Comparison between nerve conduction studies and current perception threshold test in carpal tunnel syndrome

AIM OF STUDY: Nerve conduction studies (NCS) only test large myelinated A(alpha) or A(beta) nerve fibers, whereas the current perception threshold (CPT) test has been suggested to evaluate a wide range of nerve fibers (A(beta), A(delta) and C). This study was undertaken to compare CPT and the standard NCS test by Bland's severity scale with the patient-based measurement of symptoms and functional status of the hand by Boston CTS questionnaire assessment. PATIENTS AND METHODS: We performed NCS and CPT on 31 patients (mean age 54.6+/-11.7 years; 31-79 years) with clinical diagnosis of CTS. NCS severity was classified according to Bland's scale and CPT was measured at 2000, 250 and 5 Hz and severity was graded between 0 and 12. Two-tailed Spearman's correlation analysis was performed to assess correlations between Boston questionnaire score and Bland's severity scale and CPT total score. RESULTS: The results showed that Bland's scale, based on NCS, had more significant correlations with symptoms (Spearman's rho=0.402, p=0.002) and function (rho=0.400, p=0.001) than CPT total scores (rho=0.200, p=0.135; rho=0.234, p=0.069). In CPT, only score measure at 2000 Hz showed a significant correlation with Boston CTS questionnaire scores (with symptom rho=0.308, p=0.020; with function rho=0.302, p=0.018), whereas those measured at 250 Hz and 5 Hz did not (p>0.05). CONCLUSION: Though CPT may have a supplementary role in the diagnosis of CTS, NCS better reflects patients' symptoms and functions than CPT on the patient's perspective