Cognitive disturbances in progressive supranuclear palsy.

The cognitive disturbances in progressive supranuclear palsy (PSP) gave rise to the term "subcortical dementia." PSP patients demonstrate prominent recall deficits and moderate forgetfulness although their short-term and implicit perceptual memory processes are intact. PSP patients have both slowed motor responses and dramatically slowed information processing speed. Executive dysfunction appears early in the course of the disease and is relatively severe. The combination of severely slowed information processing and marked executive dysfunction are characteristic of PSP and differentiates it from other dementias. In their landmark description of progressive supranuclear palsy (PSP) as a clinicopathological entity, Steele et al. (1964) reported that cognitive disturbances were present in seven out of their nine patients. Ten years later, Albert et al. (1974) characterized these changes to be part of a "subcortical dementia," They analyzed 5 of their own PSP cases and also reviewed the published literature; they found a common cluster of symptoms, including the presence of forgetfulness, slowness of thought process, emotional or personality changes, and impaired ability to manipulate acquired knowledge. Albert et al. analysis was qualitative, but in the authors' view, clearly differentiated PSP patients from patients with "cortical dementia" who presented with aphasia, apraxia, and/or agnosia. They also suggested that the symptoms found in PSP were similar to those that had previously been described in patients with frontal lobe lesions.