Rhythmic heart beat artefacts mimicking an ictal EEG pattern with abundant interictal epileptiform activity in both mother and child.

We present the EEG findings in a two-year-old girl with cryptogenic localisation-related epilepsy. The electroencephalogram showed fronto-temporal spike-wave discharges. In addition, the EEG repeatedly showed activity at different electrodes consisting of spikes with varying amplitude, rhythmicity and frequency, mimicking polyspikes. Both low- and high-amplitude spikes were generated from the same electrodes, however, only the low-amplitude spikes coincided with features of the child's electrocardiogram. Video monitoring showed the child's head resting on her mother's chest. This spike pattern was shown to be a heart beat artefact originating from the mother, as implied by the rhythmicity and the shift to other electrodes by moving the child's head, causing electrocardiogram artefacts on the posterior electrodes. This case study underscores the importance of routine use of simultaneous electroencephalogram and video monitoring. [Published with video sequences].