Rationale:
In the presurgical evaluation of patients with therapy resistant epilepsy, the recording of a spontaneous habitual seizure (SHS) during stereo-electroencephalography (SEEG) provides crucial information to identify the epileptogenic zone. Although the interictal activity as well as seizures captured during stimulation provides useful information, a surgical decision made solely with those results has limited value. Occasionally, some patients do not experience SHS during an SEEG study, which limits recommendations for epilepsy surgery. We sought to determine predicting factors of patients who did not have a SHS during SEEG and to analyze the clinical outcomes for this set of patients.
Method:
We conducted a retrospective analysis of all patients with therapy resistant epilepsy that underwent SEEG between 2013 and 2018.
Results:
Of the 148 patients who underwent SEEG during this period, 11 (7.4%) did not experience any clinical seizures or events, while 137 experienced at least one typical seizure during admission. The mean age in these 11 patients was 35.5 years and 55% (N=6) were males. The median antiseizure medication (ASM) was three at the time of the SEEG implantation. 55% (N=6) had a lesion on MRI and 33% (N=3) had previous epilepsy surgery. Electrographic seizures were seen in four patients in the non-SHS group (37%). During cortical stimulation, three patients had their typical seizure reproduced and these three patients underwent resective surgery. No significant differences were found between SHS and non-SHS groups in terms of demographic distribution, lesional/non-lesional epilepsy ratio, pre-SEEG seizure frequency, number of ASMs used, presence of electrographic seizures or in the postoperative seizure outcome in those who underwent resective surgery. Statistical differences were found in the average number of electrodes implanted (7.4 in the non-SHS group vs. 10.4), days in EMU (21.8 vs. 13.0 days) and the number of patients that underwent resective surgery following SEEG (36.4% vs 61.3%), respectively. None of the patients in the non-SHS group was offered neurostimulation procedures (VNS, DBS or RNS).
Conclusion:
The absence of seizures during SEEG is a significant problem that can prolong EMU admission and ultimately obviate resective surgery. We were unable to identify any factors that predicted a lack of seizures during SEEG. Resective surgery was only offered in cases where the stimulation study replicated seizures.More data is required to be able to identify factors that predict which patients will fail to develop seizures during their SEEG admission.
Funding:
:The study was self-funded
FIGURES
Figure 1