Surgical management of intractable seizures in children with epilepsy
One in 5 children with epilepsy has intractable seizures — defined as seizures that fail to respond to at least two appropriate anti-seizure medications. Surgery may be an option, but the path to that decision is complex.
At many institutions, the evaluation process can take months. At Mayo Clinic in Rochester, Minn., the surgical work-up may be done in one or two weeks and includes state-of-the-art functional brain mapping and seizure locus studies. If the child is documented to be a good surgical candidate and the family decides to proceed, surgery can be scheduled promptly.
Pediatric neurologists Elaine C. Wirrell, M.D., Lily C. Wong-Kisiel, M.D., and Katherine C. Nickels, M.D., and pediatric neurosurgeon Nicholas M. Wetjen, M.D., are experts in pediatric epilepsy. They are part of a multidisciplinary epilepsy team at Mayo Clinic that includes neuroradiologists and pediatric neuropsychologists.
As Dr. Wetjen explains: "The turnaround time here is quick because the care is not fragmented. There is immediate communication between team members. For example, a child with lesional epilepsy, such as a tumor or cavernous malformation, may come in on a Monday; have an evaluation that includes imaging, inpatient video-EEG monitoring with several recorded seizures, a SISCOM study, and neuropsychological evaluation by Thursday; and, in some cases, be in surgery by Friday. The pace is not always that fast, however. The typical range for most epilepsy patients is two to four weeks from initial consult to surgery."
Determining surgical candidacy
A pediatric epileptologist determines the frequency, severity and duration of seizures; whether the seizure onset is focal; and whether other conditions coexist. An MRI and scalp EEG help identify seizure etiology — such as cortical dysplasia, vascular malformations, arteriovenous malformation, tumor, trauma, stroke, rare metabolic conditions — and the presence (or absence) of a specific lesion and its location. A pediatric neuropsychologist then evaluates baseline cognitive function and helps establish lateralization of function.
Other tests to localize function may include functional MRI, PET or intracarotid sodium amobarbital (Wada) testing.
Inpatient pediatric EEG monitoring
Surgical candidates then undergo continuous EEG monitoring in the Eugenio Litta Children's Hospital, the 85-bed pediatric facility located within Mayo Clinic Hospital, Saint Marys Campus.
Four rooms, as well as the pediatric intensive care unit, are hardwired with ceiling cameras for behavioral observation and continuous EEG monitoring via external or intracranial EEG leads. Inpatient video-EEG monitoring is needed to record several seizures by EEG and video and to minimize risks of medication withdrawal, a process that is often required to record seizures. Monitoring may take from 24 hours to several days to record a sufficient number of seizures. Digital recording allows analysis of the EEG in a number of formats.
The video-EEG monitoring unit is specifically designed with children and families in mind. Child-life specialists not only provide toys, movies, computer games and other entertainment, but also help children and families through procedures that may be uncomfortable or unfamiliar. The single-patient rooms allow parents to stay with their child throughout the child's hospitalization.
The nurses and EEG technicians are, according to Dr. Wetjen, "remarkably attentive and good at what they do." Dr. Wirrell agrees, saying, "Our EEG technologists are superb and dedicated to their patients. I have not worked with one who is not devoted to the child."
Dr. Wirrell also notes that "unlike many centers that offer monitoring, we have the ability to monitor the patient every second of the day or night, so if the patient or family member is sleeping or the seizure is subtle, our technologists are still able to pick it up." Continuous monitoring by trained technicians not only increases safety, but also reduces the length of time a patient stays in the monitoring unit.
Localizing seizure focus through SISCOM
Pioneered at Mayo Clinic, SISCOM fuses the MRI image with the SPECT image, an innovation particularly useful in localizing seizure focus when seizures have a focal onset. A radioactive tracer is injected as soon as possible during a seizure. The first imaging study is performed shortly after the seizure; the second is done after 24 hours of seizure freedom. Dr. Wirrell notes, "SISCOM can be very helpful in pediatric epilepsy in which the MRI frequently does not show a clear structural abnormality."
If imaging studies establish a clear focus that is not in an area of critical brain function, the child may have surgery for resection. If the focus cannot be precisely localized or if it is in an area of eloquent cortex, intracranial electrodes may be implanted. Further seizures are then recorded to improve localization of seizure onset. Electrical stimulation can be performed to map important motor and language functions.
All the data for each case and the potential risks and benefits of surgery are reviewed at the epilepsy team conference where, according to Dr. Wirrell, "everyone provides input, and there is always plenty of time to discuss each patient fully." The attending neurologist then meets with the family to review the recommendations.
Multiple surgical options
Depending on the nature of the problem, the patient may have surgical resection or disconnection. Resections are generally conducted for tumors, vascular malformations and areas of cortical dysplasia. Cortical disconnection (corpus callosotomy) is used to treat drop attacks.
For patients whose epilepsy arises from an entire hemisphere, Dr. Wetjen and colleagues may perform a peri-insular hemispherotomy instead of the traditional hemispherectomy. Rather than removing the entire hemisphere, a hemispherotomy involves a much smaller resection monitored by image-guidance technology to disconnect the diseased hemisphere from the healthy one. As a result, there are fewer postoperative complications such as hydrocephalus and superficial siderosis.
Other options include:
- Endoscopic surgery in the rare case of a patient with gelastic, or laughing, seizures, in which there is a third ventricle hypothalamic hamartoma
- Radiosurgery or microsurgical resection for seizure-causing arteriovenous malformations
- Neuromodulation using vagus nerve stimulation, deep brain stimulation or cortical stimulation for focal, multifocal and generalized seizures.
Implanted pacemaker stimulation, another form of neuromodulation, is a future possibility. As Dr. Wetjen says, "We don't know yet if pacemaker stimulation will be effective in patients with epilepsy, but Mayo is always looking for better ways to manage the treatment of patients. The infrastructure is here if it is appropriate to make those kinds of advances."
Caring for the whole family
"Epilepsy impacts siblings as well as the patients and their parents. I find developing long-term relationships with the whole family important and fulfilling," says Dr. Wirrell. Adds Dr. Wetjen, "I like to spend a lot of time making the children feel comfortable. The mothers and fathers want the best possible care, and it's critical to provide extensive and effective ongoing communication throughout each patient's care. Our whole team is attentive to the ongoing mental, social and educational development of the children under our care."
Like the rest of the epilepsy team, Drs. Wetjen and Wirrell are acutely aware of the importance of the developing brain, and, as Dr. Wetjen notes, "Epilepsy is not a static situation, but an actively changing one. It's very hard to separate the problems related to continuing epilepsy from the effects of epilepsy medications, but certainly, if it is possible, stopping the seizures is best. We can't do it in every case, but that's the hope, that's the goal."