Epilepsy and brain channelopathies from infancy to adulthood.

Genetic brain channelopathies result from inherited or de novo mutations of genes encoding ion channel subunits within the central nervous system. Most neurological channelopathies arise in childhood with paroxysmal or episodic symptoms, likely because of a transient impairment of homeostatic mechanisms regulating membrane excitability, and the prototypical expression of this impairment is epilepsy. Migraine, episodic ataxia and alternating hemiplegia can also occur, as well as chronic phenotypes, such as spinocerebellar ataxias, intellectual disability and autism spectrum disorder. Voltage-gated and ligand-gated channels may be involved. In most cases, a single gene may be associated with a phenotypical spectrum that shows variable expressivity. Different clinical features may arise at different ages and the adult phenotype may be remarkably modified from the syndrome onset in childhood or adolescence. Recognizing the prominent phenotypical traits of brain channelopathies is essential to perform appropriate diagnostic investigations and to provide the better care not only in the paediatric setting but also for adult patients and their caregivers. Herein, we provide an overview of genetic brain channelopathies associated with epilepsy, highlight the different molecular mechanisms and describe the different clinical characteristics which may prompt the clinician to suspect specific syndromes and to possibly establish tailored treatments.

A functional polymorphism in the SCN1A gene does not influence antiepileptic drug responsiveness in Italian patients with focal epilepsy.

A splice site variation (c.603-91G>A or rs3812718) in the SCN1A gene has been claimed to influence efficacy and dose requirements of carbamazepine and phenytoin. We investigated the relationship between c.603-91G>A polymorphism and response to antiepileptic drugs (AEDs) in 482 patients with drug-resistant and 401 patients with drug-responsive focal epilepsy. Most commonly used AEDs were carbamazepine and oxcarbazepine. The distribution of c.603-91G>A genotypes was similar among drug-resistant and drug-responsive subjects, both in the entire population and in the groups treated with carbamazepine or oxcarbazepine. There was no association between the c.603-91G>A genotype and dosages of carbamazepine or oxcarbazepine. These findings rule out a major role of the SCN1A polymorphism as a determinant of AED response.