Review articleHippocampal sclerosis and associated focal cortical dysplasia-related epilepsy in neurofibromatosis type I

- Epilepsy is a common comorbidity of neurofibromatosis type I.
- One common form of dual pathology is hippocampal sclerosis and focal cortical dysplasia.
- Dual pathology is a rarely described epilepsy etiology within this group.
- The role of dual pathology in epilepsy surgery outcomes remains unclear.
- Both presented cases failed to achieve post-operative seizure freedom.

Neurofibromatosis type I (NF1) is a relatively common disorder associated with a range of neurologic sequelae. Refractory epilepsy occurs in 4-13% of NF1 patients. Hippocampal sclerosis and focal cortical dysplasia, both well-defined epilepsy-related entities, have been described in a subset of cases. To our knowledge, there has been only one other series describing coexistent focal cortical dysplasia and hippocampal sclerosis in the setting of NF1. We report two such patients who presented with intractable seizures requiring epilepsy surgery. Histologically, the hippocampal sclerosis specimen met criteria for the International League Against Epilepsy (ILAE) hippocampal sclerosis subtypes Ia and II respectively. The associated focal cortical dysplasia observed within the resected temporal lobe were both consistent with ILAE focal cortical dysplasia type IIIa (e.g. associated with a secondary lesion). Post-operatively, both patients had recurrence of habitual seizures, with one case continuing to have intractable seizures following two subsequent temporal lobectomies. Although hippocampal sclerosis association with focal cortical dysplasia is well document in epilepsy, it has been rarely described in the setting of neurofibromatosis type I. Although prior surgical series have shown good epilepsy surgery outcomes within neurofibromatosis type I, these two cases did not.