Nearly half of children with epilepsy experience adverse events due to invasive EEG

Some type of adverse event occurs in nearly half of children with severe epilepsy undergoing invasive electroencephalography (EEG) recordings, reports a study in the December issue of Operative Neurosurgery, a quarterly supplement to Neurosurgery, official journal of the Congress of Neurological Surgeons. The journal is published by Lippincott Williams & Wilkins, a part of Wolters Kluwer Health.

However, the EEG recordings provide critical information for planning complex epilepsy surgeries that cannot be obtained in any other way, according to the new report, led by Dr. Thomas Blauwblomme and colleagues of Great Ormond Street Hospital, London.

What Are the Risks of Invasive EEG in Children?

The researchers analyzed adverse events related to invasive EEG recordings in 95 children between 1994 and 2009. Most cases of epilepsy in children can be kept under control with medications. When drugs aren't successful, surgery is highly effective. Surgical planning requires precise information on the location of the brain area responsible for seizure activity.

In some complex cases, this information can only be obtained through invasive EEG recordings using electrodes placed on the brain surface or into the brain tissue. The new study sought to gather detailed information on the risks associated with this procedure. The children in the study averaged about 11 years of age; they had very severe epilepsy, averaging more than 200 seizures per month.

Overall, 49 percent of the children experienced some kind of adverse event. About 30 percent had more severe events that prolonged their hospital stay. However, none of the complications led to permanent neurological damage or death.

Adverse events included bleeding in 17 percent of patients, infection in 15 percent, cerebrospinal fluid leakage in 11 percent, and brain swelling in six percent. Additional surgery was required in most of the children with bleeding and some of those with infection. After surgeons started using a new type of graft material in 2002, there were no further problems with CSF leakage.

The complication rate was lower (20 percent) in children under two years old, while brain swelling was more likely in older children. The risk of adverse effects was unrelated to the length of recording, the number of electrodes used, or whether the recording used electrodes on the surface or implanted in the brain.

Invasive EEG resulted in successful recording of brain activity during seizures—allowing identification of the seizure zone—in 69 percent of patients. Overall, 89 percent of the children underwent epilepsy surgery. The more accurate the invasive EEG recordings were in localizing the seizure zone, the higher the success rate of surgery.

The study documents the significant risk of adverse events related to invasive EEG recordings in children with epilepsy. At the same time, invasive EEG provides "invaluable information" for pinpointing the source of seizure activity within the brain. The researchers note the comparatively low risk of complications in children under two years old—which adds to recent evidence supporting early surgery for children with epilepsy that doesn't respond to medications.

For all children undergoing invasive EEG recordings, parents should receive detailed information on the risks and benefits of the procedure, Dr. Blauwblomme and coauthors write. They also emphasize that the procedure should be performed at a treatment center with experience in invasive EEG recording, with careful planning before the procedure and close patient follow-up afterward.