Study: functional MRI useful to assess risk of verbal memory loss in epilepsy surgery
June 13, 2008 College News - Medical College of Wisconsin researchers have proven that functional MRI brain mapping before surgery can help identify those at highest risk for verbal memory decline after surgery for intractable temporal lobe epilepsy (TLE). This discovery should make it easier for patients to decide whether or not to have the surgery and may eliminate the need for invasive, preliminary radiology.
The study was recently reported in the journal Epilepsia.
“There are many patients out there who would benefit from the surgery but are not getting it, especially children and young adults,” said study leader Jeffrey Binder, MD, Professor of Neurology and Director of the Functional Imaging Research Center at the Medical College. “Understandable concern about verbal memory loss is likely the greatest contributing factor.”
The neurosurgical procedure done to cure TLE when medications are not effective is an anterior temporal lobectomy. Of the estimated one million Americans with uncontrolled epilepsy, about a quarter would be candidates for surgery, and the largest number, about 100,000, have TLE. However, the surgery involves risks. It involves removing part of the temporal lobe of the brain, which can include areas critical for language and memory functions.
Dr. Binder’s team tested 60 TLE patients before and after surgery. All underwent preoperative performance evaluations and neuropsychological testing, as well as language mapping using fMRI brain imaging, and language and memory mapping with the Wada test, a radiologic method using injected contrast to determine the dominance of each side of the brain in these functions.
When evaluated after surgery, more than 30 percent of the patients had suffered verbal memory decline. Good preoperative performance, late age at onset of epilepsy, left dominance on fMRI, and left dominance on the Wada test were each predictive of memory decline.
Preoperative performance and age of onset together accounted for roughly 50 percent of the variance in memory outcome, and left dominance on fMRI explained an additional 10 percent. Neither memory nor language asymmetry revealed by the Wada test added additional predictive power beyond these noninvasive measures.