Causes of epilepsy
Once your child is diagnosed with epilepsy (seizure disorder), your child’s health-care team will try to find the cause of their epilepsy. This will help them determine the treatment options available for your child. The causes of epilepsy are classified into six categories. These are described below.
Causes of epilepsy are divided into six groups
1. Structural
This means that your child has epilepsy due to an abnormality in the brain structure. These abnormalities are seen on brain imaging, such as a CT scan or an MRI. Abnormal brain structure may be caused by:
Injury or trauma: Head injury or trauma, at birth or later, may cause focal epilepsy. Older teenagers and young adults are more likely to have brain injuries that result in epilepsy because they are more active and more likely to be injured than younger children.
The more severe the injury, the higher the risk that a child will later develop epilepsy and the longer the child is at risk. Severe head trauma, where the child’s brain is bruised or the child is unconscious for more than 24 hours, increases the risk of epilepsy 17 times. Moderate trauma, where the child’s skull is fractured or the child is unconscious for more than half an hour, increases the risk three times. Ordinary bumps and bruises do not increase the risk of epilepsy.
Epilepsy does not always develop right away. The risk of developing epilepsy is highest for the first year after the injury. However, a child who has had a serious head injury may develop epilepsy years afterward.
Lack of oxygen to the brain: Lack of oxygen to the brain before, during or shortly after birth can damage the brain and result in seizures in the newborn period. This may result from various birth complications, including difficult or prolonged labour, placental abruption (when the placenta separates early from the uterus) or compression of the umbilical cord.
Lack of oxygen to the brain (for example, from an accident, drowning or heart attack) can also result in seizures in older children and adults.
Brain tumour: Brain tumours are the second most common type of cancer in children, after leukaemia, but they are still rare. Approximately 30 per cent to of people with brain tumours have seizures, but they may not develop chronic epilepsy. The type of tumour affects the risk of developing epilepsy. Some studies suggest that epilepsy is more common in people with low-grade tumours that have been present for a long time than in people with malignant tumours. Brain tumours are a fairly rare cause of epilepsy, especially in children and young adults.
The outlook for children with epilepsy caused by a brain tumour varies but is often good. With the right surgical procedure, most people become entirely seizure-free or have more than 80 per cent fewer seizures. The outcome may depend on how long a child has had epilepsy and the type of surgery they have.
- Cerebrovascular problems: A cerebrovascular problem (a problem with the blood vessels in the brain), such as a tangle of blood vessels or a stroke, can also cause epilepsy. Cerebrovascular problems such as stroke are common causes of seizures in older patients, but can also be seen in children.
- Congenital malformation: Before a baby is born, their brain is formed in a complicated process in which new brain cells travel to their intended location in a very specific pattern. Different types of congenital (present at birth) brain malformations can be caused by:
- abnormal proliferation (when too many or too few brain cells grow or when brain cells multiply abnormally)
- o abnormal migration (when brain cells stop moving at the wrong time and end up in the wrong place)
- abnormal organization (when all or part of the brain forms in the wrong shape)
- Neurocutaneous syndromes: Neurocutaneous syndromes are congenital disorders that cause tumours to grow in the brain, spinal cord or peripheral nerves. They often cause skin lesions (abnormal growths or marks on the skin) and may also cause developmental disability.
- Tuberous sclerosis is a genetic disorder in which growths or ‘tubers’ develop in the brain and, sometimes, in the kidney and heart. Hypopigmented, or pale, areas shaped like ash leaves are found on the skin, and butterfly-shaped facial acne develops over time. Approximately 80 per cent of people with tuberous sclerosis develop epilepsy. The number of tubers and their location seem to play important roles in cognitive and developmental outcome as well as seizure outcome.
- Sturge-Weber syndrome is also accompanied by a birthmark on the face and is connected with epilepsy in 70 per cent to 90 per cent of cases. Sturge-Weber syndrome may get worse with time but eventually stabilizes. Early treatment, particularly surgery, may improve seizure control and intellectual outcome.
- Neurofibromatosis, a group of genetic disorders in which many soft tumours develop throughout the body and is often accompanied by skin changes. Epilepsy occurs in less than 14 per cent of cases.
- Mesial temporal sclerosis, also known as hippocampal sclerosis, is a condition in which parts of the brain in the inner part of the temporal lobe shrink and develop scar tissue. The causes are unclear. It is more common in older children and adults, but it has been seen in children as young as two years old.
Almost any brain malformation can lead to seizures. Sometimes, these malformations can also lead to developmental disabilities. If a baby has very severe brain malformations, they may not survive.
2. Genetic
A genetic cause may be due to genes passed on from the parent to the child. Other times, a new genetic mutation occurs in the child. There are certain genetic mutations that increase the risk of having seizures.
Even though the same genetic mutation may be identified in your child and others, the degree to which each child is affected can vary.
3. Infection
Infection of the brain is thought to cause up to 25 per cent of epilepsy cases in children and 3 per cent to 6 per cent of all cases of epilepsy. Many different infections can result in seizures either at the time of infection or afterward, including:
- meningitis, a bacterial or viral infection of the tissues covering the brain
- encephalitis, an infection of the brain
- opportunistic brain infections in children with a weakened immune system, for instance from HIV infection
- infections elsewhere in the body that cause metabolic changes or a lack of oxygen to the brain
- various parasitic infections of the CNS, including trichinosis, cerebral malaria, cysticercosis and toxoplasmosis (more common in developing countries but can be acquired anywhere)
The level of risk depends on the specific infection. For instance, viral encephalitis and bacterial meningitis increase the risk of epilepsy ten times, but aseptic meningitis (when no bacterial cause is found) or viral meningitis does not appear to increase the risk.
4. Metabolic disorder
Metabolic disorders are problems with producing, absorbing, breaking down or storing specific substances in the body, including sugars, fats, proteins and vitamins. They usually happen when a child lacks a specific enzyme, often because of a genetic mutation.
5. Immune
The immune system protects our body from illness and attacks bacteria and viruses to prevent us from getting sick. However, sometimes the immune system becomes confused and these cells end up attacking our own cells. This abnormal activity can disrupt normal functioning of all our body parts. When it affects cells in the brain, it can result in epilepsy.
6. Unknown
In 60–70% of cases, no apparent cause can be identified.
Sometimes a child can have more than one cause for epilepsy. For example, in children with tuberous sclerosis, genes in the body make it more likely for the body to make benign (non-cancerous) tumours. These tumours can also grow in the brain; however, some are more likely to cause epilepsy than others. If this is the case, the child is considered to have both a structural cause (the tuber) as well as a genetic cause (the gene mutation) for their epilepsy.