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Hippocampal sparing temporal lobectomy recommended for medically refractory epilepsy



In the absence of MRI evidence of mesial temporal sclerosis (MTS), sparing the hippocampus during anterior temporal lobectomy for refractory epilepsy reduces memory loss without affecting the procedure’s efficacy, according to a review from researchers at Thomas Jefferson University in Philadelphia.

Dr. Michael Sperling, director of the Jefferson Comprehensive Epilepsy Center.

Dr. Michael Sperling

Often, the hippocampus and other mesial structures are removed even if they appear normal. The concern is that even normal looking tissue could harbor epileptogenic elements and leaving them in tact could reduce postoperative seizure control, explained senior investigator and neurologist Michael Sperling, MD, director of the Jefferson Comprehensive Epilepsy Center.

He and his colleagues wanted to see if that was really true, so they compared outcomes in 21 patients who had mesial-sparing lobectomies with 19 patients who had the standard approach. Cases and controls were matched for age, preoperative seizure frequency, side of surgery, and other factors. None of the patients had MTS.

There was no significant difference in postoperative seizure recurrence between the two groups (P = .974). The standard procedure had a slight edge early on, but at 2.5 years, just over 60% of patients in both groups were seizure free. At 5 years, about 50% were seizure free, and almost 40% in both arms at 7.5 years.

About two-thirds of patients in each arm had pre- and postoperative verbal memory testing, with similar duration from surgery to postop evaluation. There was no change among the hippocampus-sparing patients, but a roughly one standard deviation drop in delayed recall and logical memory on the California Verbal Learning Test in the standard group.

Even so, it wasn’t enough to affect employment, which the investigators used as a surrogate for disability; postoperative employment was comparable in both groups. People mostly retained their jobs, and there was no difference in job loss. A few people in each arm actually found jobs after surgery.

The investigators concluded that “it is reasonable to recommend mesial temporal sparing procedure in patients with dominant neocortical temporal lobe epilepsy when the hippocampus appears normal in the MRI. However, as resecting the mesial temporal structures was not associated with a greater chance of becoming unemployed following the surgery, there appears to be no major contraindication to performing an [anterior temporal lobectomy] if clinically warranted.”

The results are reassuring. “My bias walking in was that” seizure recurrence would be worse after hippocampal-sparing surgery. “I was pleased to see that it was about the same. If you want to try to preserve verbal memory and the MRI is normal, you can get away with sparing the mesial temporal structures, and still get a good seizure outcome,” Dr. Sperling said at the annual meeting of the American Epilepsy Society, where the study was presented.

“But if you have to take the hippocampus for whatever reason, the functional consequence of a decline in verbal memory is not severe enough as to be disabling,” which is “one of the big concerns” with temporal lobectomy, he said.

The findings “will make us more likely to recommend mesial-sparing surgery, but at the same time” perhaps not be quite as worried about disability with the standard approach.

Temporal lobe epilepsy with normal mesial structures isn’t very common, which explains the small numbers in the series. It’s possible subtle difference in seizure control and employment outcomes would have been found with a larger series, “but obviously there were no major differences. I think the fundamental questions have been answered to my satisfaction,” Dr. Sperling said.

Overall, “it’s better to operate and try to cure people than to worry that you will make their memory worse when the consequences of having uncontrolled epilepsy is a higher death rate,” he said.

There were about equal numbers of men and women in the review; patients were in their early 30s, on average; and most had left-sided surgery. Just over half in each arm had preoperative tonic-clonic seizures. The mean duration of epilepsy was 14.9 years in the mesial-sparing group, and 8.6 years in the standard arm.

There was no funding for the review, and Dr. Sperling didn’t have any relevant disclosures.

SOURCE: Goldstein L et al. AES 2019. Abstract 1.339.

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