Frontal intermittent rhythmic delta activity (FIRDA) in pial-dural arteriovenous malformation.

We report a case of FIRDA associated with a pial-dural arteriovenous malformation (AVM). The patient presented with headaches, papilledema and partial oculomotor nerve palsy. CT scan had failed to discover the AVM. After partial embolization of the AVM, the patient's symptoms and signs resolved, and the FIRDA disappeared. FIRDA has been thought to be caused by frontal lobe ischemia or periventricular edema. It has not been reported in benign intracranial hypertension (BIH). We postulate that the FIRDA in this case was due to the circulatory "steal" effect of the AVM, and not to the intracranial hypertension. Five percent of patients with dural AVM's present with a picture consistent with BIH. We recommend a diligent search for additional pathology if FIRDA is seen in association with presumed BIH.