Neurological picture. Focal botulinum toxin injections lead to rapid resolution of myogenic artefact during EEG monitoring.

A 40 year old man was admitted to the EEG monitoring unit for localization of epileptic focus and changes in medication regimen. The patient had undergone left frontal lobe resection during childhood for unknown pathology (Fig.1 A). Subsequently he developed secondary epilepsy characterized by nocturnal complex partial seizures with occasional secondary generalization. During the first two days of monitoring, a persistent myogenic artifact was seen localized to the T3 EEG electrode (Fig. 1 C). The artifact prevented localization of the patient’s clinical seizure during monitoring. We attributed the artifact to excessive muscle activity, as electrode lead replacement and repositioning did not resolve the artifact. The persistent muscle activity in the left temporalis was likely due to surgical-induced muscle damage (Fig.1 B). On the third monitoring day, a total of 80 units of botulinum toxin type A (BTX-A) were injected in the temporalis muscle, at four locations around the T3 electrode. The artifact disappeared completely within three days, demonstrating F7 interictal discharges (Fig.1 D) and the focal onset of ictal activity at F7-T3 (Fig.1 E). No BTX-A-related side effects were reported by the patient.