Infantile spasm (IS) is a convulsive disease characterized by brief, symmetric axial muscle contraction (neck, trunk, and/or extremities). IS is a type of seizure that was first described by West in 1841, who witnessed the seizure in his own son. West's syndrome refers to the classic triad of spasms, characteristic EEG, and neurodevelopmental regression. Most cases involve flexors and extensors, but either of the types may be involved independently. IS, as its name implies, most often occurs during the first year of life with an incidence of approximately 1 per 2000-4000 live births. Most, but not all, patients with this disorder have severe EEG abnormalities; this pattern was originally referred to as hypsarrhythmia by Gibbs and Gibbs. Cases with known etiology or signs of brain damage are considered as symptomatic. The Overall prognosis of the disease is poor. Peak onset age of the epileptic syndrome is 3 to 7 months, which mainly occurs before 2 years of age in 93% of patients. Hypsarrhythmia is the EEG hallmark of IS, which comprised a chaotic, bilaterally asynchronous high-voltage polyspike, and slow wave discharges interspersed with multifocal spikes and slow waves. ETIOLOGICAL CLASSIFICATION IS AS FOLLOWS: 1) Symptomatic: with identifiable prenatal, perinatal, and postnatal causes with developmental delay at the presentation time; 2) Cryptogenic: unknown underlying cause, normal development at the onset of spasms, normal neurological exam and neuroimaging, and no abnormality in the metabolic evaluation; 3) Idiopathic: pure functional cerebral dysfunction with complete recovery, no residual dysfunction, normal neuroimaging and normal etiologic evaluation, and normal neurodevelopment.
Keywords: Electroencephalography; Hypsarrhythmia; Infantile spasms.