The most common question my new patients ask is "Why do I have seizures?" After a complete history, physical, and review of their medical record, I find a likely cause in most people. Seizures are just a symptom of abnormal electrical discharges in the brain, so there are a large number of possible causes. Almost any condition that affects the brain can sometimes cause seizures. Some of these conditions are reversible or temporary, like hypoglycemia; people with these conditions will not be prone to have recurrent seizures. Other people have conditions that cause permanent changes in brain function, and these people may develop epilepsy. A person is considered to have epilepsy after they have had two or more unprovoked seizures due to an irreversible or unknown cause.
But some causes are more common than others. Consider 100 people with their very first seizure:
In most cases, a physician can diagnose a probable cause from a complete neurological history and physical. If a CT (computerized tomographic) scan or MRI (magnetic resonance imaging) scan of the brain and electroencephalogram (test of brain wave patterns) are also done, the accuracy of diagnosis is much improved, especially for problems like brain tumor. Of course, it is especially important to identify these patients because they need treatment for the brain tumor itself, not just for the epilepsy it has caused.
Even after a complete diagnostic workup, some people have epilepsy and the cause is not clear. Other people have a probable cause, but it may seem too minor to have caused epilepsy. This may happen with people who have had a minor head injury, such as a brief concussion. But lack of ability to firmly diagnose a cause is less of a problem than it may appear, because almost all the available treatments for epilepsy do not treat the underlying cause of the epilepsy, they only treat its symptom--the seizures. Patients with seizures due to head trauma and seizures due to stroke are usually treated with the same medicines. For diagnosis, the major goals are to 1) identify the seizure type, so that the best medicine can be used, and 2) to find out whether a condition is present that needs treatment other than just anti-seizure medications.