Early seizures after epilepsy surgery predict more seizures

The prevailing medical understanding of seizures in the weeks just after epilepsy surgery is that they are likely to be temporary, probably due to swelling or minor trauma suffered by the brain during the operation.

In fact, early seizures after the most common form of epilepsy surgery signal a greatly increased likelihood that the patient will continue to have seizures, according to a study published online January 24, 2005, in the Annals of Neurology (http://www.interscience.wiley.com/journal/ana).

“These findings have implications for patient counseling, but they are also interesting in terms of understanding epilepsy,” said lead author Anne M. McIntosh, Ph.D., of the University of Melbourne in Australia. “We can speculate that some individuals who undergo this procedure have epilepsy that for some reason is more persistent.”

There have been hints from smaller studies that early seizures following surgery are not all benign, but the Melbourne study, with 325 patients who underwent temporal lobe removal (lobectomy), is the largest to date. Temporal lobectomy is the most common form of epilepsy surgery, targeting the area where seizures commonly begin. It eliminates or reduces seizures in most cases.

McIntosh and colleagues found that patients who experienced a seizure in the four weeks following surgery — in the absence of surgery-related triggers such as trauma or swelling — were eight times more likely to have persistent epilepsy several months later. Even among the patients with evidence of these seizure triggers there was a three-fold increase in the likelihood of continuing epilepsy.
Given that surgery is only performed in cases where the disease is debilitating, these results do not cast doubt on the procedure itself. “Many subjects who have a return of epilepsy still have ongoing benefit from the procedure in terms of reduced seizure frequency,” said McIntosh.

Epilepsy is a chronic illness of the brain that is estimated to affect one percent of the U.S. population — about 2.5 million people. During an epileptic seizure, nerve cells in the brain fire electrical impulses much faster than normal, often leading to muscular convulsions or loss of consciousness.

Many epilepsy patients can be successfully treated with medications that prevent the formation of the “electrical storms” in the brain that cause seizures. “About 20 percent of patients have epilepsy that does not respond to medication, and perhaps a third of these may be suitable for surgery,” said McIntosh. This is particularly true of temporal lobe epilepsy, where seizures begin in the temporal lobe of the brain and spread to other regions.

Others authors of the study were Renate M. Kalnins, FRACP, Anne Mitchell, PRACR, and Samuel F. Berkovic, MD.