Cryptogenic Epilepsy

Cryptogenic epilepsy (from the Greek word “kryptos,” meaning “hidden”) is epilepsy with no obvious cause. There is neither a metabolic problem, nor a clear injury or structural problem with the brain. However, doctors suspect that there is an underlying cause for the seizures, usually because the child is developmentally delayed or has abnormal findings on her neurological exam.

Brain imaging has improved over the last several decades, so that doctors can detect smaller lesions and structural problems. As a result, many cases of epilepsy that would once have been called cryptogenic are now known to be symptomatic.

What are other terms for cryptogenic epilepsy?

Cryptogenic epilepsy may also be referred to as “probably symptomatic.”

The terms “idiopathic epilepsy” and “cryptogenic epilepsy” are sometimes used interchangeably, especially in older books and articles.

What causes cryptogenic epilepsy?

By definition, the cause of cryptogenic epilepsy is unknown. It is often assumed to be caused by a brain lesion that is not visible on CT scan or MRI. Because the quality of these tests has improved over the last several decades, the proportion of cases that are defined as cryptogenic has decreased. In other cases, a child whose epilepsy is considered cryptogenic at first is later diagnosed with a metabolic or mitochondrial disease, and the classification changes to symptomatic epilepsy.

How is cryptogenic epilepsy treated?

Cryptogenic epilepsy is treated with anti-epileptic drugs. If the seizures have a focus that can be identified, surgery may be an option. Other treatment options include vagus nerve stimulation (VNS) and the ketogenic diet.

What is the outlook for a child with cryptogenic epilepsy?

As with most types of epilepsy, the outlook for a child with cryptogenic epilepsy depends on the underlying cause and any comorbid conditions the child has.

Elizabeth J. Donner, MD, FRCPC