Transcranial Doppler Sonography as a Diagnostic Tool in Vascular Dementia

Abstract

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: Paco₂levels 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.

Cerebrovascular Reactivity in Degenerative and Vascular Dementia: A Transcranial Doppler Study

“…Blood flow reduction could indeed represent the functional correlate of a reduced arterial diameter, reflecting the presence of microangiopathy in both diseases [24], which is in accordance with previous observations [19, 20] and partially with those of Foerstl et al [25] and Biedert et al [26], who observed a significant PI increase only in the VaD group.…”

“…These findings were already reported by Provinciali et al [19], who observed reduced responses in hypocapnic conditions for both VaD and AD and, under hypercapnic conditions, only for VaD. An altered reactivity of the posterior cerebral arteries to visual stimulation was observed in VaD with respect to AD and normal controls, suggesting that the occipital cortex is partially preserved in patients with AD [33].…”

“…The predominant vascular involvement in cerebrovascular demented patients with respect to degenerative demented patients has led to the hypothesis that these two entities should exhibit differences in cerebrovascular blood FV profiles. This datum is actually controversial: studies limited to the MCA [20] reported an FV reduction even in AD when compared with controls [31], while others failed to find significant FV differences [19]. In our patients, there were no significant differences in PIs between VaD and AD and only a nonsignificant trend toward lower FV was observed in AD.…”

“…As a matter of fact, an overall reduction in cerebral blood flow – representative of microvasculature damage – has been reported not only in VaD [19] but also in AD [20]. …”

Reduced Vasomotor Reactivity in Cerebral Microangiopathy

“…6,8,9,21 Impaired cerebral autoregulation and altered pulsatility characteristics measured by TCD were found in patients with vascular dementia and lacunes [22][23][24][25] ; however, most of these studies did not distinguish between cerebral microangiopathy and lacunar and territorial brain infarction.…”