Beschreibung:
<jats:title>Abstract</jats:title><jats:p>Pathogenic variants in <jats:italic><jats:styled-content style="fixed-case">SCN</jats:styled-content>8A</jats:italic> have originally been described in patients with developmental and epileptic encephalopathy (<jats:styled-content style="fixed-case">DEE</jats:styled-content>). However, recent studies have shown that <jats:italic><jats:styled-content style="fixed-case">SCN</jats:styled-content>8A</jats:italic> variants can be associated with a broader phenotypic spectrum, including the following: (1) Patients with early onset, severe <jats:styled-content style="fixed-case">DEE</jats:styled-content>, developing severe cognitive and motor regression, pyramidal/extrapyramidal signs, and cortical blindness. Severe <jats:italic><jats:styled-content style="fixed-case">SCN</jats:styled-content>8A</jats:italic>‐<jats:styled-content style="fixed-case">DEE</jats:styled-content> is characterized by intractable seizures beginning in the first months of life. The seizures are often prolonged focal hypomotor and occur in clusters, with prominent vegetative symptoms (apnea, cyanosis, mydriasis), evolving to clonic or bilateral tonic‐clonic manifestations. Spasm‐like episodes, cortical myoclonus, and recurrent episodes of status epilepticus are also common. Electroencephalograms (<jats:styled-content style="fixed-case">EEG</jats:styled-content>s) show progressive background deterioration and multifocal abnormalities, predominant in the posterior regions. (2) Sporadic and familial patients with mild‐to‐moderate intellectual disability, discrete neurological signs, and treatable epilepsy. <jats:styled-content style="fixed-case">EEG</jats:styled-content> is abnormal in half of the cases, showing multifocal or diffuse epileptiform abnormalities. (3) Familial cases with benign infantile seizures, sometimes associated with paroxysmal dyskinesia later in life, with no other neurological deficits, normal cognition, and usually normal interictal <jats:styled-content style="fixed-case">EEG</jats:styled-content>. (4) Patients without epilepsy but with cognitive and/or behavioral disturbances, or with movement disorders. Extrapyramidal features, such as dyskinesia, ataxia, and choreoathetosis are common in all groups. Early death has been reported in about 5% of the patients, most often in the subgroup of severe <jats:styled-content style="fixed-case">DEE</jats:styled-content>. Premature death occurs during early childhood and often for causes other than sudden unexpected death in epilepsy. All epilepsy subgroups exhibit better seizure control with sodium channel blockers, usually at supratherapeutic doses in the severe cases. In severe <jats:italic><jats:styled-content style="fixed-case">SCN</jats:styled-content>8A</jats:italic>‐<jats:styled-content style="fixed-case">DEE</jats:styled-content>, ketogenic diet often has a good effect, whereas levetiracetam has a negative effect, if any. The familial <jats:italic><jats:styled-content style="fixed-case">SCN</jats:styled-content>8A</jats:italic>‐related epilepsies show an autosomal dominant pattern of inheritance, whereas the vast majority of <jats:italic><jats:styled-content style="fixed-case">SCN</jats:styled-content>8A</jats:italic>‐<jats:styled-content style="fixed-case">DEE</jats:styled-content>s occur de novo.</jats:p>