A TOPOGRAPHICAL STUDY OF SENILE PLAQUES AND NEUROFIBRILLARY TANGLES IN THE HIPPOCAMPI OF PATIENTS WITH ALZHEIMERS-DISEASE AND COGNITIVELY IMPAIRED PATIENTS WITH SCHIZOPHRENIA

Neuropsychological testing of elderly schizophrenic patients reveals t hat a significant portion of this population exhibit varying degrees o f cognitive impairment. Since Alzheimer's disease is the most common c ause of dementia in geriatric patients, we investigated whether the co gnitive decline observed in schizophrenia is the result of degenerativ e changes analogous to those characteristic of Alzheimer's disease. Fo r this purpose, the number and distribution of senile plaques and neur ofibrillary tangles were mapped in the hippocampi of 10 cognitively im paired schizophrenic patients, 10 patients with Alzheimer's disease, a nd IO patients with dementia not attributed to either schizophrenia or Alzheimer's disease. In Alzheimer's disease, degenerative changes inv ariably predominated in the CA1 subfield, subiculum, and proisocortex. By contrast, findings characteristic of Alzheimer's disease were virt ually never observed in the hippocampi of schizophrenic and other cogn itively impaired patients. In some patients with Alzheimer's disease, the presence of senile plaques in the molecular layer of the dentate g yrus suggested the existence of an underlying entorhinal cortex lesion . Similar dentate gyrus pathology was never found in any of the other patients. The authors conclude that cognitive impairment in schizophre nia is not the result of degenerative changes analogous to those found in Alzheimer's disease.