Neuroradiological correlates of frontally predominant intermittent rhythmic delta activity (FIRDA)

A correlative, retrospective review of 80 consecutive cases of EEG FIRDA was performed with regard to the neuroradiological findings: 62 of the 80 patients had had CAT scan evaluations. Of the 61 patients with structural pathology, 53 had CAT scans which were abnormal in 40 (76%); of the 19 patients with 'non-structural' (mostly metabolic) brain lesions, 10 had normal CAT scans. In the structural group with normal CAT scans, the presence of pathology was demonstrated by arteriography (5 cases), radionuclide cysternography (1 case), brain scan (1 case), or pathological examination. Patients with 'non-structural' FIRDA had a significantly higher probability of being in an altered state of consciousness and of having abnormal background activity in their EEG. Focal EEG abnormalities are more frequently associated with structural lesions and FIRDA. If FIRDA is present on the EEG, further neuroradiological studies should be considered, especially with other electroclinical information suggests a non-metabolic substrate.