Less-invasive procedure helps surgeons pinpoint epilepsy surgical candidates

Summary: A minimally invasive procedure to determine whether patients with drug-resistant epilepsy are candidates for brain surgery is safer, more efficient, and leads to better outcomes than the traditional method, according to new research by The University of Texas Health Science Center at Houston (UTHealth).

Source: University of Texas Health Science Center at Houston

The study, published this week in JAMA Neurology, revealed that patients who had the minimally invasive evaluation procedure experienced fewer complications, and those who went on to have brain surgery were more likely to be seizure-free than patients who had the more invasive evaluation procedure.

“We expected the results to show patients who had the minimally invasive procedure to have a more favorable experience. But we also found those patients who had the new evaluation procedure, and then underwent surgery, had significantly more positive outcomes, which was quite surprising,” said lead author Nitin Tandon, MD, professor in the Vivian L. Smith Department of Neurosurgery at McGovern Medical School at UTHealth. “The findings give new hope to epilepsy patients who may previously have ruled out surgery for various reasons.”

The study reviewed 239 patients with medically intractable epilepsy who had a total of 260 procedures between 2004 and 2017 to locate the source of their seizures and determine their suitability for surgery. All procedures were performed by Tandon at Memorial Hermann-Texas Medical Center.

Two surgeons are shown in an operating room with a monitor in the foreground.
Photo of Nitin Tandon, MD, surgery planning for robotic stereoelectroencephalography (SEEG). Photo credit is Memorial Hermann

Of those 260 procedures, 139 cases involved traditional subdural electrode (SDE) implantation, which includes a large opening of the skull, known as a craniotomy. A sheet of electrodes is placed on the outside of the brain to pinpoint the seizure source before the skull closed back up for an observation period, which usually lasts around a week. When the electrodes are removed, any surgery to treat the seizures is done at the same time to avoid having a separate craniotomy.

Another 121 cases involved robotic stereoelectroencephalography (SEEG), where electrodes are implanted via fine probes, which results in minimal blood loss and less pain. The probes, thinner than raw spaghetti, are threaded inside the brain through small holes in the skull and patients undergo a similar observation period. Following the electrode removal, patients are typically discharged from hospital and, if they are candidates, will return in a few weeks for surgery.

Of the patients who underwent resection or laser ablation to remove the lesion causing their seizures, more than three-fourths (76 percent) of SEEG cases were either free of disabling seizures or had them rarely at the one-year mark, compared to just over half (55 percent) of SDE cases.

The minimally invasive technique also produced more favorable outcomes among patients with nonlesional epilepsy, for which surgery tends to be less successful. Nearly 7 of 10 of SEEG cases (69.2 percent) had good outcomes at the one-year mark compared to just over a third (34.6 percent) of SDE cases. A greater proportion of SEEG cases were nonlesional epilepsy – 56.2 percent, as opposed to 28.8 percent of SDE cases.

“This makes the case for SEEG even stronger. There are two main reasons why it can achieve better results. First, the technique does not constrain where the electrodes can be implanted, enabling us to study brain networks in a much more comprehensive fashion to pinpoint the seizure source,” Tandon said. “Second, it is best to think of the electrode placement as a test. The absence of time pressure, and the fact that no craniotomy has been done, allows us to pick out patients likely to do well, fully consider various options, and implement the most optimal plan.”

In addition, results showed SEEG patients required significantly less narcotic medication than SDE patients (356 and 201 milligrams of morphine equivalents, respectively). Results also showed the minimally invasive procedure was more than twice as fast, with the average time in surgery at just over two hours (121.3 minutes) for SEEG cases compared to more than five hours (308.2 minutes) for SDE cases.

“Epilepsy surgery in the U.S. is now at a better place, and we have been at the forefront of this journey, using robotics for minimally invasive techniques that are much better tolerated by patients and more likely to be effective,” Tandon said. “Around a third of epilepsy cases cannot be controlled by medication. These findings will give more of these patients the confidence to consider surgery, and help other institutions transition more quickly to providing this minimally invasive procedure.”

About this neuroscience research article

Tandon is director of the epilepsy surgery program at Mischer Neuroscience Institute Memorial Hermann-TMC.

UTHealth co-authors of the study were Brian Tong, a third-year medical student who Tandon said played a crucial role in data compilation and analysis; Elliott Friedman, MD, neuroradiologist; Jessica Johnson, BSN, epilepsy nurse practitioner; and neurologists Giridhar Kalamangalam, MD, DPhil; Stephen Thompson, MD; Gretchen Von Allmen, MD; Melissa Thomas, MD; Omotola Hope, MD; and Jeremy Slater, MD.

University of Texas Health Science Center at Houston
Media Contacts:
Victoria Tagg – University of Texas Health Science Center at Houston
Image Source:
Photo credit: Memorial Hermann

Original Research:
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 04, 2019. doi:10.1001/jamaneurol.2019.0098


Analysis of Morbidity and Outcomes Associated With Use of Subdural Grids vs Stereoelectroencephalography in Patients With Intractable Epilepsy

A major change has occurred in the evaluation of epilepsy with the availability of robotic stereoelectroencephalography (SEEG) for seizure localization. However, the comparative morbidity and outcomes of this minimally invasive procedure relative to traditional subdural electrode (SDE) implantation are unknown.

To perform a comparative analysis of the relative efficacy, procedural morbidity, and epilepsy outcomes consequent to SEEG and SDE in similar patient populations and performed by a single surgeon at 1 center.

Design, Setting and Participants
Overall, 239 patients with medically intractable epilepsy underwent 260 consecutive intracranial electroencephalographic procedures to localize their epilepsy. Procedures were performed from November 1, 2004, through June 30, 2017, and data were analyzed in June 2017 and August 2018.

Implantation of SDE using standard techniques vs SEEG using a stereotactic robot, followed by resection or laser ablation of the seizure focus.

Main Outcomes and Measures
Length of surgical procedure, surgical complications, opiate use, and seizure outcomes using the Engel Epilepsy Surgery Outcome Scale.

Of the 260 cases included in the study (54.6% female; mean [SD] age at evaluation, 30.3 [13.1] years), the SEEG (n = 121) and SDE (n = 139) groups were similar in age (mean [SD], 30.1 [12.2] vs 30.6 [13.8] years), sex (47.1% vs 43.9% male), numbers of failed anticonvulsants (mean [SD], 5.7 [2.5] vs 5.6 [2.5]), and duration of epilepsy (mean [SD], 16.4 [12.0] vs17.2 [12.1] years). A much greater proportion of SDE vs SEEG cases were lesional (99 [71.2%] vs 53 [43.8%]; P < .001). Seven symptomatic hemorrhagic sequelae (1 with permanent neurological deficit) and 3 infections occurred in the SDE cohort with no clinically relevant complications in the SEEG cohort, a marked difference in complication rates (P = .003). A greater proportion of SDE cases resulted in resection or ablation compared with SEEG cases (127 [91.4%] vs 90 [74.4%]; P < .001). Favorable epilepsy outcomes (Engel class I [free of disabling seizures] or II [rare disabling seizures]) were observed in 57 of 75 SEEG cases (76.0%) and 59 of 108 SDE cases (54.6%; P = .003) amongst patients undergoing resection or ablation, at 1 year. An analysis of only nonlesional cases revealed good outcomes in 27 of 39 cases (69.2%) vs 9 of 26 cases (34.6%) at 12 months in SEEG and SDE cohorts, respectively (P = .006). When considering all patients undergoing evaluation, not just those undergoing definitive procedures, favorable outcomes (Engel class I or II) for SEEG compared with SDE were similar (57 of 121 [47.1%] vs 59 of 139 [42.4%] at 1 year; P = .45).

Conclusions and Relevance
This direct comparison of large matched cohorts undergoing SEEG and SDE implantation reveals distinctly better procedural morbidity favoring SEEG. These modalities intrinsically evaluate somewhat different populations, with SEEG being more versatile and applicable to a range of scenarios, including nonlesional and bilateral cases, than SDE. The significantly favorable adverse effect profile of SEEG should factor into decision making when patients with pharmacoresistant epilepsy are considered for intracranial evaluations.

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