Epilepsy affects approximately one in 26 people during their lifetime, according to the Epilepsy Foundation. The condition can develop at any age, and while up to 70% of those diagnosed achieve seizure control through medication, a significant number continue to experience seizures despite trying multiple treatments.
For individuals whose seizures remain uncontrolled after two or more medications, presurgical evaluation may be recommended. Dr. Rohit Kuruvilla, a neurologist and epileptologist at Houston Methodist, explains that this process is considered when medications fail to adequately control symptoms. “There’s a diminishing return with each new medication, so if the seizures continue despite trying adequate doses of two different medications, that’s when we say we really need to do an epilepsy presurgical evaluation,” Dr. Kuruvilla says. “Basically, after that point is when we say, ‘OK, we’re not sure if the seizures are going to be controlled by medication.'”
The first phase of presurgical evaluation involves various tests aimed at identifying where in the brain the seizures originate. Patients are typically admitted to an epilepsy monitoring unit (EMU) for several days while their brain activity is recorded using electroencephalograms (EEGs). Medication doses may be lowered or stopped temporarily to provoke seizure activity under close supervision.
“The first step is capturing seizures while patients are on EEGs (electroencephalograms), recording their seizure and seeing the electrical activity associated with that,” Dr. Kuruvilla says. Additional diagnostic tools include magnetic resonance imaging (MRI), positron emission tomography (PET scans), and neuropsychology testing.
“An MRI can help us see if there’s some structural cause of their seizures, such as a lesion, tumor, abnormal blood vessels,” Dr. Kuruvilla notes. “A PET scan will basically look at the glucose metabolism or glucose uptake of different parts of the brain.” Neuropsychology testing evaluates memory, cognition, language skills and mood changes which can inform risk assessments for surgery.
“With neuropsychology testing, what we’re testing is various functions of the brain…to see if there’s one specific part that patients have difficulty with,” Dr. Kuruvilla says.
If results from these tests clearly indicate a single area responsible for seizures and suggest surgery would pose minimal risk, patients may be offered surgical options. However, further investigation might be necessary if test results do not align.
“For some individuals, not everything matches up…That’s when we have to proceed to what we call phase two evaluation,” Dr. Kuruvilla says. In this phase, intracranial depth electrodes—known as Stereo-EEG or SEEG—are surgically implanted in targeted brain areas for more precise monitoring.
“Prior to a SEEG, all the epileptologists, neurosurgeons, radiologists and the neuropsychologist help determine what areas that we should be looking into as potential sources for seizure,” he adds.
Not all evaluations result in surgery; sometimes multiple seizure origins or inconclusive findings rule out surgical intervention. In such cases, neuromodulation devices like vagal nerve stimulation (VNS), responsive neurostimulation (RNS), or deep brain stimulation (DBS) may offer alternative management strategies tailored to individual needs.
“Responsive neurostimulation requires that you have two places where the seizures are coming from…So you have more options after the stereo EEG,” Dr. Kuruvilla states.
Dr. Kuruvilla emphasizes that undergoing evaluation does not obligate patients to proceed with surgery: “We don’t want patients to say,’Oh if I do this I’m committing and I have to have brain surgery.’ It’s all about providing information in order for patients to make that decision for themselves.”
He adds that circumstances and preferences may change over time: “Sometimes patients will say,’I’m fine with holding off on epilepsy surgery,’and then two to three years down the line it’s still a problem that hasn’t resolved…Evaluation is information gathering to meet people where they’re at.”
