The role of the entorhinal cortex in paraphrenia.

Evidence derived from postmortem brain studies has implicated the uncal cortex in paraphrenia. In the present review, we expand on the anatomic and physiologic nuances endogenous to this region that make entorhinal cortex pathology an important clinicopathological correlate to paraphrenia. First, we summarize the anatomic landmarks and histologic features that will allow the reader to define the entorhinal region in future research studies. As cortical regions usually project to neighboring cortices, inferences will be drawn as to the function of the entorhinal region based on the surrounding cortical regions. The results will help explain why patients with paraphrenia may exhibit amnestic deficits that stand in contrast to a well-preserved thought process and personality. We also review the results of surgical ablation studies in animals. These studies suggest that some risk factors currently associated with paraphrenia (eg, social isolation) may in reality be an early manifestation of entorhinal pathology. Finally, the author provides a parallelism between the hallucinations observed in some paraphrenic patients and the results of electrical stimulation of the uncal cortex. The results will help explain why hallucinations in paraphrenia are usually limited to the patient's surroundings.