Transcranial Doppler sonography. An alternative to angiography in the evaluation of vasospasm after subarachnoid hemorrhage.

With transcranial Doppler sonography (TCD) the blood flow velocity (FV) in the basal cerebral arteries can be measured non-invasively. Vasospasm produces an increase of the FV in the narrowed arterial segment which can be evaluated by TCD. A clear correlation between the diameter of the artery and the increase in FV could be demonstrated in the middle cerebral artery. Vasospasm can be detected by TCD non-invasively and angiography can be avoided during the critical phase. The time course of vasospasm can be followed by TCD instead of repeated angiographies, enabling an optimal timing of aneurysm surgery.