Types of epileptic seizures and their causes

Epileptic seizures are sudden, uncontrolled bursts of electrical activity in the brain that occur when the normal functioning of a group of neurons is disrupted¹. Seizures can lead to involuntary movements of the body, changes in the way stimuli are experienced, changes in behaviour or memory, and sometimes loss of consciousness². Seizures can last from a few seconds to a few minutes³ and are not necessarily linked to epilepsy¹. Up to 10% of the world’s population experiences at least one seizure during their lives¹. There are different types of seizures with several possible causes².

Types of epileptic seizures

Epileptic seizures can vary greatly in terms of symptoms, severity and the areas of the brain involved. However, they are generally classified into two broad categories based on how and where the abnormal electrical activity begins and occurs in the brain: generalised seizures and focal seizures (previously known as partial seizures). Understanding the different clinical manifestations between these two main types of epileptic seizures is essential for diagnosis and treatment, as each category encompasses several subtypes with distinct features and potential triggers. Below is an overview of the most common seizure types within each group.

Generalised seizures

Abnormal electrical activity occurs in both hemispheres of the brain⁴. These seizures can be further divided into several categories⁴, including:

• tonic-clonic seizures, also known as “grand mal” seizures, which cause loss of consciousness and many other symptoms⁵;
• absence seizures, also called “petit mal” seizures, more frequent in children, which involve a very short loss of consciousness, staring into space or repetitive movements, often several times a day⁵;
• atonic seizures involving a sudden loss of muscle tone, which can cause the person to fall⁵.

Focal seizures (previously called partial seizures)

The abnormal activity only affects certain areas (one side) of the brain and does not involve the entire body⁴. Focal seizures can further be divided into⁴:

• focal (partial) seizures with preserved consciousness, where the person remains conscious, with involuntary movements or jerking of the legs or arms, tingling, dizziness and/or seeing flashing lights⁶;
• focal (partial) seizures with preserved consciousness, where the person experiences confusion or impaired awareness, even for only part of the seizure. There may be staring or repetitive movements⁴;
• a focal seizure can also evolve into a generalised seizure, in which case this is known as a focal to bilateral tonic-clonic seizure⁴.

Causes of epileptic seizures

A common cause of seizures is epilepsy, which is diagnosed if there have been at least two unprovoked seizures¹.

What causes epilepsy? Contrary to what is sometimes incorrectly believed, epilepsy is not contagious and, in as many as half of patients, has no identifiable cause¹. In the remaining cases, it can be linked to specific conditions, such as brain tumours, infections, strokes and other diseases affecting the brain¹. 

In addition to epilepsy, other triggers of seizures include infections like meningitis and encephalitis, head trauma, brain tumours, congenital abnormalities, certain diseases that cause inflammation in the brain, high fever, metabolic disorders and electrolyte imbalances in the blood². Certain medicines, including some antidepressants and antihistamines, and some psychoactive substances in general can also trigger a seizure in certain people⁷.

Diagnosis and treatment

Clinical evaluation is the first tool a doctor employs to diagnose seizures and epilepsy². One test that is sometimes useful is the electroencephalogram (EEG), which records electrical activity in the brain². Sometimes polysomnography is also used, if seizures occur at night⁸. Specialists can also order specific blood tests to check for metabolic imbalances or other changes⁹. Neuroimaging techniques, such as computer tomography (CT scan) and magnetic resonance imaging (MRI/fMRI), provide visual information about the brain structures and how they function, and can help identify abnormalities¹⁰. It is important to know the causes of seizures to be able to choose the most appropriate treatment for individual cases.

There is no definitive cure for epilepsy, but current therapies are effective at preventing or blocking seizures in about 70% of patients¹¹. For the remaining cases, new technologies now make surgery a safer and more targeted option than it was in the past¹¹. 

References

1. WHO. Epilepsy. 7 February 2024
2. Huff J. S., Murr N. I., “Seizure”. [Updated 2023 Feb 7]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK430765/
3. Mayo Clinic (nonprofit, Usa), Seizures, 1 November 2024
4. Epilepsy Foundation, “Types of Seizures”, 1 March 2022
5. Epilepsy Foundation, “Generalized Onset Seizures”
6. Istituto Superiore di Sanità (ISS), “Epilessia”, 30 January 2019
7. Chen H. Y., Albertson T. E., Olson K. R. “Treatment of drug-induced seizures”. Br J Clin Pharmacol. 2016 Mar;81(3):412-9. doi: 10.1111/bcp.12720. Epub 2015 Sep 17. PMID: 26174744; PMCID: PMC4767205, https://pmc.ncbi.nlm.nih.gov/articles/PMC4767205/
8. Foldvary-Schaefer N., Alsheikhtaha Z., “Complex nocturnal behaviors: nocturnal seizures and parasomnias”. Continuum (Minneap Minn). 2013 Feb;19(1 Sleep Disorders):104-31. doi: 10.1212/01.CON.0000427210.98305.8f. PMID: 23385697, https://pubmed.ncbi.nlm.nih.gov/23385697/
9. Nass R. D., Sassen R., Elger C. E., Surges R., “The role of postictal laboratory blood analyses in the diagnosis and prognosis of seizures”. Seizure. 2017 Apr;47:51-65. doi: 10.1016/j.seizure.2017.02.013. Epub 2017 Feb 27. PMID: 28288363, https://www.sciencedirect.com/science/article/pii/S1059131117301449
10. Epilepsy Foundation, “Tests and investigation”
11. Epilepsy Foundation, “Treatment”