Abstract
BackgroundConventional motor nerve conduction studies are usually normal in early and mild carpal tunnel syndrome (CTS). Single-fiber electromyography (SFEMG) measures the mean consecutive difference (MCD) as an expression of the variability in impulse transmission over the motor endplates and along the nerve fibers distally to the last branching point and along the muscle fibers.Application of concentric needle SFEMG in a group of CTS patients who showed pure sensory abnormalities in nerve conduction studies to examine for subclinical motor involvement.MethodsThirty CTS patients having only sensory involvement proved clinically and by conventional electrophysiological studies were included in addition to 30 control subjects. Concentric needle SFEMG was performed to the abductor pollicis brevis (APB), abductor digiti minimi (ADM), and extensor digitorum communis (EDC) muscles.ResultsThere was a statistically significant difference in the MCD between the patient and control groups in the APB only (p = 0.038).ConclusionsThe results suggest the presence of a subclinical motor median neuropathy at the wrist in patients with early and mild carpal tunnel syndrome and highlight the validity of the concentric needle SFEMG in early neuropathies.Trial registrationPACTR201802002971380 registered 12 February 2018, retrospectively registered.
Highlights
Conventional motor nerve conduction studies are usually normal in early and mild carpal tunnel syndrome (CTS)
Single-fiber electromyography (SFEMG) measures the variation in the time interval between the two muscle action potentials supplied by the same axon over the motor endplates, along the nerve fibers distally to the last branching point and along the muscle fibers under investigation (Thiele and Stålberg 1975)
This study aimed at applying concentric needle SFEMG in a group of CTS patients in whom only sensory abnormalities of the median nerve were established by conventional nerve conduction studies, to examine if there is a subclinical motor involvement
Summary
Conventional motor nerve conduction studies are usually normal in early and mild carpal tunnel syndrome (CTS). Single-fiber electromyography (SFEMG) measures the mean consecutive difference (MCD) as an expression of the variability in impulse transmission over the motor endplates and along the nerve fibers distally to the last branching point and along the muscle fibers. Conventional electrophysiological studies in early and mild carpal tunnel syndrome (CTS) often show mild median sensory nerve conduction abnormalities across the wrist leading to the widely accepted assumption that sensory abnormalities precede motor abnormalities (Bland 2000). SFEMG is used mainly as a sensitive diagnostic method of myasthenia gravis and other disorders with disturbed neuromuscular transmission.
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