A method for the diagnosis of an epilepsy syndrome, including SMEI or an SMEI-related syndrome, in a patient comprising testing for an alteration in the SCN1A gene in a sample obtained from the patient; and if an alteration is identified, comparing said alteration to any one of those listed in Table 3, wherein if said alteration is identical to any one of those listed in Table 3, a diagnosis of an epilepsy syndrome, including SMEI or an SMEI-related syndrome, in said patient is made in accordance with the correlation set forth in Table 3.