Piriform Cortex Removal Did Not Predict Seizure Freedom

What was studied

Researchers looked at whether the extent of resection of a brain area called the piriform cortex during temporal lobe epilepsy surgery was associated with postoperative seizure freedom. They included patients with temporal lobe epilepsy who underwent mesiotemporal epilepsy surgery and had more than 1 year of postoperative follow-up.

They first examined a smaller retrospective discovery cohort from one center (28 patients, 15 female). Then they evaluated the findings in a larger independent validation cohort of 305 patients, including 205 with hippocampal sclerosis. They used imaging-based methods to measure resection within piriform cortex and other temporal lobe subregions, using both manual and connectivity-based definitions of piriform cortex.

What they found

This study did not find a significant association between seizure freedom and the extent of piriform cortex resection. That was the case in the smaller discovery cohort and in the larger validation cohort. It was also the case across different piriform cortex definitions and analytical approaches, including voxel-based lesion-outcome mapping.

They also did not find significant associations between ILAE I outcome and resected proportions within other mesiotemporal regions. Overall, the results suggest that piriform cortex resection should be considered on an individualized basis rather than routinely incorporated into temporal lobe resections.

Limits of the evidence

This was a retrospective study, so it identifies associations rather than proving cause and effect. The discovery cohort was small, and patients had heterogeneous etiologies, which may add variability. The abstract does not provide detailed information about age, medication use, or other clinical factors that could influence outcomes.

The study relied on imaging-based assessment of resection extent, and the abstract reports follow-up of more than 1 year but does not give more detailed long-term outcome information.

For families and caregivers

For families, this study suggests that removing a larger proportion of the piriform cortex during temporal lobe epilepsy surgery was not associated with a higher chance of seizure freedom in these cohorts. It supports the idea that surgical planning may need to be individualized rather than routinely focusing on this region.

This does not mean piriform cortex resection never matters. It means this study did not confirm earlier reports linking greater piriform cortex resection with better seizure outcomes. Families may want to ask how the surgical team decides what tissue to remove and what factors are considered in that person's case.

What to watch next

Future studies could help by following patients prospectively, examining longer-term outcomes, and assessing how findings vary across clinical subgroups and surgical approaches.

Terms in this summary

temporal lobe epilepsy

A type of epilepsy in which seizures start in the temporal lobe of the brain.

piriform cortex

A brain region near the temporal lobe that has been studied in relation to epilepsy surgery outcomes.

mesiotemporal

Referring to inner structures of the temporal lobe.

ILAE I

A seizure outcome category meaning seizure-free after surgery.

hippocampal sclerosis

Scarring in the hippocampus, a brain structure often involved in temporal lobe epilepsy.

retrospective study

A study that looks back at existing records and scans rather than following people forward in time.

validation cohort

A separate group of patients used to check whether the first study results hold up.

voxel-based lesion-outcome mapping

An imaging analysis that tests whether removal of specific small brain areas is associated with outcomes.