José M. Serratosa

OBJECTIVE: To evaluate the efficacy and safety of perampanel 2, 4, and 8 mg/day added to 1-3 concomitant antiepileptic drugs (AEDs) in patients with uncontrolled partial-onset seizures. METHODS: During this double-blind, placebo-controlled trial, patients with persisting seizures on 1-3 AEDs were randomized to perampanel 2, 4, and 8 mg/day or placebo following a 6-week baseline phase. Perampanel was titrated weekly by 2 mg/day and maintained at the dose achieved for 13 weeks. Primary endpoints were median percent change in seizure frequency and 50% responder rate. Analysis of covariance was performed on all treated patients with any seizure data (recorded in daily diaries) in the double-blind phase. RESULTS: A total of 706 patients were randomized and received trial medication; 623 completed the trial. Median percent change in seizure frequency-the primary efficacy endpoint-was -10.7%, -13.6%, -23.3%, and -30.8% for placebo, perampanel 2, 4, and 8 mg/day, respectively. The difference from placebo was statistically significant for perampanel 4 mg/day (p = 0.0026) and 8 mg/day (p < 0.0001). The corresponding 50% responder rates were 17.9%, 20.6%, 28.5%, and 34.9%. The difference from placebo was statistically significant for perampanel 4 mg/day (p = 0.0132) and 8 mg/day (p = 0.0003). An apparent dose response was suggested for dizziness, which was the most frequent treatment-emergent adverse event. CONCLUSIONS: This trial demonstrated that adjunctive perampanel effectively reduced seizure frequency and possessed a favorable tolerability profile in patients ≥12 years with partial-onset seizures (with or without secondary generalization), with a minimum effective dose of 4 mg/day. CLASSIFICATION OF EVIDENCE: This study provides Class I evidence that 4 and 8 mg/day doses of adjunctive perampanel are effective and tolerated in reducing partial-onset seizures.

OBJECTIVE: SCN8A encodes the sodium channel voltage-gated α8-subunit (Nav1.6). SCN8A mutations have recently been associated with epilepsy and neurodevelopmental disorders. We aimed to delineate the phenotype associated with SCN8A mutations. METHODS: We used high-throughput sequence analysis of the SCN8A gene in 683 patients with a range of epileptic encephalopathies. In addition, we ascertained cases with SCN8A mutations from other centers. A detailed clinical history was obtained together with a review of EEG and imaging data. RESULTS: Seventeen patients with de novo heterozygous mutations of SCN8A were studied. Seizure onset occurred at a mean age of 5 months (range: 1 day to 18 months); in general, seizures were not triggered by fever. Fifteen of 17 patients had multiple seizure types including focal, tonic, clonic, myoclonic and absence seizures, and epileptic spasms; seizures were refractory to antiepileptic therapy. Development was normal in 12 patients and slowed after seizure onset, often with regression; 5 patients had delayed development from birth. All patients developed intellectual disability, ranging from mild to severe. Motor manifestations were prominent including hypotonia, dystonia, hyperreflexia, and ataxia. EEG findings comprised moderate to severe background slowing with focal or multifocal epileptiform discharges. CONCLUSION: SCN8A encephalopathy presents in infancy with multiple seizure types including focal seizures and spasms in some cases. Outcome is often poor and includes hypotonia and movement disorders. The majority of mutations arise de novo, although we observed a single case of somatic mosaicism in an unaffected parent.