Epilepsy in Christianson syndrome: Two cases of Lennox–Gastaut syndrome and a review of literature

Abstract

Christianson syndrome (CS) is an X-linked intellectual disorder caused by mutations in the SLC9A6 gene. Clinical features of CS include an inability to speak, truncal ataxia, postnatal microcephaly, hyperkinesis, and epilepsy. Almost all patients with CS develop drug-resistant epilepsy—its most serious complication. We report two cases of CS with drug-resistant epilpesy associated with the Lennox–Gastaut syndrome (LGS). One patient experienced generalized tonic seizures since 9 months of age with cognitive regression, which evolved to include atonic seizures at the age of 7 years. Electroencephalography (EEG) showed generalized slow spike–wave complexes and generalized paroxysmal fast activity. Seizures remained drug-resistant despite multiple anti-seizure drugs. The second patient experienced generalized tonic seizures since the age of 17 months and arrested development. EEG showed generalized slow spike–wave complexes, with frequent atonic seizures since the age of 6 years. Electrical status epilepticus during slow-wave sleep (ESES) developed at the age of 7 years. Our cases illustrate that CS may cause LGS in addition to other developmental and epileptic encephalopathies of the neonatal and infantile period. We suggest that generalized tonic or tonic–clonic seizures and generalized slow spike–wave complexes in interictal EEG be included as potential electroclinical features of epilepsy in CS. Keywords: Epilepsy, Christianson syndrome, SLC9A6, Lennox–Gastaut syndrome, Electrical status epilepticus in slow-wave sleep