Introduction: Chiari malformation type 1 (CM-1) has become increasingly recognized as a significant clinical burden in approximately 3.6% of children undergoing brain and cervical spinal cord imaging. Sleep related breathing disruption can result from compression of the medullary respiratory control centers and manifest in central or obstructive sleep apnea, hypoventilation, or even sudden death. Without a widely recognized, definitive correlation between magnitude of tonsillar herniation and clinical manifestations of cervicomedullary junction compression, debate lingers over the indications for operative versus nonoperative management of CM-1. In order to gain insight into surgical technique and potential implications of sleep apnea in the management of CM-1, the present study assessed two different posterior fossa decompression techniques (duraplasty and dural splitting) and long-term symptomatic and radiographic outcomes for surgically managed pediatric patients with concurrent sleep apnea and CM-1.

Methods: The authors retrospectively reviewed eight consecutive cases of pediatric patients less than 18 years old with symptomatic sleep related breathing disorders and concurrent CM-1 (herniation of cerebellar tonsils at least 5 mm below foramen magnum). Patients underwent comprehensive multidisciplinary evaluation including child neurology, sleep specialist and otolaryngology consultations. Surgical technique was reviewed and correlated to long-term radiographic and clinical outcomes.

Results: Surgical intervention was associated with improvement of symptoms and radiographic evidence of tonsillar ectopia and syringomyelia. Overall, surgery improved sleep apnea in 62.5% of patients (100% of the duraplasty group and 50% of the dural splitting group) (p=0.43). Although duraplasty and dural splitting were both associated with a notable reduction in tonsillar herniation of 58% and 35%, respectively, there was no significant difference in radiographic findings over a median follow-up period of 45.7 months.

Conclusions: Duraplasty and dural splitting are associated with radiographic and symptomatic improvement in pediatric patients with concurrent sleep-related breathing disorders and CM-1. Sleep apnea represents an indication for surgical decompression in these patients.

Patient Care: Insofar as the indications for surgical management of CM-1 patients remain relatively undefined, coupled with a dearth of literature describing and comparing the nuances of posterior fossa decompression, there are no generally accepted criteria for selecting patients with CM-1 for surgical treatment and the decision for suboccipital decompression for symptomatic relief can be subjective. This study helps to further understand the potential role of duraplasty and dural splitting in pediatric patients with concurrent sleep apnea and CM-1. We may also move toward a more specific theory of the natural history of this malformation and diagnosis and assessment of therapeutic change.

Learning Objectives: By the conclusion of this session, participants should be able to: 1. Understand that sleep apnea represents a relative indication for posterior fossa decompression in pediatric patients with Chiari type 1 malformation 2. Recognize duraplasty and dural splitting as two reasonable techniques that offer comparable rates of radiographic and symptomatic improvement 3. Appreciate that intraoperative ultrasound can be beneficial in determining restoration of cerebrospinal fluid (CSF) circulation in the posterior fossa 4. Acknowledge that longitudinal follow-up studies of patients with either neurological deficits or severe symptoms will further elucidate the natural history of CM-1 and more appropriately gauge the risk-benefit tradeoff of surgical intervention

References: Benglis D, Jr., Covington D, Bhatia R, et al. Outcomes in pediatric patients with Chiari malformation Type I followed up without surgery. Journal of neurosurgery Pediatrics 2011;7(4):375-379. Chauvet D, Carpentier A, George B. Dura splitting decompression in Chiari type 1 malformation: clinical experience and radiological findings. Neurosurgical review 2009;32(4):465-470. Dauvilliers Y, Stal V, Abril B, et al. Chiari malformation and sleep related breathing disorders. Journal of neurology, neurosurgery, and psychiatry 2007;78(12):1344-1348. Dhamija R, Wetjen NM, Slocumb NL, et al. The role of nocturnal polysomnography in assessing children with Chiari type I malformation. Clinical neurology and neurosurgery 2013;115(9):1837-1841. Durham SR, Fjeld-Olenec K. Comparison of posterior fossa decompression with and without duraplasty for the surgical treatment of Chiari malformation Type I in pediatric patients: a meta-analysis. Journal of neurosurgery Pediatrics 2008;2(1):42-49. Limonadi FM, Selden NR. Dura-splitting decompression of the craniocervical junction: reduced operative time, hospital stay, and cost with equivalent early outcome. Journal of neurosurgery 2004;101(2 Suppl):184-188. Novegno F, Caldarelli M, Massa A, et al. The natural history of the Chiari Type I anomaly. Journal of neurosurgery Pediatrics 2008;2(3):179-187. Yeh DD, Koch B, Crone KR. Intraoperative ultrasonography used to determine the extent of surgery necessary during posterior fossa decompression in children with Chiari malformation type I. Journal of neurosurgery 2006;105(1 Suppl):26-32.