Exclusive electrophysiological motor involvement in carpal tunnel syndrome
Introduction
Median nerve entrapment in the wrist to palm segment produces a clinical condition known as carpal tunnel syndrome (CTS) which is the most common entrapment neuropathy (Stevens, 1987). It is generally accepted that median sensory conductions are more sensitive than motor conductions in the electrodiagnosis of CTS (Stevens, 1987, AAEM, 1993). There are 3 studies, employing segmentary techniques, which show that motor conduction velocity may be selectively effected in CTS and that segmental motor conduction may be even more frequently abnormal than sensory conduction (Kimura, 1979, White et al., 1988, Di Guglielmo et al., 1997). However, motor segmental studies have a number of pitfalls and technical problems, and have been considered unreliable and time consuming (Ross and Kimura, 1995).
The aim of this study is to investigate the frequency of exclusive electrophysiological motor involvement in a large population of hands with CTS.
Section snippets
Materials and methods
We reviewed the EMG reports (including history and pertinent neurological examination) of the studies performed in an 8 year period for all patients with signs and symptoms characteristic of CTS and with at least one abnormal electrophysiological test of the following: prolonged distal motor latency (DML), abnormal digit two median sensory conduction velocity (D2-SCV), abnormal median to ulnar sensory comparative test, or abnormal wrist to palm sensory segmentary test.
For median DML recording,
Results
In the 8 year period considered, there were 2727 consecutive hands with typical symptoms and signs of CTS and at least one abnormal electrophysiological test. Thirty-one hands (1.2%) presented prolonged distal motor latency (>4.4 ms) and normal sensory conduction velocities (>48 m/s) either recorded orthodromically (16 hands) or antidromically (15 hands) (Table 1). Fig. 1 reports the most significant example. In 11 of these 31 hands, we also performed a segmental SCV from wrist to palm which
Discussion
It is generally stated that sensory nerve testing is more sensitive than motor nerve testing in CTS (Stevens, 1987, AAEM, 1993). Using the inching technique, it has been found that motor conductions across the wrist may be selectively affected (Kimura, 1979) and even more sensitive than inching of sensory fibers (White et al., 1988). However, inching of motor fibers of the median nerve is technically difficult because of a lack of consistent latency changes in the sequential 1 cm steps and the
References (15)
- et al.
Conduction block and segmental velocities in carpal tunnel syndrome
Electroenceph clin Neurophysiol
(1997) - AAEM Quality Assurance Committee, Jablecki, C.K., Andary, M.T., So, Y.T., Wilkins, D.E., Williams, F.H., Literature...
- et al.
Experimental compression neuropathy in the rabbit: histologic and electrophysiologic studies
Arch Neurol
(1971) - et al.
Compression syndrome of the recurrent motor branch of the median nerve
J Hand Surg
(1982) - et al.
Anatomical course of the thenar branch of the median nerve, usually in a separate tunnel through the transverse carpal ligament
J Bone Joint Surg
(1970) - et al.
The carpal tunnel syndrome: electrophysiological aspect of 639 symptomatic extremities
Electromyogr Clin Neurophysiol
(1985) The carpal tunnel syndrome. Localization of conduction abnormalities within the distal segment of the median nerve
Brain
(1979)