Febrile seizures are convulsions of sudden onset due to abnormal electrical activity in the brain that is caused by fever . Fever is a condition in which body temperature is elevated above normal (generally above 100.4°F [38°C]).
Febrile seizures were first distinguished from epileptic seizures in the twentieth century. The National Institutes of Health defined febrile seizures in 1980 as "an event in infancy or childhood usually occurring between three months and five years of age, associated with fever, but without evidence of intracranial infection or defined cause."
There are three major subtypes of febrile seizures. The simple febrile seizure accounts for 70 to 75 percent of febrile seizures and is one in which the affected child is age six months to five years and has no history or evidence of neurological abnormalities, the seizure is generalized (affects multiple parts of the brain), and lasts less than 15 minutes, and the fever is not caused by brain illness such as meningitis or encephalitis . The complex febrile seizure shares similar characteristics with the exception that the seizure lasts longer than 15 minutes or is local (affects a localized part of the brain), or multiple seizures take place and accounts for about 20 to 25 percent of all febrile seizures. Lastly, about 5 percent of febrile seizures are diagnosed as symptomatic, in cases in which the child has a history or evidence of neurological abnormality.
The seizure activity itself is generally characterized as clonic (consisting of rhythmic jerking movements of the arms and/or legs), or tonic-clonic (commencing with a stiffening of the body followed by a clonic phase).
Fever is the most common cause of seizures in children, occurring in 2 to 5 percent of children from six months to five years of age. First onset usually occurs by two years of age, with the risk decreasing after age three; most children stop having febrile seizures by the age of five or six. Male children have been shown to have a higher incidence of febrile seizures. The majority of children who experience a febrile seizure will only have one in their lifetime; approximately 33 percent will go on to have more than one.
Causes and symptoms
Under normal circumstances, information is transmitted in the brain by means of electrical discharges from brain cells. A seizure occurs when the normal electrical patterns of the brain become disrupted. A febrile seizure is caused by fever, most commonly a high fever that has risen quickly. The average fever temperature in which febrile seizures take place is 104°F (40°C). Conversely, a healthy person's body temperature fluctuates between 97°F (36.1°C) and 100°F (37.8°C).
Fevers are caused in most cases by viral or bacterial infections, such as otitis media (ear infection), upper respiratory infection, pharyngitis (throat infection), pneumonia , chickenpox , and urinary tract infection. Other conditions can induce a fever, including allergic reactions, ingestion of toxins, teething, autoimmune disease, trauma, cancer , excessive sun exposure, or certain drugs. In some cases no cause of the fever can be determined.
Febrile seizures generally last between one and ten minutes. A child experiencing a febrile seizure may exhibit some or all of the following behaviors:
- stiff body
- twitching or jerking of the extremities or face
- rolled-back eyes
- inability to talk
- problems breathing
- involuntary urination or defecation
- confusion, sleepiness, or irritability after the seizure
Approximately one third of children who have had a febrile seizure will experience recurrent seizures. Several risk factors are associated with recurrent febrile seizures; children who exhibit all four are at a 70 percent chance of developing recurrent seizures, while those who have none of the risk factors have only a 20 percent chance. The risk factors include:
- family history of febrile seizures
- young age of the child (i.e. less than 18 months of age)
- seizure occurs soon after or with onset of fever
- seizure-associated fever is relatively low
When to call the doctor
A healthcare provider should be contacted after a febrile seizure. A visit to the emergency room is warranted if the accompanying fever is greater than 103°F (39.4°C) in a child older than three months or 100.5°F (38°C) in an infant of three months or younger or if the seizure is the child's first. Emergency medical personnel (telephone 911) should be called if a febrile seizure lasts more than five minutes; if the child stops breathing; if the child's skin starts to turn blue; or if the fever is greater than 105.8°F (41°C), a condition called hyperpyrexia.
A key focus of diagnostic tests will be to determine the underlying cause of the fever. A comprehensive medical history including the fever's duration and course, other symptoms the child is experiencing, prior or current medical conditions, recent vaccinations or exposure to communicable diseases, and the child's current behaviors may point to the fever's origin. A temperature below 100.4°F (38°C) suggests another cause for the seizure. The caregiver who was present with the child while he or she was having the seizure will be asked questions relating to the child's behaviors in an attempt to determine the type of seizure.
Physicians may administer tests to rule out conditions other than fever that could have caused the seizure, such as epilepsy, meningitis, or encephalitis. Children who suffer from recurrent febrile seizures are not diagnosed with epilepsy, a seizure disorder that is not caused by fever. In the case of children under 18 months of age, a lumbar puncture (spinal tap) may be recommended to rule out meningitis because symptoms are often lacking or subtle in children of that age. Because of the benign nature of the simple febrile seizure, tests such as computed tomography (CT) scans, magnetic resonance imaging (MRI), or electroencephalogram (EEG) are not usually recommended.
During a seizure parents or caregivers need to remain calm and take steps to make sure the child remains safe. During the period after the seizure the child may be disoriented and/or sleepy (called the postictal state), but quick recovery from this state is normal, and medical treatment is not normally needed.
During a seizure
If a parent or caregiver observes a child having a seizure, there are a number of measures that should be taken to ensure the child's safety . These include:
- staying calm
- laying the child on his or her side or front to prevent vomited matter from being aspirated into the lungs
- loosening any tight clothing or items that could constrict breathing
- marking the start and end time of the seizure
- clearing the surrounding area of unsafe items
- attending to the child for the duration of the seizure
- clearing the child's airway if it becomes obstructed with vomited material or other objects
Parents or caregivers should not attempt to stop the seizure or slap or shake the child in attempt to wake him/her. The child may move around during the seizure, and parents should not try to hold the child down. If the child vomits, a suction bulb can be used to help clear the airway.
After a seizure
A healthcare professional should be called immediately after the seizure in the event that further treatment or tests are required. Hospitalization is not normally required unless the child is suffering from a serious infection or illness or the seizure itself was abnormally long. Parents or caregivers may be instructed to take certain measures at home to reduce the child's fever, such as administering fever-reducing drugs (called antipyretics) such as acetaminophen (Tylenol) or ibuprofen (Advil). There is, however, no evidence that shows fever-reducing therapies reduce the risk of another febrile seizure occurring. If the child is suffering from a bacterial infection that is the cause of the fever, he or she may be placed on antibiotics .
Treating the fever
The treatment of pediatric fever varies according to the age of the child and the fever's cause, if known. Physicians recommend that newborns less than four weeks of age with fever be admitted to the hospital and administered antibiotics until a complete workup can be done to rule out bacterial infection or other serious illness. The same is recommended for infants ages four to 12 weeks if they appear ill. Infants of this age who otherwise appear well can often be managed on an outpatient basis with antipyretics and antibiotics in the case of bacterial infection.
For children ages three months and older, the course of treatment depends on the extent and cause of the fever. Most fevers and associated conditions can be managed on an outpatient basis. Low-grade fevers often do not need to be treated in otherwise healthy children. Antipyretics may be suggested to lower a fever and make the child more comfortable but will not affect the course of an underlying infectious disease. Aspirin should not be given to a child or adolescent with a fever since this drug has been linked to an increased risk of the serious condition called Reye's syndrome . Antibiotics may be administered if the child has a known or suspected bacterial infection.
There are some outpatient treatments that parents or caregivers may administer to reduce their febrile child's discomfort, although there is no evidence that indicates such treatments reduce the risk of febrile seizures. These include dressing the child lightly, applying cold washcloths to the face and neck, providing plenty of fluids to avoid dehydration , and giving the child a lukewarm bath or sponging the child in lukewarm water.
The risk of complications associated with febrile seizures is very low. Some of the complications that may occur are:
- biting the tongue
- choking on items that were in the mouth at the start of the seizure
- injury from falling down
- aspirating fluid or vomit into the lungs
- developing recurrent febrile seizures
- developing recurrent seizures unrelated to fever (epilepsy)
- complications related the underlying cause of the fever
Children who have had a febrile seizure are at an increased risk of having another; approximately one third of febrile seizure cases become recurrent. The risk of recurrent seizures decreases with age: infants younger than 12 months have a 50 percent chance of having a second seizure, while children over the age of 12 months have a 30 percent chance. The risk of a child going on to develop epilepsy is slightly increased at approximately 2–5 percent, compared to 1 percent for the general population; such a risk is increased in children who have a history of neurological abnormalities such as cerebral palsy or developmental delays and in children whose seizures recur or are prolonged. Research has shown that febrile seizures do not affect a child's intelligence level or achievement in school.
In some cases, a febrile seizure may be the first indication that a child is ill. Prevention is, therefore, not always possible. While the use of anticonvulsants such as Phenobarbital or Valproate has been shown to prevent recurrent febrile seizures, these drugs are associated with significant side effects such as adverse behaviors, allergic reaction, and organ injury, and have not been shown to benefit simple febrile seizures. Only rarely is anticonvulsant therapy recommended for a child with febrile seizures because of the generally benign nature of the seizures and the risk of side effects from the drugs. In some cases oral diazepam (Valium) can be administered at the first sign of fever to reduce the risk of febrile seizures; about two-thirds of children who receive this drug experience side effects such as sleepiness and loss of coordination. The majority of children who have had a febrile seizure do not need drug therapy. Parents may be directed to administer over-the-counter antipyretics at the first sign of fever.
A febrile seizure can be a frightening experience for both the child and his or her parents. It is important that parents be educated about the low risk of simple febrile seizures and the measures that can be taken to ensure their child's safety during and after a seizure.
Antipyretic drug —Medications, like aspirin or acetaminophen, that lower fever.
Autoimmune disorder —One of a group of disorders, like rheumatoid arthritis and systemic lupus erythematosus, in which the immune system is overactive and has lost the ability to distinguish between self and non-self. The body's immune cells turn on the body, attacking various tissues and organs.
Encephalitis —Inflammation of the brain, usually caused by a virus. The inflammation may interfere with normal brain function and may cause seizures, sleepiness, confusion, personality changes, weakness in one or more parts of the body, and even coma.
Hyperpyrexia —Fever greater than 105.8°F (41°C).
Meningitis —An infection or inflammation of the membranes that cover the brain and spinal cord. It is usually caused by bacteria or a virus.
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Stephanie Dionne Sherk
Febrile seizures are the most common type of convulsions in infants or small children and are triggered by fever. It is not in the strict sense an epilepsy syndrome but rather a symptom of a febrile illness, and it normally affects children between three months and five years of age, mainly toddlers. During a febrile seizure, a child may lose consciousness and move or shake the limbs. The seizure itself is normally harmless and does not cause brain damage. A child who experiences a seizure in the setting of a fever should be taken to the hospital so that any serious causes of the fever can be evaluated.
Febrile seizures (or convulsions) occur mainly in children between three months and five years of age and are associated with a fever of any cause. Toddlers are most commonly affected and there is a tendency for febrile seizures to run in families. These seizures are associated with fevers that rapidly rise to temperature up to or above 102°F, but they can also occur with lower temperatures.
There are two types of febrile seizures: simple (or benign) and complex. Benign febrile seizures account for 80–85% of all febrile seizures, and last less than 15 minutes. They usually do not recur within 24 hours. Complex febrile seizures, which suggest a more serious illness, account for 15–20% of all cases, last more than 15 minutes, and can recur within 24 hours.
Children with febrile seizures often lose consciousness and shake, moving limbs on both sides of the body. Less commonly, children become rigid or have twitches on only one side of the body.
About 2–5% of all children experience a febrile seizure and about 25% of these children have a first-degree relative with history of febrile seizures. There is a slightly higher prevalence among boys, and no ethnic differences have been reported. Less than 5% of children with febrile seizures will eventually develop epilepsy.
Causes and symptoms
The exact role of the fever in the development of seizures is not clear. However, it is known that viral infections are the most common cause of fever in children with a first febrile seizure who are admitted to hospitals, mainly caused by viruses like herpes and influenza. Meningitis causes less than 1% of febrile seizures, but should be investigated to rule out this serious infection, especially in children less than one year old or those who continue to appear ill after the fever subsides. Seizures that occur after immunizations are likely to be the febrile type due to temperature elevation, particularly those after the DTP (diphtheria, pertussis, tetanus) and measles immunizations. Upper respiratory tract infections accompanied by high fever, in combination with a low seizure threshold, can often affect infants and young children and, thus, account for the most common cause of these convulsions.
In a few studies, children with febrile seizures have been found to have decreased zinc levels in both the serum and the cerebrospinal fluid, which is the fluid that bathes the brain and the spinal cord. Deprivation of zinc may play a role in the seizures. Children with iron-deficiency anemia have been shown to have febrile seizures at a higher rate than nonanemic children.
There is a positive family history in up to 31% of all cases of febrile seizures, although the exact mode of inheritance is not known and varies among families. It has long been recognized that there is a genetic component for the susceptibility to this type of seizure; this may be caused by mutations in several genes, especially the FB4 gene.
Febrile seizures typically begin with a sudden contraction of muscles on both sides of the body, usually facial muscles, trunk, arms, and legs. The force of the muscle contraction may cause the child to emit an involuntary cry or moan. The child falls, if standing, and may bite the tongue. Urinary incontinence and vomiting can occur. The child will not breathe, and may turn blue. Children cannot respond to any stimuli, and loss of consciousness, hallucinations, confusion, and feelings of fear or other emotions may occur. Focal seizures (those without loss of consciousness) involving only a part of the body are less common, and might become generalized, affecting the whole body.
The first action of the physician is to stop the fever and find its cause(s). Physicians may ask about previous seizures without a fever, which can indicate that the child is more likely to have an underlying seizure disorder such as epilepsy rather than a febrile seizure. Physicians also consider the family history of seizures, febrile or otherwise, and must investigate any known nervous disorder in the child, such as developmental delay or severe head injury. Any medication the child has taken is suspicious, and the possibility of drug reaction or poisoning may also be considered.
It is important to rule out any infectious disease as the first cause of a seizure, especially meningitis. In the case of meningitis, the child appears particularly ill, shows neck rigidity, has an unusually long period of drowsiness after the seizure, and experiences a complex febrile seizure (often prolonged and repeated). Lumbar puncture (commonly known as a spinal tap) can be performed in this case to examine the cerebrospinal fluid for indications of meningitis. Other tests such as blood tests, urine tests, and x rays may be used in diagnosing the cause of fever.
A pediatrician is normally the first physician to be seen, and a neurologist should be considered for those cases in which a neurological disorder is thought to be the cause of the seizure rather than the fever.
During the acute phase of the seizure, the main objective is to keep the child in a position on his or her side or stomach to avoid aspiration of saliva or vomit and avoid injuries. The child should be placed on the floor or in a safe area, and all dangerous objects must be removed. A child having a seizure should not be restrained. If the child vomits, or if saliva and mucus build up in the mouth, a side posture should be used. It is also important that parents do not force anything into the child's mouth, as this could result in breaking teeth. Also, tongue swallowing will not occur. If the child inadvertently bites the tongue, it will heal. Any tight clothing should be removed, especially around the neck. Because the seizure occurs in the setting of a fever, the main target of therapy is to bring the fever down. Removing the clothes and applying cool washcloths to the child's neck and face may help, and acetaminophen or ibuprofen suppositories, if available, may control the elevated temperature.
Rarely, a child may experience a persistent seizure, which could evolve into what is called status epilepticus . Airway management and anticonvulsivants are the first line of treatment during this medical emergency.
The most commonly used medication includes benzodiazepines such as lorazepan (Ativan) and diazepam (Valium). An intravenous line is usually placed in the vein because it is the fastest and most reliable means of drug administration.
Recovery and rehabilitation
Children are normally drowsy or in a state of confusion after a seizure, but become responsive within 15–30 minutes. A simple febrile seizure stops by itself within a few seconds to 10 minutes, usually followed by a brief period of drowsiness or confusion. In this case, an anti-seizure medication may not be required. After a seizure, the child is twitchy, with jerks of the arms and legs.
As of early 2004, there are no open clinical trials for febrile seizures at the National Institutes of Health (NIH). However, the National Institute of Neurological Disorders and Stroke (NINDS), a part of the NIH, often sponsors research on febrile seizures in medical centers throughout the United States.
About 35% of children who have had a febrile seizure will have another one with a subsequent fever. Of those who do, about 50% will have a third seizure. Few children have more than three seizure episodes. A child is more likely to fall in the group that has more than one febrile seizure if there is a family history, if the first seizure happened before 12 months of age, or if the seizure happened with a fever below 102°F.
Seizures occur at the time the brain is sensitive to the effects of temperature and often cause parents great anxiety. As the onset is dramatic, parents are afraid their children will die or undergo brain damage. However, simple febrile seizures are harmless and they do not cause death, brain damage, epilepsy, mental retardation , or learning difficulties.
Parental anxiety or other factors may cause a child to be placed on long-term anticonvulsant medicine. This will not benefit the patient. Children with the possibility of having a second seizure should not engage in activities that are potentially harmful, such as taking unsupervised baths or climbing higher than 5 ft (1.5 m) off the ground.
Baram, Tallie Z., and Shlomo Shinnar. Febrile Seizures. New York: Academic Press, 2001.
Baumann, R. J., and P. K. Duffner. "Treatment of Children with Simple Febrile Seizures: The AAP Practice Parameter." Pediatr Neurol 23 (2000): 11–17.
"NINDS Febrile Seizures Information Page." National Institute of Neurological Disorders and Stroke. March 4, 2004 (April 27, 2004). <http://www.ninds.nih.gov/health_and_medical/disorders/febrile_seizures.htm>.
Marcos do Carmo Oyama
Iuri Drumond Louro, MD, PhD