Dr Nitin TandonNitin Tandon, MD
Stereoelectroencephalography (SEEG) has been shown to be capable of altering the landscape of the management of medically intractable epilepsy, according to the findings of a study.1

In 239 patients undergoing 260 consecutive intracranial evaluations of intractable epilepsy, the method was shown to be quicker, less painful, and less morbid for patients in comparison with subdural electrode (SDE) implantations. All told, better outcomes, defined by Engel class I or II status, were revealed in 76% (n = 57) of patients evaluated with SEEG compared to 54.6% (n = 59) of patients assessed with SD (P = .003).

When considering not just those undergoing definitive procedures, but all patients, Engel class I or II status was achieved by a similar number of SEEG patients (57 of 121; 47.1%) compared with SDE patients (59 of 139; 42.4%) at 1 year (P = .45).

“Stereoelectroencephalography has distinctly better procedural morbidities and, in selected cases, may have better outcomes than subdural grid electrodes, features that should influence decision making and lower the barrier to candidacy for resection or ablation among patients with intractable epilepsy,” study author Nitin Tandon, MD, and colleagues, wrote.

Data analysis revealed that survivor functions for seizure freedom (Engel class I) at 1 year was achieved by 58.4% of patients with SEEG and 45.7% for SDE cases. After 2 years, those functions were 56.6% for SEEG cases and 43.6% for SDE cases (95% CI, 1.0844 to 2.4719; P = .03). 

Tandon, a professor of neurosurgery at McGovern Medical School, told the JAMA Network podcast that the lower seizure outcomes for those treated with SEEG “was a surprising finding” in the study.2

“We were not expecting [it]. We knew going into this analysis that we would expect to see a low morbidity, a lower rate of blood transfusions, and a much lower risk of complications,” he told JAMA. “We were not expecting that there would be a difference in outcome, and not only did we find a difference in outcome that was very robust, but we also found that this outcome was much better despite the fact that a sizably larger—70%—of the SEEG population had no well-defined lesions on their MRI scans.”

In total, 99 patients evaluated with SDE were lesional compared to 53 (43.8%) patients assessed with SEEG (P < .001). Due to  differences in the proportion of cases in the 2 cohorts, Tandon and  colleagues executed subgroup analyses based on the presence of imaging abnormalities.

Compared with the lesional SDE group, a significantly greater proportion of the lesional SEEG cohort had good outcomes (Engel classes I and II) at 6 months, with this achieved by 36 of 40 (90%) patients in the SEEG group compared to 64 of 87 (73.6%) in the SDE group (P = .04). At the 1-year mark, this was the case for 30 of 36 (83.3%) patients in the SEEG group compared to 50 of 79 (63.3%) patients in the SDE cohort (P = .03).

Tandon and colleagues noted that this “distinction was more significant for non-lesional cases.” Good were outcomes observed at 6 months in 37 of 47 (78.7%) patients evaluated with SEEG compared with 13 of 28 (46.4%) patients in the SDE group (P = .004), and at 12 months in 27 of 39 (69.2%) patients compared with 9 of 26 (34.6%) patients, respectively (P = .006).

A larger number of SDE cases underwent consequent resection or ablation surgery (n = 127; 91.4%) compared to the SEEG cases (n = 90; 74.4%; P <.001). Of the last 50 cases included of each type, 48 SDE (96%) and 36 SEEG (72%) underwent 1 of the 2 procedures. Notably, 12 of the SDE cases (8.6%) and 17 of the SEEG cases (14.0%) were determined to not be candidates for resection or ablation post-evaluation. Of the aforementioned 50 cases, this was the case for 8 (4.0%) SDE cases and 16 (8.0%) SEEG.

“I say this to patients in the office when I see them before surgery, explicitly, that it’s best to think of these surgeries as a test. It’s still invasive, but it’s a test,” Tandon told JAMA. “It’s a test to see if they’re candidacy for resection, or for laser ablation, or for neuromodulation, and to determine the optimal targets and the zones around those targets that need to be addressed.”

Tandon highlighted that after the procedure is complete, SEEG implantation allows physicians time—up to several days or weeks—to assess the collected data and discuss with the patient in order to get them familiar with scenarios that they may encounter prior to proceeding.
REFERENCES
1. Tandon N, Tong BA, Friedman ER, et al. Analysis of morbidity and outcomes associated with use of subdural grids vs stereoelectroencephalography in patients with intractable epilepsy. JAMA Neurol. Published online March 4, 2019. doi:10.1001/jamaneurol.2019.0098. Accessed March 6, 2019.
2. Benjamin J. Morbidity and outcomes of subdural grids vs stereoelectroencephalography in intractable epilepsy. JAMA Network Podcast. edhub.ama-assn.org/jn-learning/audio-player/17329281. Published March 4, 2019. Accessed March 6, 2019.