Bilateral temporal lobe volume reduction parallels cognitive impairment in progressive aphasia
C. Andersen, C. Dahl, O. Almkvist, P. Ostberg, P. Julin and L. O. Wahlund
Department of Clinical Neuroscience and Family Medicine, Karolinska Institute, Huddinge University Hospital, Sweden.
BACKGROUND: Patients with isolated aphasia in the absence of other
cognitive abnormalities have been the focus of several studies during the
past decade. It has been called primary progressive aphasia (PPA), and the
typical features of this syndrome are marked atrophy of the left temporal
lobe according to the radiological examination and a language disorder as
the initial symptom. In previous studies of PPA, the selection of the
patients was based mainly on linguistic symptoms. Now, when computed
tomography or magnetic resonance imaging scans are part of the routine
investigation of cognitive impairment and suspected dementia, the patients
with lobar atrophy will be found at an earlier stage. In the present study,
we used a new approach and defined the study group by selecting patients
with obvious left temporal lobe atrophy, assessed by MRI, and we referred
to them as patients with temporal lobe atrophy (TLA). OBJECTIVE: To
identify the features that distinguish TLA from other primary
neurodegenerative disorders. PATIENTS: Six patients with TLA were compared
with patients with Alzheimer disease (AD), patients with frontal lobe
dementia (FLD), and healthy control subjects. METHODS: The investigations
included magnetic resonance imaging volumetry, single photon emission
computed tomography, and neuropsychologic and linguistic evaluations.
RESULTS: In the TLA group, the mean volume 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 the TLA group, the absolute volumes of the
temporal lobes were significantly smaller on the left side compared with
the AD and FLD groups, whereas there was no difference on the right side.
The cerebral blood flow pattern in TLA was asymmetric and differed from
that in the other study groups. All patients with TLA had a history of
progressive Wernicke-type aphasia, ranging from 2 to 6 years. They showed
primary verbal memory impairment but had preserved visuospatial functions.
The clinical 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 patients
showed an annual 8% to 9% decrease of both left and right temporal lobes.
CONCLUSIONS: The initial marked asymmetry in cognitive function found in
patients with TLA contrasts with the general decline found in patients with
AD. The bilateral degenerative process evident in patients with TLA
paralleled the clinical deterioration, indicating TLA to be a non-AD lobar
atrophy that develops into generalized cognitive dysfunction and dementia.
