Provokable bilateral vertebral artery compression diagnosed with transcranial Doppler.

BACKGROUND: Head and neck movements may cause vascular compression that produces a syndrome of vertebrobasilar insufficiency. Vertebrobasilar circulation was examined noninvasively in two patients who were able to provoke these symptoms repeatedly on demand. CASE DESCRIPTIONS: Blood flow velocities in the basilar artery (case 1) and both posterior cerebral arteries (both cases) were measured continuously by transcranial Doppler sonography while the patients voluntarily performed the offending maneuvers and reproduced their symptoms. The provocative maneuvers evoked an immediate and precipitous drop in blood flow velocity, producing symptoms within seconds. Upon relief, the blood flow velocities showed a transient overshoot before returning to baseline values. CONCLUSIONS: These observations indicate that the symptoms of vertebrobasilar insufficiency were due to real reductions in blood flow and demonstrate the usefulness of transcranial Doppler sonography to diagnose bilateral extracranial vertebral artery compression.