What Clinical Clues Could Distinguish a Psychotic Episode From a Complex Partial Seizure?

Michael R. Sperling, MD


November 28, 2000


Without the benefit of an EEG recording during an episode, can any clinical clues help to differentiate a psychotic episode from a complex partial seizure?

Leonor C. Lim, MD

Response from Michael R. Sperling, MD

There are a variety of clinical features that can be used to distinguish between postictal psychosis and complex partial seizures, but none are perfect, and an EEG is generally required to ensure the diagnosis. Nonetheless, accurate bedside diagnosis can usually be made.

Postictal psychosis, by definition, requires a history of a recent seizure or, more commonly, a cluster of seizures that are usually convulsive (tonic-clonic). Unfortunately, a history is not always available in the absence of reliable witnesses, and the clinical features must be evaluated on their own.

Postictal psychosis typically follows a cluster of seizures by 24-96 hours and can last between 2 and 14 days. It responds to treatment with antipsychotic medication, remitting more quickly with therapy than if left untreated. Patients experience auditory hallucinations, are delusional, and may display paranoid ideation, but are not typically confused and encephalopathic. The state is one of a fairly stable derangement in performance, without a cyclical pattern of behavior, although symptoms may fluctuate somewhat in severity.

Patients with postictal psychosis are typically capable of complex thought patterns and ideas; they just don't make sense. Formal tests of language, orientation, calculations, memory, and other cognitive tasks are often normal or near normal in a patient with a postictal psychosis.

By contrast, recurrent complex partial seizures are characterized by a true confusional state, perhaps with periods of altered responsiveness or consciousness and automatic behavior. The mental state often displays a cyclical pattern in complex partial seizures, with periods of lessened responsiveness (the ictal state) alternating with periods of greater responsiveness (the interictal or postictal state). A person in a prolonged postictal state will not show cyclical behavior but should demonstrate a steady improvement in responsiveness or diminishing confusion.

Testing of language and cognitive function is invariably abnormal in these patients. They are disoriented, confused, have impaired memory and ability to calculate, and may have impaired linguistic abilities as well.

The EEG aids in confirming the diagnosis. In the postictal psychosis, EEG may be normal or show mild background slowing that is unilateral or bilateral. In the patient with seizures, prolonged EEG recording will document ictal discharges, and the interictal background shows unilateral or, more often, bilateral slowing of frequencies.