Adult Epilepsy Surgical Options
Epilepsy remains one of the most common neurologic disorders affecting both adults and children alike, and over two million individuals in the United States have this disease. Approximately 30% of patients with epilepsy are considered "medically intractable" meaning that they continue to have seizures despite medical therapy. It is in this group of patients that seizures have the most significant impact on quality of life including relationships with family, friends and co-workers, and the ability to work and to drive. It is estimated that as many as half of these patients with medically intractable epilepsy would benefit from a diagnostic or therapeutic surgical procedure.
"Medically intractable" patients by definition have failed at least two antiepileptic medications, but patients have often been trialed on multiple medications for an unduly long period of time. The chance of being seizure free after failing two appropriate seizure medications is extremely low. Severe medication side effects may also be an indication for surgery. In addition, anyone with tumor, vascular malformation or other brain lesion that is causing seizures should be evaluated by an epilepsy surgeon. To determine if a patient is a candidate for epilepsy surgery, an extensive evaluation is undertaken, including video-EEG telemetry, anatomical (MRI) and functional (positron emission tomography (PET) or single photon emission computerized tomography (SPECT) imaging) and neuropsychological testing. This initial, non-invasive “Phase I” evaluation provides a comprehensive overview of the seizure syndrome.
The majority of surgery patients require no further monitoring and go on directly to surgery. The type of surgery is based on the epileptic syndrome, imaging and electrophysiological findings. When there is a lack of concordance of this initial evaluative data, meaning that the exact origin of the seizures is still not clear, or if there is concern for the proximity of the seizure focus to eloquent or functionally important areas of the brain, we recommend that the patient undergo invasive intracranial monitoring, called intracranial-EEG, or electrocorticography (ECoG).
Intracranial monitoring requires the surgical implantation of EEG electrodes in order to better lateralize and localize the seizure focus. Electrodes placed on the brain surface and directly in the brain can be used to map seizure activity and can also be stimulated in order to identify important functional areas. These data are reviewed by the comprehensive epilepsy board, and a recommendation is made for surgery based on these results. In rare cases, intracranial monitoring does not reveal the location of a single seizure focus, and further surgery is not recommended.
Surgical intervention typically consists of a resective procedure, which is most likely to result in a cure since the goal is to excise the seizure focus itself. The most common type of resective surgery is an anterior temporal lobectomy. Outcomes following resective surgery for the treatment of epilepsy have markedly improved over the last few decades. For patients with temporal lobe epilepsy, it is now widely accepted that surgery is superior to prolonged medical therapy, following the publication of the results of a randomized clinical trial in 2001. Frequently with this type of surgery, the proportion of properly selected patients who are seizure free after surgery can be above 70%. While the other types of resective surgery are less likely to have a seizure free outcome, the numbers are proportionately better than medical therapy alone. Seizure free outcomes range from 30- 70% for extra temporal lobe epilepsy syndromes.
Many patients worry about the effect of resective surgery on their mind, and wonder if they will be the same person after surgery. Although there may be subtle changes depending on the specific brain area involved, patients who achieve seizure freedom or a significant reduction in seizure frequency typically report that they feel better and can think more clearly after surgery compared to before.
In 2015, our epilepsy program became the first in western Pennsylvania to offer laser thermal ablation (LTA) as an alternative to surgical resection of a seizure focus. LTA is a procedure, like open resection, that may potentially cure a patient’s epilepsy. Rather than removing the seizure focus, however, the focus is ablated, using heat generated from laser light concentrated at the tip of a very thin probe. This minimally invasive procedure is performed through an incision about the width of a pencil’s eraser and many patients are discharged home as soon as the next day.
Disconnective procedures include multiple subpial transection (MST) and corpus callosotomy, and these surgeries are palliative rather than curative since they do not eliminate the seizures but interrupt the propagation of the seizures, limiting their generalization. Despite that, these procedures can improve the patient's quality of life by decreasing the frequency and intensity of the seizures. One other type of surgical procedure available is the implantation of a vagal nerve stimulator (VNS). The VNS was FDA approved in 1997 and has been found to significantly lessen the intensity and frequency of seizures greater than 50% in over half the patients that are treated. It is indicated for patients who are medically intractable and are not candidates for other types of surgical intervention. Easily implantable, it is similar to AED treatment in that the treatment is easily adjustable for both intensity and frequency. Unlike medications, it does not negatively impact on mental awareness and quality of life.
More recently in 2013, the FDA approved the use of responsive neurostimulation (RNS) in the treatment of adults with medically refractory partial onset seizures arising from one or two foci in the brain. RNS is a long-awaited treatment for a large group of patients who were previously determined not to be candidates for epilepsy surgery, such as patients with multifocal epilepsy or with seizures arising from areas of the brain that cannot be resected without causing a deficit. Although this surgery is not potentially curative like surgical resection, RNS has been shown to reduce seizure frequency by 44-53% in the 1-2 years after surgery, and some types of epilepsy are even more responsive. UPMC is the only center in western Pennsylvania that offers RNS.
The utility of epilepsy surgery is likely to continue to grow in the future, since the majority of patients who are potential surgical candidates have not been evaluated and treated. It is estimated that less than 3% of patients who would benefit from a surgery actually undergo treatment. With improved awareness of the benefits of surgery, improvements in neuroimaging to identify abnormal brain areas, and improved technologies for intervention, it is likely that surgery will be the option of choice for those patients who suffer the most from this disease. On the horizon, and presently an intense area of research, is the use of deep brain stimulation (DBS) to control seizures in patients who are not candidates for resective surgery. Although currently used as a treatment in Europe, DBS is not yet approved by the FDA for the treatment of intractable epilepsy in the United States, but will hopefully be available in the near future.
With improved awareness and ongoing technological advances, surgery for epilepsy is now well established and readily identified as the optimal therapy for many forms of intractable seizures.