International consensus classification of hippocampal sclerosis and etiologic diversity in children with temporal lobectomy

Abstract

Introduction: The distribution of hippocampal sclerosis (HS) subtypes, according to the classification of the International League Against Epilepsy (ILAE), has been reported mainly in adult patients. We aimed to review the pathological findings in children who had anterior temporal lobectomy accompanied with amygdalohippocampectomy, in view of the current classification, and evaluate postsurgical outcome with respect to HS subtypes in childhood.

Methods: Seventy children who underwent temporal resections for treatment of medically refractory epilepsy, with a minimum follow-up of 2 years, were included; the surgical hippocampus specimens were re-evaluated under the HS ILAE classification.

Results: Neuropathological evaluations revealed HS type 1 in 38 patients (54.3%), HS type 2 in 2 (2.8%), HS type 3 in 21 patients (30%), and no HS in 9 patients (12.9%). Of 70 patients, 23 (32.9%) had dual pathology, and the most common pattern was HS type 3 with low-grade epilepsy-associated brain tumors (LEAT). The distribution of HS types with respect to age revealed that HS type 3 and no HS subgroups had significantly more patients younger than 12 years, compared with those of HS type 1 (90.5%, 77.8% vs 47.4%, respectively). History of febrile seizures was higher in HS type 1. Prolonged/recurrent febrile seizures were most common in patients 12 years and older, whereas LEAT was the most common etiology in patients under 12 years of age (p < 0.001). Patients with HS type 1 had longer duration of epilepsy and an older age at the time of surgery compared with patients with HS type 3 and no HS (p: 0.031, p: 0.007). At final visit, 74.3% of the patients were seizure-free. Seizure outcome showed no significant difference between pathological subtypes.

Conclusions: Our study presents the distribution of HS ILAE subtypes in an exclusively pediatric series along with long-term seizure outcome. The study reveals that the leading pathological HS subgroup in children is HS type 1, similar with adult series. Hippocampal sclerosis type 2 is significantly less in children compared with adults; however, HS type 3 emerges as the second most predominant group because of dual pathology, particularly LEAT. Further studies are required regarding clinicopathological features of isolated HS in pediatric cohort. Seizure-free outcome was favorable and similar in all HS types in children. The proportion of HS types may be better defined in pediatric patients with temporal resections, as the current HS ILAE classification becomes more widely used, and may help reveal the surgical and cognitive outcome with respect to HS types.