Management and outcomes of foramen magnum stenosis in children with achondroplasia at a single center over 15 years.

Objective: Achondroplasia is associated with foramen magnum stenosis (FMS), which can lead to sudden unexpected death in infants. There is no wide consensus regarding the best management of FMS. This study aimed to analyze the prevalence of FMS in a cohort of children with achondroplasia and to evaluate screening and neurosurgical interventions of FMS regarding its effects and complications.

Methods: The authors conducted a retrospective cohort study including all children with achondroplasia assessed or treated at Karolinska University Hospital between September 2005 and June 2020. The severity of FMS was graded using the MRI Achondroplasia Foramen Magnum Score (AFMS). The AFMS was correlated with neurological examinations and polysomnography (PSG) results.

Results: Severe FMS (AFMS 3-4) was present in 35% of the 51 children included in the study. As many as 65% of the children in the cohort underwent foramen magnum decompression (FMD). Neurological examination had a high specificity (94%) but a low sensitivity (28%) for severe FMS. Signs of central apnea on PSG did not correlate with severity of FMS (p = 0.735). Surgery improved FMS (p < 0.001) with a nonsignificant trend of decreased central apnea (p = 0.070), but carried a 9% risk of severe surgery- and anesthesia-related complications.

Conclusions: This study confirmed previous reports that severe FMS is common in children with achondroplasia, that neurological symptoms may be absent even in severe FMS, and that FMD improves FMS and may improve central apnea. The finding that neurological examination had a low sensitivity for severe FMS supports the recommendation that all children with achondroplasia should undergo early MRI.