Abstracts

Rationale: Intermittent rhythmic delta activity on electroencephalography has been described from the frontal lobe (FIRDA), temporal lobe (TIRDA) and occipital lobe (OIRDA), each with different clinical implications (Watemberg et al., 2007). Central intermittent rhythmic delta activity (CIRDA) has not been specifically described in the literature. We performed a retrospective study to identify all patients undergoing EEG at Mayo Clinic from 1998 to 2009 reported as showing CIRDA. Methods: The electronic EEG report system at Mayo Clinic was queried to identify all EEG reports from 1998-2009 containing phrases indicating the presence of central intermittent rhythmic delta activity. Two cases were identified. Results: Case 1: A 30 year old right handed man presented for evaluation of a 25 year history of medically intractable partial seizures. The seizures were manifested by numbness starting at the right side of the neck and moving down the right upper extremity with associated jerking, sometimes propagating to the lower extremity. The seizures happened on a near nightly basis as he was falling asleep. CIRDA was frequently noted in the left centrotemporal derivations on interictal EEG (Figure 1). Continuous video-EEG monitoring (CV-EEG) captured 11 typical seizures, showing ictal EEG onset in the left centrotemporal region. MRI showed focal cortical thickening with non-enhancing T2 hyperintensity involving left parietal region consistent with focal cortical dysplasia. SISCOM showed a concordant hyperperfusion abnormality in the region of the dysplasia. Case 2: A 19 year old right handed man presented for medically intractable partial seizures since age 10. Seizures were manifested by a numb sensation then posturing and clonus of the right upper extremity. He often experienced post-ictal numbness and weakness of the right upper extremity lasting several minutes. These occurred multiple times a day. Left CIRDA was frequently seen on the interictal EEG (Figure 2). Fourteen typical seizures were recorded during CV-EEG. Ictal EEG showed rhythmic delta activity involving C3 and P3 at ictal onset during two seizures, but was indeterminate in 12. MRI and SISCOM were non-localizing. He ultimately underwent intracranial monitoring, stimulation mapping and an awake cortical resection which resulted in significant improvement in his seizures but a mild right upper extremity paresis. Conclusions: CIRDA was identified in two patients with intractable peri-Rolandic epilepsy. In one case, CIRDA was the most localizing abnormality in the pre-surgical work-up. In the other, the abnormality was concordant with other seizure-localizing data. CIRDA is a previously unnamed abnormality, which can be of localizing significance in patients with intractable peri-Rolandic epilepsy. 1. Watemberg N, Linder I, Dabby R, Blumkin K, Lerman-Sagie T. Epilepsia 2007; 48 (2) 330-4.