Cerebellar Atrophy and Epilepsy in Twins with a Novel SCN8A Mutation

Abstract Purpose  Pathogenic SCN8A variants are associated with a wide spectrum of clinical presentation, ranging from mild to severe epileptic phenotypes, cases of intellectual disability, or movement disorders without epilepsy. Ataxia and cerebellar atrophy are rarely described as components of the disease phenotype. Case Presentation  We present the cases of male twins, born after normal pregnancy and delivery, both with normal neuropsychological but with delayed motor development in the first 2 years of life. Between 8 months and 9 years of age, the boys experienced generalized tonic-clonic seizures, several times per year. When 9 years old, the children suffered an increase in seizure frequency, and the family reported gradual worsening in coordination, speech, communication, and social skills. When 9 and a half years of age, the patients were admitted to the Clinic of Child Neurology for the first time. They both had coordination syndrome (intention tremor, dysmetria, dysdiadochokinesia) that had worsened compared with previous reports, and magnetic resonance imaging of the brain showed cerebellar atrophy. The genetic testing confirmed a mutation c.2617G > T, p.Gly873Cys in SCN8A gene. After adding lamotrigine to valproate and levetiracetam, and adjusting the dosage of valproate and levetiracetam, we observed good seizure control accompanied by improvement in the coordination syndrome. Conclusion  The cerebellar atrophy in our patients is likely due to the underlying sodium channelopathy, as it was presented at the time of the seizure worsening, but we cannot exclude the role of the epileptic seizures as the worsening of the coordination syndrome accompanied the seizure aggravation, and the tendency toward improvement was evident after seizure control.