Cerebral hemodynamic patterns during stimuli tasks in multi-infarct and Alzheimer types of dementia

To examine differences in cerebrovascular reactivity between multi-infarct and Alzheimer types of dementia.

Using transcranial Doppler, measurements of flow velocity in the middle cerebral arteries during apnea, thumb-to-finger opposition and verbal and design discrimination tasks were recorded in patients with multi-infarct (n=10; mean age 68+/-7.5 years) and Alzheimer types of dementia (n=10; mean age 62+/-9.1 years). Controls were 20 healthy subjects matched for age and sex.

Cerebral reactivity to apnea was significantly lower (P<0.0001) in the multi-infarct group compared to the other 2 groups. During the motor task, a nearly selective increase of mean flow velocity in the middle cerebral artery contralateral to the hand performing the task occurred in both controls and Alzheimer patients. A bilateral increase, without side-to-side differences, of flow velocity during movement of each hand was observed in multi-infarct patients. With respect to baseline values, the cognitive tasks produced significant and distinct effects on the left and right side in the controls but not in the patients. Controls showed a significant increase of left middle cerebral artery mean flow velocity during a verbal task (P<0.0001), and of the right middle cerebral artery mean flow velocity during a design discrimination task (P<0.001) when side-to-side comparisons were done. Differently, a bilateral and comparable increase of flow velocity was observed in all patients during performance of the same cognitive tasks.

These data suggest that cerebrovascular reactivity to apnea could be an additional criterion for discriminating between MID and DAT patients. Transcranial Doppler assessment during cognitive and motor tasks could provide useful complementary information for comprehension changes in cerebral activity in patients with dementia.