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WASHINGTON -- Stereotactic laser ablation of seizure foci in the hippocampus appeared to reverse certain types of memory deficits that commonly occur in this population, researchers said here.

In seven patients undergoing the laser procedure, significant improvements relative to pre-surgical baseline were seen in measures of visual recall, whereas no change or decreases in memory performance were seen in 10 otherwise similar patients who underwent conventional neurosurgical ablation in the same brain regions, according to , of Emory University in Atlanta.

Of the seven patients with the laser surgery, one showed a decline in memory function, apparently connected with seizures emanating from a new or previously unnoticed focus in the contralateral brain hemisphere, Drane said at a press briefing held before his formal presentation at the American Epilepsy Society annual meeting.

In contrast, nine of the 10 conventional surgery patients showed declines, he said, with significantly worse outcomes relative to the laser group (chi-squared 9.75, P<0.002).

Neither he nor Emory colleague , one of the neurosurgeons who performed the procedures, could think of a reason to prefer conventional resection to the laser surgery for the types of patients included in the study.

Drane said a characteristic deficit in patients with hippocampal foci is in coming up with names of people and objects. He said it was common for such patients to be unable to name their own family members.

The laser procedure was conducted with a that is FDA-approved for general neurosurgical applications. Willie described it as minimally invasive, the catheter-like device being only a few millimeters in diameter.

Drane said the key difference from conventional resection is that the laser device is less damaging to nontarget tissue. Open procedures require that the surgeon cut a path to the ablation target. In doing so, he said, these surgeries "are disconnecting brain regions."

As a result, the cognitive benefits of seizure focus ablation, which Willie likened to silencing "the child in the classroom who stands up and screams every 30 seconds," are offset by the nontarget destruction.

All patients in the nonrandomized study, in which data were collected prospectively, had temporal lobe epilepsy with hippocampal foci scheduled for either standard resection or laser ablation. The target was in the language-dominant hemisphere in four of the 10 open-resection patients and in four of seven in the laser-surgery group.

Two tests of visual recall and verbal learning were administered prior to surgery and at 1 year afterward in the open-resection group, as well as 6 months later in the laser-surgery group. Drane argued that, if the difference in follow-up period created a bias, it would be toward more deficits in the laser group because of their shorter recovery period.

The improvements in function seen with laser ablation were mainly in visual recall. Percent retention of recall increased by a mean of 24.5 points (SD 19.9, P<0.05 relative to baseline) in patients undergoing laser ablation on the language-dominant side and by 13.8 points (SD 27.8, not significant) in those with nondominant side targets.

In contrast, the open-resection patients showed mean declines in retention: by 2.2 points with dominant-side targets (SD 10.1, not significant) and by 17.2 points (SD 18.6, P<0.05 relative to baseline) with nondominant side targets.

Open-resection patients undergoing dominant-side surgery showed significant decreases in verbal learning scores. No significant change was seen in those having nondominant side procedures or in either subgroup of the laser-ablation cohort.

The two procedure types were about equally effective in achieving seizure control. Five of the 10 patients undergoing open surgery and four of seven in the laser-ablation group were completely seizure-free at follow-up. One patient in each group was categorized as Engel class IV, indicating no improvement from pre-surgical baseline.

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