Hypsarrhythmia:

An epileptic syndrome characterized by the triad of infantile spasms, hypsarrhythmia, and arrest of psychomotor development at seizure onset. The majority present between 3-12 months of age, with spasms consisting of combinations of brief flexor or extensor movements of the head, trunk, and limbs. The condition is divided into two forms: cryptogenic (idiopathic) and symptomatic (secondary to a known disease process such as intrauterine infections; nervous system abnormalities; BRAIN DISEASES, METABOLIC, INBORN; prematurity; perinatal asphyxia; TUBEROUS SCLEROSIS; etc.). (From Menkes, Textbook of Child Neurology, 5th ed, pp744-8)