ESPE Abstracts (2018) 89 RFC2.5

Identification of Characteristic Neurological Complications in Infants with Achondroplasia by Routine MRI Screening

Harry Doughertya, Meera Shaunaka, Melita Irvinga, Dominic Thompsonb & Moira S Cheunga

aGuy’s and St Thomas’ NHS Foundation Trust, London, UK; bGreat Ormond Street Hospital for Children NHS Foundation Trust, London, UK

Background: Achondroplasia is the commonest type of skeletal dysplasia with an incidence of 1 in 20,000 and is due to recurrent and dominantly transmitted, activating mutations in Fibroblast Growth Factor Receptor 3 (FGFR3). Complications during infancy include foramen magnum stenosis and hydrocephalus which may lead to neurological morbidity and sudden unexplained mortality. Early detection and appropriate neurosurgical management can prevent these complications. However, consensus around routine screening has not been reached and imaging practices between centres are inconsistent.

Aim: The Achondroplasia Multi-Disciplinary Service at the Evelina London Children’s Hospital provides regular surveillance for over 140 affected children. Since 2016 all infants under one year have undergone routine MRI brain imaging, aiming to identify early changes and document natural history of pathology, with a view to informing recommendations for management.

Study Design: This retrospective cohort study investigated all children under one year with a confirmed diagnosis of Achondroplasia from January 2016 to January 2018. Details were collected of clinical evaluation, which included a detailed neurological examination and MRI scans. The presence of hydrocephalus or craniovertebral junction (CVJ) changes were evaluated by a paediatric neuroradiologist. In order to provide a more objective assessment of foramen magnum stenosis a novel scoring system was developed; The Achondroplasia Foramen Magnum Severity Score (AFMSS).

Results: Only 1 out of 18 infants who underwent surveillance MRI brain had abnormal neurological findings on clinical examination. 77% had abnormal MRI changes (n=14). Five patients demonstrated CVJ narrowing with preservation of the cerebrospinal fluid (CSF) space around the cord (AFMSS 1). Three patients demonstrated CVJ narrowing with loss of CSF space (AFMSS 2). Three patients demonstrated CVJ narrowing with flattening of the cervical cord (AFMSS 3). Three patients demonstrated CVJ narrowing and cervical cord signal change (AFMSS 4). Hydrocephalus was also present in 2 patients with AFMSS 1 and AFMSS 3. Only those with AFMSS 3 or AFMSS 4 underwent foramen magnum decompression (n=5). One patient with hydrocephalus underwent ventriculoperitoneal shunt insertion. Overall, 43% of infants required neurosurgery (n=6)

Conclusion: This data demonstrates a high prevalence of pathological neuraxis changes in infants with Achondroplasia detected on routine MRI screening without clinical signs or symptoms. Further studies are needed to explore the evolution of foramen magnum changes in children over 12 months of age. The results of this study indicate that all infants with Achondroplasia should undergo routine neuroimaging screening, given the high incidence of significant complications in this unselected population.

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