From the Journals

‘Trigger zone’ resection ups seizure-free odds in temporal lobe epilepsy



Resection of a brain area implicated in seizure modulation improves the odds of being seizure free in patients with temporal lobe epilepsy, according to results of a recent multicenter analysis.

Patients with long-term postoperative freedom from seizures had a larger proportion of the piriform cortex resected versus patients who were not seizure free. Removing at least half the piriform cortex was associated with a 1500% increase in odds of seizure freedom, first author Marian Galovic, MD, of the department of clinical and experimental epilepsy at the University College London’s Queen Square Institute of Neurology and his colleagues reported in JAMA Neurology.

“If confirmed in prospective interventional trials, these findings will have practical implications for guiding neurosurgeons about the extent of the surgical resection,” Dr. Galovic and his coinvestigators wrote.

The area tempestas in the piriform cortex has been identified as an epileptic trigger zone in animal studies, but to date, evidence of a human epileptic trigger zone in this area remain limited, according to the investigators.

To evaluate the impact of resection in this area, Dr. Galovic and his colleagues evaluated 107 patients with temporal lobe epilepsy from an ongoing, single-center, prospective study, and validated their findings with 31 patients from two other independent cohorts.

Of the 107 patients in the main cohort, 46% were completely seizure free for a median of 5 years after epilepsy surgery, with results of voxel-based morphometry showing that those patients had a more pronounced loss of gray matter in the ipsilateral piriform, compared with non–seizure-free patients.

The seizure-free patients had a median of 83% of the piriform cortex resected, compared with 52% for the non–seizure-free patients (P less than .001), results of a volumetric analysis confirmed.

Anxiety or psychosis outcomes were not influenced by the extent of piriform cortex resection, the investigators wrote, adding that poor verbal memory outcome was linked to the extent of resection of other brain regions, but not the piriform cortex.

The investigators confirmed these findings in the 31 patients of the validation cohort, with significant associations between extent of piriform cortex resection and postsurgical outcomes.

Resecting at least half of the region increased odds of being seizure free by a factor of 16 (95% CI, 5-47; P less than .001), Dr. Galovic and his colleagues added.

“Our results provide evidence suggesting that the human piriform cortex has a role in the generation of seizures that involve the temporal lobe,” they wrote in a discussion of their results.

The findings, if confirmed, could have implications not only for surgical practice, they wrote, but also for the understanding of the mechanisms underlying epileptic networks, which could lead to new drug and nondrug interventions to mitigate seizure activity.

Dr. Galovic reported receiving a grant from the Medical Research Council. His coauthors reported disclosures with the Medical Research Council, Wellcome Trust, Medtronic, Neuropace, Nevro, Eisai, UCB, and Mallinckrodt, among other entities.

SOURCE: Galovic M et al. JAMA Neurol. 2019 Mar 11. doi: 10.1001/jamaneurol.2019.0204.

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