ULNAR NERVE ENTRAPMENT AT THE ELBOW - CORRELATION OF MAGNETIC-RESONANCE-IMAGING, CLINICAL, ELECTRODIAGNOSTIC, AND INTRAOPERATIVE FINDINGS

THE DIAGNOSIS OF ulnar nerve entrapment at the elbow has relied primar ily on clinical and electrodiagnostic findings. Recently, magnetic res onance imaging (MRI) has been used in the evaluation of peripheral ner ve entrapment disorders to document signal and configuration changes i n nerves. We performed a prospective study on a population of 31 elbow s in 27 patients with ulnar nerve entrapment at the elbow. The study c orrelated MRI findings with clinical, electrodiagnostic, and operative findings. A control population consisting of 10 asymptomatic subjects also was studied by MRI. Electrodiagnostic evaluation confirmed ulnar neuropathy in 24 (77%) elbows of the 31, with localization to the elb ow region in 21 (68%). MRI using a short tau inversion recovery sequen ce, demonstrated increased signal of the ulnar nerve in 30 (97%) elbow s of the 31 and enlargement of the ulnar nerve in 23 (74%). No MRI abn ormalities were found in the control population. MRI signal increase o f the ulnar nerve occurred an average of 27 mm proximal to the distal humerus and extended distally an average of 4 mm below the distal hume rus. The mean total length of increased ulnar nerve signal was 34 mm. Ulnar nerve enlargement occurred an average of 19 mm proximal to the d istal humerus and extended distally an average of 8 mm above the dista l humerus. The mean total length of ulnar nerve enlargement was 12 mm. The 12 patients who underwent a surgical procedure for ulnar nerve en trapment were found to have ulnar nerve compression, with 9 (75%) havi ng excellent and 3 (25%) having good postoperative results. In this st udy, MRI was both sensitive and specific in diagnosing ulnar nerve ent rapment at the elbow as defined by clinical, electrodiagnostic, and op erative findings.