22 - Ulnar Neuropathy at the Elbow

Abstract

Ulnar neuropathy at the elbow (UNE) is second only to median nerve entrapment at the wrist (i.e., carpal tunnel syndrome [CTS]) as the most common entrapment neuropathy affecting the upper extremity. In contrast to CTS, localizing the site of the lesion by electrodiagnostic (EDX) studies often is much more difficult in patients with ulnar neuropathy. Indeed, the diagnosis of a nonlocalizable ulnar neuropathy is not infrequently the best that can be accomplished in the electromyography (EMG) laboratory. Additional specialized studies are often required, especially the short segment incremental study (i.e., “inching”) to localize the lesion to the elbow. At the elbow, the ulnar nerve is most commonly entrapped under the humeral-ulnar aponeurosis (i.e., the cubital tunnel proper) or at the retrocondylar groove. Although the elbow is the most common site of compression, the ulnar nerve is susceptible to entrapment at other sites, especially at the wrist. In addition, lesions of the lower brachial plexus or C8–T1 nerve roots may result in symptoms similar to UNE. It is the role of the electromyographer to identify the ulnar nerve lesion, localize it as accurately as possible, and exclude other disorders that may mimic it. Neuromuscular ultrasound is an extremely useful adjunct to EDX studies in the evaluation of UNE, as it is particularly good at visualizing the ulnar nerve throughout its course in the upper extremity.