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Dynamic TCD Assessment of Positional Vertebrobasilar Ischemia

Transient symptoms of ischemia in the vertebrobasilar territory related to head position may be caused by hemodynamic insufficiency due to a mechanical compression of the vertebral arteries. Disorders associated with extrinsic vertebral compression include osteophytic spurs, anomalous muscle insertions, osseous malformations, fractures, dislocations, rheumatoid arthritis, space opening lesions and cervical disk rupture.

Patients with this syndrome usually present with symptoms of dizziness, blurred vision and near or loss of consciousness. These symptoms are brief, brought on by a specific head position, and are relieved when the head is returned to a neutral position.

Testing includes a thorough study of the extra and intracranial vertebrobasilar system to identify flow restricting lesions and anomalous anatomy. Both posterior cerebral arteries (PCAs) are simultaneously monitored while the patient is instructed to turn their head into provocative positions. When PCA blood flow velocities drop 50 percent or more when the head is turned and there is a hyperemic response with the head back in a neutral position, the test is positive for mechanical compression of the vertebral arteries. The patient can then be evaluated further for surgical intervention to relieve the compressing mechanism.

With head turning the vertebral artery is mechanically compressed and flow is restricted.         "Click" on top and right image to view larger.	Spectral waveform of the PCA demonstrating cessation of flow with the head returned to a neutral position.
	The bilateral posterior cerebral arteries (PCA) are monitored during head turning. The flow velocities drop when the head is turned and a hyperemic response is seen with the head returnded to a neutral position.