Transcranial Doppler in cerebrovascular disease.

Thomas JH: Incidence of recurrent stenosis after carotid endarter-ectomy determined by digital subtraction angiography. Digital transvenous angiography in follow-up examinations after carotid reconstruction. SUMMARY Doppler analysis of flow in intracranlal arteries is now possible using a 2 MHz probe allowing sufficient penetration of bone to obtain signals noninvasivety. Thirty-two normal subjects, and 11 patients with cerebrovascular diseases including vasospasm following subarachnoid hemorrhage, middle cerebral artery stenosis, and extracranial internal carotid artery stenosis were studied by transcranial Doppler. Increased peak velocity and spectral broadening of the reflected signal corresponded to clinical and angiographic evidence of middle cerebral artery vasospasm or stenosis. Decreased peak velocity and blunted waveforms occurred in the middle cerebral artery ipsilateral to severe extracranial internal carotid stenosis with poor crossfilling from the contralateral carotid artery. Abnormalities resolved following carotid endarterectomy. Transcranial Doppler identifies vasospasm or stenosis of the middle cerebral artery and may allow noninvasive evaluation of collateral flow across the anterior circle of Willis in patients with extracranial carotid artery stenosis. DOPPLER EXAMINATION of the extracranial internal carotid artery permits noninvasive detection of ex-tracranial stenosis with considerable accuracy. 1 Studying intracranial vessels is now possible using a 2 MHz probe that allows sufficient ultrasound to penetrate bone. 2 This report describes preliminary results of transcranial Doppler (TCD) studies, performed in a systematic and uniform fashion, in patients with vaso-spasm of the middle cerebral artery (MCA) due to subarachnoid hemorrhage, MCA stenosis, and hemo-dynamically significant extracranial internal carotid artery (ICA) stenosis. Each group includes only a few patients, however, characteristic abnormalities are identified, in most cases correlating with clinical and angiographic evidence of vascular disease. These results provide an indication of the clinical utility of TCD for studying patients with cerebrovascular disease. Methods Instrumentation A 2 MHz pulsed Doppler instrument with an external probe diameter of 22 mm (TC2-64, EME, Uberlin-gen, W. Germany) was used for transcranial Doppler examinations. Focal depth of the Doppler signal varied in 5 mm increments from 25 to 150 mm. Pulse repetition frequencies included 5, 8 or 10 KHz depending on depth. Bidirectional signals were recorded with a 10 KHz low-pass filter and a 150 Hz high-pass filter. Spectral analysis was accomplished with fast fourier transformation and 64 point resolution. Spectral information was displayed either as KHz frequency shift or velocity. Calculation of velocity from Doppler shift frequency assumed an angle between probe and blood column of 0 degrees. 2 Technique Doppler signals …