Can transcranial Doppler really detect reduced cerebral perfusion states?

BACKGROUND AND PURPOSE: This study was designed to determine whether transcranial Doppler ultrasonography (TCD) may detect reduced perfusion states of the brain in patients with hypertension or diabetes mellitus with suspected cerebral atherosclerosis and arteriolosclerosis.

METHODS: We determined blood flow velocity with TCD in the middle cerebral artery and cerebrovascular vasodilator responses to carbon dioxide in 22 patients with or without carotid artery occlusive disease and minor stroke; we compared the results with the measurements of cerebral blood flow and oxygen metabolism by positron emission tomography (PET).

RESULTS: Blood flow velocity measured by TCD correlated with ipsilateral cerebral blood flow measured by PET in frontal, temporal, and striatal regions and throughout the entire hemisphere (P < .05 to P < .005). Relative changes in blood flow velocity and calculated cerebrovascular resistance tested by carbon dioxide inhalation both correlated closely with regional mean transit time (calculated as the ratio of cerebral blood volume divided by cerebral blood flow) in frontal, striatal, temporal, parietal, and occipital regions and also in the entire hemisphere (P < .05 to P < .0001). TCD variables did not correlate with hemispheric measurements of oxygen metabolism by PET.

CONCLUSIONS: Although TCD is not useful in assessing impairments of cerebral metabolism, it is useful for detecting abnormalities of cerebral hemodynamics among patients with risk factors for cerebrovascular disease.