Prevalence of psychosis in epilepsy as a function of the laterality of the epileptogenic lesion.

Retrospective analysis of the psychiatric diagnoses in a group of patients surgically relieved of medically intractable epilepsy tested the hypothesis that patients with left-sided temporal lobe epileptogenic lesions are at greater risk for the development of a so-called schizophrenic-like psychosis than are those with right-sided temporal lobe epileptogenic lesions. The data confirmed the hypothesis and also demonstrated an increased prevalence of sinistrals in the psychotic group. Thus, epilepsy involving the dominant hemisphere at the inception of the seizure disorder is the significant risk factors. The data also indicated that a psychosis is unlikely to develop in patients with other (nontemporal) forms of focal epilepsy. On the basis of these data and data from other studies, the prevalence of psychosis in patients with poorly controlled temporal lobe epilepsy was estimated to be approximately 10% to 15%.