Focal epilepsy in Glucose transporter type 1 (Glut1) defects: case reports and a review of literature

Mutations in SLC2A1, encoding the glucose transporter type 1 (Glut1), cause a wide range of neurological disorders: (1) classical Glut1 deficiency syndrome (Glut1-DS) with an early onset epileptic encephalopathy including a severe epilepsy, psychomotor delay, ataxia and microcephaly, (2) paroxysmal exercise-induced dyskinesia (PED) and (3) various forms of idiopathic/genetic generalized epilepsies such as different forms of absence epilepsies. Up to now, focal epilepsy was not associated with SLC2A1 mutations. Here, we describe four cases in which focal seizures present the main or at least initial category of seizures. Two patients suffered from a classical Glut1-DS, whereas two individuals presented with focal epilepsy related to PED. We identified three novel SLC2A1 mutations in these unrelated individuals. Our study underscores that focal epilepsy can be caused by SLC2A1 mutations or that focal seizures may present the main type of seizures. Patients with focal epilepsy and PED should undergo genetic testing and can benefit from a ketogenic diet. But also individuals with pharmaco-resistant focal epilepsy and cognitive impairment might be candidates for genetic testing in SLC2A1.