Syringomyelia presenting as ulnar neuropathy at the elbow.

OBJECTIVES: Syringomyelia may present with confusing, unilateral patterns of segmental muscle involvement and dissociated sensory loss. The objective of this study was to report a patient with Chiari malformation type 1 (CM1) and syringomyelia who had an unusual presentation suggesting ulnar neuropathy at the elbow. RESULTS: A 24-year-old woman presented with clinical evidence of ulnar neuropathy at the elbow except that there was disproportionate abductor digiti mini (ADM) atrophy and weakness, equivocal ipsilateral abductor pollicis brevis weakness and hyporeflexia in both arms. Nerve conduction studies revealed marked amplitude reduction of the left ulnar ADM-compound muscle action potential (ADM-CMAP) with a normal first dorsal interosseous-CMAP amplitude, no focal slowing or conduction block, and a normal ulnar sensory response amplitude. Electromyography (EMG) showed multi-segmental, left C7-T1 fibrillations and chronic reinnervation changes. Magnetic resonance imaging (MRI) of the cervical spine demonstrated CM1 and syringomyelia. CONCLUSIONS: Syringomyelia may clinically mimic ulnar neuropathy at the elbow.