Subcortical dementia. Review of an emerging concept.

Subcortical dementia is a clinical syndrome characterized by slowness of mental processing, forgetfulness, impaired cognition, apathy, and depression. First recognized in progressive supranuclear palsy and Huntington's disease, the concept has been extended to account for the intellectual impairment of Parkinson's disease, Wilson's disease, spinocerebellar degenerations, idiopathic basal ganglia calcification, the lacunar state, and the dementia syndrome of depression. Disorders manifesting subcortical dementia have pathologic changes that involve primarily the thalamus, basal ganglia, and related brain-stem nuclei with relative sparing of the cerebral cortex. Recent studies of neuropsychologic deficits following focal subcortical lesions also support a role for these structures in arousal, attention, mood, motivation, language, memory, abstraction, and visuospatial skills. The clinical characteristics of subcortical dementia differ from those of dementia of Alzheimer's type where prominent cerebral cortical involvement produces aphasia, amnesia, agnosia, and apraxia.