Distinct cognitive profiles of cortical and subcortical dementia in advanced illness.

We administered the Mattis Dementia Rating Scale (DRS) to 120 patients to evaluate the effect of dementia severity on distinct cognitive profiles. Sixty patients with Huntington's disease (HD) and 60 patients with Alzheimer's disease (AD) were separated by dementia severity into three groups: mildly demented (DRS mean total = 129), moderately demented (DRS mean total = 117), and severely demented (DRS mean total = 102). At all levels of dementia severity, HD patients demonstrated greater impairment than AD patients on the Initiation/Perseveration subscale, whereas AD patients demonstrated greater impairment than HD patients on the Memory subscale. At moderate and severe levels of dementia, HD patients demonstrated an additional impairment in constructional praxis. These profile differences were independent of dementia severity and continued to differentiate between so-called cortical and subcortical dementias in later stages of dementia severity.