Frontal intermittent rhythmic delta activity (FIRDA) in pituitary adenoma.

We report a case of FIRDA in the EEG of a patient diagnosed as major depression with pituitary adenoma and hyponatremic encephalopathy. The pituitary adenoma appeared to be a major factor responsible for FIRDA in this case. Although other factors associated with this case, i.e., diffuse encephalopathy and administration of antipsychotic drugs, have been reported to be causative, FIRDA remained in the EEG after these other factors diminished. Although size of the pituitary adenoma that might be associated with FIRDA in the EEG recording was not identified in this study, FIRDA may be associated with a small pituitary adenoma less than 10 mm in diameter. We think a diligent search for additional pathology is recommended if FIRDA is seen in the EEG of an otherwise normal patient.