What is Febrile Seizure?
Febrile seizures are generalized seizures, common in children between the ages of 6 months and 5 years, that happen when they have a high body temperature above 100.4 °F (38 °C). But they are not tied with a central nervous system (CNS) infection, known causes that could trigger a seizure (such as an imbalance of electrolytes, low blood sugar, or substance misuse), or a history of a seizure without fever. Every child’s body has a different temperature limit that may trigger a seizure, hence there is no set limit of fever required to trigger these seizures. The factors that put children at risk for febrile seizures may include having some kind of existing nervous system damage, presence of a viral infection, family history of seizures, developmental delays, or low serum zinc and iron levels, and maternal smoking and stress. Most febrile seizures resolve on their own and do not cause any complications.
However, some research shows evidence that some patients might be at a higher risk of having epilepsy or another seizure disorder later in life after a febrile seizure. It is believed by some experts that this could be influenced by any existing nervous system abnormality or the impact of a febrile seizure on the growing nervous system.
Febrile seizures can be divided into two categories: simple febrile seizures, which are single seizures lasting 15 minutes or fewer, and complex febrile seizures, which involve multiple seizures happening within 24 hours. These seizures may display focal neurological features (like changes in vision or mood) or a seizure lasting more than 15 minutes. The majority of febrile seizures fall into the simple category. A rare subtype of febrile seizures is febrile status epilepticus, which refers to seizures lasting longer than 30 minutes and is associated with more negative outcomes than simple febrile seizures.
In assessing febrile seizures, doctors primarily focus on identifying the type of seizure and the root cause of the fever through clinical assessment and diagnostic tests. Most febrile seizures resolve on their own and may not require extensive management. However, complex or long-lasting febrile seizures may require medication to stop the seizure. This helps healthcare professionals manage febrile seizures, equipping them with the latest knowledge and strategies for effective evaluation, timely treatment, and improved care coordination, leading to improved outcomes for the patient.
What Causes Febrile Seizure?
Febrile seizures are a type of seizures that usually occur in children aged between 6 months and 5 years and happen when a child has a fever above 100.4 °F (38 °C). These seizures are not caused by an infection in the central nervous system (CNS), known triggers of seizures like imbalance of salts in the body, low blood sugar level, substance misuse, or a history of similar seizures without fever. The temperature at which these seizures occur can vary from child to child. Some of the main factors that can increase the risk of febrile seizures include an existing neurological issue, the presence of a virus, a family history of seizures, developmental delays, low levels of zinc and iron in the blood, and stress or smoking during pregnancy.
It is estimated that 10% to 33% of children who have febrile seizures have a close relative who has also had seizures. In fact, studies of twins suggest that there may be a genetic factor involved in febrile seizures. Additionally, there might be specific genes that increase the risk of febrile seizures that are found at certain locations in our DNA. These locations are referred to as loci, and the implicated ones include 1q31, 2q23*34, 3p24.2*23, 3q26.2*26.33, 5q14*15, 5q34, 6q22*24, 8q13*21, 18p11*2, 19p13*3, 19q, and 21q22.
The highest temperature reached during a fever, rather than the speed at which the temperature rises, may also influence the risk of febrile seizures. Additionally, the seizure threshold, or the level at which a seizure can occur, varies among individuals and changes with age and development. Infants generally have a lower seizure threshold, which means they may be more likely to experience febrile seizures than older children, especially if they were premature or if they were given medications containing steroids after being born. Babies may also have a lower seizure threshold if they have certain nutrient deficiencies such as iron, zinc, vitamin B12, folic acid, selenium, calcium, and magnesium, or imbalances in bodily fluids and salts, like with low sodium levels.
It’s also important to note that febrile seizures aren’t caused by any specific type of fever. However, they are more commonly associated with viral infections than bacterial infections. The Roseolovirus is the most common virus linked to febrile seizures in the US and Europe, especially in children under 2 years. Some research also shows that febrile seizures caused by the Roseolovirus can be more complicated and have a higher chance of happening again. In Asian countries, the influenza A virus has been frequently linked to febrile seizures. Other viral infections that are often associated with these seizures include human herpesvirus 7 (HHV-7), human coronavirus HKU1, adenovirus, RSV, cytomegalovirus, shigella, and herpes simplex virus (HSV).
Sometimes, a few days after a child has received certain vaccines, there can be a small increase in the risk of febrile seizures. These vaccines include the DTaP-IPV-Hib, MMRV, conjugated pneumococcal vaccine, and some types of inactivated influenza vaccines. The risk is slightly higher if a child gets more than one vaccination at the same time. However, this risk is still considered low. For instance, one study found that if children were given IIV3, PCV, and DTaP-containing vaccines at the same time, there would be an additional 30 febrile seizures for every 100,000 children vaccinated, compared to giving these vaccines on separate days.
Risk Factors and Frequency for Febrile Seizure
Febrile seizures are the most common type of seizure in children, specifically those aged between 6 months to 5 years. They’re particularly common in boys, and affect around 2% to 5% of children in the U.S and Europe. The highest frequency of these seizures is seen in children aged 12 to 18 months. It’s also been noted that they are more likely to occur in the afternoon and in winter.
- Febrile seizures commonly affect children between 6 months to 5 years old.
- Boys are slightly more likely to have these seizures.
- About 2% to 5% of children in the U.S. and Europe experience these seizures.
- They are most common in children aged 12 to 18 months.
- They are more likely to happen in the afternoon and during winter.
- While some children only have one febrile seizure event, around 30% have multiple seizures during their early childhood.
Signs and Symptoms of Febrile Seizure
Febrile seizures often happen in children and it’s crucial to understand their medical and vaccination history, any recent sickness, and their development. This information, along with a detailed description of the seizure can help healthcare providers figure out if it’s a simple febrile seizure or a more complicated one.
Simple febrile seizures often have one episode of convulsive movements, usually affecting the face and respiratory muscles, lasting less than 15 minutes with a little bit of drowsiness afterwards. On the other hand, complex febrile seizures can involve seizures on one side of the body, lasting 15 minutes or more, and can happen again within 24 hours. These are often followed by weakness or paralysis on one side of the body. Both types can have associated symptoms including loss of consciousness, frothing at the mouth, difficulty breathing, and turning blue. It is also necessary to investigate any possible brain infection and underlying structural abnormalities to see if the episode was a febrile seizure or a symptom of a more severe illness.
Patients should have a general and neurologic exams after a seizure to ensure they have returned to their normal state. However, if a patient still presents symptoms like headaches, cognitive problems, or weakness, other diagnoses should be considered. During the physical check-up, vital signs should be observed multiple times and factors that could suggest the cause of the fever should be noted. This could include red, bulging eardrums, a red throat, large and inflamed tonsils, neck stiffness, bulging soft spots on the head, and signs like the Brudzinski sign. A full neurological examination, including a check of the back of the eye to evaluate for increased pressure in the brain, should also be done. Lastly, skin abnormalities that might indicate a cause should be looked at. This can include things like a port-wine stain on one side of the body (associated with Sturge-Weber syndrome), light-colored spots that could indicate tuberous sclerosis, or multiple ‘café au lait’ spots and Lisch nodules which could suggest neurofibromatosis.
Testing for Febrile Seizure
In simpler terms, if a person shows signs of a simple febrile seizure, which is usually harmless, they typically don’t need any additional tests. But if their symptoms suggest a more complex febrile seizure, a more detailed check-up is required. This will usually involve ruling out underlying causes such as infections or physical abnormalities and also include an electroencephalogram (EEG), a test that checks the electrical activity in the brain.
The doctors will also carry out blood tests and urine tests, especially if the patient is showing signs of dehydration, excessive vomiting, or diarrhea. In severe cases of complex febrile seizures, a person may have to stay in the hospital for careful observation and further tests.
Doctors don’t usually recommend a spinal tap (also called lumbar puncture) for somebody who had a simple febrile seizure and is quickly back to their normal state. However, it may be needed if there is a worry about a potential brain and spinal cord (CNS) infection. This test may also be considered for infants who experience a feverish seizure, who are under 1 year old, unvaccinated against two important bacterial infections caused by Streptococcus Pneumoniae and Haemophilus Influenza type B, had a seizure two days after developing a fever, or are taking antibiotics (which can potentially conceal a meningitis or other CNS infection).
Imaging tests (such as MRI or CT scans) of the head are not commonly needed after febrile seizures, unless there’s a concern about increased pressure inside the skull, a focal neurologic abnormality (a smaller area of damage in the nervous system), potential brain defects, or if the size of the head is abnormally large, or there’s been a severe head injury.
Treatment Options for Febrile Seizure
When a child experiences febrile seizures, which are seizures caused by a fever, the primary focus is on providing comfort and care to them and determining if there might be any underlying health conditions causing the fever. There’s no particular treatment for simple or complex febrile seizures.
Medicines to reduce fever, known as antipyretics, have not been proven to stop further febrile seizures from happening. Preventing recurrent febrile seizures is quite tricky. Some studies have looked at the use of benzodiazepines, a type of medication, to prevent further seizures during future febrile illness. However, the side effects of these drugs were more significant than the potential benefits, so they are not typically recommended.
While most of the time, febrile seizures occur once and then resolve on their own, there are cases when continuous seizures happen, a condition termed “febrile status epilepticus”. This occurs in less than 10% of children during their first febrile seizure. If a patient experiences febrile status epilepticus, or if the seizures last more than 5 minutes, certain medications may be used. These could include benzodiazepines given through a vein (such as lorazepam), diazepam given rectally, or midazolam given through the nose.
Additionally, non-drug methods such as undressing the child, fanning them directly, or sponging them with lukewarm water have not been shown to be effective in preventing further fevers or seizures.
What else can Febrile Seizure be?
When diagnosing febrile seizures, doctors often review a list of conditions that may cause similar symptoms. These include:
- Breath-holding spells
- Central nervous system infections, such as aseptic meningitis, viral or bacterial meningitis, and encephalitis
- Reactions due to medication
- Febrile delirium (a state of confusion caused by a high fever)
- Febrile myoclonus (random muscle jerking due to fever)
- Febrile Infection-Related Epilepsy Syndrome (FIRES)
- Genetic epilepsy with febrile seizures plus (GEFS+)
- Metabolic disturbances such as low blood sodium (hyponatremia)
- Severe shaking due to fever (shaking chills or rigors)
- Simple febrile seizure
- Tonic-clonic seizures (where the body stiffens and then the limbs begin to jerk)
What to expect with Febrile Seizure
Febrile seizures, caused by fever, are usually safe and don’t result in long-term issues related to the brain or cognitive functions. In fact, most children who have febrile seizures develop normally. Research shows that nearly 30% of children with a history of febrile seizures could face a higher chance of them happening more than once. If a child is under the age of 12 months when they have their first febrile seizure, they have a 50% possibility of having a second one within that same year. However, this risk goes down to 30% in the next year.
It might be more likely to have multiple febrile seizures if the child’s initial seizure happens at a young age, there is a family history of febrile seizures, the fever intensity during the seizure isn’t high, and the time period between the fever starting and the seizure is short. However, having complex febrile seizures doesn’t always mean the risk of recurrence is higher.
About 1% to 2% of children who have simple febrile seizures might develop epilepsy later in life; this rate is only slightly higher than the rate of the general population, which stands at around 0.5% to 0.9%. However, if a child has a history of complex febrile seizures, started having febrile seizures at a younger age, has endured long-lasting febrile seizures, shows signs of unusual brain development, has an abnormal EEG (a test that captures brain activity), or has a family history of epilepsy, they could face a 2% to 10% risk of developing epilepsy later in life, depending on how many of these risk factors are present.
Importantly, a single instance of febrile seizure doesn’t seem to be connected to future issues such as learning disabilities, decreased intelligence levels, behavioural issues, or problems with executive functions (the skills that help us organize and act on information). However, kids with repetitive febrile seizures might have a slightly increased risk of having delayed vocabulary development.
Possible Complications When Diagnosed with Febrile Seizure
While febrile seizures generally resolve on their own and have positive outcomes, there are a few rare complications that can occur. These can include:
- Unexpected death
- Development of epilepsy
- Brain disease (Encephalopathy)
- Autism spectrum disorder
- Intellectual disability
- Attention-deficit/hyperactivity disorder
- Tourette syndrome
- Allergic rhinitis (hay fever)
- Asthma
Remember, these complications are rare, but it’s important to be aware of the risks associated with febrile seizures.
