Dynamic transcranial Doppler assessment of positional vertebrobasilar ischemia.

BACKGROUND AND PURPOSE

A hemodynamic as opposed to an embolic origin of vertebrobasilar ischemia may be suspected when symptoms are brief and triggered by changes in the position of the head or neck. It may be difficult, and not without risk, to reproduce the symptoms and to prove the short-lived hemodynamic changes during angiography. If transcranial Doppler sonography (TCD) could detect these changes, it would be useful as a noninvasive screening method to select patients for further diagnostic evaluation.

METHODS

TCD monitoring of the P1 segments of both posterior cerebral arteries was performed during different head movements in 14 patients referred for evaluation of suspected hemodynamic vertebrobasilar ischemia and in 10 healthy control subjects with a two-channel, 2-MHz, computerized Doppler system. Patients' symptoms were correlated with the Doppler findings.

RESULTS

Four patients with stereotypical symptoms had a severe drop in posterior cerebral artery blood flow velocities (BFVs) to 20% of baseline (mean; SD, 14.3; range, 0% to 48%) and subsequent reactive hyperemia with an increase in BFV to 149% (mean; SD, 20.6; range, 110% to 186%) dependent on head rotation to one side (group 1). Compared with the values found in group 2 patients and in control subjects, these drops were significant (P = .0001 for both). Symptoms together with BFV changes could be reproduced several times. Angiography confirmed severe vertebral artery obstruction during head rotation and the presence of anomalies in the posterior circulation. In 10 patients (group 2), symptoms were not short-lived, stereotyped, or clearly dependent on head movements and could not be reproduced during TCD testing. Their BFVs dropped to 88% (mean; SD, 9.0; range, 64% to 102%) of baseline values during maximal head rotation, to 86% (mean; SD, 10.3; range, 64% to 100%) during flexion, and to 88% (mean; SD, 6.7; range, 75% to 103%) during extension. In the 10 control subjects, BFVs dropped to 86% (mean; SD, 8.8; range, 61% to 98%) of baseline values during rotation, to 90% (mean; SD, 10.3; range, 74% to 107%) during flexion, and to 76% (mean; SD, 17.1; range, 54% to 104%) during extension.

CONCLUSIONS

Monitoring posterior cerebral artery BFV during head movements is a simple, noninvasive method to document a hemodynamic etiology of symptoms in patients with suspected positional vertebrobasilar ischemia. The correlation of symptoms to the hemodynamic findings proved a useful screening method to identify those patients with true position-evoked hemodynamic insufficiency in the posterior circulation. These patients should be selected for angiographic evaluation to identify the source and site of arterial compression.