Resection of the temporal piriform cortex in mesial temporal lobe epilepsy: Association with seizure freedom in a retrospective cohort study

OBJECTIVE: This study evaluated the association between temporal piriform cortex (tPC) resection and long-term postoperative outcomes in temporal lobe epilepsy (TLE). METHODS: We conducted a retrospective analysis of patients with TLE undergoing surgery between 2012 and 2022, with a minimum follow-up of 2 years. The extent of resection, including the tPC, hippocampal head/body, and amygdala, was assessed using magnetic resonance imaging scans. These measurements, along with demographic data and other presurgical evaluations, were analyzed for their associations with Engel class postoperative outcomes and antiseizure medications (ASMs) withdrawal across different TLE subtypes. RESULTS: Among 216 included patients, 158 had mesial TLE (MTLE). At the final follow-up, 131 MTLE and 35 neocortical TLE (NTLE) patients were seizure-free. Multivariable logistic regression revealed that unresected tPC significantly predicted seizure recurrence (p < .001, odds ratio OR = 4.415, 95% confidence interval CI = 2.032-9.594), along with older age at surgery (p = .018, OR = 1.034, 95% CI = 1.006-1.063) and nonspecific pathology (p = .017, OR = 3.899, 95% CI = 1.278-11.894). In NTLE, tPC resection did not significantly affect outcomes. However, in MTLE, unresected tPC was strongly associated with poorer seizure outcomes at both 2-year (p = .012, OR = 3.362, 95% CI = 1.311-8.621) and 5-year (p = .014, OR = 5.750, 95% CI = 1.423-23.242) follow-ups. Among seizure-free MTLE patients, those with tPC resection had higher rates of ASMs reduction and withdrawal after 5 years (p < .05). In hippocampal sclerosis (HS) patients, unresected tPC correlated with seizure recurrence (p < .05), whereas no such association was observed in non-HS cases. SIGNIFICANCE: Our findings suggest that tPC involvement in the epileptogenic zone varies by TLE subtype, with tPC resection strongly linked to favorable outcomes in MTLE, particularly in HS patients. These results reinforce the understanding of the hippocampus-amygdala-piriform complex as crucial to the epileptogenic zone in MTLE.