The Entorhinal Cortex in First-Episode Psychotic Disorders: A Structural Magnetic Resonance Imaging Study

OBJECTIVE: Neuropathological findings regarding the entorhinal cortex in schizophrenia are conflicting. The authors used structural magnetic resonance imaging to examine the entorhinal cortex volumes of healthy subjects and medication-naive patients experiencing their first episode of psychotic illness. METHOD: The study included 33 patients with schizophrenia and related disorders, 11 patients with nonschizophrenic disorders, and 43 matched healthy subjects. All subjects were rated on the Scale for the Assessment of Positive Symptoms and the Scale for the Assessment of Negative Symptoms, and volumetric measurements of the entorhinal cortex were obtained for all subjects. The authors examined differences across the groups as well as clinical correlations of entorhinal cortex volumes adjusted for intracranial volume. RESULTS: A significant diagnosis effect was seen in the left entorhinal cortex: patients with schizophrenia and related disorders and patients with nonschizophrenic psychotic disorders had smaller left entorhinal cortex volumes than healthy subjects. The mean entorhinal cortex volume of patients with schizophrenic disorders did not differ from that of patients with nonschizophrenic psychotic disorders. In patients with schizophrenic disorders, the entorhinal cortex volume positively correlated with severity of delusions. The mean entorhinal cortex volume of patients with nondelusional psychotic disorders was significantly smaller than that of patients with delusional psychotic disorders and healthy subjects. CONCLUSIONS: Smaller entorhinal cortex volume in first-episode, neuroleptic-naive psychotic disorders may not be a confound of the effects of illness chronicity or antipsychotic treatment. Entorhinal cortex pathology appears to have a significant association with positive symptoms, specifically delusions. The impairment of functions in which the entorhinal cortex participates—such as novelty detection, associative learning, and processing episodic, recognition, and autobiographical memory—could be responsible for its association with psychotic disorders and delusions.