Short answer · Medically reviewed summary · Last updated: 2026-05-08
West Syndrome, also known as infantile spasms, is primarily diagnosed through a combination of clinical observation of characteristic seizure clusters and an electroencephalogram (EEG) showing a distinct pattern called hypsarrhythmia. Early diagnosis is critical, as West Syndrome requires prompt medical intervention to improve long-term neurodevelopmental outcomes. How is West Syndrome diagnosed? The diagnostic process for West Syndrome typically begins when a caregiver notices sudden, brief muscle contractions—often described as "jackknife" spasms—in an infant.
How is West Syndrome diagnosed?
How West Syndrome is diagnosed: tests, specialists and the diagnostic journey, told by patients and reviewed against medical sources.
West Syndrome, also known as infantile spasms, is primarily diagnosed through a combination of clinical observation of characteristic seizure clusters and an electroencephalogram (EEG) showing a distinct pattern called hypsarrhythmia. Early diagnosis is critical, as West Syndrome requires prompt medical intervention to improve long-term neurodevelopmental outcomes.
How is West Syndrome diagnosed?
The diagnostic process for West Syndrome typically begins when a caregiver notices sudden, brief muscle contractions—often described as "jackknife" spasms—in an infant. Because these spasms can be subtle, the "diagnostic odyssey" is often fraught with frustration; parents may initially be told the movements are colic or gastroesophageal reflux. A pediatric neurologist or epileptologist is essential to confirm the diagnosis by reviewing the infant's seizure semiology and ordering an urgent EEG. The hallmark of West Syndrome on an EEG is hypsarrhythmia, characterized by high-voltage, disorganized, and chaotic brain waves.
What tests confirm West Syndrome?
Once a specialist suspects West Syndrome, they utilize specific investigations to identify the underlying cause, as the syndrome is a manifestation of various underlying brain disorders:
- EEG (Electroencephalogram): The gold standard for identifying the characteristic hypsarrhythmia pattern.
- Neuroimaging: MRI of the brain is standard to rule out structural abnormalities like cortical dysplasia or tuberous sclerosis.
- Genetic Testing: Targeted panels or chromosomal microarrays are used to identify mutations, such as those in the CDKL5 or ARX genes.
- Metabolic Screening: Blood and urine tests to rule out rare metabolic conditions that can trigger spasms.
What is the differential diagnosis for West Syndrome?
Clinicians must differentiate West Syndrome from benign infantile myoclonus, gastroesophageal reflux (Sandifer syndrome), and startle responses. Because West Syndrome is a rare, time-sensitive diagnosis, if your primary pediatrician is unfamiliar with the presentation of infantile spasms, it is vital to seek a referral to an epilepsy center or a pediatric neurologist immediately.
Next steps
- Consult a board-certified pediatric neurologist or epileptologist immediately if you suspect infantile spasms.
- Video record the episodes to show your specialist, as this is often more helpful than a verbal description.
- Connect with the 7 families currently sharing their experiences with West Syndrome at DiseaseMaps.org for peer support.
- Request genetic counseling to understand if there is a hereditary component to your child's specific case.
Medical disclaimer: This information is for educational purposes and should not replace professional medical advice, diagnosis, or treatment.
References
- Orphanet: Infantile Spasms (ORPHA:3335)
- NIH GARD: West Syndrome (Infantile Spasms)
- OMIM: West Syndrome (308350)
- Child Neurology Foundation: Infantile Spasms Resources
