Febrile seizure

Definitions & Key takeaways

Febrile seizures are a type of seizure that can occur in children with fever (>38 ��). A seizure is a sudden, uncontrolled electrical disturbance in the brain. Febrile seizures typically affect children from 6 months to 5 years old, who do not have epilepsy or any other defined cause of seizures.

Febrile seizures usually occur in about 2% �4% of children younger than 5 years of age. Boys are more likely than girls to have febrile seizures, and there is a risk for recurrence if a child has had one before. Even though most febrile seizures are self-limiting and last for just a few seconds to minutes, some can last for up to 30 minutes, and antiseizure medications are recommended for those that continue for more than 5 minutes.

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Introduction0:00–0:13

Febrile seizures are seizures that happen with a fever, and they typically occur in young children between six months and five years of age.
Now, neurons are the main cells of the nervous system. They’re composed of a cell body, which has all the cell’s organelles, and nerve fibers, which are projections that extend out from the neuron cell body.

Physiology0:13–1:40

Nerve fibers are either dendrites that receive signals from other neurons, or axons that send signals signals called action potentials along to other neurons.
Where two neurons come together is called a synapse, and that’s where one end of an axon sends neurotransmitters to the dendrites or directly to the cell body of the next neuron in the series.
Some neurotransmitters bind to the receptors and tell the cell to open up the ion channels and relay an electrical message and these are called excitatory neurotransmitters.
But there are others which can close the ion channels and prevent an electrical message from going through and these are called inhibitory neurotransmitters.
The main excitatory neurotransmitter in the brain is glutamate. Glutamate binds to NMDA receptors which tell the cell to open up calcium ions channels.
Since calcium has a positive charge, it makes the inside of the cell more positive and that helps triggers an action potential.
On the flip side, the main inhibitory neurotransmitter in the brain is GABA. GABA binds to GABA receptors, which tell the cell to open up chloride ion channels.
Since chloride has a negative charge, it makes the inside of a cell more negative and that inhibits an action potential.

Pathology1:40–2:45

During a seizure, large groups of neurons become active synchronously, meaning all at the same time. And in a febrile seizure, the trigger for that neuronal activity is a fever.
So that makes you wonder, why? Well, we actually don't know for sure, but there are some possible explanations.
The first is that a fever, raises the core body temperature and it makes neurons more excitable than usual - meaning that action potentials are more likely to happen.
The second is that fever causes hyperventilation, which is when you breathe faster and have a decreased level of carbon dioxide in the blood.
That leads to a respiratory alkalosis, or an increase in blood pH, which also seems to make neurons more excitable. The third is that fevers are caused by cytokines like interleukin-1β, that get released by white blood cells during the body’s innate immune response.
Cytokines are thought to also enhances the activity of the NMDA receptors. Of course, most of the time, people have fevers without having seizures, so these factors are just part of the story.

Risk factors2:45–3:35

While we don't know for sure what causes febrile seizures we do know there are certain risk factors. Genetics seems to play a role as children whose parents had febrile seizures are more likely to also have them.
Age seems to also be a factor, because although febrile seizures happen in children between the age of 6 month to 5 years, the majority happen in children that are 12 to 18 months of age.
Generally speaking, febrile seizures happen more often when the fevers develop rapidly or are higher in magnitude. Febrile seizures seem to be more associated with some infections like human herpesvirus-6 which causes roseola.
Febrile seizures can also develop after vaccinations that really stimulate the immune system like the measles, mumps, rubella, varicella vaccine, but the frequency is quite low and the benefits of vaccination outweigh this risk.

Symptoms3:35–4:43

Febrile seizures also always involve a high temperature, or fever, of above 38 degrees Celsius or 100.4 degrees Fahrenheit, and they can be classified as either simple or complex.
A simple febrile seizure lasts for less then 15 minutes, affects the whole body, and doesn't repeat within 24 hours. A complex febrile seizure is one that lasts for over 15 minutes or affects a specific part of the body which corresponds to a specific part of the brain, or one that repeats within 24 hours.
Basically, if a seizure doesn’t meet the criteria for being considered simple, then it’s considered complex. Having said that, most febrile seizures are simple febrile seizures that last a couple of minutes, and they’re tonic-clonic, which means there's a tonic phase when muscles throughout the body suddenly tense up and go rigid, followed by a clonic phase, when muscles rapidly start contracting and relaxing, causing convulsions.
After the seizure itself, there’s usually a postictal state, which is when a child might feel confused and may not remember the episode.
They can also have residual arm or leg weakness. Treatment isn't needed for most febrile seizures because they usually stop by themselves.

Treatment4:43–5:38

During a febrile seizure, it's a good idea to lay a child on their side, and keep track of the time. It’s a bit more concerning if a seizure lasts for a long time or if there are other serious symptoms -- like vomiting, trouble breathing, or a stiff neck.
Oftentimes, it’s important to distinguish febrile seizures from other underlying causes of fevers and seizures like encephalitis and meningitis, which are infections of the brain and the tissue surrounding the brain.
In young infants a lumbar puncture can be helpful in identifying the underlying cause of the seizure. In some cases anti-seizure medications can be used, but typically they’re not needed in cases of simple febrile seizures.
Finally, the fever itself can be uncomfortable for a child, so antipyretic medications like ibuprofen or acetaminophen can be used to reduce the fever.
All right, as a quick recap... Febrile seizures are seizures that happen together with a fever in children.

Review5:38–6:58

Whether it's through an increase in body temperature, the alkalosis of the blood, or the release of certain chemicals, like interleukin-1β, fever seems to excite neuronal activity, which makes it easy for groups of neurons to start firing simultaneously, over and over again.
Most febrile seizures are generalized tonic clonic seizures that cause stiffness, jerking and loss of consciousness. Thankfully, most febrile seizures resolve themselves without any treatment and don’t cause long term harm.