P58-T Electrophysiological assessment of small fibres in carpal tunnel syndrome

Abstract

Background Conventional nerve conduction techniques have limitations on carpal tunnel syndrome (CTS) diagnosing, because dysfunction of small fibres is beyond the resolution of these studies. The lack of the gold standard of CTS evaluation and common misdiagnosis underlie the treatment failure. Evaluation of small fibres susceptibility to damage and the sequence of decline of different types of fibres in CTS were analyzed. Materials and methods 75 hands, in 43 patients, 35 females, 8 males, with elecrophysiologically confirmed CTS were studied. The control group consisted of 35 volunteers (63 hands), sex and age-matched. Standard motor and antidromic sensory nerve conduction velocity studies in the median and ulnar nerves, with distal onset latency, conduction velocity, and amplitude assessment were done. Conduction velocity distribution test (CVD) was performed in the same nerves with estimation of conduction velocities in 10, 50, 90 decyl, and the conduction spread between 90 and 10 decyl. Quantitative sensory testing (QST) for detection temperature, pain and vibratory theresholds were done from thenar and hypothenar skin. Results CVD values of the median nerve in all decyls differed significantly between the carpal tunnel syndrome group and the control group, without any significant differences in the spread of conduction values. The thresholds of temperature and pain were similar, but the vibratory thresholds were significantly higher in the CTS group. Conclusions Mainly large fibers of the median nerve are damaged in the initial stage of CTS. Evaluation of small fibers is not useful in the early diagnosis of CTS.