Laser Ablation: An Alternative to Standard Epilepsy Surgery?

Kate Johnson

July 03, 2013

MONTREAL — Stereotactic laser ablation of the hippocampus (SLAH) may result in fewer cognitive deficits and similar seizure freedom compared with standard resection for the treatment of temporal lobe epilepsy (TLE), 2 new studies suggest.

"I believe this technique can revolutionize how we approach brain surgery, as long as it continues to prove safe and shows adequate efficacy for seizure control," study investigator Daniel Drane, PhD, told Medscape Medical News here at the 30th International Epilepsy Congress (IEC).

"It is a minimally invasive procedure that is more cosmetically appealing (no craniotomy), decreases the length of hospital stay, and appears to avoid any cognitive morbidity," said the neuropsychologist, who is assistant professor of neurology and pediatrics at Emory University School of Medicine in Atlanta, Georgia.

His colleague Jon Willie, MD, PhD, a neurosurgeon also at Emory University, who presented a second study, told Medscape Medical News, "these are early results, but it suggests that SLAH may have rates of seizure freedom that could be comparable to selective amygdalohippocampotomy, but with less negative neuropsychological impact."

Dr. Drane said it is well known that standard temporal lobe surgery such as selective amygdalohippocampectomy results in cognitive morbidity involving potential deficits in material-specific memory and visual confrontational naming.

However, work by his group suggests there may be broader deficits in object recognition and category-specific naming that have, to date, gone largely unrecognized.

"The reasons we haven't noticed this is our standard clinical tests don't typically look at these things," he said.

For example, the Boston Naming Test generally tests common nouns such as manmade objects (eg, park bench or teacup), whereas "we found that proper nouns (eg, names of familiar persons, landmarks) are more vulnerable [after standard resection] and sometimes decline when manmade objects do not."

Collateral Damage

He noted that object recognition deficits occur immediately following temporal resection and that object recognition is almost never studied.

Some of these less recognized deficits may be caused by "collateral damage" as the surgeon accesses the hippocampal region, said Dr. Drane. Traditionally, the procedure requires a fairly large resection that cuts through other temporal lobe regions and white matter pathways.

The investigators hypothesized that laser ablation, which leaves these areas largely intact, would result in fewer deficits by preserving "critical white matter pathways and other important network regions."

The study compared neuropsychological outcomes at 6-month follow-up in 33 patients undergoing standard surgical treatment for TLE with the outcomes in 7 patients were treated with laser ablation for TLE.

A separate study led by Dr. Willie assessed seizure freedom at 6 months in a prospective, noncontrolled study in 52 patients with mesial TLE treated with laser ablation at 9 US epilepsy centers.

In the neuropsychological study, all patients were tested pre- and postsurgically using modified versions of the Boston Naming Test (BNT) and Iowa Famous Faces Test (IFFT) with "significant impairment" determined using reliable change index for the BNT and as more than 1 standard deviation of decline on the IFFT.

Although the mean age of patients undergoing standard was significantly younger than that of ablation patients (36 vs 41years), there were no other significant differences between the groups at baseline, reported Dr. Drane.

Postsurgical testing revealed that significantly more standard surgery patients experienced declines on 1 or more naming or recognition tasks compared with ablation patients (29 of 33 vs 0 of 7; P < .00001).

When comparing patients who had left vs right TLE, 17 of 18 standard surgery patients experienced declines on 1 or both of the tasks compared with 0 of 4 ablation patients (P < .0001).

For patients with right TLE, 12 of 15 standard surgery patients showed a decline on the famous face recognition test compared to 0 of 3 ablation patients (P < .01).

In Dr. Willie's seizure freedom study, early outcome data (6 months) in 52 patients showed a 59% rate of seizure freedom. This compares favorably to outcomes with standard resection with the "gold standard" study, a randomized, controlled trial of anterior temporal lobectomy vs medical management alone, showing a seizure freedom rate of 69% for surgery ( N Engl J Med 2001;345:311-8), he said.

"There is not an equivalent study of selective amygdalohippocampotomy (SAH), but a recent meta-analysis of many small studies suggests an 8% lower rate of seizure freedom with SAH relative to ATL," ( Neurology 2013;80:1669-76) he said.

Role of Ablation Surgery TBD

When challenged by an audience member about the lack of strong efficacy data, Dr. Drane and several of his colleagues argued that even if laser ablation proves to be less efficacious that standard resection in terms of providing seizure freedom, it might represent an acceptable compromise for many patients, who can always return for a standard resection later if the ablation is not adequate.

"If you can reduce seizures by 50% with a technique that has less cognitive impairment, I know a lot of patients that would rather take that," said coauthor Kimford Meador, MD, professor of neurology and director of the epilepsy program at Emory University. "I have a whole series of patients who don't want to have a chunk of their brain cut out — so this [technique] might have a role. What that role is we can't answer today."

"I think there will be a place for laser ablation even if it never supplants traditional surgical approaches," said Dr. Drane. "Many epilepsy specialists do not fully appreciate the full impact of cognitive deficits on patients. I have patients who cannot reliably name their own family members or street addresses."

Dr. Drane noted that the impact of such problems range from social embarrassment to being unable to spontaneously provide adequate information to a responder in an emergency situation.

"I have been told repeatedly by the standard resection patients that they are happy to be seizure free, if indeed they are, but that they wish they hadn't lost various abilities. They often tell the neurosurgeon that they are 'doing well,' but don't even go into the functions they have lost, as it seems to be embarrassing to them and they don't figure anything can be done now."

Still Early Days

Commenting on the findings for Medscape Medical News, Samuel Wiebe, MD, professor, division chief of neurology, and director of the Calgary comprehensive epilepsy program at the University of Calgary in Canada said that the laser ablation technique "seems promising."

"The short-term data regarding seizure control in mesial temporal lobe epilepsy and in hypothalamic hamartomas appear to be comparable to those obtained from standard surgery," he said.

Dr. Wiebe added that "the data pertaining to cognitive outcomes after hippocampal ablation are interesting, and the epilepsy community will be expecting more robust results from larger, comparative studies."

Dr. Wiebe said that it is encouraging to see the development of new, less invasive surgical techniques for drug-resistant epilepsy. However, he noted, it is early in the game.

"We must be reminded that for most new interventions, initial small studies tend to show a larger effect size than larger, confirmatory studies; the latter also provide a more complete assessment of complications and morbidity."

He pointed out that previous minimally invasive techniques, such as ultrasound and thermal amygdala and hippocampal ablation were eventually shown to be substantially less effective than standard surgery ( Epilepsia 1999;40:1408-1416), "suggesting that parahippocampal unresected structures should also be targeted."

This theory is borne out by his own recent meta-analysis demonstrating better seizure control with standard than with selective resections ( Neurology 2013;80:1669-1676), he said.

"Finally, the rate of complications needs to be observed carefully and put into

Perspective, taking into account that this may decline as the learning curve for the new technique improves," he said.

Dr. Drane receives funding from the National Institutes of Health to study outcome in TL epilepsy surgery, and one of his coauthors (Dr. Gross) receives funding from Visualase, which is funding studies on MRI-guided laser thermal ablation for epilepsy as well as brain tumors. Dr. Willie and Dr. Wiebe have disclosed no relevant financial relationships..

30th International Epilepsy Congress (IEC). Abstracts 0047 and P923. Presented June 25 and 26, 2013.

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