A correlative electrophysiologic study of nerve fiber involvement in carpal tunnel syndrome using current perception thresholds

Objective: To relate clinical severity of idiopathic carpal tunnel syndrome (CTS) to current perception threshold (CPT). Methods: Subjects were 51 patients with CTS (involving 51 hands), and 50 healthy control subjects (50 hands). Involved hands were grouped into three clinical grades (mild, moderate, severe). Using a neurometer (Neurotron, Baltimore, MD), we investigated the relationship between clinical grade and CPT abnormalities. Results: In the mild CTS group, most hands showed CPT abnormalities only at 2000 Hz stimulation. The moderate group included a higher percentage of hands showing abnormalities at both 2000 and 250 Hz stimulation increased. The severe group included the highest percentage of hands with abnormal values at all frequencies tested. Conclusions: CPT showed abnormalities appear progressively from ‘higher to lower’ frequency stimulations relative to the increasing severity of CTS. Significance: Sensory nerve fiber dysfunction apparently begins in larger fibers, extending stepwise to smaller fibers as the clinical grade of CTS progresses