Seizures in children have a wide range of causes, from high fevers and low blood sugar to epilepsy, infections, head injuries, and accidental poisoning. The most common trigger depends heavily on the child’s age. In newborns, oxygen deprivation during birth is the leading cause. In toddlers and preschoolers, fever-related seizures dominate. In older children, epilepsy and structural brain differences become more prominent. Understanding the possibilities can help you recognize what’s happening and communicate clearly with your child’s medical team.
Febrile Seizures: The Most Common Cause in Young Children
Febrile seizures, triggered by a rapid rise in body temperature during an illness, affect roughly 2% to 5% of children between 6 months and 5 years old. They are the single most frequent cause of seizures in this age group. The seizure itself is typically brief, lasting under five minutes, and involves stiffening, shaking, or jerking of the limbs. It can look alarming, but most febrile seizures do not cause lasting harm and do not mean a child has epilepsy.
What triggers a febrile seizure isn’t the height of the fever so much as how quickly the temperature spikes. Common illnesses like ear infections, flu, and roseola are frequent culprits. A small number of children who have one febrile seizure will have another during a future illness, particularly if the first episode happened before age 18 months.
Low Blood Sugar and Electrolyte Imbalances
The brain depends on a steady supply of glucose to function. When blood sugar drops below about 50 mg/dL, neurons can become hyperexcitable, and seizures can follow. Hypoglycemia is especially dangerous in newborns, who have high metabolic demands, and in children with diabetes whose blood sugar swings unpredictably. Symptoms leading up to a hypoglycemic seizure often include shakiness, sweating, confusion, and behavioral changes.
High blood sugar can also provoke seizures. A sudden spike, particularly during diabetic ketoacidosis, disrupts the brain’s electrical activity through a different mechanism. Children with diabetes occasionally develop focal motor seizures during these episodes.
Beyond glucose, imbalances in sodium, calcium, or magnesium can all lower the seizure threshold. These electrolyte shifts sometimes happen during severe dehydration, prolonged vomiting, or kidney problems.
Oxygen Deprivation at Birth
In newborns, the most significant cause of seizures is hypoxic-ischemic encephalopathy, a condition where the brain doesn’t receive enough oxygen during or around delivery. This can result from complications like umbilical cord problems, placental abruption, or prolonged labor. Seizures are often the first visible sign that a newborn’s brain has been injured, sometimes appearing within hours of birth.
Birth trauma, including physical injury to the head during a difficult delivery, can also lead to seizures in the first days of life. Perinatal stroke, where a blood vessel in the baby’s brain becomes blocked, is another cause. It can be triggered by blood clotting disorders, cardiac problems, or the trauma of delivery itself.
Head Injuries
Traumatic brain injury is a well-established seizure trigger in children of all ages. About 25% of children treated for severe traumatic brain injury experience post-traumatic seizures. The risk is highest in the youngest children: nearly 48% of those under 2 years old develop seizures after a severe head injury, compared to about 18.5% of older children.
Seizures after head trauma are classified by timing. Impact seizures happen within minutes. Early seizures occur within the first week. Late seizures develop after seven days and carry a higher risk of becoming recurrent. The presence of bleeding between the brain and skull (subdural hemorrhage) roughly doubles the odds of post-traumatic seizures, regardless of the child’s age. In cases of abusive head trauma, the combination of young age, abuse, and subdural bleeding creates the highest risk, with an estimated 60% chance of seizures.
Brain Infections
Meningitis and encephalitis, infections of the membranes surrounding the brain or the brain tissue itself, can both trigger seizures. Among children with confirmed infectious meningoencephalitis, roughly 14% experience seizures as part of their illness. These seizures may occur alongside fever, headache, neck stiffness, vomiting, or altered consciousness.
Bacterial meningitis tends to cause more severe seizures than viral forms. Encephalitis caused by herpes simplex virus is particularly dangerous in young children and can lead to prolonged or repeated seizures if not treated quickly. Any seizure accompanied by high fever, severe headache, a stiff neck, or a rash that doesn’t fade when pressed warrants urgent medical attention.
Epilepsy and Genetic Causes
Epilepsy, defined as a tendency toward recurrent unprovoked seizures, has many genetic roots in children. Some forms are relatively mild. Benign familial neonatal seizures, caused by mutations in genes that control potassium channels in the brain, typically appear in the first week of life and often resolve on their own. Benign familial infantile seizures, linked to a different gene, begin around 6 months and also tend to have a good outlook.
Other genetic epilepsies are far more serious. Dravet syndrome usually begins in the first year of life with prolonged, fever-triggered seizures that progress to multiple seizure types and developmental delays. It’s caused by a mutation in a gene responsible for sodium channels in the brain. Lennox-Gastaut syndrome, which typically starts between ages 3 and 5, involves multiple difficult-to-control seizure types and is often accompanied by intellectual disability. A rare X-linked form of epilepsy affects only girls and is tied to a gene involved in how brain cells connect to each other.
Chromosomal abnormalities, including fragile X syndrome and Wolf-Hirschhorn syndrome, also carry a significant seizure risk. In many of these conditions, seizures are one feature of a broader pattern that includes developmental differences, distinctive physical features, or intellectual disability.
Structural Brain Differences
Some children are born with differences in how the brain formed during pregnancy, and these structural abnormalities are a common cause of seizures that begin in infancy or early childhood. The most frequently identified include cortical dysplasia (where a patch of brain tissue didn’t develop its normal layered structure), gray matter heterotopia (where clusters of neurons ended up in the wrong location during development), and problems with the corpus callosum, the bridge connecting the brain’s two halves.
Focal cortical dysplasia is a particularly common finding in children with seizures that don’t respond well to medication. Children with heterotopia almost always develop epilepsy, with the severity depending on how widespread the misplaced tissue is. Sturge-Weber syndrome, a condition involving abnormal blood vessels on the brain’s surface, is another structural cause that frequently presents with seizures in infancy.
Accidental Poisoning and Drug Ingestion
Young children explore the world by putting things in their mouths, and accidental ingestion of certain medications or household chemicals can cause seizures. In one review of over 1,500 pediatric poisoning cases, seizures developed in about 1.6% of them. Tricyclic antidepressants, an older class of medication sometimes found in family medicine cabinets, were responsible for 42% of poisoning-related seizures in children. Nearly a quarter of those children developed status epilepticus, a prolonged seizure that doesn’t stop on its own.
Other substances known to trigger seizures in children include certain antihistamines, stimulants, insecticides, and camphor-containing products. Poisoning should be considered as a possible cause whenever a previously healthy child has an unexplained seizure without fever, especially in toddlers, even if no one witnessed the child swallowing anything.
How Doctors Identify the Cause
After a child’s first seizure, doctors work to determine whether it was provoked by something temporary (like a fever or low blood sugar) or whether it signals an ongoing condition. The process typically starts with a detailed history: what the seizure looked like, how long it lasted, whether the child was ill or injured, what medications are in the home, and whether there’s a family history of seizures.
An EEG, which records the brain’s electrical activity through sensors on the scalp, is a standard part of the evaluation. It can reveal patterns associated with specific epilepsy syndromes or show where abnormal electrical activity originates. An MRI of the brain is the preferred imaging study because it can detect structural differences like cortical dysplasia, heterotopia, tumors, or evidence of prior injury. An MRI is especially recommended when there’s a family history of epilepsy, abnormal findings on a neurological exam, or physical features suggesting a genetic condition. Blood tests to check glucose, electrolytes, and signs of infection round out the initial workup.