Frontal-subcortical dementias.

Frontal-subcortical dementias are a heterogeneous group of disorders that share primary pathology in subcortical structure and a characteristic pattern of neuropsychologic impairment. Their clinical presentation is characterized by memory disorders, an impaired ability to manipulate acquired knowledge, important changes of personality (apathy, inertia, or depression), and slowed thought processes (or bradyphrenia). It also has marked frontal dysfunction. Classic frontal-subcortical dementias include Huntington chorea, Parkinson disease dementia, progressive supranuclear palsy, thalamic degeneration, subcortical vascular dementia, multiple sclerosis, the acquired immunodeficiency syndrome dementia complex, depressive pseudodementia, and some other rare dementias like spinocerebellar degenerative syndromes, Hallervorden-Spatz disease, choreoacanthocytosis, idiopathic basal ganglia calcification, Guamanian parkinsonism-dementia complex, corticobasal degeneration multiple system atrophy, Wilson disease, metachromatic leukodystrophy, adrenoleukodystrophy, hypoparathyroidism, sarcoidosis, and other CNS inflammatory disorders. Anatomic data suggest that the frontal signs result from a disconnection of the frontal cortex from the basal ganglia. However, most frontal-subcortical dementias show cortical atrophy in later stages, and cortical dementias have subcortical pathology at some point. In fact, the concept might be seen as a continuum, and only the 2 extremes would be represented by pure cortical or subcortical pathology. Anyway, subcortical disorders may still be more similar to one another than they are to AD. Possibly, frontal-subcortical and cortical dementias are the description of the prior main target of the disease process, ending up in both cases in a global dementia. Although the dichotomy cortical versus frontal-subcortical dementia is not strict, the 2 concepts still seem to have advantages.