Abstract
Background: There is remarkable heterogeneity in clinical Alzheimer’s disease
(AD) or vascular dementia (VaD).
Objectives: 1) To statistically examine neuropsychological data to determine
dementia subgroups for individuals clinically diagnosed with AD or VaD and then 2) examine
group differences in specific gray/white matter regions of interest.
Methods: A k-means cluster analysis requested a 3-group solution from
neuropsychological data acquired from individuals diagnosed clinically with AD/VaD. MRI
measures of hippocampal, caudate, ventricular, subcortical lacunar infarction, whole brain
volume, and leukoaraiosis (LA) were analyzed. Three regions of LA volumes were quantified
and these included the periventricular (5 mm around the ventricles), infracortical (5 mm
beneath the gray matter), and deep (between periventricular and infracortical)
regions.
Results: Cluster analysis sorted AD/VaD patients into single domain amnestic
(n = 41), single-domain dysexecutive (n = 26), and
multi-domain (n = 26) phenotypes. Multi-domain patients exhibited worst
performance on language tests; however, multi-domain patients were equally impaired on
memory tests when compared to amnestic patients. Statistically-determined groups
dissociated using neuroradiological parameters: amnestic and multi-domain groups presented
with smaller hippocampal volume while the dysexecutive group presented with greater deep,
periventricular, and whole brain LA. Neither caudate nor lacunae volume differed by group.
Caudate nucleus volume negatively correlated with total LA in the dysexecutive and
multi-domain groups.
Conclusions: There are at least three distinct subtypes embedded within
patients diagnosed clinically with AD/VaD spectrum dementia. We encourage future research
to assess a) the neuroradiological substrates underlying statistically-determined AD/VaD
spectrum dementia and b) how statistical modeling can be integrated into existing
diagnostic criteria.
