Pure thalamic dementia with a single focus of spongiform change in cerebral cortex.

An absence of spongiform change differentiates the pure thalamic degeneration (PTD) from the thalamic form of Creutzfeldt Jakob Disease (CJD). This report describes a case which in addition to the neuropathological changes typical of primary thalamic degeneration showed a single small focus of spongiform change in the cerebral cortex. The exceptional instances of thalamic degeneration associated with limited spongiform change among which this case is unique by virtue of the size of the single focus of vacuolation probably represent a variant of the thalamic form of CJD. In the context of potential infectious etiology the fact that the patient had a blood transfusion five months before the onset of neurological illness is of interest.