Uncommon neurodegenerative causes of dementia.

A group of neurodegenerative diseases is outlined that affect cortical and subcortical areas of the brain. These diseases give rise to atypical forms of dementia and, unlike Alzheimer's disease (AD), are often associated with neurological symptoms. Clinical symptoms reflect the localization of the degenerative process rather than the nature of the underlying histopathology. Degeneration of the frontal and anterior temporal lobe presents initially with behavioral alterations, but later in the course, impairment of cognition and activities of daily living develops. Posterior cortical atrophy affects the parietal and occipital association cortices and causes complex visual disturbances. In corticobasal degeneration (CBD) the focus of pathology includes the frontoparietal cortex and several subcortical nuclei, causing symmetrical rigidity, bradykinesia, myoclonus and dystonia. Progressive supranuclear palsy (PSP) involves the frontal, temporal and parietal cortex as well as parts of the brain stem. Clinical features include a hypokinetic rigid syndrome with nuchal dystonia and vertical gaze palsy. Huntington's disease is a prototypical autosomal dominant disorder that affects the extrapyramidal system and causes choreatic movements in combination with personality changes and cognitive deterioration. Amyotrophic lateral sclerosis (ALS) with dementia is a neurodegeneration of the frontotemporal cortex and of the anterior horn of the spinal cord. Behavioral change similar to frontotemporal dementia (FTD) is paralleled or followed by the classic features of motor neuron disease.