Best practices in the evaluation and treatment of foramen magnum stenosis in achondroplasia during infancy

Abstract

Achondroplasia is the most common inherited disorder of bone growth (skeletal dysplasia). Despite this fact, consistent and evidence-based management approaches to recognized, life-threatening complications, such as foramen magnum stenosis, are lacking. This study aims to outline best practice, based on evidence and expert consensus, regarding the diagnosis, assessment, and management of foramen magnum stenosis in achondroplasia during infancy. A panel of 11 multidisciplinary international experts on skeletal dysplasia was invited to participate in a Delphi process. They were: 1) presented with a list of 26 indications and a thorough literature review, 2) given the opportunity to anonymously rate the indications and discuss in face to face discussion; 3) edit the list and rate it in a second round. Those indications with more than 80% agreement were considered as consensual. After two rounds of rating and a face-to-face meeting, consensus was reached to support 22 recommendations for the evaluation and treatment of foramen magnum stenosis in infants with achondroplasia. These recommendations include indications for surgical decompression, ventriculomegaly, and hydrocephalus, sleep-disordered breathing, physical exams and the use of polysomnography and imaging in this condition. We present a consensus-based best practice guidelines consisting of 22 recommendations. It is hoped that these guidelines will lead to more uniform and structured evaluation, standardizing care pathways, and improving mortality and morbidity outcomes for this cohort.

Current Care and Investigational Therapies in Achondroplasia

“…No specific marker has been identified so far to distinguish which asymptomatic patients need prophylactic decompression of the foramen magnum, and there is no evidence-based strategy; it is currently recommended that only symptomatic infants (with some clinical neurological signs and/or pathologic polysomnography) undergo brain imaging [36••]. Careful clinical surveillance by a multidisciplinary team experienced in achondroplasia may prove to be as sensible as investigations in detecting critical brainstem compression: increased generalized hypotonia, changes in osteotendinous reflexes (hyperreflexia, clonus, asymmetry), and subtle signs of intracranial hypertension (prominent fontanella, rapid increase of OFC) should be monitored, preferably by the same professional, every 2 months [36 •• ]; family doctors should be informed about signs and symptoms to be surveyed in between the visits at the specialized center. Some centers propose sleep studies and even matrasses with detectors of sleep apnea; the utility of these measures has not been proven and the occurrence of sleep apnea appears to be only poorly correlated with foramen magnum stenosis [37, 38].…”

Pediatric Craniovertebral Junction Surgery

“…Ventriculomegaly requiring a ventriculoperitoneal (VP) shunt reportedly occurs in about 10% of children with achondroplasia, while reports of the numbers of children requiring FMD offer widely varying figures of 5%–10% to nearly 50%. 34,40,42,43) …”

“…43,48,49) The symptoms and signs attributed to FM stenosis are difficult to diagnose. The author has performed FMD in 26 children with achondroplasia since 2003 (aged 5 months to 3 years, median age: 10 months), all of whom fulfilled at least one of the following criteria along with FM stenosis.…”

“…46) The surgical indication seemed to accord with the recently published guidelines for the management of FM stenosis in achondroplasia during infancy. 43) Abnormal signal intensity on MRI: presence of intramedullary signal change on T2 weighted sagittal image of the site of FM stenosis.Delayed motor development: if a child is unable to stand and walk at the age of 2, delayed motor development is assumed.Central type sleep apnea on polysomonography: 43,50) central type sleep apnea strongly suggests that FMD should be performed. Clinical signs such as opistotonic posture, snoring or reluctance in the supine position during sleep are also considered signs of respiratory complications caused by FM stenosis.…”

“…Central type sleep apnea on polysomonography: 43,50) central type sleep apnea strongly suggests that FMD should be performed. Clinical signs such as opistotonic posture, snoring or reluctance in the supine position during sleep are also considered signs of respiratory complications caused by FM stenosis.…”