Association of Piriform Cortex Resection With Surgical Outcomes in Patients With Temporal Lobe Epilepsy

Importance

A functional area associated with the piriform cortex, termed area tempestas, has been implicated in animal studies as having a crucial role in modulating seizures, but similar evidence is limited in humans.

Objective

To assess whether removal of the piriform cortex is associated with postoperative seizure freedom in patients with temporal lobe epilepsy (TLE) as a proof-of-concept for the relevance of this area in human TLE.

Design, Setting, and Participants

This cohort study used voxel-based morphometry and volumetry to assess differences in structural magnetic resonance imaging (MRI) scans in consecutive patients with TLE who underwent epilepsy surgery in a single center from January 1, 2005, through December 31, 2013. Participants underwent presurgical and postsurgical structural MRI and had at least 2 years of postoperative follow-up (median, 5 years; range, 2-11 years). Patients with MRI of insufficient quality were excluded. Findings were validated in 2 independent cohorts from tertiary epilepsy surgery centers. Study follow-up was completed on September 23, 2016, and data were analyzed from September 24, 2016, through April 24, 2018.

Exposures

Standard anterior temporal lobe resection.

Main Outcomes and Measures

Long-term postoperative seizure freedom.

Results

In total, 107 patients with unilateral TLE (left-sided in 68; 63.6% women; median age, 37 years [interquartile range {IQR}, 30-45 years]) were included in the derivation cohort. Reduced postsurgical gray matter volumes were found in the ipsilateral piriform cortex in the postoperative seizure-free group (n = 46) compared with the non-seizure-free group (n = 61). A larger proportion of the piriform cortex was resected in the seizure-free compared with the non-seizure-free groups (median, 83% [IQR, 64%-91%] vs 52% [IQR, 32%-70%]; P < .001). The results were seen in left- and right-sided TLE and after adjusting for clinical variables, presurgical gray matter alterations, presurgical hippocampal volumes, and the proportion of white matter tract disconnection. Findings were externally validated in 2 independent cohorts (31 patients; left-sided TLE in 14; 54.8% women; median age, 41 years [IQR, 31-46 years]). The resected proportion of the piriform cortex was individually associated with seizure outcome after surgery (derivation cohort area under the curve, 0.80 [P < .001]; external validation cohorts area under the curve, 0.89 [P < .001]). Removal of at least half of the piriform cortex increased the odds of becoming seizure free by a factor of 16 (95% CI, 5-47; P < .001). Other mesiotemporal structures (ie, hippocampus, amygdala, and entorhinal cortex) and the overall resection volume were not associated with outcomes.

Conclusions and Relevance

These results support the importance of resecting the piriform cortex in neurosurgical treatment of TLE and suggest that this area has a key role in seizure generation.

Levetiracetam and Partial Seizure Subtypes: Pooled Data from Three Randomized, Placebo-controlled Trials

PURPOSE

To determine the effect of levetiracetam (LEV) on partial seizure subtypes (simple partial, complex partial, and secondarily generalized seizures) in patients with refractory epilepsy.

METHODS

Pooled results from three placebo-controlled trials were analyzed.

RESULTS

A statistically significant reduction in the frequency of all partial seizures and all seizure subtypes was observed in the LEV group (p < 0.001 vs. placebo). The proportion of patients in whom secondarily generalized seizures could be prevented over and above the reduction of partial seizures was significantly greater in the LEV group as compared with placebo, with an odds ratio of 1.83 [95% confidence interval (CI), 1.10-3.05]. CONCLUSIONS; LEV reduces frequency of simple and complex partial seizures. In addition, it demonstrates a specific, independent reduction of secondarily generalized seizures.

Partial epilepsy with pericentral spikes: a new familial epilepsy syndrome with evidence for linkage to chromosome 4p15

The genetic analysis of simple Mendelian epilepsies remains a key strategy in advancing our understanding of epilepsy. In this article, we describe a new family epilepsy syndrome, partial epilepsy with pericentral spikes, which we map to chromosome 4p15. We distinguish it clinically, electrophysiologically, and genetically from previously described Mendelian epilepsies. The family described is a large Brazilian kindred of Portuguese extraction in which affected family members manifest a variety of seizure types, including hemiclonic, hemitonic, generalized tonic-clonic, simple partial (stereotyped episodes of epigastric pain), and complex partial seizures consistent with temporal lobe epilepsy. The syndrome is benign, either requiring no treatment or responding to a single antiepileptic medication. Seizure onset is in the first or second decades of life, with seizures in individuals up to the age of 71 years and documented encephalogram changes up to the age of 30 years. A key feature of partial epilepsy with pericentral spikes is a characteristic encephalogram abnormality of spikes or sharp waves in the pericentral region (centroparietal, centrofrontal, or centrotemporal). This distinctive encephalogram abnormality of pericentral spikes unites these several seizure types into a discrete family epilepsy syndrome. As with other familial epilepsies, the inherited nature of this new syndrome may be overlooked because of the variability in penetrance and seizure types among affected family members.