Case 15

Abstract Ulnar nerve lesions are the second most common mononeuropathies encountered in clinical practice. The majority of ulnar neuropathies are across the elbow, more specifically due to entrapment or compression of the ulnar nerve at the cubital tunnel or ulnar groove. This case highlights the clinical and electrodiagnostic findings of ulnar neuropathies across the elbow and discusses the challenges in making an accurate diagnosis. Focal slowing of conduction velocities and/or conduction block are the main findings that pinpoint the site of the lesion, while the needle electromyography is poor in accurate localization, mostly due to the limited number of ulnar innervated muscles in the forearm. Important additional testing that often is recommended to aid in the accurate diagnosis of ulnar nerve lesions across the elbow includes the dorsal ulnar sensory nerve action potential, ulnar motor conduction study recording the first dorsal interosseous, and inching studies across the elbow.