What Causes Epilepsy?

Epilepsy is a neurological condition involving recurrent seizures. A seizure occurs when there is an abnormal surge of electrical activity from neurons—a type of nerve cell that’s responsible for sending signals throughout your brain the rest of your nervous system. While symptoms will vary depending on the affected brain region, signs of a seizure commonly involve rhythmic movements, strange sensations, and a potential loss of consciousness.

Having a single seizure doesn’t mean you have epilepsy. A healthcare provider, such as a neurologist (a doctor who specializes in brain and nerve conditions) will provide a diagnosis for epilepsy—usually only after a person has two or more unprovoked seizures.

There are several causes and risk factors associated with epilepsy. In some cases, the process of developing epilepsy, called “epileptogenesis”, can take years. Some factors that may contribute to causing epilepsy include traumatic brain injury, tumors, and genetic mutations. However, for at least half of people with epilepsy, their seizures have no known underlying cause.

Stroke and Traumatic Brain Injury

A stroke and traumatic brain injury are two types of medical emergencies that are also common triggers for seizures. A stroke occurs when there is a lack of blood flow to the brain and a part of the brain stops working, whereas a traumatic brain injury (craniocerebral trauma) can occur when a blunt force physically hits the head—such as during a car accident or sports injury—or an injury like whiplash occurs. 

After a head injury or stroke, the brain may try to repair itself in damaged areas—such as by creating new connections between neurons, along with regenerating affected blood vessels. It is possible for abnormal connections between neurons and blood vessels (known as arteriovenous malformations) to form as the brain tries to repair itself. These changes may disrupt neuronal signaling (the neuron’s ability to communicate), leading to the development of epilepsy.  

Head trauma also activates the brain’s immune cells, causing inflammation that may contribute to epilepsy as well. These immune cells might interfere with the repair process.

Brain Inflammation

Epilepsy may also be triggered by inflammation in the brain. This is relatively uncommon, but still possible.

The medical term for brain inflammation is encephalitis. Several factors can lead to encephalitis, including certain infections, insect bites, and autoimmune disorders (health conditions that cause an overactive immune response that mistakenly attacks healthy tissue).

During encephalitis, the body produces antibodies—specific immune proteins that target and attack neurons. This can cause these neurons to malfunction, leading to epilepsy. 

Brain inflammation is more likely to trigger focal epileptic seizures (which start only on one side of the brain) rather than generalized epileptic seizures (which starts on both sides of the brain).

Infections Associated with Brain Inflammation

As a common factor that can lead to brain inflammation, infections can trigger epilepsy. Various types of pathogenic infections are associated with the development of recurrent seizures. These include:

• Bacterial meningitis, a brain infection that can be due various types of bacteria
• Tuberculosis, an infectious lung disease that can be spread from person to person through the air
• Fungal infections, such as those caused by Candida, Aspergillus, and more
• Viral herpes infections, including those caused by herpes virus type 6 (HHV-6) and herpes simplex virus type 1 (HSV-1)
• HIV, the human immunodeficiency virus, which attacks your white blood cells, limiting your body’s ability to fight infections
• Parasitic infections, such as toxoplasmosis (often acquired due to eating undercooked meat) or neurocysticercosis (often acquired due to eating tapeworm eggs)

These infections can lead to seizures around the time of infection, as well as recurrent seizures in the future.  

Brain Tumors

Brain tumors are the abnormal growth of brain cells. Several types of brain tumors are linked to epilepsy. Brain tumors can affect the neurons, as well as glial cells, a type of nerve cell that surrounds and supports neurons.  For instance, astrocytes are a type of glial cell that supports metabolism, blood flow, and other functions in the brain. The tumors can cause an imbalance in metabolism or disrupt typical neuron signaling in the brain. 

This is most likely to occur when the tumors grow in the temporal lobe or frontal lobe of the brain.

Is Epilepsy Hereditary?

Epilepsy is sometimes caused by genetic mutations. This can be the result of large mutations to chromosomes (our DNA molecules that carry genetic material) or small mutations to genes (which are made up of DNA). Fifteen to 20% of generalized seizure epilepsies, which affect both sides of the brain, involve genetic causes.

If a parent has a genetic generalized epilepsy, their children will have an 8% chance of developing it as well. However, scientists aren’t sure why specific genetic factors don't always cause epilepsy. As an example, a child with the genes that caused epilepsy in their parents might not get epilepsy.

Who Gets Epilepsy?

Some people are more likely to develop epilepsy than others. Here is what scientists know about who is more likely to develop the condition:

• Age: Epilepsy is most common in early childhood and after the age of 85. 
• Sex: The rates of epilepsy are slightly higher in people assigned male at birth than people assigned female at birth.
• Ethnicity: In the US, Black and Hispanic Americans are more likely to develop epilepsy than white people. This may be because they are more likely to develop conditions like stroke, which can cause epilepsy.

Risk Factors

There are also risk factors that may make some people more likely to develop epilepsy, including where they live and illnesses or injuries experienced earlier in life. Here is what scientists know about the risk factors so far.

Geography

The rates of epilepsy are almost three times higher in low and middle-income countries than in high-income countries. This may be explained by higher exposure to infections and brain injury.

Socioeconomic Class 

People within the lowest socioeconomic class within a country have higher rates of epilepsy compared to people in high income classes. This risk factor can most effectively be mitigated by addressing socioeconomic health gaps.

High Blood Pressure 

People with high blood pressure (hypertension) are more likely to develop conditions like stroke, which can cause epilepsy. Screening and treating high blood pressure could reduce your risk of developing epilepsy. 

Medications

Certain medicines may put you at a higher risk of developing epilepsy. It is important to speak with your prescribing healthcare provider if you are concerned about the risk. It isn’t always clear why a drug increases your chances of developing epilepsy. These medications include:

• Opioid medications like Oxycontin (morphine)
• Anti-cancer drugs like Busulfex (busulfan)
• Antibiotics or antimicrobials like Amoxil (penicillin)
• Immune-suppressing drugs like Progag (Tacrolimus)
• Antidepressants like Zoloft (sertraline)
• Antipsychotics like Risperdal (risperidone)
• Drugs for treating lung disease like Theobid (theophylline)
• Stimulants like Adderall/Ritalin (methylphenidate)
• Decongestants like Sudafed (pseudoephedrine)

Brain Injury Earlier in Life

High-impact sports like football, car accidents, and military service are associated with higher rates of traumatic brain injury. This can set off the process of “epileptogenesis,” leading to the development of the disease years later.

A Quick Review

Epilepsy is a neurological condition involving multiple seizures. Seizures occur due to abnormal electrical firing of the brain’s neurons. In most cases, the cause of epilepsy is unknown. However, doctors can pinpoint traumatic brain injury, strokes, and inflammation as causes for some of the cases. Other factors like geography, blood pressure, socioeconomic status, and medications can also increase your risk of developing epilepsy in the future.