Middle Cerebral Artery Spasm after Subarachnoid Hemorrhage: Detection with Transcranial Color-coded Duplex US

Abstract

To prospectively determine the accuracy of transcranial color-coded duplex ultrasonography (US) used alone and in conjunction with carotid artery US for diagnosis of middle cerebral artery (MCA) spasm, with intraarterial digital subtraction angiography (DSA) used as the reference standard. The institutional ethics committee approved the study. Each patient, or members of the patient's family, gave informed consent. One hundred twenty consecutive patients (64 women, 56 men; mean age, 45.5 years +/- 13.6 [standard deviation]) were routinely referred for DSA after subarachnoid hemorrhage. Vasospasm was graded as mild (< or =25% reduction in vessel diameter), moderate (>25% to 50% reduction), or severe (>50% reduction). US was performed 2 hours or less before angiography. The ratio of flow velocity in the middle cerebral artery (V(MCA)) to flow velocity in the ipsilateral extracranial internal carotid artery (V(ICA)) was calculated. Diagnostic accuracy was evaluated by calculating the area under the receiver operating characteristic curve (Az). The significance of the difference between the two Az values (for US vs DSA) was determined by using the z test with correction for correlated data. Nine of 120 patients were excluded because of inadequacy of acoustic windows in the squama of temporal bones. Spasm was mild in 17, moderate in 16, and severe in only nine of 222 arteries studied. Arteries with moderate or severe vasospasm were combined in one group. The best-performing parameters were peak systolic velocity and V(MCA)/V(ICA) ratio. Az values for these two parameters in diagnosis of moderate-to-severe vasospasm were 0.93 and 0.95, and in diagnosis of mild vasospasm, 0.90 and 0.91. Accuracy of the V(MCA)/V(ICA) ratio calculated on the basis of end-diastolic velocity for diagnosis of mild MCA narrowing was significantly better than that of end-diastolic MCA velocity alone (Az = 0.88 vs 0.84, P < .05). The stepwise approach with use of the V(MCA)/V(ICA) ratio after flow velocity measurements in the MCA resulted in a decreased number of false-negative findings in both vasospasm subgroups. The thresholds of highest efficiency were at a mean velocity of 94 and 108 cm/sec and a peak systolic V(MCA)/V(ICA) ratio of 3.6 and 3.9 for diagnosis of mild and moderate-to-severe vasospasm, respectively. Transcranial color-coded duplex US alone or in conjunction with carotid artery US has excellent accuracy for angiographic detection of vasospasm. Use of MCA velocity measurements and V(MCA)/V(ICA) ratio can increase the accuracy of Doppler US.