Aims To determine the effectiveness of helmet therapy compared with the natural course in children aged five months with positional skull deformation, measured at 24 months.

Methods Pragmatic randomised controlled trial in 84 healthy five-month old infants with moderate to severe skull deformation in The Netherlands. Infants were randomly assigned to six-month helmet therapy (Helmet Therapy, n = 42) or no helmet therapy (Natural Course, n = 42). Baseline measurements were performed at 5 months, follow-up measurements at 8, 12 and 24 months. Primary outcome was change in skull shape from 5 to 24 months assessed using plagiocephalometry (anthropometric measurement instrument). Furthermore, parental satisfaction (5-point Likert scale), side effects and motor development (BSID-III composite score) were assessed. Groups were compared using the independent t-test or chi square test. Change scores for plagiocephaly (Oblique Diameter Difference Index – ODDI) and brachycephaly (Cranio Proportional Index – CPI) were each included in an analysis of covariance (ANCOVA) using baseline values as covariate.

Results The adjusted mean change scores from 5 to 24 months, were equal in both groups for plagiocephaly (ODDI: Natural Course: 2.6 (1.8 to 3.4); Helmet Therapy: 3.4 (2.6 to 4.2); p = 0.13) as well as brachycephaly (CPI Natural Course: 7.4 (6.4 to 8.5); Helmet Therapy: 6.4 (5.3 to 7.5); p = 0.20). The numbers of children showing full recovery were comparable in both groups (Natural Course: 9/40 (23%); Helmet Therapy: 10/39 (26%); p = 0.74). Parental Satisfaction was higher for parents of infants in the Helmet Therapy group (5 (4–5) than the Natural Course group (4 (4–5); p = 0.09). Motor development showed comparable scores (Natural Course 99.0 (11.6); Helmet Therapy 97.2 (9.4); p = 0.18). Almost all parents reported side effect of helmet therapy: acceptation problems (24%), skin irritation (96%), augmented sweating (71%) unpleasant smell of the helmet (76%) pain due to the helmet (33%) and feeling hindered to cuddle their baby (77%).

Conclusion Based on the equal effectiveness of helmet therapy and natural course, a high prevalence of side effects and high costs of treatment, we discourage the use of a helmet as a standard treatment for healthy infants with moderate to severe skull deformation.