Rationale:
Approximately 30% of epilepsy patients remain refractory to medical therapy.
1 In the presurgical evaluation invasive procedures such as stereo-electroencephalography remain necessary especially with MRI-negative epilepsy.
2 SEEG consists of stereotactic implantation of depth electrodes to identify the location of the epileptogenic area and pathways of propagation. Radiofrequency thermocoagulation (RF-TC) can be applied during SEEG investigation.
Seizure outcomes following SEEG guided RF‐TC remain variable, in the meta-analysis by Bourdillon et al.4 The seizure‐free rate one year after RF‐TC varied from 4% to 71%, with a pooled seizure free rate of 23% the lowest rate was in patients with normal MRI.
Methods:
The patient is a 32-year-old male, seizure semiology consists in focal aware, focal unaware, and focal to bilateral tonic clonic seizures. The aura consists of a rising epigastric sensation and anxiety. Focal to bilateral tonic clonic seizures commence as focal aware or impaired awareness seizures. He would often have auditory symptoms before generalization.
Long term EEG showed frequent repetitive bursts of low-amplitude repetitive spikes and bursts of low-amplitude fast activity seen maximally over the right mid to hemisphere and decelerated to a 3 Hz rhythmic discharge.
MRI head 3 T is normal, electrical source imaging with HD-EEG and MEG revealed a source in the right lateral mid to posterior temporal neocortex
Results:
A total of 13 electrodes were implanted and 11 seizures were recorded. The first EEG changes comprised simultaneously in the electrodes Rla 1-4, RIp 1-7, RHe 3-12, RIm 4-8 and late propagation to the temporobasal and mesiotemporal area.
Stimulation study at 50 Hz was conducted with segments of the habitual seizures and parts of the auras were recorded in the electrodes Rla, RIp, RHe, and RIm.
RF-TC was conducted with two methods: Axial coagulation (along an electrode) and Cross-Coagulation (between electrodes).
The RF lesions were done axial in the electrodes Rim 1-8, Rip 1-7 and RHe 5-12 (20 lesions) and cross between RIm and RIp , RIm and RHe (12 lesions) with 32 RF lesions in total.
MRI head reported thermocoagulation cavity in the right superior temporal gyrus and posteroinferior insula.
After 20 months of follow up, the patient presents no auras and no seizures (Engel class Ia).
Conclusions:
Despite the increasing studies reporting results of SEEG RF‐TC the efficacy of this approach remains unclear.
3(3)
The MRI negative are the less likely to present seizure freedom(3). In the series of Cossu et al(6) 89 patients treated with RF-TC 46 were MRI negative and five were seizure free after one year. A series of Oliveira et al(7) 31 MRI negative patients that underwent RF-TC in a mean follow up of 30,9 months eight were seizure free accounting for 20% of the patients.
Despite the fact that they have the lowest percentage of seizure freedom, RF-TC is a less invasive approach that uses electrodes that are already implanted and has a very low risk of complications.
We hypothesize that in our patient the success could be because of the number of electrodes coagulated, accounted for 32 lesions that makes a considerable size lesion that remains visible in the MRI after one year of follow up.
Funding: None