Comprehensive Surgical Evaluations for Epilepsy
Pediatric epilepsy specialists at Cook Children's aim to efficiently complete complex surgical evaluations for patients and their families, allowing optimal treatment to begin quickly.
Epilepsy syndromes in children differ greatly from those that manifest in adulthood. While adult-onset epilepsy often results from symptomatic causes (i.e., head injury or stroke), pediatric epilepsy can present as isolated seizures that may not recur, as part of a syndrome that may ultimately remit, or as a result of genetic mutations or cerebral malformations that result in hard-to-control seizures.
“Seizures differ in children, especially during the first year of life when the brain is going through extensive development,” said Neurology Medical Director M. Scott Perry, M.D., an epileptologist at Cook Children's. “Every member of our group has specialized training in pediatric epilepsy that allows them to accurately identify the seizure type and determine the best treatment options for each patient.”
Determining candidates for surgery
Most pediatric patients referred for surgical evaluation have been diagnosed with medically intractable epilepsy—the failure of two appropriately chosen and appropriately used anti-epileptic medications. The first step for clinicians in the Comprehensive Epilepsy Program at Cook Children's is to dig deep into the patients' medical histories to determine if their cases are truly intractable to treatment.
“Pseudo-intractability can occur when a patient has been treated with the wrong medication for his or her type of epilepsy,” said Dr. Perry. “Simply changing a patient's medication regimen to one which best treats his or her epilepsy type may result in significant improvement. Likewise, we often evaluate patients who have intractable spells, movement disorders, behavioral events or cardiac arrhythmia that can be misdiagnosed and treated as epileptic seizures. Once we have a thorough medical history and have determined the patient's seizures are intractable to treatment, we move to the next step in surgical evaluation—a video electroencephalogram [VEEG].”
The purpose of a VEEG is to capture several typical seizures for each patient. On average, it requires three to five days of video recording and monitoring, the VEEG helps clinicians identify seizure patterns and localize seizure onset as originating from a single spot—best for surgery— or from multiple locations. The features of a child's seizure—such as one arm moving before the other or eye deviation—can help indicate the seizure onset location in the brain.
“In our 10-bed Epilepsy Monitoring Unit [EMU], children can leave their beds or rooms while VEEG information is transmitted wirelessly,” said Dr. Perry. “The aim is to allow the children to act and play as they normally do while we gather the data necessary to treat their epilepsy.”
Anatomic structure of the brain
Dr. Perry and his colleagues use magnetic resonance imaging (MRI) to determine the anatomic structure of the brain as part of the surgical evaluation. Typical MRIs for new-onset seizures often have less detail, taking thick (5 millimeter) slices. For surgical evaluations, Cook Children's uses 3-Tesla MRI, with 1 millimeter slices to provide the superior anatomic definition needed for surgical evaluation and 3-D modeling.
“MRI will serve as the basis for co-registering all other imaging we do, thus the anatomic definition must be precise,” said Dr. Perry. “Another study we use is positron emission tomography [PET], which examines how the brain functions using metabolism of glucose. Places where seizures originate often are dysfunctional and do not metabolize glucose well and thus will not light up like other areas on the PET scan.”
Additional tests include the single-photon emission computed tomography (SPECT) scan that looks at brain perfusion. A nurse at the patient's bedside administers an isotope intravenously when the EEG technician records a seizure in progress. The isotope deposits in the area of the brain where maximum blood flow is present, which often corresponds to the region of seizure onset.
“We do the same test when a child is not having a seizure to compare the baseline brain perfusion and subtract the two images, leaving only the area of maximum abnormality,” Dr. Perry said. “Comparing again to the MRI, we can find malformations just a few millimeters in size.”
Eloquent cortex mapping without surgery
While stimulation of subdural-EEG electrodes is the gold standard to map eloquent brain function, magnetoencephalography (MEG) has the precision to map locations of eloquent cortex noninvasively. In addition, MEG records magnetic fields that are not altered by muscle, skin or skull (as occurs with typical EEG), and can provide more precise localization of the abnormal tissue that causes seizures.
“When evaluating a pediatric epilepsy patient for surgery, it is important to know where seizures are originating as well as the functions of the brain near the area of seizure onset,” said Dr. Perry. “We also can perform functional MRI to determine centers of language, motor, sensory and vision function. Once all imaging tests are complete, we build a 3-D model that is presented, along with the patient's history and VEEG, to our Epilepsy Case Conference—a group that includes epileptologist, neurosurgeons, neuropsychologists, radiologists, nurses, social workers and Child Life specialists. We discuss whether surgery would help the child, the benefits of surgery versus the risks, the likelihood of seizure reduction or freedom, and how the surgery should be performed. We then invite the family back to the clinic to discuss all the results and recommendations in detail with the epileptologist and neurosurgeon.”
Advancing epilepsy surgery with a minimalist approach
The Comprehensive Epilepsy Program at Cook Children's has provided the most advanced approaches to surgical treatment of epilepsy for many years. Most recently, the team has increasingly utilized minimally invasive techniques which provide comparable seizure free outcomes with lower risks. Cook Children's was the first North Texas facility to offer laser thermal ablation for the treatment of epilepsy. The integrated system of software, disposable components and reusable hardware used for planning and targeting is the only technology that enables minimally invasive neurosurgery under continuous MRI guidance, with superior visualization of the brain's tissue. We also offer stereo-electroencephalography, a procedure which allows for detailed monitoring from within the brain using depth electrodes placed with precision through robotic guidance. This method allows the team to map the region of brain responsible for seizure onset without requiring the patient to have a larger surgery to place grids or strips over the brain for monitoring. Finally, Daniel Hansen, M.D. has recently joined the neurosurgery service and provides options for endoscopic brain surgeries such as callosotomy and disconnection procedures which can achieve seizure free outcomes with much smaller incisions.
Collaborating to improve pediatric epilepsy surgery
The Pediatric Epilepsy Research Consortium (PERC) was founded in 2011 as a network of US Pediatric Epilepsy Centers dedicated to collaborative research into the diagnosis, evaluation, and treatment of pediatric epilepsy. M. Scott Perry M.D. leads the surgery subgroup of PERC and recently initiated a multicenter collaborative database collecting common data elements on every patient evaluated for epilepsy surgery, including epilepsy characteristics, components of evaluation, surgical procedures performed, and outcome. The combined epilepsy centers of PERC perform an enormous number of pediatric epilepsy surgeries in the US, yet individually they each perform evaluations and surgeries differently. The study currently includes 18 centers across the US and provides a unique opportunity to standardize common data elements captured for all patients evaluated for epilepsy surgery. From this data, there is potential to characterize the vast landscape of epilepsy surgery evaluation in the US, utilizing baseline data to match programs in a collaborative framework investigating the relative value of differing decision trees, approaches, surgical techniques and ultimately patient outcomes. Through this collaboration, the group hopes to expand the types of patients referred for epilepsy surgery, understand characteristics of patients unlikely to be helped by surgery, create standardized evaluation algorithms, and improve understanding of newly developed surgical procedures.