In a 5‑month‑old infant with moderate‑to‑severe positional plagiocephaly unresponsive to 4–6 weeks of repositioning and normal cranial sutures, how long should helmet therapy be continued and at what age/month should it be discontinued?

Duration and Discontinuation of Helmet Therapy for Positional Plagiocephaly

Helmet therapy should be continued until complete correction is achieved (diagonal difference <5 mm) or until 18 months of age, whichever comes first, with treatment duration typically ranging from 14-18 weeks when started before 6 months of age. 1, 2

Treatment Duration Based on Age at Initiation

The duration of helmet therapy correlates directly with the age at which treatment begins:

• Infants starting before 6 months of age: Treatment typically requires 14 weeks to achieve optimal correction 1
• Infants starting after 6 months of age: Treatment extends to approximately 18 weeks on average 1
• Infants starting at 18 months or older: Treatment may require 16.4 months on average, though this represents a much longer commitment with potentially less dramatic results 3

The earlier treatment begins, the shorter the duration needed and the better the outcomes achieved. 1, 4

Age Cutoff for Discontinuation

Helmet therapy should be discontinued by 18 months of age, as this represents the practical endpoint where cranial growth velocity slows significantly and treatment effectiveness diminishes. 2

Key Age-Related Considerations:

• Optimal treatment window: 5-6 months of age at initiation provides the best balance of skull malleability and treatment efficiency 1, 4
• Treatment started before 24 weeks: Shows the highest absolute and relative rates of correction 4
• Treatment started after 32 weeks: Still effective but requires longer duration and achieves less dramatic improvement 4

Treatment Endpoints

Helmet therapy should be discontinued when either of these criteria is met:

1. Complete correction achieved: Diagonal difference <5 mm AND/OR cranial ratio <0.85 2
2. Age limit reached: 18 months of age, regardless of correction status 2

In the moderate-to-severe cases that warrant helmet therapy, 94.4% of patients achieve complete correction when helmet therapy is used as first-line treatment, and 96.1% achieve correction even after failed conservative therapy. 2

Important Clinical Caveats

Compliance is critical: Poor compliance is the strongest predictor of treatment failure (relative risk 2.40-2.42), so families must be counseled that consistent 23-hours-per-day wear is essential for success. 2

Severity matters for timing: In mild plagiocephaly, age at initiation doesn't significantly impact outcomes, but in moderate-to-severe cases (which is your clinical scenario), starting before 6 months dramatically improves results and shortens treatment duration. 4

Don't delay unnecessarily: While the Congress of Neurological Surgeons guidelines recommend a trial of conservative therapy first, delaying helmet therapy beyond 6 months of age in severe cases presenting late significantly deteriorates outcomes and should be avoided. 5, 1