Background. Previous work suggests that temporal lobe
magnetic resonance imaging (MRI) can
distinguish those with dementia of the Alzheimer type (DAT) from healthy
However, its specificity with regard to conditions such as vascular dementia,
depression and other
disorders associated with cognitive impairment has not been determined.
Methods. We studied 222 subjects using T1 weighted MRI with
5·1 mm coronal slices throughout
the temporal lobe. Subjects included: healthy controls (N=40);
DSM-III-R major depression
(N=61); NINCDS/ADRDA DAT (N=77) and OTHER (N=44,
comprising subjects with
vascular dementia, Huntington's disease, schizophrenia,
alcohol related cognitive impairment and
a group of ‘memory complainers’). Hippocampus,
amygdala, entorhinal cortex, parahippocampal
gyrus and cerebral cortex were rated visually on a 0–3
scale by two experienced neuroradiologists blind to clinical diagnosis.
Results. Ratings of temporal lobe atrophy provided good separation
between those with AD and
all other groups. For example, anterior hippocampal atrophy had a sensitivity
of 83% for detecting
DAT, a specificity of 80% for controls, 87% for depressed subjects and
regions were less sensitive, but more specific for the diagnosis of
DAT. In particular
parahippocampal gyrus and entorhinal cortex had high specificity (97%
for depressed subjects and
98% for OTHER). Because of an age-related increase in atrophy, sensitivity
was highest for those
over the age of 75, while specificity was highest for younger subjects.
Significant correlations were
observed between atrophy ratings of hippocampus, amygdala, entorhinal cortex
and parahippocampal gyrus and CAMCOG memory score and length of history.
Conclusions. Temporal lobe MRI may have an important role in
with the clinical diagnosis
of DAT, particularly its differentiation from depression and other disorders
that may cause diagnostic difficulties in clinical practice.