West syndrome is characterized by the onset of epileptic spasms, typically in the first year of life. Global developmental impairment (with or without regression) is typically seen.
NOTE West syndrome may be associated with 'epileptic encephalopathy'. This term denotes the concept that the epileptic activity itself might directly contribute additional cognitive and behavioral impairments over those expected from the underlying etiology alone, and that suppression of epileptic activity might minimize this additional impairment.
This syndrome is characterized by onset of epileptic spasms between 3 and 12 months of age, although later onset may occur. Infants may have had no antecedent history, or the antecedent history may reflect the underlying cause e.g. acquired structural brain abnormality. In some cases, infants with Ohtahara syndrome or other early onset epilepsies (typically with focal seizures) may evolve to have clinical and EEG features of West syndrome after 3-4 months of age. Both sexes are affected, with a higher incidence in males. Head size and neurological examination may be normal or findings may reflect underlying brain abnormalities. Global developmental impairment (with or without regression) is typically seen at onset of epileptic spasms. Occasionally development may be normal and developmental trajectory continues as expected.