Current perception threshold. Reproducibility and comparison with nerve conduction in evaluation of carpal tunnel syndrome.

Neuro-selective current perception threshold (CPT) values quantify peripheral nerve (n) integrity and provide an index of adequate hemodialysis (HD). Evaluation of polyneuropathy (PN) by CPT correlates with nerve conduction testing (NCT). CPT is convenient, painless, and may be performed during HD. Early detection of carpal tunnel syndrome (CTS), a complication of uremia, permits curative intervention. Utility of CPT and NCT measurements in detecting CTS in 29 stable HD patients were evaluated. Reproducibility of seven CPT determinations over 4 weeks was determined in each of 9 HD patients. The coefficient of variation for repeated 2000 Hz CPT measures was 6%. PN was detected by CPT in 92% of the patients and by NCT in 79% (r = 0.79, p less than 0.001). In 38% of the hands there was a CPT impairment in both the median and ulnar nerves (n), of which 25% were symptomatic for CTS. CPTs consistent with CTS (sufficiently greater impairment of the median vs ulnar n) were observed in 31% of the hands with combined median and ulnar n CPT abnormalities, and 11% were identified with CTS by NCT. The unique ability of the CPT exam to quantify hyperesthesia may account for its superior CTS detection sensitivity. These findings demonstrate that repeated CPT determinations are consistent and are diagnostic for CTS.