S2082 NEUROPHYSIOLOGICAL METHODS IN THE DIAGNOSIS OF ENTRAPMENT NEUROPATHIES

Entrapment neuropathies are chronic local nerve lesions caused compression of anatomical structures around the nerves. The entrapment neuropathies are localized to regions where the nerves pass through anatomically narrow tunnels. The best example is carpal tunnel syndrome, which is also the most common entrapment. In literature more than 60 different entrapments have been described. Only a small number of the suggested entrapments have been reported according to standards required by evidence based medicine. Examples of these doubtful syndromes are the pronator and piriformis syndromes. The diagnosis of entrapments is based on the subjective symptoms, clinical findings and an electrodiagnostic consultation, consisting of EMG and neurography. Needle EMG can be used to demonstrate axonal lesions of motor axons. It is quite useful in moderate or severe lesions of mixed nerves. However, in purely neurapraxic lesions needle EMG is normal. Neurography across the site of entrapment is the most sensitive method. Surface electrodes can be used in the diagnosis of carpal tunnel syndrome and ulnar nerve lesions at the elbow. The nerve lesion can be localized very accurately using short segment studies. In deeply located nerves or small nerve branches, neurography must be done using needle electrodes (Morton’s metatarsalgia and meralgia paresthetica). The sensitivity and specificity of modern neurophysiological methods are high. The syndromes with consistently normal neurophysiological findings cannot be accepted as neuropathic, other etio-logic causes must be considered in these cases.