The 'subcortical dementia' of progressive supranuclear palsy.

Progressive supranuclear palsy (Steele et al.) has a characteristic pattern of dementia: (1) forgetfulness, (2) slowing of thought processes, (3) emotional or personality changes (apathy or depression with occasional outbursts of irritability), and (4) impaired ability to manipulate acquired knowledge. In many neurological disease states associated with subcortical pathology a similar pattern of dementia exists. The neurobehavioural changes of progressive supranuclear palsy thus typify a clinical pattern which may be referred to as subcortical dementia. The subcortical dementias have a striking clinical resemblance to the dementia which occurs after bifrontal lobe disease. However, the subcortical dementias can be clearly distinguished clinically from cortical dementias, other than frontal dementias. We propose as a tentative hypothesis that there may be common pathophysiological mechanisms underlying the subcortical dementias-in particular, disturbances of timing and activation. There are immediate practical implications of this hypothesis: drugs which have an effect on subcortical timing and activating mechanisms may be useful in the treatment of subcortical dementias.