DYNAMIC TRANSCRANIAL DOPPLER ASSESSMENT OF POSITIONAL VERTEBROBASILARISCHEMIA

Background and Purpose A hemodynamic as opposed to an embolic origin o f vertebrobasilar ischemia may be suspected when symptoms are brief an d 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 prov e the short-lived hemodynamic changes during angiography. If transcran ial Doppler sonography (TCD) could detect these changes, it would be u seful as a noninvasive screening method to select patients for further diagnostic evaluation. Methods TCD monitoring of the P1 segments of b oth posterior cerebral arteries was performed during different head mo vements in 14 patients referred for evaluation of suspected hemodynami c vertebrobasilar ischemia and in 10 healthy control subjects with a t wo-channel, 2-MHz, computerized Doppler system. Patients' symptoms wer e correlated with the Doppler findings. Results Four patients with ste reotypical symptoms had a severe drop in posterior cerebral artery blo od 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 pati ents and in control subjects, these drops were significant (P=.0001 fo r both). Symptoms together with BFV changes could be reproduced severa l times. Angiography confirmed severe vertebral artery obstruction dur ing head rotation and the presence of anomalies in the posterior circu lation. In 10 patients (group 2), symptoms were not short-lived, stere otyped, or clearly dependent on head movements and could not be reprod uced during TCD testing. Their BFVs dropped to 88% (mean; SD, 9.0; ran ge, 64% to 102%) of baseline values during maximal head rotation, to 8 6% (mean; SD, 10.3; range, 64% to 100%) during flexion, and to 88% (me an; SD, 6.7; range, 75% to 103%) during extension. In the 10 control s ubjects, BFVs dropped to 86% (mean; SD, 8.8; range, 61% to 98%) of bas eline values during rotation, to 90% (mean; SD, 10.3; range, 74% to 10 7%) during flexion, and to 76% (mean; SD, 17.1; range, 54% to 104%) du ring extension. Conclusions Monitoring posterior cerebral artery BFV d uring head movements is a simple, noninvasive method to document a hem odynamic etiology of symptoms in patients with suspected positional ve rtebrobasilar 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 c irculation. These patients should be selected for angiographic evaluat ion to identify the source and site of arterial compression.