A case of clinical worsening after stereo-electroencephalographic-guided radiofrequency thermocoagulation in a patient with polymicrogyria

Abstract

Radiofrequency thermocoagulation (RF-TC) is a wide-used procedure for drug-resistant epilepsy. The technique is considered safe with an overall risk of 1.1% of permanent complications, mainly focal neurological deficits. We report the case of a patient with drug-resistant epilepsy who complained of immediate seizure worsening and an unexpected event seven months following RF-TC. A 35-year-old male with drug-resistant epilepsy from the age of 18 years underwent stereoelectroencephalography (SEEG) implantation for a right peri-silvian polymicrogyria. He was excluded from surgery due to extent of the epileptogenic zone and the risk of visual field deficits. RF-TC was attempted to ablate the most epileptogenic zone identified by SEEG. After RF-TC, the patient reported an increase in seizure severity/frequency and experienced episodes of postictal psychosis. Off-label cannabidiol treatment led to improved seizure control and resolution of postictal psychosis. Patients with polymicrogyria (PwP) may present with a disruption of normal anatomy and the co-existence between epileptogenic zone and eloquent cortex within the malformation. RF-TC should be considered in PwP when they are excluded from surgery for prognostic and palliative purposes. However, given the complex interplay between pathological and electrophysiological networks in these patients, the remote possibility of clinical exacerbation after RF-TC should also be taken into account.

Keywords: CBD, Cannabidiol; Cannabidiol; EEG, electroencephalography; EZ, Epileptogenic Zone; Epilepsy; FDG-PET, Fluorodeoxyglucose-Positron Emission Tomography; Post-ictal psychosis; PwP, Patients with polymicrogyria; RF-TC, Radiofrequency thermocoagulation; Radiofrequency thermocoagulation; SEEG, stereo-electroencephalography; Stereo-EEG.

Fig. 1

Upper part: median PET cortical metabolism superimposed on 3D Freesurfer pial model shows abnormal right perisylvian gyration and hypometabolism compared to the left hemisphere (color palette coldtohot: blue, lower metabolism, red, higher metabolism). Bottom part: T1-weighted anatomical MRI superimposed with SEEG electrodes disclosed diffuse perisylvian polymicrogyria involving the right temporal, frontal and parietal cortex. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 2

A: implantation scheme on the 3D model. B: 30-seconds SEEG trace shows low-voltage fast activity over K 5–6 and P 3–4 preceding typical subjective sensation warning. C 120-second SEEG trace shows low voltage fast activity over K electrodes with a fast propagation over mesial temporal structures (B, C); after 2 s all temporal lobe and perisylvian area are involved in the discharge. D: MRI position of P internal contact (upper) and K internal contact (lower) where RF-TC were performed. SEEG contacts position. B2-3: para-hippocampal gyrus; B5-6: hippocampus head; B13-14: middle temporal gyrus; C3-4:hippocampus body; C11-12 = posterior middle temporal gyrus; Z2-3: fusiform gyrus; K2-3 5–6: lower precuneus; Y10-11: inferior parietal gyrus; U5-6: superior temporal gyrus; P3-4: higher precuneus; P11-12: inferior parietal gyrus; N6-7: post-central gyrus; S6-7: parietal operculum; L10-11: pre-central gyrus; M2-3: supplementary motor area; R2-3: posterior short insular gyrus; X3-4: frontal operculum; F9-10: middle frontal gyrus.