Laser Ablation Promising in Patients With Epilepsy

Pauline Anderson

December 09, 2013

WASHINGTON, DC — New research shows that cognitive outcomes and seizure freedom rates following MRI-guided stereotactic laser ablation of the hippocampus are as good as, if not better than, those of standard epilepsy surgery.

Results of studies investigating this novel procedure were presented at the American Epilepsy Society (AES) 67th Annual meeting here.

One trial showed that patients who had laser ablation do better on tests of episodic memory than those who receive standard surgical resections. This is probably because the laser ablation procedure is more targeted than standard surgical approaches, leaves more of the brain intact and preserves more brain "interconnections," according to the study's lead researcher, Daniel Drane, PhD, assistant professor, neurology and pediatrics, Emory University School of Medicine, Atlanta, Georgia.

If such superior outcomes are sustained, this treatment approach could have a huge impact on brain surgery in the future, said Dr. Drane.

Collateral Damage

Previous studies have already shown that the laser ablation technique spares other cognitive functions: object recognition and category-specific naming.

The hippocampus is presumed to be critical to episodic memory, and so some "collateral damage" would be expected with procedures that affect this area of the brain, said Dr. Drane. "We thought that on the way to deeper structures in the brain — the hippocampus and amygdala — we were damaging white matter and areas that connect other places, and that was causing deficits."

However, these laser ablation patients do pretty well, he said, possibly because the technique "is selectively taking out the hippocampus and amygdala but is leaving everything else intact."

This study included 7 patients who received MRI-guided selective laser amygdalohippocampectomy (SLAH) and 10 patients who had standard surgeries: open anterior temporal lobectomy or selective amygdalohippocampectomy.

A minimally invasive technique, the laser ablation procedure is performed using laser interstitial thermal therapy. Surgeons make a 1-cm incision in the skull through which a tiny fiber is inserted and guided to the hippocampus by MRI. Physicians can watch the procedure in real time.

The procedure spares memory-related structures, such as the perirhinal and entorhinal cortex.

Before and after their procedure, patients in the study were tested on visual memory (recall of simple geometric figures) and verbal memory (remembering words on a list).

Although 9 of the 10 patients having standard resection experienced a significant decline on one or both memory tasks (P < .002), only 1 of the 7 undergoing laser ablation had such declines.

This sole laser ablation patient had declines on the verbal memory task. He had left language dominance and underwent right hippocampal ablation but is now presenting with left temporal lobe seizures, said Dr. Drane.

It's likely that this person had bilateral seizures that weren't captured and that his decline is not a result of the surgery, said Dr. Drane.

Although 6 of the 7 patients undergoing laser ablation had significant improvement on one or more memory measure, only 4 of the 10 in the standard resection group had a similar improvement (P < .02).

Significant change on these episodic memory tasks was defined as an improvement or decline of 1 or more standard deviations based on normative data.

Additional Patients

"I'm excited about these results," even though they're preliminary, said Dr. Drane. He added that researchers now have data on 10 patients who have undergone the laser ablation procedure and that the results for the additional patients also show strong statistical effects.

"With a small sample, you usually worry about not having enough power to see the effect, but we're seeing strong effects with small numbers, and very striking outcomes."

Although this study didn't examine depression, Dr. Drane said that anecdotally the laser ablation procedure seems to have a positive effect in this area too. One 64-year-old patient had been so clinically depressed as a teenager that she had attempted suicide. Following the laser ablation procedure, not only did this patient achieve seizure freedom but her depression disappeared.

 
It's one case but we are getting some very striking mood findings. Dr. Daniel Drane
 

"She is off all antidepressants for the first time since her teens. She's getting a car, and is going to Europe," commented Dr. Drane. "It's one case but we are getting some very striking mood findings."

This analysis was included in results of another study reported at the AES meeting, a multicenter study carried out at 13 epilepsy centers that evaluated SLAH outcomes in 69 patients with mesial temporal lobe epilepsy.

Results of that study, presented by Jon T. Willie, MD, PhD, assistant professor, neurology, Emory University School of Medicine, suggested that postsurgery seizure freedom rates in SLAH patients approached those of open procedures.

Fifty-eight percent of the patients undergoing SLAH (40 patients) achieved Engel 1 status at 6 months and 50% (18 patients) did so at 1 year.

Seizure-free rates could improve over time as neurosurgeons become more experienced with this novel technique, according to Dr. Willie. Of the 69 patients, 5.8% had a hemorrhage.

Promising Technique

Asked to comment on laser ablation, Jacqueline French, MD, AES president and professor, New York University Comprehensive Epilepsy Center, said "it's a very promising and exciting technique for patients with discreet epileptic foci such as mesial temporal lobe epilepsy."

Dr. French noted that in addition to being "less invasive and causing less disruption of memory and other function, another advantage of laser ablation is that if doesn't prove to be effective, a standard temporal lobectomy can still be performed."

"It makes sense to start with a less invasive technique," she added.

She also noted that laser ablation represents "a major advance" over previous mechanisms to use noninvasive radiosurgery (Gamma Knife). For one thing she said, Gamma Knife radiosurgery does not produce its effect for several months, whereas laser ablation works immediately.

"We now need to consider how to do a controlled trial to determine the risks and benefits of this technique as compared to more invasive surgical techniques," Dr. French concluded.

American Epilepsy Society (AES) 67th Annual Meeting. Platform B.07; Abstract 2.198. Presented December 7, 2013.

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