'Pseudo-Alzheimer's' and primary brain tumour.

Primary brain tumour may present in the elderly purely as a dementing illness before the onset or detection of sensorimotor neurological symptoms or signs. Although neurological examination may indicate no definite signs, close attention to accepted DSM-IIIR and NINCDS-ADRDA diagnostic criteria for primary degenerative dementia and ''probable'' Alzheimer''s disease respectively will suggest a process other than a degenerative one. This was the case in two patients with primary brain tumour presenting clinically with dementing illness similar to but distinct from Alzheimer''s disease.