Temporal Lobe Hypoperfusion in Isolated Amnesia with Slow Onset: A Single Photon Emission Computer Tomography Study

Abstract

Single photon emission computer tomography (SPECT) applied early in the course of Alzheimer’s disease (AD) may identify regions with impaired brain function. Moreover, it may be relevant to characterize SPECT perfusion patterns in patients with mild cognitive impairment (MCI), in particular the subgroup of MCI patients with isolated amnesia, as these patients have been demonstrated to convert to AD in more than half of the cases within 3 years. The primary aim of the present study was to characterize the regional cerebral blood flow (CBF) in patients with neuropsychologically verified isolated amnesia. We examined 32 patients (11 men/21 women) with isolated amnesia according to strict neuropsychological criteria and 15 healthy volunteers (11 men/4 women). All subjects had an SPECT-^99mTc-d,l-HMPAO perfusion study and neuropsychological assessments. Cranial MRI or CT was performed in all subjects. Semiquantitative (cerebellar relative) flow values were calculated and statistically compared. Patients with isolated amnesia had significant hypoperfusion in several cortical regions of interest compared to control subjects, most prominently in the left temporal cortex. Additionally, there was a trend towards globally reduced CBF in the patients, although this was not significant. These findings may indicate the presence of a progressive degenerative illness affecting multiple brain regions at its early or preclinical stage.

Brain SPECT in subtypes of mild cognitive impairment

“…On the other hand, perfusion reduction in the posterior cingulate did not reach statistical significance. Posterior cingulate hypoperfusion has been frequently reported in series of MCI patients [18,20,21], but often hypoperfusion has been rather reported in the posterior parietal cortex and the precuneus [3,12,16,17]. Of note among SPECT studies, only those performed using 99m Tc-HMPAO [18,21] or 123 I-iodoamphetamine [20] disclosed posterior cingulate hypoperfusion, which has not, however, been reported by 99m Tc-ECD studies [3,12].…”

“…The finding of hippocampal hypoperfusion raises the question about why hippocampal dysfunction has not been reported as an early marker of aMCI by a portion of the SPECT/PET literature [3,6,12,14,17,18,21], despite it being largely expected on the basis of current knowledge on the pathophysiology of AD. This issue has been discussed by a recent review [31], pointing to the problems of low spatial resolution of first-generation SPECT/PET equipment and to the smoothing procedure needed by the software programs performing voxelbased analysis (VBA).…”

“…In aMCI, brain perfusion-metabolic failure has been found by SPECT [3, 12, 14, 16-18, 20, 21] and PET [1,6,8,9,30,31] studies especially in the posterior associative cortex [1,3,6,8,12,14,17], medial temporal lobe [1,9,15,20,30] and posterior cingulate/precuneus [1,3,8,14,16,20,21], thus reproducing the typical functional deficit of early Alzheimer's disease (AD). However, data on brain perfusion-metabolic failure in naMCI is still lacking.…”

Does Alzheimer’s Disease with Early Onset Progress Faster than with Late Onset? A Case-Control Study of Clinical Progression and Cerebrospinal Fluid Biomarkers

“…Impairment of attention skills, apraxia, visuospatial dysfunction, and language problems are described early in the course of EOAD [4,5,6,7]. Studies on functional imaging in isolated slow progressing amnesia in the elderly have demonstrated that these patients may have a primary involvement of the temporal lobe [8], whereas the clinical profile of EOAD patients may reflect a primary involvement of the parietal region, which has also been suggested in both imaging studies and cerebrospinal fluid (CSF) studies of different EOAD presentations (posterior cortical atrophy and familial AD) [9,10]. Regarding clinical progression of the disease, several studies have demonstrated a faster progression [11,12,13,14] and a higher mortality [15] in EOAD patients compared to LOAD patients.…”

Carotid Artery Ultrasound and Echocardiography Testing to Lower the Prevalence of Alzheimer's Disease

“…[48][49][50][51][52][53] More specifically, neuroimaging data indicate that one of the earliest preclinical markers of AD in people with MCI is the presence of brain hypoperfusion, specifically in brain regions destined to atrophy and die. [54][55][56][57][58][59][60][61][62][63][64][65] Atrophic changes in brain regions that initially show pathology typical of AD appear to follow brain hypoperfusion 6 not amyloid beta peptide accumulation as previously believed. 66 This conclusion is supported using perfusion and diffusion-weighted magnetic resonance imaging for evaluating tissue pathophysiology, which confirmed that microvascular perfusion impairment was the genesis of atrophy in AD.…”