Bilateral distal upper limb amyotrophy and watershed infarcts from vertebral dissection.

BACKGROUND Vertebral artery disease may give rise to lower motor neuron deficits, but the pathogenesis is unknown. I describe a man with a right vertebral artery dissection who developed bilateral distal upper extremity amyotrophy. He had symmetrical bilateral focal hyperintensites of the anterior cervical spinal cord on magnetic resonance imaging, compatible with watershed infarction. CASE DESCRIPTION A 39-year-old man developed sudden vertigo, chest and bilateral arm pain, bilateral arm weakness, and wasting involving muscles innervated by the sixth cervical to the first thoracic spinal cord segments. Magnetic resonance imaging showed an extensive right vertebral artery dissection and a right posterior inferior cerebellar infarct. Magnetic resonance scans showed a small focal hyperintensity in the region of each anterior horn, extending from the mid to lower cervical spinal cord. Minimal recovery of function was present after 3 months. CONCLUSIONS Unilateral vertebral artery dissection may give rise to disabling bilateral upper extremity amyotrophy. Watershed infarction within the anterior spinal artery territory, involving both anterior horns, appears to be the mechanism of the lower motor neuron injury.