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

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- 99m Tc-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.