Phenotypic and genetic spectrum in Chinese children with SCN8A-related disorders

BACKGROUND

Pathogenic variants in SCN8A have been demonstrated with a wide spectrum of epilepsy phenotypes, ranging from benign infantile epilepsy (BIE), to early onset developmental and epileptic encephalopathy (DEE) with moderate to severe developmental delay. In order to provide further insight on the spectrum of SCN8A-related epilepsy, we aimed to explore the clinical and genetic phenotype in Chinese children.

METHODS

A cohort of fifty Chinese patients with SCN8A-related disorders was included in the retrospective study. Genetic and clinical features and treatment effect of patients were further assessed based on phenotype parameters. The pathogenicity of variants was classified using the next-generation sequencing variation study.

RESULTS

We found 50 patients who presented with severe developmental and epileptic encephalopathy (DEE, 70%), benign infantile epilepsy (BIE, 12%), developmental encephalopathy with epilepsy (16%), and severe developmental delay without epilepsy (2%). The seizure onset age ranged from 1 day to 1 year and 11 months. After anti-seizure treatment, 28% of patients obtained seizure control. Sodium channel blockers showed good prognosis in 26% of patients with severe DEE. Oxcarbazepine (OXC) monotherapy was obviously effective in patients with BIE and developmental encephalopathy with epilepsy, most importantly, 87.5% received the anti-seizure therapy with sodium channel blockers in combination. All the variants were de novo missense with exception of one splice site variant. We reported three new variants, Asn1887Ser, Ile1605Thr, and Met1869Thr, which were associated with SCN8A-BIE.

CONCLUSION

The phenotypic spectrum of SCN8A-related disorders in Chinese children ranged from severe developmental delay without epilepsy to severe DEE. Three new variants were associated with SCN8A-BIE. Sodium channel blockers were effective in treating seizures for some SCN8A-related disorders however may not be relevant to the mutant location.

Sodium channel blockers are effective for benign infantile epilepsy

OBJECTIVE

To examine the efficacy and tolerance of the antiseizure medications lacosamide (LCM) and levetiracetam (LEV) in patients with benign infantile epilepsy (BIE).

METHODS

The clinical data of 24 children with BIE seen between 2014 and 2020 were collected retrospectively, and treatment, effectiveness, and adverse effects were examined. PRRT2 gene analysis was performed using Sanger sequencing.

RESULTS

Of the 24 children with BIE, 14 were treated with antiseizure medications. PRRT2 gene analysis was performed in 14 children, and mutations were identified in 4, including a pair of siblings. All five children treated with LCM became seizure-free, similar to those treated with carbamazepine. The LCM does was 2 mg/kg/day in all cases. There were no adverse effects in any patient treated with LCM. By contrast, both patients treated with LEV had seizure recurrence. In one patient, LEV was replaced with CBZ, resulting in seizure freedom.

CONCLUSIONS

Low-dose LCM was effective and well tolerated in patients with BIE, whereas LEV was insufficiently effective.

Splenial Lesions in Benign Convulsions With Gastroenteritis Associated With Rotavirus Infection

OBJECTIVE

To investigate clinical risk factors for acute magnetic resonance imaging (MRI) abnormalities in patients with benign convulsions with mild gastroenteritis or benign infantile epilepsy.

STUDY DESIGN

We investigated clinical and diffusion-weighted imaging findings in 32 patients with benign convulsions with mild gastroenteritis and 22 patients with benign infantile epilepsy who underwent MRI within seven days of seizure onset between 2010 and 2015.

RESULTS

Diffusion-weighted imaging showed signal hyperintensity in the splenium of the corpus callosum in seven patients with benign convulsions with mild gastroenteritis, but no abnormalities in patients with benign infantile epilepsy. Patients with benign convulsions with mild gastroenteritis with splenial lesions showed a higher rate of rotavirus detection from feces (P = 0.006), higher serum level of C-reactive protein (P = 0.04), and shorter interval between seizure onset and MRI (P = 0.002) than patients with benign convulsions with mild gastroenteritis without splenial lesions. Multivariate analysis revealed rotavirus infection as a significant risk factor for splenial lesions on diffusion-weighted imaging in patients with benign convulsions with mild gastroenteritis (P = 0.02).

CONCLUSIONS

Splenial lesions are often seen during acute period in patients with benign convulsions with mild gastroenteritis. Rotavirus infection is a risk factor for splenial lesions in patients with benign convulsions with mild gastroenteritis, suggesting the role of rotavirus to cause edema in the corpus callosum. From our observations, benign convulsions with mild gastroenteritis with a splenial lesion on diffusion-weighted imaging suggests good outcomes, and extensive evaluation of these patients may be unnecessary.

Focal seizures and epileptic spasms in a child with Down syndrome from a family with a PRRT2 mutation

We describe a girl with Down syndrome who experienced focal seizures and epileptic spasms during infancy. The patient was diagnosed as having trisomy 21 during the neonatal period. She had focal seizures at five months of age, which were controlled with phenobarbital. However, epileptic spasms appeared at seven months of age in association with hypsarrhythmia. Upon treatment with adrenocorticotropic hormone, her epileptic spasms disappeared. Her younger brother also had focal seizures at five months of age. His development and interictal electroencephalogram were normal. The patient's father had had infantile epilepsy and paroxysmal kinesigenic dyskinesia. We performed a mutation analysis of the PRRT2 gene and found a c.841T>C mutation in the present patient, her father, and in her younger brother. We hypothesized that the focal seizures in our patient were caused by the PRRT2 mutation, whereas the epileptic spasms were attributable to trisomy 21.