Regional cerebral blood flow single-photon emission tomography with 99m Tc-HMPAO and the acetazolamide test in the evaluation of vascular and Alzheimer's dementia

Abstract

The diagnostic potential of technetium-99m hexamethylpropylene amine oxime (HMPAO) following systemic administration of the cerebral vasodilator acetazolamide (acetazolamide test) was evaluated by regional cerebral blood flow (rCBF) single-photon emission tomography (SPET) in patients with Alzheimer's disease (AD) or vascular dementia (VD). An initial, high-resolution SPET study was performed with 99mTc-HMPAO, and after 2 days the patients were re-evaluated with 99mTc-HMPAO following systemic administration of acetazolamide. Reconstructed SPET slices were evaluated visually and semiquantitatively by a semi-automatic rCBF map method. When 99mTc-HMPAO alone was used, bilateral hypoperfusion was found in the temporal and/or parietal regions in 33% (6/18) of the VD patients and in 70% (23/33) of the AD patients. The corresponding data obtained by quantitative evaluation were 41% (7/17) and 71% (15/21), respectively. The vascular reserve capacity, as determined with the acetazolamide test, was preserved visually in 22% (4/18) and quantitatively in 29% (5/17) of the VD patients, but in 73% (24/33) and 76% (16/21) of the AD patients. The differences in the perfusion patterns between the VD and AD patients were statistically significant (P<0.01, Fischer's exact test). Of the VD patients with hypoperfusion (bilateral temporal and/or parietal), 4/6 (67%, visual evaluation) and 4/7 (57%, quantitative evaluation) had a decreased vascular reserve capacity as determined with the acetazolamide test. In the AD group of patients the corresponding results were 3/23 (13%) and 4/15 (27%). It is concluded that the acetazolamide test is promising in rCBF SPET to differentiate VD from AD.

Simultaneous Measurement of Arterial Transit Time, Arterial Blood Volume, and Cerebral Blood Flow Using Arterial Spin-Labeling in Patients with Alzheimer Disease

“…For example, Nagata et al 5 measured MTT and VR to carbon dioxide inhalation in patients with AD and VD and found that MTT was prolonged and VR was depressed in patients with VD, whereas the 2 indices were preserved in patients with AD. 5 Impairment in the responsiveness to vascular activation in VD was reported by De Reuck et al, 15 whereas other groups found no such impairment in AD based on SPECT [16][17][18] and xenon-enhanced CT 19 analysis. Moreover, Puls et al 20 revealed, by using transcranial sonography, that tissue transit time is prolonged in VD but not in degenerative dementia.…”

Cerebral Hypoperfusion Generates Cortical Watershed Microinfarcts in Alzheimer Disease

“…19 -25 Several earlier studies reported reduced cerebral blood flow in AD. [5][6][7][22][23][24][25]28,29 Pavics et al, 30 studying regional cerebral blood flow, showed that bilateral cerebral hypoperfusion occurs in the temporal and/or parietal region in 70% (23/33) of patients with AD and in 33% (6/18) of patients with vascular dementia. Many authors have concluded that diffuse cerebral hypoperfusion is responsible for leukoaraiosis in AD.…”

Are Alzheimer’s disease, hypertension, and cerebrocapillary damage related?☆

“…Clinical measurements of regional CBF by the noninvasive SPECT method have indicated that AD is accompanied by a decreased regional CBF in the hippocampal formation, the temporal cortex, the parietal cortex and the frontal cortex [4,11,13,29,36,40,41,46,53]. The region specificity is remarkable because the typical neuropathological hallmarks of AD also appear first and most extensively in the entorhinal region and the temporal cortex.…”