Treatment:
           - realease of humeral head of pronator teres and the superficialis bridge as well as associated compressing structures;
      
      
    • Anterior Interosseous Syndrome
    • Carpal Tunnel Syndrome
    • Digital neuropathy
  • Ulnar Nerve
    • Cubital Tunnel Syndrome

      Cubital Tunnel Syndrome:

      From: www.wheelessonline.com


      - See: Nerve Entrapment
      
      - Discussion:
           - cubital tunnel serves as major contraint for the ulnar nerve as it passes behind elbow;
           - the syndrome occurs most commonly between 30 to 60 years, and is exceptionally uncommon in children under 15 years;
           - inciting events:
                 - symptoms may appear several years after trauma (hence tardy ulnar palsy)
                 - common injures: fx of medial epicondyle, supracondylar fx w/ cubitus valgus deformity,
                        exuberant callus, or dislocation of the elbow;
                 - also consider prior iatrogenic injury from intraoperative positioning;
           - effects of elbow flexion:
           - neural anatomy:
                 - the internal anatomy of the ulnar nerve can partially explain the predominace of hand symptoms from in cubital tunnel syndrome;
                 - nerve fibers to the FCU and FDP are located centrally, where as sensory fibers and nerve fibers to the hand intrinsics are located peripherally;
                        - generally, the peripheral nerve fibers are more sensitive to external compression, and this may explain
                                why the hand intrinsics are often more involved than the FCU and FDP;
           - ulnar neuropathy following head injury;
                 - some form of ulnar neuropathy is common in pts w/ brain injury;
                 - one of the main causes is heterotopic ossification;
                 - it usually occurs w/ a spacit extremity;
                 - because of spacitity and lack of fine motor control, combined w/ the patients inability
                        to complain, atrophy of the intrinsic musculature is the first sign of detection;
           - differential diagnosis: 
           - concomitant disorders:
                 - thoracic outlet syndrome may occur in upto 1/3 patients;
                 - carpal tunnel syndrome may occur in upto 40% of patients;
           - anatomy & sites of nerve compression 
      
      

      - Clinical Findings:
      
      - EMG in Cubital Tunnel Syndrome:
      
      - Radiographs:
           - look for osteophytes and associated DJD which may occur frequently w/ cubital tunnel syndrome;
      
      

      - Non Operative Treatment:
           - sleeping w/ the elbow flexed will worsen symptoms;
           - consists mainly of exension splinting at night or wearing a soft (sheep skin) elbow pad;
           - splints should hold arm in 70 deg of flexion;
           - vitamin B6 50 mg PO tid: some patients will note substantial relief w/ vit B6;
           - w/ good compliance 50% of patients can avoid surgery;
           - avoidance of repetitive elbow flexion and pronation, and avoidance of vibrating tools;
           - NSAIDS
           - references: 
                  - Treatment of ulnar nerve palsy at the elbow with a night splint.
      
      

      - Surgical Treatment:
           - indications:
                  - many surgeons will refuse to operate for sensory changes alone;
                  - surgical procedure is reserved for those with disability & weakness;
                  - if weakness is early and mild, esp if Tinel's sign is present or EMG suggests cubital tunnel syndrome,
                          simple release is performed;
                  - if associated DJD of the elbow is present, then consider debridement arthroplasty (see lateral approach);
                  - as noted by Seradge et al 1998, w/ resistant symptoms, prolonging nonoperative treatment does not reduce
                          the cost of care and does not positively influence outcome;
                          - as noted by Kaempffe et al 1998, those w/ the most severe nerve entrapment (intrinsic atrophy or
                                  abnormal EMG) tend to have worse surgical outcomes;
                  - note that concomitant nerve compression syndromes may be associated w/ a higher rate of recurrence;
           - preoperative considerations:
                  - if the patient believes that their CTS syndrome is work related, then he/she should work this out ahead of time;
                  - be clear with the patient ahead of time, regarding the goals of surgery;
                         - if the patient tends to over-react to painful stimuli, then they will probably react the same following surgery;
                         - in patients at risk for poor outcome or delayed return to work (such as workers compensation), consider 10 days
                                  of aggressive nonoperative therapy inorder to assess their subjective response to treatment;
                         - for instance, consider combining oral steroids, casting w/ elbow in 45 deg flexion (to ensure compliance), and cessation
                                  of repetitive activity for 10 days;
                                  - if the patient insists that no relief has been obtained, then the subjective results of surgery may be in doubt;
           - surgical technique options: (anatomy & sites of nerve compression) 
                  - Isolated Division of the Aponeurosis:
                  - Medial Epiondylectomy:
                  - Subcutaneous Anterior Transposition:
                  - Submuscular Anterior Transposition;
           - complications:
                  - recurrent nerve compression:
                         - in the report by Caputo and Watson, the authors identified 20 patients w/ recurrent compression who underwent 
                                 anterior subcutaneous transposition of the ulnar nerve;
                         - most common sites of compression were the medial intermuscular septum and the flexor-pronator aponeurosis;
                         - 15 patients had a good or excellent outcome; 5 patients had a fair or poor outcome;
                         - relief of pain and paresthesias were the most consistent favorable results;
                         - ref: Subcutaneous anterior transposition of the ulnar nerve for failed decompression of cubital tunnel syndrome.
                                     Andrew E. Caputo and H. Kirk Watson. J Hand Surg 2000;25A:544-551
      
    • Guyon’s canal neuropathy

      Tunnel of Guyon:

      From: www.wheelessonline.com


      - Discussion:
           - depression between pisiform & hook of hamate is converted into fibrosseous tunnel, the tunnel of Guyon, by pisohamate ligament;
           - roof is formed by volar carpal ligament and pisohamate ligament;
                  - the ulnar nerve bifurcates within the canal into superficial and deep branches;
           - tunnel of Guyon is clinically significant because it contains ulnar nerve and artery & is site for compression injury;
                  - consider anomalous muscles, ganglia, hamate fractures ect.
      
      - Technique of Decompression:
           - the pisiform and the hamate are marked;
           - a curvilinear incision is made between the pisiform and the hamate, and is extended proximally across the
                   wrist crease and is then continued along the medial border of the FCU;
           - the ulnar nerve and artery are identified beneath the FCU;
           - the deep dissection proceeds distally over the ulnar tunnel;
           - incise thru the palmaris brevis and palmar carpal ligament;
           - examine the floor of Guyon's canal, and attempt to identify any anomalous muscles or ganglion cysts;
      
    • Palmar branch neuropathy
    • Digital neuropathy

In the lower extremities common neuropathies include:

  • Femoral neuropathy

    Femoral Nerve:

    From: www.wheelessonline.com


    - Anatomy:
         - arises from posterior divisions of Ventral Rami of L2, L3, L4
         - see innerv. musc. lower limb;
         - passes inferolaterally thru psoas, & then runs between this muscle & iliacus;
         - it passes over Iliacus muscle to enter thigh underneath the inguinal ligament;
         - it supplies quadriceps & anteromedial thigh, & then continues on as the saphenous nerve;
         - branches:
               - Pectineus : arises at the level of the inguinal ligament;
               - Sartorius
               - Quadriceps
    
    - Femoral Nerve Palsy:
         - may result from iliacus hematoma (either from anticoagulation or hemophilia);
    
  • Lateral femoral cutaneous neuropathy

    Lateral Femoral Cutaneous Nerve:


    From: www.wheelessonline.com
     
    - Anatomy:
         - LFCN, as its name suggests, is purely sensory;
         - it arises from L2 and L3, travels downward lateral to the psoas muscle, crosses the iliacus muscle (deep to fascia),
                passes either thru or underneath the lateral aspect of the inguinal ligament, and finally travels onto innervate the lateral thigh;
                - it divides into anterior and posterior branches and supplies skin on lateral aspect of thigh;
         - in the study by Hospodar et al (JTO 1999), the course of the nerve was variable, but was most commonly found at 10-15 mm from the ASIS and as
                far medially as 46 mm from the ASIS;
                - in no specimen did the nerve pass lateral to the ASIS (eventhough historically the nerve is thought to pass lateral to the ASIS in 10% of population);
                - in all specimens the nerve passed underneath the ilioginal ligament and anterior to the iliacus muscle;
     
    - Meralgia Paresthetica:
         - entrapment syndrome of the lateral femoral cutaneous nerve causing burning, numbness, and paresthesias down the
                proximal-lateral aspect of the thigh;
         - may be idiopathic, be a result of trauma, previous operations, and in some cases may arise from Perthes Disease abduction splints;
                - in idiopathic cases, the nerve may be encased in bone by the growing apophysis of the anterior superior iliac spine,
                      or may be entrapped in fascia either proximal or distal to the ASIS;
         - diagnosis is made by:
                - reproduction of the pain by deep palpation just below the anterior superior iliac spine and by hip extension;
                - relief of pain by localized injection of lidocaine;
         - treatment: when diagnosis is not in doubt and the symptoms are severe, consider operative decompression at the site of constriction;
  • Sciatic neuropathy

    Sciatic Nerve:

    From; www.wheelessonline.com


    - Anatomy:
         - arises from lumbrosacral plexus: L4, L5, S1, S2, S3;
         - nerve emerges from pelvis below piriformis & enters thigh between ischial tuberosity & greater trochanter;
         - in 10% of patients, the sciatic nerve is separated in greater sciatic foramen by all or part of the piriformis;
         - sciatic nerve is accompanied by PFCN & by inferior gluteal artery and its special branch to nerve;
         - nerve enters thigh beneath lower border of maximus;
         - descends near middle of thigh, lying on adductor magnus muscle & being crossed obliquely by long
                head of biceps femoris ;
         - nerve usually separates in upper part of popliteal space;
    
    - Tibal Nerve  Branch:
         - from anterion branches of LS plexus: L4, L5, S1, S2, S3;
         - 2 branches from tibial division: below quadratus femoris:
              - upper branch passes to long head of  biceps femoris  & upper portion of semitendinosus;
              - lower branch: innervates lower portion of  semitendinosus  &
                   semimembranous  & ischiocondylar portion of adductor magnus ;
    
    - Common Peroneal Nerve:
         - from posterior branches: L4, L5, S1, S2;
         - nerve to short head of biceps femoris arises from lateral side of sciatic nerve (common peroneal portion)
                in middle of thigh & enters superficial surface of the muscle;
    
    - Sciatic Nerve in THR: (see: nerve injuries from THR)
         - in THR the sciatic nerve may be injured by excessive tension when extremity has been lengthened significantly, especially in pts w/ DDH ;
         - sciatic nerve is at risk during leg lengthening;
         - peroneal division is most often affected;
         - w/ sciatic nerve injury following THR, keep pts leg flexed over side of bed;
                - if injury was due to traction, the nerve may recover in the relaxed position;
    
    - Sciatic Nerver Injury from Kocher Langenbock Approach;
         - sciatic nerve palsy from Kocher Langenbock Approach;
         - can be prevented by intraop monitoring of amount of tension applied by assistants retracting the nerve;
         - early treatment consists of AFO
         - sciatic nerve recovery may occur over a 3 yr period;
         - tendon transfers are usually not performed unitl 3 yr post op;
    
    
  • Peroneal neuropathy – common; deep; superficial branch

    Peroneal Nerve:

    From: www.wheelessonline.com


    - See:
           - Innerv. Musc. Lower Limb
           - Innervation of the Leg and Foot:
    
    - Anatomy:
          - common peroneal nerve is derived from (L4, L5, S1, S2) as a part of the sciatic nerve;
          - posterior component, supplies short head of biceps femoris in thigh, crosses posterior to lateral
                 head of gastrocnemius, and becomes subcutaneous behind head of fibula;
          - it penetrates the posterior intermuscular septum, and becomes closely opposed to the periosteum of the proximal fibula;
          - it then divides into superficial & deep peroneal nerves;
          - the nerve also gives off a lateral sural cutaneous brach which joins with the the medial sural cutaneous
                 nerve (from tibial nerve) to form the sural nerve;
          - superficial peroneal nerve:
                 - supplies lateral compartment of leg, first passing between peroneus longus
                 - passes in a straight line from the common peroneal nerve;
                 - along the length of the proximal one third of the fibula, the superficial peroneal nerve is on the lateral cortex of the fibula;
                 - passes between peroneus longus & peroneus brevis;
                 - superficial sensory nerves:
                       - subcutaneous superficial sensory branch lies between peroneus brevis and EDL msucles.
                       - superficial peroneal nerve is accompanied by a true vascular axis that is supplied by tibialis anterior artery along its course.
                       - about 10-12 cm above the tip of the lateral malleolus, the superficial peroneal nerve pierces the fascia;
                       - about 6-7 cm distal to the fibula, the superficial peroneal nerve bifurcates into intermediate and medial dorsal cutaneous nerves;
                       - location of cutaneous nerves: (from Huene and Bunnell 1995)
                             - branches of the superficial peroneal nerve or the sural nerve may be injured during ORIF of Ankle frx;
                             - these nerves are most at risk at the junction of the distal and middle thirds of the lateral border of the fibula;
                             - in 22% of legs, braches of either nerve will cross the frx site;
                             - in 54% of legs, branches of superficial peroneal will lie within 5 mm of the anterolateral border of the fibula;
                             - safest interval is 12 mm posterior to the anterolateral border of the fibula at 10 cm from the
                                    fibular tip, and 10 mm posterior to the anterolateral border at 5 cm proximal to the tip;
                 - references:
                       - Surgical anatomy of the superficial peroneal nerve in the ankle and foot.
                       - Anatomical variations in the course of the superficial peroneal nerve.
                       - Operative anatomy of nerves encountered in the lateral approach to the distal part of the fibula.
                       - Anatomic relations between ankle arthroscopic portal sites and the superficial peroneal and saphenous nerves.
                              A. Saito MD and S. Kikuchi.  Foot and Ankle International. Vol 19. No 11. Nov 1998. p 748.                         
                       - Operative Anatomy of Nerves Encountered in the Lateral Approach to the Distal Part of the Fibula.
                              D.B. Huene MD, and W.P. Bunnell MD. JBJS Vol 77-A. No 7. Jul 1995.
          - deep peroneal nerve:
                 - courses anteriorly around fibula, taking a sharp turn as it rounds the fibular neck, to enter anterior compartment of leg;
                       - because of the sharp turn, the nerve is more tethered than the superficial branch;
                 - immediately below the fibular head, the deep peroneal nerve lies on the anterior cortex of the fibula for a distance of 3-4 cm;
                 - the nerve passes under the intermuscular septum (between lateral and anterior compartments) which is a point of entrapment;
                       - note that when this septum is pulled taunt, it compresses the deep peroneal nerve w/o affecting the superficial nerve;
                 - it supplies anterior compartment muscles as it travels w/ the the anterior tibial artery, lying between the tibialis anterior and the EHL;
                 - it passes underneath the extensor retinaculum, sends a motor branch to the EDB,
                       and finally sends a sensory branch to the interspace between the first and second toes;
          - references: 
                 - Palsy of the deep peroneal nerve after proximal tibial osteotomy. An anatomical study.
                 - Relationship of the common peroneal nerve and its branches to the head and neck of the fibula.
    
    
    

    - Peroneal Nerve Palsy:
         - peroneal palsy following TKR
         - nerve injury
         - discussion:
              - peroneal nerve palsy may lead to severe disability w/ foot drop and paresthesias;
              - note that in contrast to other types of nerve palsies, peroneal palsy may demonstrate a greater motor deficit (than sensory
                   deficit) because the deep motor brach is subject to tethering a two points: the fibular neck and the intermuscular septum;
              - traumatic peroneal palsy: may result from supracondylar frx, knee dislocation, and proximal tibial frx;
              - atraumatic peroneal nerve palsy:
                   - may result from a large fabella which impinges on peroneal nerve behind the
                          knee or may result from a proximal tibiofibular synovial cyst (which is identifed by MRI);
                   - these patients will often have a history of lumber disc disease, ETOH use, and diabetes.
                   - references:
                          - Unusual manifestations of proximal tibiofibular joint synovial cysts. TA Damron, MG Rock.  Orthopedics. Vol 20, 1997. p 225-230.
         - exam:
              - always consider lumbar radiculopathy during the examination;
              - there may be an obvious foot drop;
              - sensory loss may be difficult to determine because of variable & small autonomous zone of sensation;
              - Tinel's sign over the fibular neck, helps localize the site of nerve compression;
              - always check for a fabella and check to see if direct compression reproduces nerve symptoms;
              - in cases of knee dislocation it is important to test for function of the tibial branch of the sciatic nerve as well;
                    - in some cases of peroneal nerve avulsion, there will also be a sciatic nerve traction injury;
         - EMG:
              - useful to objectively document the conduction block;
              - if possible should be performed w/ in one month of injury;
              - amplitude of the sensory potential and decreases in nerve conduction velocities are used to
                      confirm sensory and motor deficits, respectively;
         - prognosis;
              - w/ partial nerve palsy, > 80% will recover completely;
              - w/ complete palsy, < 40% will have complete recovery;
              - peroneal nerve in continuity which arises from a well defined etiology will tend to do better than
                     nerve palsies arising from idiopathic causes;
         - treatment:
              - if there is no neurologic improvement after 2-3 months, then operative decompression is indicated;
              - nerve in continuity:
                     - operative treatment invovles external neurolysis of peroneal nerve at the level of the fibular head;
                     - the nerve and its branches need to be freed from its adherence to the proximal fibula, particularly at its most proximal
                            4 cm as well as a 2nd region of adherence which may lie between 7 and 15 cm from the fibular head;
                     - the nerve may be entrapped by thick fibrous bands which arch over the nerve as it crosses the fibular neck;
                            - the arch has a superficial band and a deep band;
              - nerve not in continuity: (neurotomesis)
                     - see nerve repair
                     - one of the problems encountered in peroneal nerve repair following knee dislocations
                            (or other injuries) is that the location of the nerve injury may be well above the knee joint;
                            - in the case of knee dislocation, there may be concomitant tibial nerve division palsy;
              - references:
                     - Nerve grafting for traction injuries of the common peroneal nerve. A report of 17 cases.
                     - Nerve grafting for traction injuries of the common peroneal nerve. A report of 17 cases.
                     - The operative treatment of peroneal nerve palsy.  MA Mont et al. JBJS Vol 78-A. 1996. p 863-869.
                     - Decompression of the common peroneal nerve: experience with 20 consecutive cases.
                     - Fibular fibrous arch.  Anatomical considerations in fibular tunnel syndrome.
                             H Goobe and D Chain. Acta Anat. Vol 85. 1973. p 84-87.
                     - Anatomic variations related to decompression of the common peroneal nerve at the fibular head.
    
    
    
    
    
  • Tibial neuropathy (TTS)

    Tarsal Tunnel Syndrome:

    From: www.wheelessonline.com


    - Tarsal Tunnel Syndrome:
         - compression syndrome of the tibial nerve in the tarsal tunnel;
         - tarsal tunnel is formed by the flexor retinaculum behind and distal to the medial malleolus;
         - inciting causes:
                - lipoma, ganglia, or neoplasms within the tarsal tunnel;
                - an accessory flexor digitorum longus muscle is a common cause;
                - exostosis within the tarsal tunnel;
                - hindfoot valgus deformity will potentiate the deformity;
                       - in the study by Daniels et al 1998, tibial nerve tension was increased by erversion and dorsiflexion of the foot;
         - diff dx:
                - stress fractures (identified on 45 deg medial oblique view)
                - inflammatory arthritides (RA or Reiter's Syndrome)
                - plantar fasciitis
                - herniated disk
                - peripheral neuropathy
                - disc herniation;
         - clinical findings:
                - patients may note pain when the ankle is placed in extremes of dorsiflexion (from nerve tension);
                - patients note pain, paresthesias, foot numbness, and in somes cases atropy of foot intrinsics;
                - pain will radiate along the plantar side of the foot, sometimes up into the calf;
                - positive Tinel sign behind medial malleolus;
                - manual compression for 30 sec. may reproduce symptoms;
                - consider performing 2 point discrimination test both on medial and lateral sides of the foot (and opposite foot);
                       - if the 2 point discrimination is increased on one side of the foot, it may indicate which branch of the
                               plantar nerve is compressed;
                - in most cases, symptoms will be improved w/ rest;
         - EMG
                - can be useful when the operator has experience w/ this condition;
                - prolonged distal motor latency;
                       - terminal latencies of the ADQ (lateral plantar nerve) more than 7.0 msec are abnormal;
                       - terminal latencies of abductor hallucis (which is innervated by the medial plantar nerve) more than 6.2 msec is abnormal;
                - fibrillations in the abductor hallucis;
                - in the series by DS Bailie MD and AS Kelikian 1998, 81% of patients had abnormal EMG studies;
         - MRI: may be used to identify ganglia or extrinsic masses and the specific site of compression;
         - operative decompression:
                - is considered for patients w/ space occupying lesions (there are numerous case reports of neurolemoma
                       involving the tibial nerve within the tarsal tunnel);
                       - concerns have been raised about tarsal tunnel decompressions, noting that the decompression would not alter
                               stretch forces on the nerve (rather this would have to be managed by stabilization of the foot  in a corrected position;
                - the nerve is decompressed from the posterior tibial nerve from its flexor retinaculum to a point past the bifurcation;
                - if an anomalous muscle if found with in the tunnel and is thought to be the cause of nerve
                       compression then the muscle should be resected;
                - cautions: nerve decompression of the tarsal tunnel may not produce the favorable long term results seen in other
                       nerve decrompression procedures;
    
    

    - Distal Tibial Tarsal Tunnel Syndrome:
         - a cause of heel pain arising from compression of the distal branches of the posterior tibial
                nerve by the deep fascia along the medial border of the abductor hallucis;
         - this can be exacerbated by by hyperpronation, thickening of the plantar fascia, thickening of the
                deep fascia of the abductor hallucis;
         - first branch lateral plantar nerve:
                - this nerve supplies the abductor digiti quinti (and possibly it innervates the quatratus plantae and FDB)
                       as well as deep sensory innervation;
                - nerve runs deep to the deep fascia of the abductor hallucis and then runs laterally and transversely superficial to
                       the quadratus (and deep to the FHB) on its way to innervate the abductor digiti quinti;
                - nerve may be compressed by the superior-deep edge of abductor hallucis fascia & most medial edge of the plantar fascia,
                       and in addition the nerve may be compressed by medial edge of quadratus;
                       - the nerve is best exposed by superior retraction of the abductor hallucis, or in some cases, the abductor must
                              be mobilized or divided inorder to adequately expose (and decompress) the nerve;
                - entrapment of the first branch occurs as the nerve changes from vertical to a horizontal direction around
                       the medial plantar aspect of the heel;
                - the calcaneal heel spur lies just plantar to the course of the nerve and may be contributing to nerve compression or irritation;
                - pts w/ flat feet are thought to be at risk for this compression;
                - the nerve is decompressed by elevating the abductor hallucis and then releasing the deep fascia beneath the abductor
                       and the contiguous medial plantar fascia;
         - medial calcaneal nerve:
                - nerve branches that innervate the plantar medial aspect of the heel pass medial (superficial) to the abductor hallucis muscle and are
                       usually not involved with the entrapment of the first banch;
                - some have theorized that a valgus hindfoot predisposes joggers to compression of this nerve branch;
                - terminal latencies of abductor hallucis (which is innervated by the medial plantar nerve) more than 6.2 msec is abnormal;
    
    

    - Complications:
         - iatrogenic nerve compression:
                - as noted by JTC Lau and TR Daniels, a tarsal tunnel release w/ a concomitant pes planus may have the effect
                       of increasing posterior tibial nerve tension, which may explain the high rate of poor surgical results;
                       - in the same study, distraction calcaneo-cuboid arthrodesis reduced nerve tension;
    
  • Plantar neuropathy

    Tarsal Tunnel Syndrome:

    From: www.wheelessonline.com


    - Tarsal Tunnel Syndrome:
         - compression syndrome of the tibial nerve in the tarsal tunnel;
         - tarsal tunnel is formed by the flexor retinaculum behind and distal to the medial malleolus;
         - inciting causes:
                - lipoma, ganglia, or neoplasms within the tarsal tunnel;
                - an accessory flexor digitorum longus muscle is a common cause;
                - exostosis within the tarsal tunnel;
                - hindfoot valgus deformity will potentiate the deformity;
                       - in the study by Daniels et al 1998, tibial nerve tension was increased by erversion and dorsiflexion of the foot;
         - diff dx:
                - stress fractures (identified on 45 deg medial oblique view)
                - inflammatory arthritides (RA or Reiter's Syndrome)
                - plantar fasciitis
                - herniated disk
                - peripheral neuropathy
                - disc herniation;
         - clinical findings:
                - patients may note pain when the ankle is placed in extremes of dorsiflexion (from nerve tension);
                - patients note pain, paresthesias, foot numbness, and in somes cases atropy of foot intrinsics;
                - pain will radiate along the plantar side of the foot, sometimes up into the calf;
                - positive Tinel sign behind medial malleolus;
                - manual compression for 30 sec. may reproduce symptoms;
                - consider performing 2 point discrimination test both on medial and lateral sides of the foot (and opposite foot);
                       - if the 2 point discrimination is increased on one side of the foot, it may indicate which branch of the
                               plantar nerve is compressed;
                - in most cases, symptoms will be improved w/ rest;
         - EMG
                - can be useful when the operator has experience w/ this condition;
                - prolonged distal motor latency;
                       - terminal latencies of the ADQ (lateral plantar nerve) more than 7.0 msec are abnormal;
                       - terminal latencies of abductor hallucis (which is innervated by the medial plantar nerve) more than 6.2 msec is abnormal;
                - fibrillations in the abductor hallucis;
                - in the series by DS Bailie MD and AS Kelikian 1998, 81% of patients had abnormal EMG studies;
         - MRI: may be used to identify ganglia or extrinsic masses and the specific site of compression;
         - operative decompression:
                - is considered for patients w/ space occupying lesions (there are numerous case reports of neurolemoma
                       involving the tibial nerve within the tarsal tunnel);
                       - concerns have been raised about tarsal tunnel decompressions, noting that the decompression would not alter
                               stretch forces on the nerve (rather this would have to be managed by stabilization of the foot  in a corrected position;
                - the nerve is decompressed from the posterior tibial nerve from its flexor retinaculum to a point past the bifurcation;
                - if an anomalous muscle if found with in the tunnel and is thought to be the cause of nerve
                       compression then the muscle should be resected;
                - cautions: nerve decompression of the tarsal tunnel may not produce the favorable long term results seen in other
                       nerve decrompression procedures;
    
    

    - Distal Tibial Tarsal Tunnel Syndrome:
         - a cause of heel pain arising from compression of the distal branches of the posterior tibial
                nerve by the deep fascia along the medial border of the abductor hallucis;
         - this can be exacerbated by by hyperpronation, thickening of the plantar fascia, thickening of the
                deep fascia of the abductor hallucis;
         - first branch lateral plantar nerve:
                - this nerve supplies the abductor digiti quinti (and possibly it innervates the quatratus plantae and FDB)
                       as well as deep sensory innervation;
                - nerve runs deep to the deep fascia of the abductor hallucis and then runs laterally and transversely superficial to
                       the quadratus (and deep to the FHB) on its way to innervate the abductor digiti quinti;
                - nerve may be compressed by the superior-deep edge of abductor hallucis fascia & most medial edge of the plantar fascia,
                       and in addition the nerve may be compressed by medial edge of quadratus;
                       - the nerve is best exposed by superior retraction of the abductor hallucis, or in some cases, the abductor must
                              be mobilized or divided inorder to adequately expose (and decompress) the nerve;
                - entrapment of the first branch occurs as the nerve changes from vertical to a horizontal direction around
                       the medial plantar aspect of the heel;
                - the calcaneal heel spur lies just plantar to the course of the nerve and may be contributing to nerve compression or irritation;
                - pts w/ flat feet are thought to be at risk for this compression;
                - the nerve is decompressed by elevating the abductor hallucis and then releasing the deep fascia beneath the abductor
                       and the contiguous medial plantar fascia;
         - medial calcaneal nerve:
                - nerve branches that innervate the plantar medial aspect of the heel pass medial (superficial) to the abductor hallucis muscle and are
                       usually not involved with the entrapment of the first banch;
                - some have theorized that a valgus hindfoot predisposes joggers to compression of this nerve branch;
                - terminal latencies of abductor hallucis (which is innervated by the medial plantar nerve) more than 6.2 msec is abnormal;
    
    

    - Complications:
         - iatrogenic nerve compression:
                - as noted by JTC Lau and TR Daniels, a tarsal tunnel release w/ a concomitant pes planus may have the effect
                       of increasing posterior tibial nerve tension, which may explain the high rate of poor surgical results;
                       - in the same study, distraction calcaneo-cuboid arthrodesis reduced nerve tension;
    

Cubital Tunnel Syndrome:

From: www.wheelessonline.com


- See: Nerve Entrapment

- Discussion:
     - cubital tunnel serves as major contraint for the ulnar nerve as it passes behind elbow;
     - the syndrome occurs most commonly between 30 to 60 years, and is exceptionally uncommon in children under 15 years;
     - inciting events:
           - symptoms may appear several years after trauma (hence tardy ulnar palsy)
           - common injures: fx of medial epicondyle, supracondylar fx w/ cubitus valgus deformity,
                  exuberant callus, or dislocation of the elbow;
           - also consider prior iatrogenic injury from intraoperative positioning;
     - effects of elbow flexion:
     - neural anatomy:
           - the internal anatomy of the ulnar nerve can partially explain the predominace of hand symptoms from in cubital tunnel syndrome;
           - nerve fibers to the FCU and FDP are located centrally, where as sensory fibers and nerve fibers to the hand 
           intrinsics are located peripherally;
                  - generally, the peripheral nerve fibers are more sensitive to external compression, and this may explain
                          why the hand intrinsics are often more involved than the FCU and FDP;
     - ulnar neuropathy following head injury;
           - some form of ulnar neuropathy is common in pts w/ brain injury;
           - one of the main causes is heterotopic ossification;
           - it usually occurs w/ a spacit extremity;
           - because of spacitity and lack of fine motor control, combined w/ the patients inability
                  to complain, atrophy of the intrinsic musculature is the first sign of detection;
     - differential diagnosis: 
     - concomitant disorders:
           - thoracic outlet syndrome may occur in upto 1/3 patients;
           - carpal tunnel syndrome may occur in upto 40% of patients;
     - anatomy & sites of nerve compression 


- Clinical Findings:

- EMG in Cubital Tunnel Syndrome:

- Radiographs:
     - look for osteophytes and associated DJD which may occur frequently w/ cubital tunnel syndrome;


- Non Operative Treatment:
     - sleeping w/ the elbow flexed will worsen symptoms;
     - consists mainly of exension splinting at night or wearing a soft (sheep skin) elbow pad;
     - splints should hold arm in 70 deg of flexion;
     - vitamin B6 50 mg PO tid: some patients will note substantial relief w/ vit B6;
     - w/ good compliance 50% of patients can avoid surgery;
     - avoidance of repetitive elbow flexion and pronation, and avoidance of vibrating tools;
     - NSAIDS
     - references: 
            - Treatment of ulnar nerve palsy at the elbow with a night splint.


- Surgical Treatment:
     - indications:
            - many surgeons will refuse to operate for sensory changes alone;
            - surgical procedure is reserved for those with disability & weakness;
            - if weakness is early and mild, esp if Tinel's sign is present or EMG suggests cubital tunnel syndrome,
                    simple release is performed;
            - if associated DJD of the elbow is present, then consider debridement arthroplasty (see lateral approach);
            - as noted by Seradge et al 1998, w/ resistant symptoms, prolonging nonoperative treatment does not reduce
                    the cost of care and does not positively influence outcome;
                    - as noted by Kaempffe et al 1998, those w/ the most severe nerve entrapment (intrinsic atrophy or
                            abnormal EMG) tend to have worse surgical outcomes;
            - note that concomitant nerve compression syndromes may be associated w/ a higher rate of recurrence;
     - preoperative considerations:
            - if the patient believes that their CTS syndrome is work related, then he/she should work this out ahead of time;
            - be clear with the patient ahead of time, regarding the goals of surgery;
                   - if the patient tends to over-react to painful stimuli, then they will probably react the same following surgery;
                   - in patients at risk for poor outcome or delayed return to work (such as workers compensation), consider 10 days
                            of aggressive nonoperative therapy inorder to assess their subjective response to treatment;
                   - for instance, consider combining oral steroids, casting w/ elbow in 45 deg flexion (to ensure compliance), and cessation
                            of repetitive activity for 10 days;
                            - if the patient insists that no relief has been obtained, then the subjective results of surgery may be in doubt;
     - surgical technique options: (anatomy & sites of nerve compression) 
            - Isolated Division of the Aponeurosis:
            - Medial Epiondylectomy:
            - Subcutaneous Anterior Transposition:
            - Submuscular Anterior Transposition;
     - complications:
            - recurrent nerve compression:
                   - in the report by Caputo and Watson, the authors identified 20 patients w/ recurrent compression who underwent 
                           anterior subcutaneous transposition of the ulnar nerve;
                   - most common sites of compression were the medial intermuscular septum and the flexor-pronator aponeurosis;
                   - 15 patients had a good or excellent outcome; 5 patients had a fair or poor outcome;
                   - relief of pain and paresthesias were the most consistent favorable results;
                   - ref: Subcutaneous anterior transposition of the ulnar nerve for failed decompression of cubital tunnel syndrome.
                               Andrew E. Caputo and H. Kirk Watson. J Hand Surg 2000;25A:544-551

Tunnel of Guyon:

From: www.wheelessonline.com


- Discussion:
     - depression between pisiform & hook of hamate is converted into fibrosseous tunnel, the tunnel of Guyon, by pisohamate ligament;
     - roof is formed by volar carpal ligament and pisohamate ligament;
            - the ulnar nerve bifurcates within the canal into superficial and deep branches;
     - tunnel of Guyon is clinically significant because it contains ulnar nerve and artery & is site for compression injury;
            - consider anomalous muscles, ganglia, hamate fractures ect.

- Technique of Decompression:
     - the pisiform and the hamate are marked;
     - a curvilinear incision is made between the pisiform and the hamate, and is extended proximally across the
             wrist crease and is then continued along the medial border of the FCU;
     - the ulnar nerve and artery are identified beneath the FCU;
     - the deep dissection proceeds distally over the ulnar tunnel;
     - incise thru the palmaris brevis and palmar carpal ligament;
     - examine the floor of Guyon's canal, and attempt to identify any anomalous muscles or ganglion cysts;

Pelvic girdle mononeuropathies

Lesions of the individual branches of the lumbar plexus are most frequently due to trauma. Differential diagnosis with lumbo-sacral radiculopathy is the most frequent question for the electromyographer.

Pelvic girdle mononeuropathies include:

  • Superior and Inferior Gluteal (Gluteus Medius and Gluteus Maximus; EMG abnormal)

    Superior Gluteal Nerve:

    From: www.wheelessonline.com


    
    - Anatomy:
           - from the lumbo-sacral plexus, arises from posterior branches L4, L5, S1;
           - exits the pelvis and enters the gluteal regioin through the upper margin
                  of the greater sciatic notch, just superior to the piriformis muscle.
           - it courses with superior gluteal artery  between gluteus medius and minimus,
                  and supplies motor branches to both as well as the tensor fascia lata.
    
    

    Inferior Gluteal Nerve:

    From: www.wheeless.com


    - Discussion:
         - arises from posterior branches of L5, S1, and S2;
         - passes from the pelvis below the piriformis muscles in the greater sciatic foramen;
         - it enters the deep surface of the gluteus maximus muscle, to which it is the sole supply;
    
    
  • Obturator (rare syndrome; Adductors and Gracilis; EMG abnormal)

    Obturator Nerve:

    From: www.wheelessonline.com


    - Anatomy:
         - formed from anterior branches of L2, L3, L4 (see innervation of muscles of the lower limb)
         - largest nerve formed from anterior divisons of  lumbar plexus ;
         - roots unite within the posterior part of psoas, & then descends thru psoas & runs downward over
                sacral ala into lesser pelvis, lying lateral to ureter & internal iliac vessels;
         - enters the upper part of the obturator foramen and then subsequently divides into
                anterior and posterior branches;
    
    - Anterior Branch:
         - runs in front of obturator externus  & adductor brevis ;
         - it runs behind the   pectineus  and adductor longus muscles;
         - gives off articular twig that enters hip joint thru acetabular notch;
         - supplies muscular branches to hip adductors & then divides into cutaneous, vascular, and communicating vessels;
    
    - Cutaneous Branch:
         - when present, it assists in innervation of skin and fascia over distal 2/3 of thigh;
    
    - Posterior Branch:
         - pierces anterior part of obturator externus;
         - nerve then runs downward behind the adductor brevis & and in front of
                 the adductor magnus;
         - it then splits into branches that are distributed to upper (adductor) part of adductor magnus  & sometimes to adductor brevis;
    
  • Femoral (Quadriceps and possibly Iliopsoas depending on the site of lesion; NCS and EMG abnormal)
  • Lateral femoral cutaneous (pure sensory; abnormal sensory NCS; technically difficult NCS)
  • Sciatic (Hamstrings with sparing of Gluteus Maximus and paraspinals thus excluding S1 lesion; NCS and EMG abnormal)

Radial neuropathy

The most common lesion of the radial nerve is at the spiral groove of the humerus due to external pressure of a fracture. Another radial neuropathy of frequent medico-legal interest is a pure sensory neuropathy at the wrist caused by pressure form handcuffs. This can be easily documented by performing nerve conduction studies.

Radial Nerve:

From: www.wheelessoneline.com


- See:
       - Posterior Interosseous Nerve Syndrome :
       - Radial Nerve Palsy Associated w/ Humeral Shaft Frx:
       - Radial Nerve Block
       - Tendon Transfers  for Radial Nerve Palsy:

- Anatomy:
     - three posterior divsions of brachial plexus form posterior cord: (C5 , C6 , C7, C8, T1)
          - radial nerve (C5, C6, C7 , C8 , and T1 ) is largest of & most frequently injured branch of both the posterior cord (as well as the brachial plexus);
     - in axilla, it gives off:
          - posterior cutaneous nerve of arm;
          - branch to long & medial heads of triceps;
          - between axilla & spiral groove of humerus:
                 - it distributes a branch to the lateral head of the triceps;
          - nerve may or may not travel in spiral groove and is often separated by the humerus by 1 to 5 cm of muscle;   

     - course of nerve through the intermuscular septum;
          - nerve travels from deep to the lateral head of the triceps, piercing the intermuscular septum;
          - after piercing lateral intermuscular septum, the nerve comes to lie between the brachialis and brachioradialis, and
                 goes on to pass in front of elbow:
                 - radial nerve emanates from the spiral groove approximately 10 cm proximal to the lateral epicondyle;
                 - branch to brachioradialis & ECRL ;
                 - nerve remains anterior relative to the humerus, and passes along the lateral column of the distal humerus;
          - reference: One-third, two-thirds: relationship of the radial nerve to the lateral intermuscular septum in the arm.
          - each of motor branches, arising from radial nerve & passing to lateral head of triceps, is accompanied closely by a branch of profunda brachi artery and vein;
          - as noted by Gerwin et al (JBJS Am. 1996 Nov;78(11):1690-5.), the nerve crosses the posterior aspect of the humerus at 20-21 cm proximal to the
                 medial epicondyle and 14-15 cm proximal to the lateral epicondyle;
          - posterior interosseous nerve :
                 - it divides in front of radial head, w/ deep branch (PIN) passing backward thru supinator (arcade of Froshe) to supply 9 muscles on extensor aspect  of forearm;
                 - because of the numerous branches into which the deep radial nerve breaks up at the lower border of the supinator, surgical repair of the nerve here is difficult;
                 - remaining part PIN, runs downward parallel to posterior interosseous artery to supply all of deeper lying extensor muscles & ends as a twig to wrist joint;
                 - in this course, it passes superficial to long abductor & EPB  of thumb, but its terminal branch to wrist joint passes deep to EPL  & EIP;
     - Sensory Branch:
          - superficial branch of radial nerve passes into forearm deep to brachioradialis muscle;
          - approx 8 cm from tip of radial styloid, nerve emerges from under tendon of BR between tendon of BR & tendon of ECRL;
          - sensory branch passes downward emerging dorsally from beneath BR tendon about 5 cm proximal to radial styloid;
                 - it lies just deep to the superficial veins;
          - distally, it provides sensation to dorsum of thumb, excluding subungual region which is supplied by branches of median;
          - superficial branch innervates dorsal aspect of first web space & hand as far ulnarward as middle of ring finger & as far distally as proximal interphalangeal joint.
          - references:
                 The radial sensory nerve . An anatomic study.
                 The superficial branch  of the radial nerve: an anatomic study with surgical implications.
                 Transfer of sensory branches of radial nerve in hand surgery.

- Physcial Exam:
     - signs of a radial nerve lesion include:
          - inability to exten thumb, proximal phalanges, wrist or elbow;
          - hand is pronated and the thumb adducted.
     - termainal branches of superficial radial nerve are palpable in the anatomic snuff box  where they cross EPL;
     - paralysis of PIN will result in total loss of extension of fingers &, though rare occurrence, must be entertained in diff dx of extensor tendon rupture (w/ the R.A. pt):
     - exam for brachial plexus injury:
            - brachioradialis (C5-6)
            - supinator (C5-C6)
            - ECRB (C6-C7)
            - triceps (C6-8)


- Radial Tunnel Compression Syndrome:
     - compression of the radial nerve at the elbow can involve the PIN or the superficial branch;
     - radial tunnel syndrome refers to the syndrome of forearm pain without muscular weakness;
     - it is often misdiagnosed as resistant tennis elbow or PIN syndrome;
     - unlike tennis elbow, there is tenderness about 4 cm distal to the lateral humeral epicondyle;
     - sites of compression:
            - fibrous bands anterior to the radial head at the entrance of radial tunnel;
            - radial recurrent vessels;
            - tendinous origin of ECRB
            - tendinous proximal border of supinator (arcade of Frohse)
                  - this is the most common location of nerve compression in radial tunnel syndrome;
            - distal edge of the supinator at exit;
     - exam:
            - look for tenderness over the radial tunnel;
            - pain may be experienced when the long finger is extended against resistance;
            - active supination from a pronated position (tightening supinator) along w/ wrist flexion (which tighens the ECRB) may reproduce the patient's symptoms;
            - also consider differential injection of the deep radial nerve;
     - treatment:
            - as noted by Jebson and Engber et al 1997, about 2/3 patients with radial tunnel syndrome had good to excellent results, however, complete pain relief
                    and return to normal activities is not always predictable;
            - treatment includes division of the fibrous edge of the supinator muscle (most common reason for impingement), and division of the medial border of the ECRB;
     - reference:
            - Radial nerve entrapment at the elbow: surgical anatomy.
            - Radial tunnel syndrome caused by ganglion cyst: Treatment by arthroscopic cyst decompression 





Possible sites of lesion for the radial nerve include:

Lateral Femoral Cutaneous neuropathy

Lateral Femoral Cutaneous (LFC) mononeuropathy (Meralgia Paresthetica) causes sensory symptoms in the lateral portion of the thigh. Differential diagnosis includes lumbar radiculopathy. Sensory nerve conduction of the LFC nerve is somewhat difficult to obtain, especially in obese patients.

Myasthenia Gravis

Myasthenia Gravis is the most common disorder of the neuromuscular junction. It is characterized by muscular fatigability after exercise. Repetitive stimulation test is an electrodiagnostic technique used to evaluate for this condition. Furthermore, single fiber EMG can be performed in a situation where repetitive stimulation test is inconclusive.

Peroneal neuropathy

Peroneal mononeuropathy is the most commonly seen with compression at the fibular head. The most common differential diagnosis includes L5 radiculopathy. EMG can show the exact localization of the lesion and evaluate for an axonal vs. demyelinating type of injury.

  • Abnormal NCS with slowing across the fibular head
  • Abnormal EMG (TA and EDB with sparing SHBF, TP, TFL and paraspinals thus excluding L5 lesion)

Another site of a possible lesion is distal to the Tibialis Anterior branch, which is a common issue in elderly secondary to a chronic trauma to the Extensor Digitorum Brevis.

Peroneal neuropathy

Tarsal Tunnel Syndrome (TTS) is an entrapment of the tibial nerve at the ankle which clinically presents as pain and sensory disturbance in the plantar aspect of the foot and big toe.

Plantar nerve neuropathies are seen with entrapment at the ankle or more distally in the foot. Standard nerve conduction techniques are available for testing of the medial and lateral plantar nerves.

Stiff Person Syndrome

Stiff Person Syndrome is an acquired condition with fluctuating muscle stiffness and spasms. It begins in the axial muscles and progresses to involve proximal leg muscles. EMG shows that the stiffness is caused by motor unit activity at rest. Two thirds of patients have antibodies to glutamic-acid-decarboxylase (GAD).