Increasing Surgical Options for Epilepsy Patients
A baby is born with cortical dysplasia and has several seizures a day. At three months old, he undergoes surgery at Massachusetts General Hospital (MGH) and is now seizure-free and developing normally.
A 32-year-old woman with recurrent episodes of altered consciousness with asystole is evaluated by cardiologists who want to implant a pacemaker. Diagnostic testing at the MGH Epilepsy Center reveals a benign tumor close to the insula, the brain region that controls heart function. Following surgical resection of the tumor, she no longer has seizures or “near-death” episodes. “It wasn’t a cardiac problem, it was a neurological problem,” says Emad Nader Eskandar, MD, Director of Stereotactic and Functional Neurosurgery, MGH Department of Neurosurgery. (See more details in an article about the case published in the June 2013 issue of the New England Journal of Medicine: http://www.nejm.org/doi/full/10.1056/NEJMcpc1215969)
Intensive Pre-Surgical Evaluation
Advances in pre-surgical evaluation methods have made it possible to more accurately identify the epileptogenic region and minimize risk of injury to the functional cortex, enabling more epilepsy patients to receive surgical treatment. “The challenge is precisely delineating the seizure focus to achieve seizure freedom while preserving neurological function,” says Dr. Eskandar.
The MGH Epilepsy Service uses a variety of imaging modalities and EEG monitoring (the most important aspect of pre-surgical evaluation) to evaluate surgical candidates. It is one of a few epilepsy centers to offer high-resolution (7 tesla) MRI, which generates exceptionally detailed images, and magnetoencephalography (MEG), which “maps electrical activity in greater detail and is useful for detecting areas of abnormal activity and assessing which parts of the brain are active during important functions,” says Dr. Eskandar.
About half of patients are evaluated using imaging modalities and noninvasive EEG recordings (with video). When those methods aren’t adequate to determine the seizure focus and brain functions, intracranial electrodes are surgically implanted. In addition to depth and subdural electrodes, foramen ovale electrodes are a less invasive option and are used to record electrical activity of themedial part of the temporal lobe, the hippocampus and amygdala, that are often implicated in epilepsy. “Our goal is to precisely identify the seizure focus so that patients can undergo surgery safely and hopefully become seizure free,” says Dr. Eskandar.
For patients who cannot undergo a resection, less-invasive surgical approaches are increasingly being used (see section below).
Comprehensive Surgical Care Provided by a Multidisciplinary Team
The MGH approach to epilepsy surgery is multidisciplinary: the surgical team can include epileptologists, neurosurgeons, neuroradiologists, neuropsychiatrists and anesthesiologists. “By working together, we can achieve a level of excellence impossible without collaboration,” says Dr. Eskandar.
MGH neurosurgeons perform all types of epilepsy surgery – including lesionectomy, temporal lobe and extra-temporal resections, hemispherectomy and corpus callosotomy – in both adult and pediatric patients. “Patients with a clearly localized seizure focus in an area that we can resect have a very good chance of becoming seizure free or nearly seizure free,” says Dr. Eskandar. Temporal lobe resection, the most common epilepsy surgery procedure, provides good to excellent results in 75 to 85 percent of cases.
The new MGH Lunder Building features intraoperative MRI and CT imaging in its dedicated neurosurgical operating rooms, providing real-time information and allowing surgeons to monitor the patient’s brain at any time during the procedure without moving the patient. “Intraoperative imaging is extremely helpful in ensuring that we are in the correct area of the brain and do not damage critical tissue,” says Dr. Eskandar.
Neurostimulation Devices Provide a Less Invasive Alternative
For patients who are not candidates for surgery, implanted neurostimulation devices are becoming more effective alternatives. “Over the past decade, there’s been great interest in developing devices to treat epilepsy,” says Andrew J. Cole, MD, Director of the MGH Epilepsy Service.
Vagus nerve stimulation (VNS) is an option for patients with intractable focal or generalized seizures; the VNS device sends electrical signals to the vagus nerve at varying intervals, depending on the patient’s seizure response. At MGH, VNS has proved most effective in treating pediatric patients, decreasing seizure frequency 30 to 50 percent.
MGH was a clinical trial site for a new neurostimulation device, the NeuroPace® System, which recently received FDA approval. Patients were eager to participate in the clinical trial and try this new approach. NeuroPace® features a “smart” device that can treat partial onset seizures by detecting specific types of electrical activity in the area of seizure focus and delivering small amounts of electrical stimulation to reduce seizure frequency. “It is an attractive option for many patients that are not surgical candidates,” says Dr. Eskandar.
Future Directions in Surgical Treatment
In the coming years, less invasive surgical approaches, such as neurostimulation devices and ablation, will play an increasing role in epilepsy treatment. Stereotactic laser and radiation ablation have received greater attention in recent years as minimally invasive means of destroying seizure foci in inoperable brain regions.
In addition, ongoing advances in neuroimaging “will allow for detection of lesions that we can’t even see today. They will make surgery safer and allow more patients to get treatment,” says Dr. Eskandar.