The utility of segmental nerve conduction studies in ulnar mononeuropathy at the elbow

Patients with clinical evidence of ulnar mononeuropathy at the elbow may have normal routine motor and sensory nerve conduction studies, suggesting a low sensitivity for these methods. Other, more specialized techniques may have a higher sensitivity, increasing diagnostic yield, and provide more specific localization of the lesion. We compared the sensitivity and specificity of ulnar segmental nerve conduction studies (SgNCS or "inching") at 2-cm intervals with those of routine ulnar motor and sensory studies. We studied 21 arms with symptoms or signs of ulnar neuropathy and 25 asymptomatic control arms. SgNCS proved significantly more sensitive than more routine studies in diagnosing ulnar neuropathy at the elbow, with a sensitivity of 81%, whereas motor conduction velocity in a longer (10-14 cm) segment across the elbow was the next most sensitive at 24%. Recording from the first dorsal interosseous muscle did not improve sensitivity when compared with recording from the abductor digiti quinti. Short SgNCS significantly improves detection of ulnar mononeuropathy at the elbow and should be considered when routine studies are negative and clinical suspicion remains high.