More often, as in the case of the germline Slc2A1 gene mutation (haplodeficiency), infantile-onset epilepsy with persistently low cerebrospinal fluid glucose concentrations, delayed development, microcephaly with intellectual disability, and complex movement difficulties which include gait abnormalities are encountered and referred to as GLUT1 deficiency syndrome [133,134]. Here, SLC2A1 is linked to microcephaly.