Abstracts

Rationale: Ictal manual automatisms are a common feature in temporal lobe epilepsy and occur less frequently in patients with extratemporal epilepsy. Despite decades of invasive epilepsy surgery evaluation, there are only few reports on automatisms elicited by electrical stimulation of the brain excluding stimulation associated seizures with automatisms. Areas involved in the generation of ictal automatisms are currently not well defined and their pathophysiological mechanism is controversial.

Methods: Between 01/2020 and 05/2021 24 patients considered for epilepsy surgery underwent invasive evaluation including electrical stimulation for screening of automatisms. A total of 1862 electrode contacts were stimulated with currents ranging from 1 to 15mA. If afterdischarges occurred in association with the automatisms, the response would not be included in this study. The exact position of each electrode contact was determined by superimposing CT scans after electrode implantation on previously acquired individual MRI scans in all patients.

Results: We identified five patients with temporal (n=2), frontal (n=2) and frontal and temporal (n=1) epilepsies aged 14 – 51 years, in whom we could consistently elicit manual automatisms or stereotyped complex motor sequences of the upper limbs by electrical stimulation of a small area (two electrode contacts) in the anterior third of the cingulate sulcus. Electrical currents between 4 and 15mA were required to trigger the automatisms. These ten electrode contacts were located in the white matter underneath the anterior third of the cingulum and in the adjacent part of the superior frontal gyrus, approximately 1.5cm from the midline. The automatisms occurred exclusively on the contralateral upper limbs in all patients and comprised fumbling, rotatory movements of the hand, flexing of the arm and the hand towards the head and neck. In two patients, a negative motor response of the ipsilateral upper limb occurred simultaneously. No patient showed the elicited automatisms as part of their habitual seizures. The triggering electrode contacts were not part of the patients’ epileptogenic zone.

Conclusions: Our five patients show that electrical stimulation of a very circumscribed area at the boundary between the anterior cingulum and the superior frontal gyrus can consistently cause automatisms of the contralateral upper limb. An interaction between the limbic system and the supplementary motor system may play a role in the generation of these automatisms. Since these electrodes were in the white matter, future DTI-MRI studies should define the ortho- and antidromically connected brain regions which were activated by the electrical stimulation in order to further our understanding of the generation of ictal automatisms.

Funding: Please list any funding that was received in support of this abstract.: No funding.