Why Seizures Happen After Head Trauma

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Seizures are a risk following head trauma. Also called traumatic brain injury, head trauma can range from mild (such as a concussion) to severe. Severe injuries have a higher chance of causing a seizure.

About 10% of people who experience a traumatic brain injury that's severe enough for them to be hospitalized will end up having a seizure. Most of the time, it happens within the first few days or weeks after the accident.

However, for a smaller percentage of the head injury population, seizures can start months or years later. The symptoms of becoming unresponsive, with jerking, uncontrolled movements, may indicate a lifelong challenge with a seizure disorder.

This article explains how traumatic brain injury increases the risk of seizures, even those with mild symptoms. It will help you to know more about what to expect if and when seizures occur.


Knowing What to Do When Someone Has a Seizure

Seizure Types Related to Brain Trauma

Seizures that occur as a result of traumatic brain injury are classified on the basis of when the first seizure happens. These definitions include:

  • Early post-traumatic seizure: These happen within the first seven days after the traumatic brain injury. About 25% of people who experience an early post-traumatic seizure have another seizure at some point in the future
  • Late post-traumatic seizure: These are seizures that happen more than a week after the traumatic brain injury. What’s interesting with late post-traumatic seizures, is that about 80% of people who experience one after traumatic brain injury will go on to have at least one more seizure during their lifetime.
  • Epilepsy: Any time there are repeated seizures, the person is considered to be an epileptic. About half of individuals with epilepsy as a result of traumatic brain injury continue to have seizures for the rest of their lives.

What Happens During a Seizure

A seizure occurs when the normal electrical function of the brain is thrown off balance. This disruption may happen for a variety of reasons after head trauma, including:

Seizure symptoms occur as the electrical signals lose their normal pathways, sometimes with a surge of electrical activity. Some symptoms are mild and difficult to detect by observation, while others involve violent and uncontrollable body movements, loss of memory and unconsciousness.

Signs and Symptoms of Seizure

Some signs of seizure include:

  • Staring out into space and not responding to voice or touch
  • Headache, sudden fatigue, or dizziness
  • Lip smacking, chewing, biting of the mouth
  • Changes or difficulty with breathing
  • Inability to speak or understand others
  • Uncontrolled jerking of the head, arms legs, torso

In addition to the seizure activity, there may be a loss of bowel or bladder function. After the seizure, it may take a while to “wake up,” realize you had a seizure, and become aware of the environment.

For seizures that last longer than two minutes, it may take several days to fully recover and you may experience complications like increased confusion, difficulty walking, or trouble talking.

Increased Risks of Seizure

There are a number of factors that play into one’s risk of developing a seizure disorder after head trauma.

Penetrating injuries, such as gunshot wounds, have a high likelihood of leading to seizures. Up to half of all people with penetrating traumatic brain injuries will develop epilepsy, and it's the leading cause of a new diagnosis for people whose age is in their 20s and 30s.

If two or more brain surgeries were needed to repair damage or remove blood clots from the brain after head trauma, the risk for seizure is about 35%.If the head trauma is entirely contained within the skull (no penetrating injuries or surgery) the risk is about 20%.

Contributing Factors to Seizures

The seizure risk after a head injury also is influenced by other factors, some of which you have control over.

Drug and alcohol use greatly increases the likelihood of having a seizure. You may be more likely to vomit during the seizure, and you will not have adequate control over your gag and cough reflexes. This can lead to aspirating (inhaling) stomach contents into the lungs, which can be fatal.

Other illnesses not related to head trauma can also increase seizure risk. Having a high fever, as well as having an electrolyte imbalance such as low sodium, may lead to seizure activity.

Not getting enough sleep and being stressed lower the seizure threshold. Sometimes a seizure happens years after a brain injury when the person is under a great amount of pressure and feeling fatigued.


A traumatic brain injury increases your risk of seizures both immediately after the injury and, in some cases, across a lifetime. This is due to disruption of the normal electrical signals in the brain, caused by swelling or other conditions after the injury.

Gunshot wounds, in particular, can lead to seizures and an epilepsy diagnosis after head injury. Other factors, including an underlying illness or alcohol and drug use, can increase the risk of seizures as well.

It's less common, but some people who have a history of a head injury won't experience seizures for many months or even years after the incident. Be sure that your healthcare provider is aware of your medical history and that you maintain any treatments prescribed to prevent seizures.

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Englander J, Cifu DX, Diaz-arrastia R. Information/education page. Seizures and traumatic brain injury. Arch Phys Med Rehabil. 2014;95(6):1223-4. doi: 10.1016/j.apmr.2013.06.002

  3. Model Systems Knowledge Translation Center. Seizures After Traumatic Brain Injury.

  4. Icahn School of Medicine at Mount Sinai. Generalized tonic-clonic seizures.

  5. Esquenazi Y, Kalamangalam GP, Hope OA, Krish SN, Slater J, Tandon N. Surgical Resection for Epilepsy Following Cerebral Gunshot Wounds. World Neurosurg. 2016 Nov;95:276-284. doi:10.1016/j.wneu.2016.08.041. 

  6. Modern Systems Knowledge Translation Center. Seizures After Traumatic Brain Injury.

  7. Weil ZM, Corrigan JD, Karelina K. Alcohol Use Disorder and Traumatic Brain Injury. Alcohol Res. 2018;39(2):171-180.

Additional Reading

By Eva Hvingelby, NP, PhD
Eva Hvingelby NP, PhD, is a nurse practitioner, researcher, educator, and health consultant specializing in trauma.