A prospective study of the anatomic variations of the median nerve in the carpal tunnel in Asians

A prospective study of anatomic variations of the median nerve and its rela tionship to the surrounding structures was performed of 354 consecutive ope rations in 192 patients with carpal tunnel syndrome at Korea University Ana m Hospital from July 1995 to September 1997. A total of 184 patients were w omen and 8 patients were men. A total of 162 patients were bilateral and 30 were unilateral. Regarding the course of the motor branch, the extraligame ntous type was most common (96.1%, 340 patients). A total of 81.1% of patie nts (N = 287) had the origin of the motor branch at the radial side of the median nerve (or radial one third), and 17.2% of patients (N = 61) had the origin of the motor branch at the anterior portion of the median nerve. Of these 61 patients, 30 patients (49.1%) were of the preligamentous type. Onl y one motor nerve branch was found in 89.5% of patients (N = 317), and mult iple branches were found in 10.5% of patients. As a result of the compariso n between two hands when both hands were operated, the origin and number of motor branches and their courses were identical in most patients (>60%). H ypertrophy of the flexor pollicis brevis was found in 8.5% of patients (N = 30), hypertrophy of the palmaris brevis was found in 4.2% of patients (N = 15), absence of the palmaris longus was discovered in 0.6% of patients (N = 2), existence of the median artery was found in 0.6% of patients (N = 2), and high division of the median nerve rejoining with the thenar motor nerv e was found in 0.3% of patients (N = 1). Clearly, the anatomy of the carpal tunnel in Koreans is somewhat different, in part, from the results obtaine d from studies of whites, but overall results are not significantly differe nt. These results can help obtain a better surgical outcome and complete de compression of the median nerve during operation while preventing inappropr iate or inadvertent injury to the motor branch of the median nerve in Korea ns.