[Diagnosis of middle cerebral artery spasm by determination of flow velocity and the Lindegaard index with transcranial color Doppler sonography].

BACKGROUND AND PURPOSE

Recent reports have demonstrated the high utility of transcranial color-coded duplex sonography (TCCS) in the diagnosis of advanced spasm of the middle cerebral artery, whereas its accuracy in the diagnosis of mild vasospasm is reported to be lower. Relation of blood flow velocity in the middle cerebral artery (MCA) to that in the extracranial internal carotid artery (VMCA/VICA index) is recommended as being helpful in the diagnosis of vasospasm (the so called Lindegaard Index). Nevertheless, the exact diagnostic value of this index using the TCCS method remains to be established. The purpose of this study is to estimate the accuracy of TCCS in the diagnosis of MCA vasospasm, as based on the VMCA/VICA index.

MATERIAL AND METHODS

The VMCA/VICA index was calculated in 195 patients (285 middle cerebral arteries) who were scheduled for cerebral arteriography. The TCCS study and color-coded duplex sonography of the internal carotid arteries were performed immediately before arteriography.

RESULTS

A mild grade of MCA spasm was diagnosed angiographically in 21, and moderate-to-severe spasm in 29 MCAs out of 285 successfully insonated arteries. Peak-systolic, mean and end-diastolic blood velocities were measured using transcranial color sonography in the MCA and related to the respective velocities in the ipsilateral extracranial internal carotid artery. Receiver-operating characteristic curves (ROC) were calculated for particular velocities and for the related VMCA/VICA indices. By comparison of the areas under the ROC curves it was shown that the use of the VMCA/VICA index does not improve the accuracy of TCCS in the diagnosis of advanced MCA spasm, whereas it improves accuracy in the diagnosis of mild vasospasm. In particular, accuracy can be improved by the use of the VMCA/VICA index based on the end-diastolic velocity. The optimal diagnostic threshold of the VMCA/VICA index was determined at 3.9.

CONCLUSIONS

The use of VMCA/VICA index improves the accuracy of TCCS in the diagnosis of mild vasospasm of the middle cerebral artery.