1. What is epilepsy? What are the different types of epilepsy?
Epilepsy is a tendency to have epileptiform seizures, and some of the children who have spasms are epileptic. There can be several types of epilepsy, the most common being generalized tonic-clonic seizures, a type of seizure in which the child loses consciousness and has rhythmic jerking throughout the body. Another type of seizure is an aphasic seizure, which involves a brief loss of consciousness accompanied by blinking or twitching at the corners of the mouth. Aphasic seizures have a very characteristic EEG presentation.
Partial seizures occur when an abnormality in a specific area of the brain causes a convulsion. Simple partial seizures do not cause altered consciousness, however, complex partial seizures cause some changes in consciousness. The manifestations and symptoms of epilepsy depend on which part of the brain the epilepsy comes from. For example, a partial seizure from the area of the brain that controls hand movement, such as this, will cause hand twitching. In contrast, a partial seizure from an area of the brain that controls emotions can cause feelings of fear. Sometimes it is difficult to distinguish between a partial seizure and a disoriented seizure, but they have different EEG presentations.
2. What causes epilepsy in children?
Many factors can cause epilepsy. Many people with epilepsy have epileptic seizures in their early years. Any factor that interferes with brain development or brain function can cause epilepsy in children. Some children are deprived of oxygen before or at birth, and this can lead to cerebral palsy and epilepsy. Some children are born prematurely or have brain hemorrhage due to cerebrovascular malformations, which can also cause epilepsy.
Epilepsy can also be caused by changes in genetic factors. Some children are born with the “epilepsy gene,” so they can develop epilepsy. These epilepsies can occur early or late in life, and in those who develop them late, they can occur as late as their 30s. Often, genetic factors cause a wide range of epilepsy. This means that epilepsy does not occur in just one specific area of the brain, but affects the entire brain at the same time. Other causes of epilepsy in children include brain tumors, brain infections (encephalitis), head trauma, and problems with the production of chemicals in the body and brain, among others. In all cases, what we must remember is that a child’s brain is more susceptible to epilepsy than an adult’s brain.
3. Is epilepsy bad for children?
Epilepsy can be life-threatening, but this is quite rare. Persistent status epilepticus (sustained convulsions for more than 30 minutes) can cause damage to the brain, but this too may be rare. However, uncontrolled epilepsy can lead to a variety of learning and developmental disabilities in children. The goal of treatment for childhood epilepsy is not just to control seizures, but to advance the child’s potential for brain development.
4. How is epilepsy treated?
Most people with epilepsy are treated with relatively simple medications (70-80%). There are many antiepileptic drugs available today. The choice of medication is based on several factors: the type of epilepsy, the age of the child, other clinical problems, and potential side effects of the medication. However, in some patients who do not respond to medications, surgery or other treatment should be considered.
5. What is surgical treatment of epilepsy?
Surgical treatment of epilepsy is used to control seizures, and recently, there are three main classifications.
Focal resection: the part of the brain that causes the epilepsy is removed.
Corpus callosotomy: The main part of the brain that connects the two sides is cut off, thus reducing some types of seizures.
Vagus nerve stimulation: stimulation of the vagus nerve in the neck with a tiny metal wire, again this procedure is done to reduce seizures.
Each of these three procedures will be discussed below.
6. Who performs epilepsy surgery?
Epilepsy surgery in children must be performed by a neurosurgeon who is trained and experienced in epilepsy surgery in children. Most cases are performed at a large academic medical center affiliated with a medical university. Prior to surgery, the patient must be evaluated several times by a qualified epileptologist (usually a brain surgeon with special training in pediatric EEG and epilepsy). A team of epileptologists and brain surgeons will plan the relevant surgery for each child depending on the situation.
A. Focal Resection
7. What is a focal resection?
For patients with partial seizures, focal resection is the best surgical treatment. A portion of the cerebral cortex that is causing the seizures is removed. The most common type of focal resection is a temporal lobectomy, or partial temporal lobectomy. The temporal lobe is the structure that tends to cause epilepsy. The primary functions of the temporal lobe are memory and emotion. The part of the temporal lobe where epilepsy occurs usually does not have these functions and is replaced by other parts of the temporal lobe. Therefore, removal of this lesioned temporal lobe does not cause memory or emotional disturbances. In fact, these functions are often better after surgery. Younger children sometimes have malformations of several lobes, and if this occurs on one side of the cerebral hemisphere, then this patient is a candidate for a multileaf resection (most of the affected cerebral hemisphere is removed) or a hemispherectomy (total removal of the entire affected cerebral hemisphere cortex).
8. Which patients are suitable for focal resection?
There are a number of criteria that must be met in order to be a suitable candidate for epilepsy surgery. First, it must be clear that medication is not controlling the epileptogenesis or that medication is causing unacceptable side effects. Second, the epileptic lesion must be focal, that is, it must occur in one area of the brain or on one side of the brain. Third, it must be clear that removal of the lesioned area of the brain will not result in unacceptable impairment, such as loss of speech or severe motor deficits. Once a child meets these criteria, surgery should be considered. Otherwise, there is no benefit to the child. In fact, it has been well documented that the younger the child is operated on, the greater the potential for recovery of brain function after surgery. In general, children with epilepsy younger than 3 years of age who have been treated with medication for 1-2 months should consider seeing a pediatric neurosurgeon for surgical treatment of epilepsy; children with epilepsy older than 3 years of age who have been treated with medication for six months should also consider surgery, otherwise the side effects of epilepsy itself and medication lead to delayed brain development with far greater consequences than the side effects of surgery.
9. What tests do I need to do before my child undergoes lesion removal surgery?
First, MRI can detect abnormalities in the area to be operated on, such as a brain tumor or certain cerebrovascular malformations. MRI can also distinguish areas of abnormal development, prior hemorrhage, stroke, or other problems. An EEG can be used to detect any abnormal discharges in a particular part of the brain. If this is the case, or if the results of the original EEG are suspicious, the child may be hospitalized for a prolonged EEG and video EEG. The purpose of this is to “capture” the epilepsy on video and EEG and to distinguish the area of the brain where the epilepsy originates, which will vary from child to child. In some children, PET or SPECT scans are performed when the seizures are not occurring. Often, the areas of the brain that are causing the epilepsy are shown, while these lesions appear normal on MRI. In patients with temporal lobe epilepsy, the lesion may be in an important area for language comprehension, and the WADA test can clarify whether lesion removal causes language or memory impairment.
Finally, some patients require invasive monitoring, which involves placing the electrodes of the EEG directly on top of the brain. This monitoring is done to more precisely localize the lesion. Invasive testing can be done during the procedure or take several days to complete, depending on the characteristics of the case itself.
Additional tests to evaluate patients for epilepsy surgery will not be described in detail, including seizure SPECT (SPECT scans performed during seizures), magnetic brain wave tracings, and functional MRI.
B callosotomy
10. What is a corpus callosotomy?
Corpus callosotomy is the severing of the corpus callosum. The corpus callosum is the main pathway for the connection between the left and right hemispheres of the brain.
11.What patients are suitable for corpus callosotomy?
Corpus callosotomy is rarely done nowadays. It is usually done in people who have frequent epilepsy, called “cataplexy”. Sudden collapse is a brief form of epilepsy that can cause a patient to lose muscle tone and fall to the ground, often resulting in injury. A corpus callosotomy can prevent frequent transmission of seizure activity between the two sides of the brain, thus preventing falls.
12. What are the side effects of corpus callosotomy?
The side effects of corpus callosotomy are similar to those listed for focal resection, but there are far fewer severe neurological deficits after corpus callosotomy than after focal resection. There is, however, a significant risk that callosotomy will produce more sensitive problems. Patients who have relatively little postoperative mental impairment may experience strange difficulties in distinguishing or speaking certain objects placed on one side of their body, due to the inability of both brains to communicate with each other. The same patients will face other more sensitive thinking abnormalities called “corpus callosum syndrome”.
C Vagus nerve stimulation
13. What is vagus nerve stimulation?
A vagus nerve stimulator is an instrument manufactured by Cyberonics that is buried under the skin of the chest and connected to the vagus nerve by a metal wire extension. The vagus nerve runs from the brainstem (a very small part of the lower part of the brain) to many organs of the body. Once the VNS is implanted, it stimulates the vagus nerve at a certain intensity and frequency, called the basic stimulation frequency, which can be adjusted by specially trained personnel according to the frequency and severity of the seizures. In addition, those patients who have a premonition of a seizure can adjust the magnetic handheld apparatus around them to temporarily increase the frequency of stimulation and thus stop the seizure.
14. Which patients are suitable for vagus nerve stimulation?
Those patients who have multiple types of epilepsy and for whom medication has not been effective, or for whom other forms of surgery have not been effective, may use this method. Again, as with corpus callosotomy, vagus nerve stimulation can help prevent falls from occurring.
15. What are the side effects of vagus nerve stimulation?
Potential side effects of vagus nerve stimulation are general anesthesia, inability of the implant to work, and infection at the implant site. In addition, vagus nerve stimulation can cause hoarseness and coughing, and even change the heart rate. Because the implant is outside the skull, there are few other neurological changes.
In summary, pediatric epilepsy surgery can be used to treat some highly selected patients whose epilepsy cannot be controlled by standard methods. Epilepsy surgery must be performed by a multidisciplinary team that includes neurologists, neurosurgeons, brain surgery nurses, and clinical medicine practitioners.