Rationale: Following the identification of the epileptogenic zone, surgical resection is a highly effective treatment option and the gold standard of treatment for pharmacoresistant temporal lobe epilepsy (TLE). This study aimed to identify determinants for seizure freedom following TLE surgery, with a long follow-up period.
Methods: Data from
213 consecutive adult patients with TLE who underwent temporal lobe resection at a tertiary epilepsy center between 2004 and 2022 were retrospectively analyzed. Exclusion criteria were: less than 12 months postoperative follow-up (n=31), coexisting psychogenic non-epileptic seizures (n=2), previous epilepsy surgery (n=18) and high-grade tumors (n=2). 26% of patients underwent invasive EEG, 46% had FDG-PET, 42% had an ictal SPECT. Patients underwent individualized temporal resections of variable extent.
Results: 160 patients were analyzed (57% female; mean age 40 years, range 18-73). At the last follow up (mean 7.1 years, range 1-19), 78% of patients (n=125) were seizure-free (Engel I), 8% (n=12) were nearly seizure-free (Engel II). A worthwhile improvement (Engel III) was seen in 4% (n=7), and 10% (n=16) experienced no worthwhile improvement (Engel IV).
Disease duration (mean 18.6 years; p=0.91), age at surgery (p=0.31), seizure frequency (mean 14.7/month; p=0.15), presence of GTCS (n=112; p=0.87), presence of a visible MRI lesion (n=138; p=0.19), and lateralization (n=93 left TLE; p=0.17) did not significantly influence seizure freedom rates.
Good outcome (Engel I) was achieved in 93% of patients with gliosis (n=14), in 80% with hippocampal sclerosis (n=41), 79% with dual pathology (n=34), 79% with mild malformation of cortical development (mMCD) (n=19), 78% with low-grade gliomas (n=23), 75% with encephalitis (n=4), 56% with focal cortical dysplasia (FCD) (n=9), 67% mMCD with oligodendroglial hyperplasia (MOGHE) (n=3), and 50% with nonspecific pathology (n=2).
A lower percentage of contralateral interictal epileptiform discharges (IEDs) was significantly associated with better seizure-free outcome. Patients with less than 5% contralateral IEDs had an 82% chance for Engel I outcome, those with >5% only 57% (p=0.03, r=0.17). Similarly, patients with < 35% extratemporal IED had am Engel I outcome in 81%, those with >35% extratemporal IED only in 50% respectively (p=0.05).
Conclusions: After a mean follow up of 7.1 years, 78% of patients were seizure free.
Contrary to some previous reports, we did not see significant outcome differences between certain patient subgroups or etiologies. A comprehensive presurgical evaluation with a high utilization of invasive EEG and complementary neuroimaging seems to be able to sufficiently identify and delineate even less well-defined pathologies, such as mMCD, or dual pathologies.
Individually tailored resection plans, based on the multimodal evaluation may also contribute to the good outcome across most subgroups.
The presence of contralateral IED, but also ipsilateral extratemporal IED seem to reflect a more widespread epileptogenic network, associated with a less favorable outcome. Detailed quantitative analysis of IEDs may benefit individual outcome prediction.
Funding: None