Introduction: Achondroplasia may be associated with compression at the cervicomedullary spinal junction. Determining which patients are at greatest risk for neurological complications of cervicomedullary spinal compression can be difficult. In the current study, the authors review their records to determine the incidence and clinical significance of dynamic cervicomedullary spinal stenosis and obstruction of CSF flow along with surgical outcomes following posterior fossa and cervical spine decompression.

Methods: The authors reviewed 34 consecutive cases involving symptomatic children with achondroplasia undergoing cervicomedullary spinal decompression performed by a single surgeon over 11 years. Of these patients, 29 had undergone preoperative dynamic MRI of the cervicomedullary-spinal 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.

Results: 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). 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 decompression performed at our medical center required reoperation.

Conclusions: Patients with achondroplasia and symptomatic cervicomedullary spinal compression have increased risk of dynamic stenosis evident upon dynamic cine MRI. Operative decompression may be offered with low risk of complications or need for reoperation.

Patient Care: Findings of this study demonstrate the utility of dynamic magnetic resonance imaging in identifying dynamic spinal pathology in specific patient populations. The findings further demonstrate the long-term safety and efficacy of decompression in patients with dynamic cervicomedullary spinal symptoms. Such findings lend objective support to clinical judgement favoring operative intervention within this challenge patient cohort.

Learning Objectives: At the conclusion of this session, participants should be able to: 1. Describe the importance of dynamic magnetic resonance imaging of the spine in the diagnosis and management of dynamic cervicomedullary spinal stenosis. 2. Discuss the safety profile and effectiveness of cervicomedullary decompression in the treatment of dynamic cervicomedullary spinal compression in children with achondroplasia.

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