Seizures in children are estimated to occur in approximately 4 percent of children. But when seizures often recur, a child is said to have epilepsy.
Causes of Epilepsy
In most cases there is no specific acute cause of epilepsy. Instead, perhaps a minor brain injury in the period surrounding birth or an inherited tendency for seizures produced the episodes. Occasionally, head trauma or a brain infection (meningitis or encephalitis) at an early age produces slight scarring of the brain causing seizures. Most children with epilepsy are healthy between episodes and develop normally.
Symptoms of Epilepsy
Some children may face difficult problems due to epilepsy, depending on type of seizure pattern, age of onset, and presence of associated conditions. Seizures can cause a wide range of symptoms including:
- strange sensations,
- changes in behavior or emotions,
- muscle spasms,
- and sudden loss of consciousness.
Despite aggressive treatment with anticonvulsant therapy, some children experience uncontrolled frequent seizures, called intractable epilepsy. Consequences of intractable epilepsy include:
- the possibility of physical injury during a seizure,
- impairment of learning and attention,
- adverse effects of medications, brain injury, and disruption of family life brought about by frequent medical crises.
Sophisticated diagnostic techniques are used to assess and visualize abnormalities and structural problems associated with epilepsy that may be targets for surgery. These methods include:
- encephalograms (EEGs),
- video-EEG telemetry,
- computed tomography (CT) scan,
- magnetic resonance imaging (MRI),
- and positron emission tomography (PET) scan.
In the past, surgical treatment of epilepsy was reserved for adults with long-term intractable epilepsy. However, poorly controlled seizures and chronic use of anti-epileptic medication may cause permanent problems. Therefore, the medical community and parents now lean toward earlier neurosurgical intervention.Much like epilepsy surgery in adults, epilepsy surgery in children is used either to remove the source of the seizures (resective surgery) or in some cases to disrupt pathways that spread seizures (disconnection surgery). Disconnection surgery is done more frequently in children than adults. Hemispherectomy, a procedure performed almost exclusively in children, involves components of both resective and disconnection surgery.
For resective surgery, a team of epilepsy specialists work to identify the part or region of the brain which causes an infant's or child's seizures, and then remove this "epileptic zone." The resection may be quite small, such as the area surrounding a small developmental abnormality, or may include a significant portion of brain matter.
A battery of diagnostic tests is essential to successful resective surgery, which isolate specific abnormalities and steer surgeons clear of essential structures.
For disconnection surgery, seizure pathways are disrupted to reduce the spread of a seizure through the brain. The major type of disconnection surgery is used to separate the two halves (hemispheres) of the brain. This procedure is used particularly in children who experience "drop attacks," generalized seizures that cause falls due to loss of muscle control, or any other child with seizures that spread rapidly. More than three quarters of children with "drop attacks" or other severe generalized seizures experience a significant reduction in seizure frequency and severity after this procedure.
A similar technique gaining acceptance is subpial transection that also works by severing the pathways along which seizures propagate. Vertical connections between nerves cells are thought to be associated with normal brain function, while horizontal connections appear to help seizures spread. This procedure involves the cutting of horizontal connections to prevent seizures from spreading.
In some children with epilepsy, one side of the brain is dramatically affected by severe disease, causing uncontrolled seizing. In these epilepsy cases limited resection may not be enough to control the seizures. These children also are born with, or develop, severe weakness or motor impairment on one side of their body. In these severe cases, hemispherectomy, a form of epilepsy surgery only performed on children, may be considered as a treatment option.
Hemispherectomy is the removal of as much as half the brain. The hemispherectomy performed today involves both resection and disconnection of pathways along which seizures travel. The procedure is effective because of the unique ability of a young child's brain to re-organize, re-assign important functions, and relearn tasks. This ability, known as plasticity, makes hemispherectomy a safe surgical tool for treatment of childhood epilepsies in which an entire hemisphere of the brain is involved in seizure initiation. There still will be side effects, however, including weakness and a loss of movement on one side of the body and language difficulties. Usually the ability to walk will return if the patient was able to walk before the operation, and language function can recover if surgery is performed at an early age.