Transcranial Doppler monitoring of the flow velocity at the level of the middle cerebral artery was performed in 40 demented patients, 20 with multi-infarct dementia (MID) and 20 with senile dementia of the Alzheimer type (SDAT), and in 25 age-matched controls. The following conditions were evaluated: (1) rest; (2) 60 s hyperventilation; (3) longest possible apnea, and (4) 5 min closed-circuit air rebreathing. We also measured: Paco₂ levels at rest and under stimulus conditions; mean flow velocity and pulsatility index (PI) at rest, and percentage velocity variations. The Pis were higher and the velocity decrease during hyperventilation was lower in all demented patients than in the healthy group; no side-related asymmetry in rest values or in vasomotor responses to CO₂ changes was regularly detected in any group. On the contrary, rest flow velocities and vasomotor responses to hypercapnia induced by both apnea and rebreathing tests proved to be lower in MID patients than in the SDAT and healthy groups. These alterations were neither exclusive to MID patients nor homogeneous, therefore some caution should be taken when evaluating single cases.

A group of 30 patients with symptomatic internal carotid artery (ICA) occlusion and different computed tomography (CT) patterns of cerebral ischemia (14 borderzone and/or terminal, 16 territorial) were studied by means of transcranial Doppler (TCD) to determine the relationship between vasomotor reactivity and the topography of the infarct on CT scan. The vasomotor reactivity was evaluated by assessing the mean flow velocity changes observed in the middle cerebral artery (MCA) after the longest possible apnea and i.v. Diamox injection (12–15 mg/kg body weight). An impairment in the vasomotor response was found in 13 out of 14 patients with borderzone and/or terminal ischemia but in only 1 out of 16 with complete territorial ischemia. No relationship with the basal MCA flow velocity was observed. Diamox and apnea tests in TCD examination can be considered useful tools for investigating the hemodynamic changes following ICA occlusion.

The application of the same criteria in different laboratories may facilitate the standardization of TCD examinations and support the reproducibility of clinical reports based on TCD parameters.

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