Surgical management of intractable seizures in children with epilepsy
One in five 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 can be done in one or two weeks and includes state-of-the-art functional brain mapping and seizure focus studies. If the child is documented to be a good surgical candidate and the family decides to proceed, surgery can then be scheduled promptly. 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, scalp electroencephalography (EEG) and blood tests 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, positron emission tomography or intracarotid sodium amobarbital (Wada) testing.
Inpatient pediatric EEG monitoring
Surgical candidates then undergo continuous EEG monitoring in the Mayo 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. The single-patient rooms allow parents to stay with their child throughout the child's hospitalization and provide continuous monitoring by trained technicians.
Localizing seizure focus through SISCOM
Pioneered at Mayo Clinic, SISCOM is an advanced imaging technology that fuses an MRI image with a 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. 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.
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, Mayo neurosurgeons 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
Mayo Clinic's multidisciplinary epilepsy team individualizes the most appropriate management strategy for each child seen and evaluated.
Points to remember
- Mayo Clinic's multidisciplinary epilepsy team includes pediatric epileptologists, pediatric neurosurgeons, neuroradiologists and pediatric neuropsychologists.
- Surgical candidates undergo continuous electroencephalographic monitoring, which may take from 24 hours to several days to record a sufficient number of seizures.
- Depending on the nature of the problem, surgical options include cortical resection, peri-insular hemispherotomy, endoscopic surgery, radiosurgery or microsurgical resection, or neuromodulation.