Refer right away to the epileptologist for diagnosIS

Whenever possible, refer directly to the epileptologist. As noted by Rao et al in the ASSIST study, the first neurologist did not always make the diagnosis. This meant additional time—sometimes months—was unnecessarily added until a provider who correctly diagnosed and began appropriate first-line treatment was seen.1

See the ASSIST study results

Every day from onset matters

Delays to diagnosis of >7 days have been shown to increase life-long neurodevelopmental impairment.2-4

Obstacles to diagnosis

Obstacles to diagnosis

Infantile spasms is a “never miss, never delay” diagnosis. However, this necessary urgency is hindered by additional realities:

  • Navigating referrals and health insurance can be time consuming5
  • There may be no specialists within reasonable distance2
  • Because infantile spasms is rare, even some specialists might not recognize it1
  • Most hospitals don’t have a pediatric neurologist1
  • There may only be a handful of pediatric neurologists within a large geographic area1

Have a plan of action


Prioritize referral to the epileptologist—and have a plan if resources are scarce

“Some refer within a week. But others the diagnosis is completely missed. Maybe months after these events have started.”6


Evaluating the EEG

Evaluating the EEG

The hypsarrhythmic pattern will be evident in many cases. However, it is not required for a diagnosis and may not be seen on the EEG of cases of infantile spasms.7

Infantile spasms
HypsarrHythmic pattern8
  • Chaotic/disorganized background
  • High voltage slow delta (1-3 Hz) waves
    • Very high amplitude slow waves
    • Discharges of waves and spikes varying in amplitude, morphology, duration, and site
  • Spike/sharp waves from multiple foci
Abnormal EEG (no hypsarrhythmic pattern)9
  • Distinctive, diffuse high-amplitude slow wave
  • Superimposed fast activity
  • Followed by electrodecrement (diffuse attenuation), which may appear to be more normal activity

Pattern may not record in awake state—order a sleep EEG of at least 20 minutes.7

Hypsarrythmia may not always show up on the EEG

Obtaining a sleep EEG is very important as the hypsarrhythmic features are many times not recorded in the awake state.7

Hypsarrythmia may not always show up on the EEG9,10

Subtle infantile spasms may be more difficult to capture on EEG, which may account for at least some treatment delay.2

Overemphasis on the presence of hypsarrhythmia can have serious consequences for children presenting with infantile spasms, especially if clinicians inappropriately withhold standard therapies from children with EEG reports that do not include hypsarrhythmia.10

Prolonged EEG will identify abnormal activity and/or hypsarrhythmia to confirm IS.9

Differential EEG from similar symptoms

Differential EEG

Some seizure types or movements can mimic IS. The International League Against Epilepsy strongly encourages clinicians to assess patient video together with the EEG.4,7

Brief tonic seizures in clusters7 Myoclonic jerks7 Infantile Spasms7
Symptoms Sustained tonic contraction Split second jerk
(about 200 milliseconds)
Brief but slow jerks lasting about 1 second each
EEG Appearance of diffuse fast rhythms on the ictal EEG Associated with fast (4–6 Hz) spike and wave discharge on the ictal EEG Associated with a prominent slow wave ictal discharge

With or without super imposed fast waveforms
Video-EEG can help differentiate IS from other seizure types
Differential diagnosis of infantile spasms

Differential diagnosis of infantile spasms requires only 1 of:

  • Video-EEG confirmed spasms with typical ictal correlate10*
  • Either home video of spasms with typical features or definite typical clustering spasms by history, PLUS probable or definite epileptic encephalopathy on EEG10

West syndrome is a subset of infantile spasms. It often is accompanied by identifiable developmental delay or regression, which were previously a necessity for diagnosis. However, because developmental delay or regression may not necessarily be evident at onset and can be difficult to determine in infants, its presence or absence is no longer considered relevant for establishing the diagnosis.10

*Diffuse high amplitude slow wave with subsequent electrodecrement.10

Infantile spasms9


(<2 years old; Usually presents first year of life)

Spasms (ictal episodes)

Hypsarrhythmia/abnormal EEG


Seizures on the EEG can be subtle—look for them.

  1. Hussain SA, Lay J, Cheng E, Weng J, Sankar R, Baca CB. Recognition of infantile spasms is often delayed: the ASSIST study. J Pediatr. 2017;190:215-221.e1. doi:10.1016/j.jpeds.2017.08.009
  2. Rao CK, Nordli DR III, Cousin JJ, Takacs DS, Sheth RD. The effect of smartphone video on lead time to diagnosis of infantile spasms. J Pediatr. 2023;258:113387. doi:10.1016/j.jpeds.2023.02.035
  3. Wusthoff CJ, Shellhaas RA. Can a smartphone jump start care for infantile spasms? J Pediatr. 2023;258:113442. doi:10.1016/j.jpeds.2023.113442
  4. Wilmshurst JM, Gaillard WD, Vinayan KP, et al. Summary of recommendations for the management of infantile seizures: Task Force Report for the ILAE Commission of Pediatrics. Epilepsia. 2015;56(8):1185-1197. doi:10.1111/epi.13057
  5. Gali K, Joshi S, Hueneke S, et al. Barriers, access and management of paediatric epilepsy with telehealth. J Telemed Telecare. 2022;28(3):213-223. doi:10.1177/1357633X20969531
  6. Market research. Data on file. Pyros Pharmaceuticals, Inc.
  7. Chopra SS. Infantile spasms and West syndrome — a clinician’s perspective. Indian J Pediatr. 2020;87(12):1040-1046. doi:10.1007/s12098-020-03279-y
  8. Pavone P, Polizzi A, Marino SD, et al. West syndrome: a comprehensive review. Neurol Sci. 2020;41(12):3547-3562. doi:10.1007/s10072-020-04600-5
  9. Messer R, Knupp KG. Infantile spasms: opportunities to improve care. Semin Neurol. 2020;40(2):236-245. doi:10.1055/s-0040-1705121
  10. Mytinger JR. Definitions and diagnostic criteria for infantile spasms and West syndrome — historical perspectives and practical considerations. Semin Pediatr Neurol. 2021;38:100893. doi:10.1016/j.spen.2021.100893