Temporal intermittent rhythmic theta activity (TIRTA): A marker of epileptogenicity?

Abstract

To describe a novel EEG rhythm, temporal intermittent rhythmic theta activity (TIRTA), and its potential association with epilepsy. We report TIRTA on scalp EEG in a series of 12 patients, all of whom were found to have epilepsy. The clinical and electroencephalographic characteristics of each patient were reviewed. In addition, features that may distinguish TIRTA from benign EEG patterns, including rhythmic temporal theta bursts of drowsiness (RTTBD), were identified. TIRTA was unilateral in all cases. For all patients, TIRTA was seen in the awake and drowsy states. Eight patients also had TIRTA observed during N2 sleep. The average frequency of TIRTA was 5.5Hz and the average duration of a train of TIRTA was 5.25s. In seven cases the morphology was notched in appearance. Temporal intermittent rhythmic delta activity (TIRDA) was seen in seven patients on the same side as TIRTA. Eleven patients also had ipsilateral temporal sharp waves. Abnormal MRI (6/12) and or PET (5/5) findings were ipsilateral to TIRTA. In this preliminary report we suggest that TIRTA may be a novel marker of potential epileptogenicity, possibly representing a higher frequency variant of TIRDA.