Serial transcranial Doppler flow velocity and cerebral blood flow measurements for evaluation of cerebral vasospasm after subarachnoid hemorrhage.

Serial transcranial Doppler (TCD) and cerebral blood flow (CBF) examinations were performed in 73 patients with subarachnoid hemorrhage (SAH) due to ruptured intracranial aneurysm to evaluate cerebral vasospasm. Twenty-six (35.6%) of the 73 patients developed ischemic neurological symptoms associated with cerebral vasospasm, which were reversible in all except four patients (5.5%) who demonstrated low-density areas associated with vasospasm on computed tomographic scans. In general, the flow velocities in the middle cerebral arteries began to increase soon after onset of SAH, reaching the maximum between days 8 and 10, subsequently decreasing gradually. There was no significant difference in the highest value and the time course of flow velocities between symptomatic vasospasm and asymptomatic vasospasm patients. Patients with symptomatic vasospasm demonstrated two typical time courses of flow velocities: rapid increases in flow velocities that preceded the clinical manifestations of vasospasm (16 patients, 61.5%), and no rapid increases in flow velocities despite the presence of ischemic symptoms (10 patients, 38.5%). In the latter, angiograms demonstrated vasospasm in segments distal to those evaluated by TCD examination. These results showed that the degree of cerebral vasospasm cannot be assessed only by the absolute flow velocities. CBF was measured two to 10 (mean 4.7) times within 3 weeks of SAH using the 133Xe intravenous injection method. The CBF value remained stable even during the period of major risk of vasospasm. However, the CBF was significantly lower in patients with symptomatic vasospasm on days 8, 9, 10, 13, 14, and 15, when compared with patients without symptomatic vasospasm. Patients who developed ischemic neurological symptoms due to vasospasm without increased flow velocity also showed a low CBF value. The combination of serial TCD and CBF measurements, using the former for early detection of vasospasm and the latter for evaluation of cerebral ischemia, is at present the best method for diagnosis of vasospasm.