West Syndrome (Infantile Spasms)
The diagnosis is B) West Syndrome (Infantile Spasms). The combination of clusters of sudden flexor spasms in an infant with hypsarrhythmia on EEG is pathognomonic for this condition 1, 2.
Clinical Presentation
West Syndrome presents with three cardinal features that define the diagnosis:
- Epileptic spasms occurring in clusters, typically flexor or mixed flexor-extensor spasms 2, 3
- Hypsarrhythmia on EEG, characterized by very high amplitude irregular slow waves with superimposed multifocal epileptiform discharges 4
- Neurodevelopmental regression or arrest, though this may not be immediately apparent at presentation 2, 3
The peak age of onset is between 4-7 months, with most cases occurring before 12 months of age 2, 5.
Why Other Options Are Incorrect
Lennox-Gastaut Syndrome typically presents later (ages 3-5 years) with multiple seizure types including tonic, atonic, and atypical absence seizures, and shows slow spike-wave patterns on EEG rather than hypsarrhythmia 2.
Juvenile Myoclonic Epilepsy occurs in adolescence (ages 12-18 years) with myoclonic jerks upon awakening, generalized tonic-clonic seizures, and 4-6 Hz polyspike-wave discharges on EEG 2.
Absence Epilepsy presents in school-age children (4-8 years) with brief staring spells and 3 Hz spike-wave discharges on EEG, not hypsarrhythmia 2.
Diagnostic Confirmation
Video-EEG is essential for definitive diagnosis, as it captures both the clinical spasms and the characteristic EEG pattern 5. Initial diagnosis requires video-EEG studies, especially in infants with symptomatic etiology who may show only subtle spasms that can be easily missed 5.
Critical pitfall: Spasms may be subtle, asymmetric, or asynchronous, particularly in symptomatic cases, and can be mistaken for benign movements 5. Subtle spasms and asymmetric presentations are associated with symptomatic etiology and poor cognitive and seizure outcomes 5.
Etiologic Workup
The most common identifiable causes include:
- Hypoxic-ischemic injury (46-65% of cases), particularly in term and preterm infants 6
- Tuberous sclerosis, which has specific treatment implications 6
- Intracranial hemorrhage and perinatal ischemic stroke (10-12% of cases) 6
- Infections occurring beyond the seventh day of life 6
Brain MRI is essential for identifying structural etiologies 7. Genetic and metabolic testing should be pursued to identify treatable causes 2.
Treatment Urgency
Immediate referral to pediatric neurology is mandatory 7. Treatment within the first month of symptom onset significantly improves neurodevelopmental outcomes 7. A longer lag time to diagnosis and effective treatment is associated with poorer long-term neurodevelopmental outcomes 4.
First-Line Treatment Options
The FDA-approved first-line treatments are:
- ACTH (Acthar Gel): 86.7% response rate for complete suppression of spasms and hypsarrhythmia, compared to 28.6% with prednisone 1
- Vigabatrin: Particularly effective for tuberous sclerosis-associated infantile spasms 6, 2
- Corticosteroids: Oral prednisolone 40-60 mg/day for 14 days has been considered effective 2
Critical management consideration: If steroids or ACTH are used, cardiology consultation is required due to risk of cardiomyopathy 6, 7.
Monitoring Treatment Response
Video-EEG is the only reliable method for assessing treatment response, as spasms and interictal EEG abnormalities are modified by treatment and may become subtle 5. Treatment response is defined as complete suppression of both clinical spasms and hypsarrhythmia on full sleep cycle video-EEG 1.
Cessation of spasms usually precedes disappearance of hypsarrhythmia or multifocal spikes, but persistence of multifocal spikes over several weeks is always associated with existing spasms 5.
Long-Term Management
Multidisciplinary care is essential and should include 6:
- Neurology for seizure management
- Early intervention services for developmental support
- Physical therapy, occupational therapy, and speech/language evaluation
- Ongoing developmental assessments alongside seizure management