title: Comparison of posterior fossa volumes and clinical outcomes after decompression of Chiari malformation Type I.
abstract: OBJECTIVE Previous studies have indicated an association of Chiari malformation Type I (CM-I) and a small posterior fossa. Most of these studies have been limited by 2D quantitative methods, and more recent studies utilizing 3D methodologies are time-intensive with manual segmentation. The authors sought to develop a more automated tool to calculate the 3D posterior fossa volume, and correlate its changes after decompression with surgical outcomes. METHODS A semiautomated segmentation program was developed, and used to compare the pre- and postoperative volumes of the posterior cranial fossa (PCF) and the CSF spaces (cisterna magna, prepontine cistern, and fourth ventricle) in a cohort of pediatric patients with CM-I. Volume changes were correlated with postoperative symptomatic improvements in headache, syrinx, tonsillar descent, cervicomedullary kinking, and overall surgical success. RESULTS Forty-two pediatric patients were included in this study. The mean percentage increase in PCF volume was significantly greater in patients who showed clinical improvement versus no improvement in headache (5.89% vs 1.54%, p < 0.05) and tonsillar descent (6.52% vs 2.57%, p < 0.05). Overall clinical success was associated with a larger postoperative PCF volume increase (p < 0.05). These clinical improvements were also significantly associated with a larger increase in the volume of the cisterna magna (p < 0.05). The increase in the caudal portion of the posterior fossa volume was also larger in patients who showed improvement in syrinx (6.63% vs 2.58%, p < 0.05) and cervicomedullary kinking (9.24% vs 3.79%, p < 0.05). CONCLUSIONS A greater increase in the postoperative PCF volume, and specifically an increase in the cisterna magna volume, was associated with a greater likelihood of clinical improvements in headache and tonsillar descent in patients with CM-I. Larger increases in the caudal portion of the posterior fossa volume were also associated with a greater likelihood of improvement in syrinx and cervicomedullary kinking.
authors.affiliation: Department of Neurosurgery, University of Michigan Health System, Ann Arbor, Michigan.
authors.forename: Siri Sahib S
authors.initials: SSS
authors.lastname: Khalsa
authors.affiliation: Department of Neurosurgery, George Washington University.
authors.forename: Alan
authors.initials: A
authors.lastname: Siu
authors.affiliation: Division of Neurosurgery, Children's National Health System, Washington, DC.
authors.forename: Tiffani A
authors.initials: TA
authors.lastname: DeFreitas
authors.affiliation: George Washington University School of Medicine and Health Sciences; and.
authors.forename: Justin M
authors.initials: JM
authors.lastname: Cappuzzo
authors.affiliation: Division of Neurosurgery, Children's National Health System, Washington, DC.
authors.forename: John S
authors.initials: JS
authors.lastname: Myseros
authors.affiliation: Division of Neurosurgery, Children's National Health System, Washington, DC.
authors.forename: Suresh N
authors.initials: SN
authors.lastname: Magge
authors.affiliation: Division of Neurosurgery, Children's National Health System, Washington, DC.
authors.forename: Chima O
authors.initials: CO
authors.lastname: Oluigbo
authors.affiliation: Division of Neurosurgery, Children's National Health System, Washington, DC.
authors.forename: Robert F
authors.initials: RF
authors.lastname: Keating
mesh_terms: D000465:Algorithms; D001139:Arnold-Chiari Malformation / Q000000981:diagnostic imaging* / Q000601:surgery*; D002648:Child; D003388:Cranial Fossa, Posterior / Q000000981:diagnostic imaging*; D019299:Decompression, Surgical; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008297:Male; D019635:Neurosurgical Procedures; D009929:Organ Size; D010363:Pattern Recognition, Automated; D012189:Retrospective Studies; D016896:Treatment Outcome
keywords: CM-I = Chiari malformation Type I; Chiari malformation Type I; PCF = posterior cranial fossa; outcomes; posterior fossa volume; volumetric analysis