About half of the time, the cause of epilepsy is unable to be identified. When a cause can’t be found, it is called cryptogenic epilepsy. For the other half of epilepsy cases, the causes may be more easily identifiable, such as head trauma or a known genetic syndrome.
Read on to learn more about how genetics can play a role in the development and treatment of epilepsy.
Genetics and Epilepsy
Genetic epilepsy means that the person has one or more genes that increase the likelihood of developing seizures.
Often in idiopathic generalized epilepsy (also called genetic generalized epilepsy), these abnormal genes only increase the risk of seizures by a small amount individually, but if several of these genes are present, epilepsy becomes more likely.
Idiopathic epilepsies include:
- Childhood absence epilepsy
- Juvenile absence epilepsy
- Juvenile myoclonic epilepsy
- Epilepsy with generalized tonic-clonic seizures alone
There are over 200 genes that have been identified as “epilepsy genes.” Many other genes have also been shown to cause genetic disorders that can involve epilepsy or seizures.
These genes can be linked to epilepsy in several ways, including:
- Causing epilepsy directly (may be part of a genetic disorder that has epilepsy as a characteristic or symptom)
- Causing epilepsy as a result of an interaction between genetic and environmental factors
- Causing brain malformations that can lead to epilepsy
- Inherited conditions that increase the likelihood of seizures, such as inherited metabolic conditions
Affected genes can have:
- Mutations in the mitochondrial DNA
- Missing or mutated chromosomes
- Changes in the activity of genes
In some cases, a genetic cause may be suspected, but the exact cause of epilepsy can’t be pinpointed.
Some gene mutations don’t cause epilepsy to develop but can still affect a person with epilepsy. For example, some people with epilepsy have an abnormally active version of a certain gene, making them more resistant to anti-seizure drugs.
Inherited Epilepsy vs. Genetic Pathogenic Variants
If epilepsy results from a known or presumed genetic variant, it is considered to have a genetic cause. This does not necessarily mean the person inherited their epilepsy.
Changes in genes, called genetic pathogenic variants, can occur spontaneously, meaning a child can have these affected genes even if neither biological parent does.
Just having gene mutations that increase the risk of epilepsy doesn’t necessarily mean you will develop epilepsy. In many cases, other factors, such as environmental conditions, are needed for the genetic predisposition to lead to the development of epilepsy.
Inheritance can play a role too. The risk of epilepsy is increased 2 to 4 times for first-degree relatives of a person with inherited epilepsy. Even with this increased risk, the overall risk of developing epilepsy is still low.
The risk is higher if the biological mother has epilepsy than if the biological father does. (Note that when research or health authorities are cited, the terms for sex or gender from the source are used.)
Having a sibling with epilepsy can also increase the risk, especially an identical twin.
Inherited epilepsy can be complex. For example:
- Siblings who have different gene mutations can develop the same epilepsy syndrome.
- Family members with the same gene mutation can have epilepsy but experience the effects differently.
- An epilepsy syndrome may be known to have a genetic basis, but the specific affected gene or genes haven’t been identified.
Types of Genetic Disorders
Five types of genetic disorders are:
- Single gene or Mendelian disorders: Changes occur in a single gene, or a single gene is missing. This may be passed from parent to child or may occur spontaneously in the child.
- Multifactorial or complex disorders: Mutations occur in a number of genes. Often these disorders are influenced by environmental factors such as substance use, birthing parent infections, or exposure to hazardous materials. These tend to run in families, but a pattern of inheritance can be difficult to determine.
- Chromosomal disorders: Entire (or parts of) chromosomes are missing or altered. These often occur spontaneously in the affected person, but can be inherited.
- Mitochondrial disorders: These are caused by mutations in DNA found in mitochondria (structures outside the cell nucleus that make energy for the cells). Mitochondrial DNA is only inherited from the egg-contributing (maternal) parent.
- Epigenetic disorders: These are related to changes in the activity of genes, instead of a mutation in the structure of the DNA.
Symptoms of Genetic Epilepsy
“Epilepsy” is an umbrella term for a group of disorders, each with its own characteristics. The symptoms of genetic epilepsy can vary.
Idiopathic generalized epilepsy involves both sides of the brain and can affect all areas of the body. It usually starts in childhood or adolescence.
Symptoms of generalized seizures include:
- Convulsions (uncontrollable shaking)
- Making motions that are jerky, twitching, or rhythmic
- Crying out/making a noise
- Falling down
- Not breathing
- Losing consciousness
- Confusion after regaining consciousness
- Losing bladder control
- Biting the tongue
Some people with epilepsy experience partial seizures (also called focal seizures). Partial seizures start in a specific area of the brain and can affect just one part or side of the body.
Symptoms of partial seizures include:
- Movements that are jerky, rhythmic, and/or repetitive
- Sensations such as tingling
- Feeling full in the stomach
- Altered senses
- Emotional changes
If the epilepsy is caused by a genetic syndrome, additional symptoms may be present.
Who Should Get a Genetic Assessment?
Once diagnosed with epilepsy, a genetic assessment might be helpful for people with at least one of the following:
- Ongoing seizures that have not responded to at least two medications
- A family history of epilepsy
- Developmental regression or skill loss
- Conditions in addition to epilepsy, such as global developmental delay, autism spectrum disorder, intellectual disability, cerebral palsy, atypical development of organ systems (such as bones, heart, skin, kidneys, or other areas)
Genetic epilepsy is usually treated with anti-seizure medication.
If medication isn’t effective or isn’t a viable option, other treatments may be tried, such as:
- Surgery to remove the area of the brain that is causing the seizures
- Vagus nerve stimulation with a placed or implanted electrical device
- Special diets, such as a ketogenic diet or a specific supplement (always check with your healthcare provider before trying a special diet or supplement)
Therapies targeting specific rare genes may provide beneficial treatments in the future but are still in the research phase.
Other Causes of Epilepsy
Epilepsy can be caused by a number of factors in addition to genetics.
Head trauma that causes brain injury, such as a car accident, can lead to epilepsy. Seizures may not show up immediately after the traumatic head injury, but appear later on.
Clinically significant elevated risk comes from moderate and severe traumatic brain injury (TBI), where there is at least 30 minutes of unconsciousness or more than 24 hours of disorientation, usually paired with hemorrhage or other traumatic findings on a brain scan.
Infections such as meningitis, human immunodeficiency virus (HIV), and viral encephalitis, can cause epilepsy. Infections experienced by a pregnant parent may contribute to the development of epilepsy in their baby.
Epilepsy can be caused by damage to the brain, such as from a stroke or brain tumors. The leading cause of epilepsy in people over the age of 35 is damage from a stroke.
Brain malformations, including vascular malformations, may also result in epilepsy.
Brain injury in the womb leading to epilepsy can result from several factors, including:
- Oxygen deficiencies or deprivation
- Nutritional deficiencies
- Infection in the pregnant person
Some developmental conditions, such as autism spectrum disorder or neurofibromatosis, can coexist with epilepsy.
Risk Factors for Epilepsy
While it’s often not known why a person develops epilepsy, some factors may increase the risk, including:
- Significant head injury
- Brain tumor
- Brain infection
- Alzheimer’s disease
- Lack of oxygen at birth
- Hardening of the arteries in the brain
- Age (more common in children and in older adults than in ages in between)
- A family history of epilepsy
Epilepsy can have a genetic component, which may or may not be inherited. Mutations in genes that can lead to epilepsy may be passed down from a biological parent or occur spontaneously.
Being genetically predisposed to epilepsy (having one or more affected genes) doesn’t necessarily mean you will develop epilepsy. Often epilepsy develops through an interaction between genetic and environmental factors.
Epilepsy is usually treated with medication, but other treatments such as surgery, vagus nerve stimulation, or diet therapy, may be suggested.
If you have or suspect you or your child has epilepsy, talk to your healthcare provider. It’s important to get a proper diagnosis and start any necessary treatment as early as possible.
FREQUENTLY ASKED QUESTIONS
What are the odds of inheriting epilepsy from a parent?
Most children who have a parent with epilepsy don’t develop epilepsy, but there is an increased risk. The level of risk varies depending on factors such as the type of epilepsy, how many family members have epilepsy, and age of onset, among others.
Can you diagnose epilepsy with a genetic test?
A genetic assessment may be suggested after an epilepsy diagnosis is made to look for a genetic cause. These assessments are not done routinely for people with epilepsy, but rather a referral is made if a person’s epilepsy healthcare provider or specialist feels it is warranted.
Can genetic epilepsy go away?
Some people with epilepsy need treatments to control seizures for their whole lives, while for others, seizures can stop or decrease over time. Becoming seizure-free is less likely for adults or for children with severe epilepsy syndromes.
Source: verywellhealth.com, Heather Jones