Abstracts

Rationale:
laser interstitial thermal therapy (LITT) is a recent method of selective amygdalohippocampectomy in patients with refractory mesial temporal lobe epilepsy. However, seizures sometimes relapse following this surgery, which often leads to a second surgery, in most cases the traditional anterior temporal lobectomy. In this study we evaluate the outcome of LITT, and investigate whether the clinical and scalp electroencephalogram (EEG) characteristics of patients are helpful in identifying those who benefit most from LITT.
Method:
14 patients with refractory focal epilepsy who had undergone mesial temporal laser ablation were included in a retrospective cohort study. The primary outcome was seizure freedom based on the Engel outcome classification. Engel outcome class I (no disabling seizures) was considered the favorable outcome versus Engel class II, III, or IV that was considered the unfavorable outcome. We evaluated the clinical and diagnostic workup including ictal and interictal scalp EEG findings for the two groups with favorable and unfavorable outcomes.  The scalp EEG analysis was performed on the last epilepsy monitoring unit (EMU) admission prior to the LITT with a 6-hour sleep sample from the first night of that admission chosen for the interictal analysis.
Results:
Table 1 summarizes the clinical information for the patients, diagnostic workups and seizure outcomes. The average follow-up time was 12 months (range 7-22 months). The Engel classification outcome was class I, II, and IV for 6/14, 5/14 and 3/14 patients respectively. We did not find any statistically significant correlation between the outcome and clinical features including age at epilepsy onset, age at LITT, the gap between the epilepsy diagnosis and the surgery, and reported seizure frequency prior to LITT. In 7 out of the 11 patients who had one or more seizures following the LITT, the breakthrough seizures were linked to a wean or change in their antiepileptic drug regimen. Table 2 depicts the findings on the scalp EEGs. The amplitude and field extension of the main interictal epileptiform discharges (IED) did not differ between the two groups. Although the number of IEDs was higher in the patients with favorable outcome (mean (SD) of 255(333) versus 13(14), this difference was not significant (ANOVA, p 0.2). The ictal scalp EEG analysis during the EMU admission also did not show any significant difference between the groups in terms of the seizure duration and the number of seizures recorded. The individualized electrographic ictal onset patterns and ictal onset fields are listed in table 2.
Conclusion:
There was no significant association between the LITT outcome and the clinical and scalp EEG (ictal and interictal) findings in this study. Sample size is a major limitation. A majority of the seizure relapses occurred in the setting of a drug-taper or other changes in the antiepileptic medications.
Funding:
:none