• Causes of epilepsy vary by age of the person
  • Many without a clear cause of epilepsy may have a genetic form
  • One-third of children with autism spectrum disorder may have seizures
  • Infections are also common causes of epilepsy
  • Seizures commonly begin in people over 65 
  • Stroke is one of the most frequent causes of seizures in seniors

How does epilepsy begin? What causes a seizure?

Causes of epilepsy vary by age of the person. Some people with no clear cause of epilepsy may have a genetic cause. But what's true for every age is that the cause is unknown for about half of everyone with epilepsy.

  • Some people with no known cause of epilepsy may have a genetic form of epilepsy. One or more genes may cause the epilepsy or epilepsy may be caused by the way some genes work in the brain. The relationship between genes and seizures can be very complex and genetic testing is not available yet for many forms of epilepsy. 
  • About 3 out of 10 people have a change in the structure of their brains that causes the electrical storms of seizures.
  • Some young children may be born with a structural change in an area of the brain that gives rise to seizures. 
  • About 3 out of 10 children with autism spectrum disorder may also have seizures. The exact cause and relationship is still not clear. 
  • Infections of the brain are also common causes of epilepsy. The initial infections are treated with medication, but the infection can leave scarring on the brain that causes seizures at a later time. 
  • People of all ages can have head injuries, though severe head injuries happen most often in young adults.
  • In middle age, strokes, tumors and injuries are more frequent.
  • In people over 65, stroke is the most common cause of new onset seizures. Other conditions such as Alzheimer’s disease or other conditions that affect brain function can also cause seizures.

Acute Symptomatic Causes of Epilepsy

In Newborns: 

  • Brain malformations
  • Lack of oxygen during birth
  • Low levels of blood sugar, blood calcium, blookd magnesium or other eletrolyte disturbances
  • Inborn errors of metabolism
  • Intercranial hemorrage
  • Maternal drug use 

In Infants and Children: 

  • Fever (febrile seizures)
  • Brain tumor (rarely)
  • Infections

In Children and Adults:

  • Congenital conditions (Down's syndrome; Angelman's syndrome; tuberous sclerosis and neurofibromatosis)
  • Genetic factors
  • Progressive brain disease (rare)
  • Head trauma

In Seniors:

  • Stroke
  • Alzheimer's disease
  • Trauma
Authored by: Steven C. Schachter, MD | Patricia O. Shafer, RN, MN | Joseph I. Sirven, MD on 7/2013
Reviewed by: Joseph I. Sirven, MD | Patricia O. Shafer, RN, MN on 3/2014
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When the Cause is Unknown

Idiopathic seizures are those whose cause is unknown. Unfortunately, about 6 out of 10 seizures are idiopathic.

In the case of focal seizures, we presume that there is an irritation to or scar on some part of the brain, but the scar is invisible to MRI. With generalized seizures, the genetic or metabolic abnormality is unidentified.

Patients and families are mystified by the absence of answers, typified by the common refrain, "The doctor’s told me everything was normal." As frustrating as this may be, two points should be reassuring. First, no tumor, stroke, infection, vascular malformation or other problem was found. Second, we do not need to know the cause to use medicines to treat the seizures.

As MRI and other forms of imaging the brain continue to improve, more and more causes of seizures will be identified.

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