Localization of Ulnar Neuropathy at the Wrist Using Motor and Sensory Ulnar Nerve Segmental Studies

Background and Purpose Diagnosing ulnar neuropathy at the wrist (UNW) is often challenging, and performing several short segmental studies have been suggested for achieving this. We aimed to determine the utility of ulnar nerve segmental studies at the wrist (UNSWs) in patients with suspected UNW. Methods Fourteen patients with typical symptoms of unilateral UNW were evaluated using conventional electrophysiological tests, UNSWs, and ultrasonography (US). In UNSWs, the ulnar nerve was stimulated at three sites (3 cm distal, just lateral, and 2 cm proximal to the pisiform), and recordings were made at the first dorsal interosseous (FDI) muscle and the fifth digit. Four types of UNW were identified by conventional ulnar nerve conduction studies based on motor and sensory fiber involvement. UNW was also categorized as either a proximal or distal lesion relative to the pisiform based on the UNSWs. The relationships between the conventional electrophysiological type, UNSW categorization results, and lesion location as verified by US were analyzed. Results Proximal UNW lesions were associated with involvement of the entire deep motor and the superficial sensory fibers (type I). Distal lesions were more closely related to deep motor fibers that innervated the FDI (type III). All five proximal and six distal lesions seen in US matched the lesion locations found on UNSWs. Conclusions Motor and sensory UNSW are considered useful assistive techniques for diagnosing UNW and localizing its lesion sites.