Can neurologic examination predict pathophysiology of ulnar neuropathy at the elbow?

OBJECTIVE: To explore the utility of neurologic examination to predict the pathophysiology of ulnar nerve lesions in patients with ulnar neuropathies at the elbow (UNE).

METHODS: We prospectively recruited consecutive patients with suspected UNE. Four blinded investigators took a history and performed neurologic, electrodiagnostic (EDx) and ultrasonographic (US) examinations. In patients with axonal UNE, conduction block and conduction slowing, the pathophysiologies of UNE and neurologic examination findings were compared.

RESULTS: We found significant differences in muscle bulk and strength of the ulnar hand muscles between 96 arms with axonal UNE, 34 with conduction block, and 45 with isolated conduction slowing. Severe muscle atrophy and weakness (0-3/5 on MRC) predicted axonal UNE, and moderate weakness (-4/5 on MRC) with normal muscle bulk predicted UNE with conduction block. Using more restrictive criteria for axonal and conduction block UNE, muscle strength of 4-5/5 on MRC was predictive of isolated conduction slowing.

CONCLUSION: Although we found significant differences in patterns of muscle bulk and strength between groups of UNE patients with different UNE pathophysiologies, in the majority of arms, neurologic examination could not reliably predict UNE pathophysiology.

SIGNIFICANCE: Results confirm that nerve conduction studies are essential for determination of the pathophysiology of ulnar neuropathy at the elbow.