EEG abnormalities and outcome in first-episode psychosis

There is widespread consensus that the EEG is not useful for the detection of clinically relevant abnormalities in patients with psychosis. Given that the EEG records brain dysfunction, this study examines whether an abnormal EEG in first-episode psychosis patients is associated with poorer prognosis, compared with a normal EEG.

At their initial assessment, 61 patients with first-episode psychosis had an EEG classified according to the following modified Mayo Clinic system: normal, essentially normal (that is, one or more elements of questionable normality), or dysrhythmia (grade I to V). We assessed psychiatric symptoms using the Scale for Assessment of Negative Symptoms (SANS) and the Scale for Assessment of Positive Symptoms (SAPS) on entry and after 1 year of treatment. Psychosis is considered to have remitted if there are no, or minimal, psychotic symptoms (that is, a rating of 2 or less on every SAPS global rating), maintained for 1 month.

At the end of 1 year, 19/21 (90.5%) patients with a normal EEG had a remission of their positive symptoms, compared with 18/28 (64.3%) of those with an essentially normal EEG and only 7/12 (58.3%) of those with dysrhythmia. Negative symptoms were reduced by more than 50% in 11/18 (61.1%) patients with a normal EEG, compared with 10/28 (35.7%) patients with an essentially normal EEG. None of the 8 patients with dysrhythmia on their EEG experienced reduced negative symptoms.

The above findings suggest that an abnormal EEG in patients with first-episode psychosis is associated with a poorer prognosis.