The median nerve terminal latency index in carpal tunnel syndrome: a clinical case selection study.

Muscle Nerve 1999 May;22(5):573-7

Simovic D, Weinberg DH.

St. Elizabeth’s Medical Center, Division of Neurology, Boston, Massachusetts 02135, USA.

The terminal latency index (TLI) adjusts the distal motor latency (DL) for the terminal distance and the proximal nerve conduction velocity. We prospectively studied 66 patients in order to assess the sensitivity of the median nerve TLI for the diagnosis of carpal tunnel syndrome (CTS). Clinical and electrophysiological evaluations were completed by separate, blinded examiners. Based on the clinical diagnosis, 54 patients were judged to have CTS (CTS group) and 12 were believed not to have CTS. Control data were obtained from 38 healthy hands. The mean TLI was 0.26 +/- 0.04 in the CTS group and 0.43 +/- 0.04 in the control group (P < 0.001). The sensitivity of the TLI was 81.5%. The TLI was statistically better than the median motor DL and sensory peak latency (PL) to the second digit. The TLI was always abnormal when the median mixed-nerve palmar latency was abnormal. In three cases from the CTS group, the TLI was the only abnormal electrophysiological parameter. The median TLI is a useful, sensitive electrodiagnostic parameter for CTS.Publication Types:

  • Clinical Trial

PMID: 10331355 [PubMed – indexed for MEDLINE]

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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;

EMG and NCS

Electromyography (EMG) and nerve conduction studies (NCS) are tests that measure the electrical activity of muscles and nerves. Nerves send out electrical signals to make your muscles react in certain ways. Nerves also send signals from your skin to your brain, which then processes the signals, so you can experience a variety of skin sensations.

  • An EMG Test looks at the electrical signals your muscles make when they are at rest and when they are being used.
  • A Nerve Conduction Study measures how fast and how well the body’s electrical signals travel along your nerves. EMG and nerve conduction studies are used to help diagnose a variety of muscle and nerve disorders and to quantify the severity of your condition.


An EMG test helps find out if muscles are responding the right way to nerve signals. Nerve conduction studies help diagnose nerve damage or disease. When EMG tests and nerve conduction studies are done together, they help doctors tell if your symptoms are caused by a muscle disorder or a nerve problem. With EMG and NCS studies, your doctor can next select the best therapeutic option to help you.