Dynamic cervicomedullary cord compression and alterations in cerebrospinal fluid dynamics in children with achondroplasia: review of an 11-year surgical case series

Abstract

<jats:sec> <jats:title>Object</jats:title> <jats:p>Achondroplasia may be associated with compression at the cervicomedullary junction. Determining which patients are at greatest risk for neurological complications of cervicomedullary compression can be difficult. In the current study the authors reviewed their records to determine the incidence and clinical significance of dynamic cervicomedullary stenosis and obstruction of CSF flow along with surgical outcomes following posterior fossa decompression.</jats:p></jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>The authors reviewed 34 consecutive cases involving symptomatic children with achondroplasia undergoing cervicomedullary decompression performed by a single surgeon over 11 years. Of these patients, 29 had undergone preoperative dynamic MRI of the cervicomedullary junction with cine (cinema) CSF flow studies; 13 of these patients underwent postoperative dynamic MRI studies. Clinical outcomes included changes in polysomnography, head circumference percentile, and fontanel characteristics. Radiographic outcomes included changes in dynamic spinal cord diameter, improvement in CSF flow at the foramen magnum, and change in the Evans ratio.</jats:p></jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>Patients were predominantly female, with a mean age at presentation of 6.6 years and mean follow-up of 3.7 years (range 1–10 years).</jats:p> <jats:p>All patients had moderate to excellent improvement in postoperative polysomnography, slight decrease in average head circumference percentile (from 46.9th percentile to 45.7th percentile), and no subjective worsening of fontanel characteristics. The Evans ratio decreased by 2%, spinal cord diameter increased an average of 3.1 mm, 5.2 mm, and 0.2 mm in the neutral, flexed, and extended positions, respectively, and CSF flow improved qualitatively in all 3 positions. There were no postoperative infections, CSF leaks, or other major complications. None of the patients undergoing initial foramen magnum decompression performed at our medical center required reoperation.</jats:p></jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>Patients with achondroplasia and symptomatic cervicomedullary compression have increased risk of dynamic stenosis at the foramen magnum evident upon dynamic cine MRI. Operative decompression may be offered with low risk of complications or need for reoperation.</jats:p></jats:sec>

Achondroplasia: a comprehensive clinical review

“…Better visualization of neural tissue is forthcoming, but usually sedation or general anesthesia will be needed because of the length of the procedure. Often multiposition MRI is elected [126, 129]. Flow studies may be of some help as well in determining whether surgical intervention is warranted [126, 128].…”

“…Although this is likely the most important mechanism, there is also evidence that obliteration of cerebrospinal fluid flow at the craniocervical junction may be a factor in development of hydrocephalus, too [128, 129, 201, 202]. It is not unreasonable to posit that there are two distinct processes that can give rise to increased intracranial pressure in those with achondroplasia.…”

“…Third ventriculostomy has been carried out in a few children with achondroplasia, apparently successfully [196, 204]. Good outcomes with this procedure (which should not be effective if intracranial venous hypertension rather than obstruction is the mechanism of hydrocephalus) could mean either that intervention was not really needed, or that a second, obstructive mechanism such as flow restriction at the craniocervical junction may sometimes be important [129].…”

The Role of Dynamic Magnetic Resonance Imaging in Cervical Spondylotic Myelopathy

“…This was managed by adding instrumented fusion with cross-links to maintain distance between the paraspinal muscles and the cord. dMRI studies in achondroplasia and rheumatoid arthritis patients have shown increased risk of dynamic compression at the cervico-medullary junction [ 37 38 39 ]. Dynamic imaging has also proven to be useful in children with skeletal dysplasia.…”

Early impairment of somatosensory evoked potentials in very young children with achondroplasia with foramen magnum stenosis

“…Conversely, spinal cord and cauda equina compression related to thoracolumbar stenosis are more prominent in adolescence or adulthood . Early cervicomedullary decompression leads to neurological and developmental improvement, although mortality and morbidity remain worth considering and indications for surgical treatment are still debated . Indeed, a close neurological and neuroradiological follow‐up is often necessary from the first months of life.…”