West syndrome: Infantile spasms, a seizure disorder of infancy and early childhood with the onset predominantly in the first year of life of myoclonic seizures, hypsarrhythmia (abnormal, chaotic electroencephalogram), and mental retardation. The spasms are sudden, brief contractions of one or more muscle groups, and may be followed by a longer (less than 10 seconds) tonic phase. Most often the spasms occur in clusters during which the intensity or the frequency of the spasms may increase progressively to a peak, decline, or cease. The clusters tend to occur soon after arousal from sleep. They are not a feature of falling asleep. The spasms usually involve the muscles of the neck, trunk, and extremities.
Some patients may be treated successfully with either ACTH (adrenocorticotrophic hormone) or prednisone. Newer antiepileptic medications, such as vigabatrin, and occasionally surgical resection of a seizure focus which triggers the spasms, may be useful in selected patients.
West syndrome is one of the most devastating seizure disorders affecting infants. Spontaneous cessation of spasms occurs in most patients with increasing age. Overall, however, the intellectual prognosis for patients is generally poor because a large number of these babies have neurological impairment prior to the onset of spasms. Many go on to have different types of seizures in later childhood.