BILATERAL TEMPORAL-LOBE VOLUME REDUCTION PARALLELS COGNITIVE IMPAIRMENT IN PROGRESSIVE APHASIA

Background: Patients with isolated aphasia in the absence of other cog nitive abnormalities have been the focus of several studies during the past decade. It has been called primary progressive aphasia (PPA), an d the typical features of this syndrome are marked atrophy of the left temporal lobe according to the radiological examination and a languag e disorder as the initial symptom. In previous studies of PPA, the sel ection of the patients was based mainly on linguistic symptoms. Now, w hen computed tomography or magnetic resonance imaging scans are part o f the routine investigation of cognitive impairment and suspected deme ntia, the patients with lobar atrophy will be found at an earlier stag e. In the present study, we used a new approach and defined the study group by selecting patients with obvious left temporal lobe atrophy, a ssessed by MRI, and we referred to them as patients with temporal lobe atrophy (TLA) Objective: To identify the features that distinguish TL A from other primary neurodegenerative disorders. Patients: Six patien ts with TLA were compared with patients with Alzheimer disease (AD), p atients with frontal lobe dementia (FLD), and healthy control subjects . Methods: The investigations included magnetic resonance imaging volu metry, single photon emission computed tomography, and neuropsychologi c and linguistic evaluations. Results: In the TLA group, the mean volu me of the left temporal lobe was 35% smaller than the right, while in the AD and FLD groups, the atrophy was symmetrical and bilateral. In t he TLA group, the absolute volumes of the temporal lobes were signific antly smaller on the left side compared with the AD and FLD groups, wh ereas there;was no difference on the right side. The cerebral blood fl ow pattern in TLA was asymmetric and differed from that in the other s tudy groups. All patients with TLA. had a history of progressive Werni cke-type aphasia, ranging from 2 to 6 years. They showed primary verba l memory impairment but had preserved visuospatial functions. The clin ical condition of all patients with TLA. deteriorated during the study period; severe aphasia developed, and the patients exhibited signs of frontal lobe dysfunction. Serial volumetric measurements in 4 of 6 pa tients showed an annual 8% to 9% decrease of both left and right tempo ral lobes. Conclusions: The initial marked asymmetry in cognitive func tion found in patients with TLA contrasts with the general decline fou nd in patients with AD. The bilateral degenerative process evident in patients with TLA paralleled the clinical deterioration, indicating TL A. to be a nan-AD lobar atrophy chat develops into generalized cogniti ve dysfunction and dementia.