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April 1994

Schizophrenia and Temporal Lobe EpilepsyA Neuropsychological Analysis

Author Affiliations

From the Clinical and Research Services Branch (Dr Gold) and the Clinical Brain Disorders Branch (Drs Goldberg and Weinberger), Division of Intramural Research Programs, National Institute of Mental Health, Washington, DC; the EpiCare Center, Baptist Memorial Hospital, Departments of Psychiatry and Neurosurgery, University of Tennessee, and Semmes-Murphey Clinic, Memphis (Drs Hermann and Wyler); and the Experimental Therapeutics Branch, National Institute of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, Md (Dr Randolph).

Arch Gen Psychiatry. 1994;51(4):265-272. doi:10.1001/archpsyc.1994.03950040009001

Background:  Recent neuroimaging studies have reported structural abnormalities of mesial temporal lobe structures in schizophrenia. This study compared the neuropsychological performance of patients with schizophrenia with patients with either left or right temporal lobe epilepsy to determine if lateralized, developmental temporal lobe dysfunction provides a model of the congnitive impairments observed in schizophrenia.

Methods:  A total 66 patients with schizophrenia and 101 patients with medically intractable focal temporal lobe epilepsy (48 left temporal, 53 right temporal) received a comprehensive neuropsychological battery.

Results:  The three groups did not differ on age, years of education, or Full-Scale IQ. However, clear differences were noted in performance profiles. Patients with schizophrenia scored significantly higher than either epilepsy group on a measure of word reading thought to reflect premorbid competence. Patients with schizophrenia demonstrated greater attentional impairment and motor slowing than either epilepsy group. The patients with schizophrenia had superior semantic knowledge and verbal memory compared with the left temporal lobe group. On the Wisconsin Card Sorting Test the patients with schizophrenia obtained significantly fewer categories than either temporal lobe group, but were not significantly more perseverative.

Conclusions:  Data suggest lateralized temporal lobe dysfunction does not provide an adequate model of the cognitive impairments seen in schizophrenia. The disorders seem to follow different developmental paths: In earlyonset epilepsy, the acquisition of cognitive skills and academic knowledge is compromised, while in schizophrenia congnitive functions are lost. Extratemporal pathologic features, most likely of the frontal lobe, are implicated in the cognitive dysfunction of schizophrenia.