The majority of patients with this syndrome have structural brain abnormalities. A proportion of cases have a genetic etiology and the inheritance pattern depends on the gene involved.
Genes associated with this syndrome include ARX, CDKL5, SPTAN1, STXBP1 and genes that underlie structural brain abnormalities, e.g. TSC1 (on 9q34, encoding hamartin) and TSC2.
A number of chromosomal abnormalities (e.g. Trisomy 21) and copy number variations have been associated with this syndrome, so karyotype and microarray should be considered.
Family history of seizures or epilepsy is rare. The presence of a family history should lead to investigation for specific genetic or metabolic etiologies.