A gelastic seizure is a partial seizure that begins in the hypothalamus area of the brain. A person experiencing a gelastic seizure may uncontrollably laugh or smile, even though they may feel scared.

During a gelastic seizure, individuals may also look panicked, stare, smirk, or smack their lips.

This article provides an overview of these seizures, including typical accompanying symptoms and the potential outlook for people living with them. It also discusses the causes, diagnosis, and treatment of gelastic seizures.

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Gelastic seizures are a form of partial seizure. This means they start in one part of the brain rather than the whole organ. They originate in the hypothalamus, an area at the base of the brain.

These seizures often cause involuntary laughing or giggling, even though people may feel scared or anxious.

Individuals experiencing gelastic seizures may also uncontrollably smile, grimace, or smirk, potentially in moments that seem unusual or inappropriate to others.

An individual may experience many gelastic seizures every day. The Epilepsy Foundation states that they typically last 10–20 seconds or less.

However, a 2022 study suggests gelastic seizures may last around 100 seconds.

Gelastic seizures typically affect children and infants. According to the Epilepsy Foundation, symptoms of gelastic seizures may include:

  • an initial look of panic or fear, possibly due to experiencing an aura, which is a feeling or sensation before a seizure occurs
  • lip smacking or swallowing
  • slight smiling, which may seem forced
  • staring
  • the eyes seeming vacant with dilated pupils, which may move around
  • grunting or unusual squirming
  • running to safety or seeking comfort for no obvious reason

Individuals are often aware of what is happening around them during the seizures.

Gelastic seizures arise from atypical electric-chemical activity within the hypothalamus.

According to the Epilepsy Foundation, this brain activity often occurs due to a lesion or area in the hypothalamus that doctors call a hypothalamic hamartoma (HH). This is a congenital abnormality, which means it is present at birth. It is also nonmalignant, meaning that it is not cancerous.

According to a 2018 case study, gelastic seizures may also occur in individuals who have lesions in the frontal and temporal lobes of the brain.

Gelastic seizures may be challenging for healthcare professionals to diagnose definitively, even if they think someone is experiencing this type of seizure based on their symptoms.

According to the Epilepsy Foundation, this difficulty with diagnosis is because electroencephalograms (EEGs) cannot easily detect the unusual brain activity that prompts gelastic seizures.

Gelastic seizures often start from deep within the brain, and an EEG may not pick up unusual activity in this area unless a person has a seizure during a routine test.

People with gelastic seizures usually receive a diagnosis only after they start developing other forms of seizures.

In the first instance, a healthcare professional may explain what gelastic seizures are to people who have them and their loved ones. People may then have a better awareness of what steps to take during a seizure and how to recognize them with more accuracy.

Research suggests that gelastic seizures do not generally respond well to antiepileptic drugs, so surgical treatment may be more beneficial.

Doctors can use a variety of surgical techniques to remove the HH that is causing the seizures. These may include different types of craniotomy, which involves open surgery, or endoscopic surgery.

Other treatments may include radiofrequency ablation and gamma knife radiation.

Gelastic seizures can be unpleasant and scary for those who experience them. Children with an HH may experience many seizures within a day. Over time, the HH can cause issues with the following:

  • memory
  • cognition
  • mood

Gelastic seizures can also progress to other kinds of seizures.

However, treatment may help improve the outlook for people with an HH. According to studies researchers cite in a 2023 review, surgery to remove HH lesions may lead to more than a 90% reduction in seizure frequency.

Below are answers to some of the most common questions about gelastic seizures.

Are gelastic seizures serious?

A gelastic seizure is a form of partial seizure that causes uncontrollable laughter or smiling. People are usually aware of what is happening around them during the seizure.

However, gelastic seizures may be unsettling or frightening for those who experience them. Additionally, individuals who experience gelastic seizures often go on to experience other types of seizures.

How rare is gelastic epilepsy?

Gelastic seizures are very rare. The principal cause is a hypothalamic hamartoma (HH). Research suggests that only in 1 in every 100,000 children may experience an HH and that males are slightly more likely than females to have gelastic seizures.

Do gelastic seizures show up on an EEG?

In theory, an EEG should be able to detect a gelastic seizure. However, because gelastic seizures begin in the hypothalamus, deep within the brain, EEGs often cannot detect them during routine tests. For this reason, doctors may find it challenging to confirm a gelastic seizure diagnosis.

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Gelastic seizures originate from deep inside the brain, in the hypothalamus. They often cause a person to laugh or smile uncontrollably. Individuals with gelastic seizures may experience fear or discomfort before or during their seizures. They may also stare into space, move their eyes, or smack their lips.

These rare seizures often arise during infancy or childhood. Doctors may have difficulty confirming a gelastic seizure diagnosis, as EEGs do not always pick up on the unusual brain activity that prompts them. Healthcare professionals often diagnose gelastic seizures only when an individual has developed other kinds of seizures.

Treatment for gelastic seizures typically involves surgery. A person can speak with a doctor if they think they or a child they are caring for may be experiencing gelastic seizures.