Abnormal cerebral hemodynamics during attacks of alternating hemiplegia.

Frequent episodes of bilateral weakness and apathy, followed later by hemiplegia of alternating sides were observed in a now 32-month-old girl. Transcranial Doppler ultrasonography showed reduced flow velocities in the middle cerebral artery of the affected side during a hemiplegic attack and increased flow velocities at different sites of the basilar artery during a bilateral episode. These abnormal cerebral hemodynamics appear to indicate that alternating hemiplegia and some forms of migraine have a similar pathophysiology.