Overview
- 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.
Clinical Context
- Onset of epileptic spasms occurs 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 structural brain abnormalities.
- Global developmental impairment (with or without regression) is typically seen at the onset of epileptic spasms.
- Occasionally, development may be normal, and the developmental trajectory continues as expected.
Causes
- Structural Brain Abnormalities: Common and include developmental abnormalities and pre- or peri-natal acquired brain injuries (e.g., hypoxic-ischemic encephalopathy, cerebrovascular accidents, intracranial infection). Conditions like Aicardi syndrome, lissencephaly, and tuberous sclerosis are common. Woods lamp assessment of all infants is advisable.
- Chromosomal Disorders: Associated with West syndrome, including Down syndrome and Miller-Dieker syndrome.
- Gene Abnormalities: Associated with West syndrome include ARX, CDKL5, SPTAN1, STXBP1.
- Metabolic Etiologies: Rare but important cause.
Seizures
- Epileptic Spasms: Mandatory seizure type, usually occur in a series on awakening but may also occur in sleep. Asynchronous, asymmetric, or unilateral spasms suggest seizure onset in a focal region of the brain.
- Focal Seizures: May occur, lead into a series of spasms, or occur at the end of a series of spasms.
EEG
- Background/Interictal EEG: Typically abnormal with high voltage irregular slowing. The awake EEG may be normal early after onset of epileptic spasms. Abnormality may only be seen in sleep or on wakening.
- Interictal: Highly disorganized with high voltage irregular slow waves intermixed with multifocal spikes and polyspikes (termed 'hypsarrhythmia'). Asymmetry and other patterns of modified hypsarrhythmia occur in one-third of cases. Hypsarrhythmia may not be present early after the onset of epileptic spasms. The EEG may need to be repeated.
- Activation: In the early period after onset of epileptic spasms, the EEG may only be abnormal in sleep. EEG abnormality is enhanced by sleep and on wakening. REM sleep shows relative EEG normalization.
- Ictal: Epileptic spasms are most commonly accompanied by a high voltage generalized sharp or slow wave followed by low amplitude fast activity and generalized voltage attenuation. This EEG pattern may be seen in sleep with or without clinical seizures.
Imaging
- Neuroimaging is often abnormal as structural brain abnormalities are commonly seen, however, imaging may also be normal.
Genetics
- Pattern of Inheritance: The majority of patients with West syndrome have structural brain abnormalities. A proportion of cases have a genetic etiology, and the inheritance pattern depends on the gene involved.
- Known Genes: Gene abnormalities associated with West syndrome include ARX, CDKL5, SPTAN1, STXBP1. Genetic etiologies are also recognized to underlie structural brain abnormalities, such as TSC1 and TSC2 in tuberous sclerosis.
- Family History of Seizures/Epilepsy: Rare. The presence of a family history should lead to an investigation for specific genetic or metabolic etiologies.
Differential Diagnosis
- Ohtahara syndrome
- Early myoclonic encephalopathy
- Shuddering attacks
Cite this:
Cite this: CNKE contributors.West syndrome. CNKE.org, The Child Neurology Knowledge Environment. 29 December 2024. Available at: https://cnke.org/articles/268 Accessed 29 December 2024.