West syndrome

West syndrome, also known as infantile spasms syndrome or epileptic spasms syndrome, is a severe age-dependent epileptic encephalopathy that typically presents in the first year of life, most commonly between 3 and 7 months of age. It is characterized by a classic triad of: (1) epileptic spasms — brief, sudden flexion or extension movements of the trunk and limbs that often occur in clusters, particularly upon awakening; (2) hypsarrhythmia — a chaotic, high-amplitude electroencephalographic (EEG) pattern with disorganized slow waves and multifocal spikes; and (3) developmental regression or arrest, with loss of previously acquired milestones such as social smiling, visual tracking, and motor skills. West syndrome primarily affects the central nervous system and has profound consequences for neurodevelopment. The etiology is heterogeneous and can be classified as structural (e.g., tuberous sclerosis complex, cortical malformations, hypoxic-ischemic encephalopathy), genetic (e.g., mutations in ARX, CDKL5, STXBP1, KCNQ2, SCN2A, and many others), metabolic, or of unknown cause. Approximately 60–70% of cases have an identifiable underlying cause, while the remainder are classified as of unknown etiology. First-line treatments include adrenocorticotropic hormone (ACTH) or oral corticosteroids and vigabatrin, with vigabatrin being particularly effective in cases associated with tuberous sclerosis complex. Early and aggressive treatment is critical, as prompt cessation of spasms is associated with better neurodevelopmental outcomes. Despite treatment, the long-term prognosis remains guarded: a significant proportion of children develop other seizure types, including Lennox-Gastaut syndrome, and most experience some degree of intellectual disability. Ongoing research into targeted genetic therapies and novel antiseizure medications offers hope for improved outcomes in the future.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

Common questions about West syndrome