Clinical approach to psychotic symptoms in temporal lobe epilepsy: vulnerability hypothesis of "epileptic psychosis".

Neuropsychiatric disorders such as epilepsy, schizophrenia and mood disorder usually develop with a repetition of attacks or episodic exacerbations. It is assumed that a vulnerability to episode (or attack) may last in a remission state between episodes (or attacks). Such a vulnerability would probably exist before the onset of illness and would be a major determinant of the manifestation of illness. Search for a vulnerability marker has been extensively made in the study of schizophrenia, and a vulnerability hypothesis has become to be a focus in the framework of the pathophysiology of schizophrenia.’ l4 It is suggested that the vulnerability to schizophrenia would be heterogeneous in terms of clinical manifestations, and indeed its indicators can be divided into at least two categories; positive symptom-linked markers and negative symptom-linked markers.’ We found that the remitted schizophrenic patients showed a disturbance of an endogenous negativity termed NA potential’ in the visual event-related potentials (ERPs), and that the disturbance may relate to a psychotic relapse characterized by positive symptoms such as the first-rank symptoms of S ~ h n e i d e r . ~