Introduction. Studies on the cognitive performance of patients with early Alzheimer's disease (AD) have disclosed the existence of different subgroups reflecting different patterns of cognitive impairment. AD patients with selective deficits of episodic and semantic memory and preservation of executive functions are classified as having a focal temporal lobe dysfunction (FTLD). In comparison to other AD patients with a more diffuse pattern of cognitive impairment (dAD), FTLD patients have been reported as presenting a slower rate of progression of their cognitive deficits, with visual-constructive skills virtually spared. Material and methods. We studied 10 FTLD and 14 dAD patients in early stages of the disease. The two groups were homogeneous for demographic characteristics and duration of illness. All patients underwent MRI, [99mTc]-HMPAO SPECT and a baseline neuropsychological examination. A second neuropsychological examination was performed at a 15 to 18-month interval from the first one. Results. While MRI did not clearly differentiate between FTLD and dAD patients, [99mTc]-HMPAO SPECT yielded two distinctive patterns of abnormalities, shaping a double dissociation between the two groups: a bilateral mesial temporal hypoperfusion, characteristic of FTLD, and a posterior temporal parietal hypoperfusion, characteristic of dAD patients. The neuropsychological results obtained in the test/re-test conditions pointed out a dramatic worsening of dAD in several measures of memory, language, visual-constructive abilities, and executive functions, contrasting the moderate decrease of FTLD performance, restricted to memory tasks . Conclusions. These SPECT and neuropsychological results indicate that FTLD is not a mere stage but a distinct form of AD, with specific patterns of neuropsychological and SPECT abnormalities. The combination of neuropsychological tests and [99mTc]-HMPAO SPECT is very useful in identifying FTLD patients from the wider group of dAD patients. This issue is particularly worthwhile, since - as the present study confirms - FTLD patients progress more slowly (and maintain some specific cognitive abilities), at least over a course of 15-18 months. Results of the present study also suggest that the mechanisms underlying FTLD and dAD may be different, thus providing support to the hypothesis that FTLD might represent a distinct 'biological' variant of AD.
|Issue number||4 SUPPL.|
|Publication status||Published - 2000|
ASJC Scopus subject areas
- Clinical Neurology