Intracranial blood flow velocities in acute ischemic stroke.

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Abstract
Transcranial Doppler sonography (TCD) can evaluate noninvasively the blood flow velocities and patency of the main trunk of the middle cerebral artery (MCA). Using TCD we evaluated MCA patency and patterns of flow through the circle of Willis in patients with acute stroke. Patients with symptoms of hemispheric stroke were evaluated with serial TCD tests during admission. The Canadian Neurological Scale was used to assess neurological deficits. In all cases computed tomographic scan, 99mTc hexamethylpropyleneamine oxime single-photon emission computed tomography, and carotid duplex were performed, and in some cases cerebral angiography. Seventy-five consecutive patients with symptoms of acute ischemic stroke (mean time, 8 +/- 4 hours) were studied. Four circle of Willis perfusion patterns were observed: normal, collateral, stenotic, and occlusive. MCA occlusion or stenosis was seen in 70% of initial TCD studies in the stroke group (n = 50) but not in patients with transient ischemic attacks (n = 25). Eighty-six percent of the initial MCA occlusions had recanalized by 2 weeks after onset. Four patients, evaluated within the first 4 hours after onset, illustrated different patterns of MCA flow. TCD findings were compared with cerebral angiography, computed tomography, and single-photon emission computed tomography. TCD allows early differentiation of patency and natural history of MCA thromboembolic events. This may have important implications in the decision for thrombolytic therapy.