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Contralateral hippocampal sclerosis following functional hemispherectomy in children: A report of three cases
Ranjith Kumar Manokaran1, Ivanna Yau2, Robyn Whitney3
1Division of Neurology, Department of Paediatrics, Hospital for Sick Children, University of Toronto, Toronto, ON, Canada.
Insights
This study reports three children who developed contralateral hippocampal sclerosis (HS) after functional hemispherectomy (FH) for drug-resistant epilepsy. The cause remains unclear, but genetic factors may influence outcomes in epilepsy surgery.
Area of Science:
- Pediatric Neurology
- Epilepsy Surgery
- Neurodevelopmental Disorders
Background:
- Hippocampal sclerosis (HS) often co-exists with other brain lesions in pediatric epilepsy.
- Dual pathology, involving both temporal and extratemporal lesions, is a known challenge in epilepsy management.
- Functional hemispherectomy (FH) is a surgical option for severe, intractable epilepsy.
Purpose of the Study:
- To report on three pediatric cases of drug-resistant epilepsy with extensive hemispheric cortical malformations.
- To investigate the development of contralateral hippocampal sclerosis (HS) after functional hemispherectomy (FH).
- To explore potential factors influencing seizure outcomes post-epilepsy surgery.
Main Methods:
- Retrospective review of clinical, EEG, radiological, and pathological data.
- Inclusion criteria: children who underwent FH and subsequently developed contralateral HS.
- Analysis of genetic data, specifically searching for pathogenic variants in relevant pathways.
Main Results:
- Three out of 95 children (3.2%) met the study criteria.
- All eligible patients had unilateral extensive hemispheric cortical malformations and underwent FH in early infancy.
- Contralateral HS developed 2.2 to 3.7 years post-FH, with persistent seizures; two patients had GATOR1 pathway gene variants.
Conclusions:
- The development of contralateral HS after FH in these cases is not fully explained.
- The study suggests that "second-hit" somatic mutations might be crucial in determining seizure outcomes.
- Further research is needed to understand the role of genetic factors in epilepsy surgery outcomes for malformations of cortical development.
Purpose:
Hippocampal Sclerosis (HS) may co-exist with temporal or extratemporal lesions (dual pathology) in children and is usually ipsilateral to the radiological lesion. Here were report three cases with extensive hemispheric cortical malformation and drug resistant epilepsy who had persistent seizures after functional hemispherectomy (FH) and developed contralateral HS after the surgery.
Methods:
This retrospective study enrolled children who underwent FH and developed contralateral HS after surgery. Their clinical, EEG, radiological and pathological data were reviewed and summarized.
Results:
Ninety-five children underwent FH during the study period; Three cases (3.2%) were eligible. They all had unilateral extensive hemispheric cortical malformation who underwent FH between 3 and 5 months of age with no clinical, EEG or radiological suggestion for involvement of contralateral hemisphere prior to FH. All three patients had persisting seizures after FH. Contralateral HS was detected between 2.2 to 3.7 years after FH in all three cases. Two of the patients showed pathogenic variants in GATOR1 pathway genes.
Conclusions:
The genesis of contralateral HS in the reported patients remains unexplained. The presence and distribution of "second-hit" somatic mutations may play an important role in governing the seizure outcomes of epilepsy surgery in patients with apparently unilateral malformations of cortical development.
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