What is epilepsy?
Epilepsy is a disorder of the nervous system, characterized by seizures that range from mild, episodic loss of attention or sleepiness to severe convulsions with loss of consciousness.
How is epilepsy diagnosed in children?
If a child exhibits signs of epilepsy, a thorough evaluation by a pediatric neurologist is needed to decide on the best treatment option, including surgery.
- Your doctor will conduct a thorough physical and will ask for a detailed family and patient history.
- Your doctor may order imaging of the brain using an MRI. There are other diagnostic procedures that can be used to examine the electrical activity within the brain.
There are three surgical diagnostic procedures that will sometimes lead to surgical treatment of epileptic seizures. These procedures are used to assist a physician in evaluating the cause of a patient’s seizures and locate the place within the brain from where the seizures are generated. After the procedure, a patient remains within the epilepsy monitoring unit (EMU) for observation.
- Depth Electrodes — Depth electrodes are used to allow for EEG monitoring of electrical activity inside the brain. Depth electrodes are multiple contact polyurethane “probes that are inserted into specified areas of the brain via small holes made in the skull and covering of the brain. The insertion is stereotactically guided using MRI imaging techniques, targeting a specific area within the brain monitored by magnetic resonance imaging (MRI) during surgery. The entry point, trajectory and depth are calculated by a computer to allow for precise placement of the electrode.
- Subdural Grid Placement — Subdural grids are sheets or strips of electrodes embedded in a thin, flexible sheet of polyurethane. Within the grid are electrode discs made of a platinum alloy. The grids are surgically placed, by way of an open craniotomy (the skull is opened to expose part of the brain), over and around areas suspected to be linked to a patient’s seizures. The exact number of discs used and specific location of placement depends on the individual needs of the patient.
- Subdural Strips — Subdural strips are generally used to determine in which hemisphere the brain seizures originate. They are also used when access to a particular area of the brain may be somewhat limited. When used alone, these strips are implanted through small burr holes in the skull, the size of a nickel. After the holes are drilled, the strips are placed under fluoroscopic guidance. After the grids have been placed, the patient is observed for seizure activity in the EMU. The patient may also undergo cortical stimulation or functional brain mapping several times. This procedure helps the physician define the relationship between the area causing the seizures and the functional areas of the brain that need to be preserved. This information is used to define and plan the second surgery — removal of the grids and potentially removal of the area causing the seizures (the epileptogenic zone). The mapping is done by applying a small amount of electrical current through a pair of electrodes to see what function, if any, is directly under that electrode.
Treatment for pediatric epilepsy
The Johns Hopkins difference involves multiple specialties in reviewing the cases of children with epilepsy. Neurosurgeons, pediatric neurologists, nutritionists, neuropsychologists, among others, join together to develop the treatment plan. The team will decide if surgery is the best option. Learn more about multidisciplinary care.
The purpose of surgery is to eliminate or lessen the severity of the seizures. Learn more about our surgical expertise.
Surgical treatment options
The surgical treatments provided by our fellowship trained pediatric neurosurgeons include:
The Vagus Nerve Stimulator (VNS)
The Vagus Nerve Stimulator (VNS) is a device, somewhat like a heart pacemaker, placed in the upper chest below the left collarbone. It is connected to a wire which leads to a nerve in the neck. By stimulating this vagus nerve, the device can help reduce the number of seizures. In fact, about a third of patients experience a thirty to fifty percent reduction of seizures. Around three percent of patients actually become seizure-free.
The device stimulates automatically and periodically throughout the day and night. Patients can also learn to "turn on" the stimulator if they feel a seizure coming on, which can often stop the seizure from occurring. Because the vagus nerve affects the throat, patients may experience hoarseness or sore throat and may have difficulty speaking when using this device. Adjusting the strength of the stimulation can often address this side effect.
Vagus nerve stimulator placement requires surgical implantation under general anesthesia. Patients need multiple clinical appointments after implantation to turn the VNS on and adjust stimulation strength.
In very rare cases where a patient has seizures that start independently on either side of the brain and spread, a corpus callosotomy may be recommended. This procedure involves severing the fibers connecting the two halves (hemispheres) of the brain.
Disconnecting the two hemispheres helps stop the spread of seizures in the brain and may protect some patients from injury caused by seizure-related falls. This procedure does not usually stop the patient from having seizures and may actually increase the frequency of certain kinds of localized seizures.
After surgery, the patient may experience temporary or permanent limitations of speech, movement of certain body parts or behavior alteration. It is important for patients and their families to be informed of these risks and understand that this surgery is not performed with hope of curing seizures, but rather with hope of helping to reduce their severity.
Hemispherectomy (also known as hemidecortication or functional hemispherectomy) is the complete removal or partial removal and disconnection of almost an entire half of the brain (hemisphere).
This procedure is usually performed on children with severe and very frequent seizures at select centers in the world including Johns Hopkins. These patients typically have a severely damaged hemisphere for assorted reasons (hence the seizures) and generally are weaker on the side of the body opposite of the diseased hemisphere.
Experience has shown that less extensive surgery is not useful in this situation. Suitable for only a very few patients, hemispherectomy has proven to be a very successful type of seizure surgery. Potential risks including hydrocephalus and infection. The severe one-sided weakness present before surgery is likely to persist after surgery, although most patients are usually able to walk with some rehabilitation.
Patients also experience loss of the visual field on the weak side. When successful, this surgery cures the epilepsy. Johns Hopkins has performed this surgery over 125 times since the 1980s and helps coordinate a reunion for patients every three years.
Follow-up care is extremely important in tracking the progress of a child’s recovery. Your pediatric neurosurgeon will schedule follow-up appointments to make sure your child is making a full recovery.