BY LIZETTE BORRELI
Traditionally, in the U.S., the evaluation of epilepsy in patients with intractable epilepsy requires a craniotomy to determine eligibility for surgery. Now, the availability of a minimally invasive procedure for seizure location challenges the principal approach for intracranial electroencephalographic (EEG) recordings.
In a retrospective analysis published online on March 4 in JAMA Neurology, the use of stereoelectroencephalography (SEEG) led to better outcomes in patients with intractable epilepsy, compared with subdural electrode (SDE) implantation at one year.
SDE implantation requires a craniotomy that allows for the precise functional mapping of brain surfaces in relation to epileptogenic zones. With SEEG, depth electrodes are inserted into the brain to specific targets without requiring a craniotomy. SEEG provides the advantage of improved coverage and precise targeting of deeper structures, the authors of the study wrote, making it better at localizing the epilepsy focus in many patients. SDE implantation is associated with an increased risk of hemorrhage, while SEEG has lower complication rates, they pointed out.
In a comparative analysis, a team of researchers evaluated the efficacy, procedural morbidity, and epilepsy outcomes of SEEG and SDE in 239 patients with medically intractable epilepsy who underwent 260 consecutive intracranial EEG procedures to localize their epilepsy. The procedures were performed by a single surgeon at one center from November 2004 to June 2017.
Researchers chose implant type and the locations for implant placement based on the epileptogenic zone implicated by noninvasive data.
The SDE group included 139 SDE implantations in 136 patients; three patients had two distinct SDE implantations and two hospital stays. Six of the 136 patients underwent additional SDE electrode placements during the same hospital stay. A total of 99 cases were lesional by MRI and 44 had hippocampal sclerosis of varying severity.
The SEEG group included 121 cases in 116 patients; five patients had two distinct SEEG implantations in two hospital stays. Six of the 116 patients underwent additional SEEG electrode placements performed during the same hospital stay. In this group, 53 cases were lesional and 22 had hippocampal sclerosis of varying degrees of severity.
The researchers noted a larger proportion of the SDE cases were lesional (p< .001).
The SEEG method was associated with quicker, less painful, and fewer morbid outcomes for patients, compared with SDE implantations.
A significantly greater proportion of SDE cases (91.4 percent) had resection or ablative surgery compared with those who were assessed using SEEG (74.4 percent). And study participants who had SEEG implantation had better outcomes at one year compared with those who underwent SDE implantation (76 percent versus 54.6 percent, p= .003). A total of 64 percent of SEEG cases were seizure free compared to 44.4 percent of SDE cases.
When considering all patients undergoing evaluation, not just those undergoing definitive procedures, favorable outcomes (Engel class I [free of disabling seizures] or II [rare disabling seizures]) for SEEG compared with SDE were similar at one year (47.1 percent vs 42.4 percent; p= .45).
Patients with SEEG and SDE achieved survivor functions for seizure freedom of 58.4 percent and 45.7 percent at year one, respectively.
After year two, 56.6 percent of the SEEG group and 43.6 percent of the SDE achieved these functions.
The study "reveals greater efficacy in seizure localization and therapy of SEEG compared with that of SDE, the current criterion standard," the researchers, led by Nitin Tandon, MD, a professor of neurosurgery at McGovern Medical School, wrote.
They added: "These features of the SEEG method should lower the barrier for surgical candidacy in intractable epilepsy."
Study limitations ranged from the retrospective nature of the analysis to the vastly different complication rates.
Dr. Tandon did not report any relevant conflicts of interest.
LINK UP FOR MORE INFORMATION:
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 2019; Epub 2019 Mar 4.