Protocol of neurophysiologic studies in the carpal tunnel syndrome

Abstract

Background: Entrapment of the median nerve at the wrist, called also “carpal tunnel syndrome” (CTS), is the most common neuropathy. Clinically it presents as tingling in the fi rst 3½ fi ngers that are worst during the night or in the morning, and get relieved by hand shaking. To confi rm CTS nerve conduction studies (NCS) are very useful. Th e aim of the present study was to present and validate standardized protocol for neurophysiologic studies in patients with suspected CTS. Methods: A standard NCS protocol includes bilateral median (pathologic latency > 4.4 ms) and unilateral ulnar motor NCS, and 3 comparison sensory studies of median nerve 2 with ulnar nerve (4th fi nger detection, and across the wrist; pathologic latency diff erences > 0.4 and > 0.3), and 1 with radial nerve (1st fi nger detection; pathologic > 0.6 ms). In addition, the Carpal Sensory Index (CSI) was calculated by summation of all 3 sensory differences (pathologic > 0.9 ms). A group of 91 patients referred for NCS by plastic surgeons due to suspected CTS, and a group of 52 asymptomatic controls were studied using this protocol. Sensitivity, specifi city, positive and negative predictive values were calculated. Results: In controls all motor, and sensory responses were obtained. CTS was confi rmed in 155 of 182 (85 %) hands aft er motor and 4th fi nger sensory studies were concluded. Calculation of CSI demonstrated CTS in additional 11⁄15 (73 %) hands, which raised overall sensitivity to 91 %. Specifi cities were 89 % and 82 %, positive predictive values 93 % and 89 %, negative predictive values 73 % and 79 % for 4th fi nger sensory comparison study and CSI, respectively. Conclusions: Study demonstrated that most CTS are confi rmed by 4th fi nger sensory comparison study. Additional two comparison studies are needed only rarely, and confi rm CTS in about ¾ of remaining hands.