Foramen magnum decompression in children with achondroplasia : - a retrospective cohort analysis

Abstract: Introduction 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. Aim The study aimed to describe the prevalence of FMS in a population of children with achondroplasia and to evaluate screening and neurosurgical interventions of FMS in regard to its effects and complications. Material and Methods This is a retrospective cohort study including all children with achondroplasia assessed or treated at Karolinska University Hospital between September 2005 to June 2020. Severity of FMS was graded using MRI Achondroplasia Foramen Magnum Score (AFMS). AFMS was correlated to neurological exams and polysomnography results. Results 51 children were included and severe FMS (AFMS3-4) was present in 35%. Sixty-five percent of the children 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 polysomnography did not correlate to severity of FMS (p=0.735). Surgery improved FMS (p<0.001) and decreased central apnea (p=0.070), but carried a risk of 9% for severe complications. Conclusions This study suggests that severe FMS is common in children with achondroplasia, that neurological symptoms may be absent even in severe FMS, and that FMD improves both FMS and central apnea. In order to limit morbidity and mortality by identifying children with severe FMS in need of FMD, we recommend routine MRI on all children with achondroplasia.