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Chiari 1
Susan I. Blaser, MD, FRCPC; Anne G. Osborn, MD, FACR
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KEY FACTS

  • Terminology

    • Top Differential Diagnoses

      • Pathology

        • Clinical Issues

          • Diagnostic Checklist

            TERMINOLOGY

            • Abbreviations

              • Chiari 1 malformation (CM1)
            • Synonyms

              • Chiari type I
            • Definitions

              • No clear consensus definition of what constitutes CM1
                • Traditional: Elongated, peg-shaped cerebellar tonsils extend below foramen magnum into upper cervical spinal canal
                  • The "5 mm" criterion for tonsillar displacement below basion-opisthion line is flawed criterion
                    • Tonsillar position is a morphometric distribution and also changes with time
                • CM1: Constellation of findings (not a disease, not simply a measurement)
                  • Tonsillar position plus shape/configuration (elongated, pointed)
                    • Tonsillar position also risk factor for syrinx (the lower the tonsils, the higher the risk)
                  • "Crowding" of posterior fossa with compression of CSF spaces
                  • Evaluate skull base, upper cervical spine
                    • Short clivus, craniovertebral junctioni (CVJ) assimilation anomalies common

            IMAGING

            • General Features

              • Radiographic Findings

                • CT Findings

                  • MR Findings

                    • Nonvascular Interventions

                      • Imaging Recommendations

                        DIFFERENTIAL DIAGNOSIS

                          PATHOLOGY

                          • General Features

                            • Staging, Grading, & Classification

                              • Gross Pathologic & Surgical Features

                                • Microscopic Features

                                  CLINICAL ISSUES

                                  • Presentation

                                    • Demographics

                                      • Natural History & Prognosis

                                        • Treatment

                                          DIAGNOSTIC CHECKLIST

                                          • Consider

                                            • Image Interpretation Pearls

                                              Selected References

                                              1. Alperin N et al: Imaging-Based Features of Headaches in Chiari Malformation Type I. Neurosurgery. ePub, 2015
                                              2. Bond AE et al: Changes in cerebrospinal fluid flow assessed using intraoperative MRI during posterior fossa decompression for Chiari malformation. J Neurosurg. 1-8, 2015
                                              3. Quon JL et al: Multimodal evaluation of CSF dynamics following extradural decompression for Chiari malformation Type I. J Neurosurg Spine. 1-9, 2015
                                              4. Roller LA et al: Demographic confounders in volumetric MRI analysis: is the posterior fossa really small in the adult Chiari 1 malformation? AJR Am J Roentgenol. 204(4):835-41, 2015
                                              5. Strahle J et al: Syrinx location and size according to etiology: identification of Chiari-associated syrinx. J Neurosurg Pediatr. 1-9, 2015
                                              6. Godzik J et al: Relationship of syrinx size and tonsillar descent to spinal deformity in Chiari malformation Type I with associated syringomyelia. J Neurosurg Pediatr. 13(4):368-74, 2014
                                              7. Lee S et al: Surgical outcome of Chiari I malformation in children: clinico-radiological factors and technical aspects. Childs Nerv Syst. 30(4):613-23, 2014
                                              8. McVige JW et al: Imaging of Chiari type I malformation and syringohydromyelia. Neurol Clin. 32(1):95-126, 2014
                                              9. Moore HE et al: Magnetic resonance imaging features of complex Chiari malformation variant of Chiari 1 malformation. Pediatr Radiol. 44(11):1403-11, 2014
                                              10. Bollo RJ et al: Complex Chiari malformations in children: an analysis of preoperative risk factors for occipitocervical fusion. J Neurosurg Pediatr. 10(2):134-41, 2012
                                              11. Hwang SW et al: Outcomes of Chiari I-associated scoliosis after intervention: a meta-analysis of the pediatric literature. Childs Nerv Syst. 28(8):1213-9, 2012
                                              12. Brockmeyer DL: The complex Chiari: issues and management strategies. Neurol Sci. 32 Suppl 3:S345-7, 2011
                                              13. Strahle J et al: Chiari malformation Type I and syrinx in children undergoing magnetic resonance imaging. J Neurosurg Pediatr. 8(2):205-13, 2011
                                              Related Anatomy
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                                              Related Differential Diagnoses
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                                              References
                                              Tables

                                              Tables

                                              KEY FACTS

                                              • Terminology

                                                • Top Differential Diagnoses

                                                  • Pathology

                                                    • Clinical Issues

                                                      • Diagnostic Checklist

                                                        TERMINOLOGY

                                                        • Abbreviations

                                                          • Chiari 1 malformation (CM1)
                                                        • Synonyms

                                                          • Chiari type I
                                                        • Definitions

                                                          • No clear consensus definition of what constitutes CM1
                                                            • Traditional: Elongated, peg-shaped cerebellar tonsils extend below foramen magnum into upper cervical spinal canal
                                                              • The "5 mm" criterion for tonsillar displacement below basion-opisthion line is flawed criterion
                                                                • Tonsillar position is a morphometric distribution and also changes with time
                                                            • CM1: Constellation of findings (not a disease, not simply a measurement)
                                                              • Tonsillar position plus shape/configuration (elongated, pointed)
                                                                • Tonsillar position also risk factor for syrinx (the lower the tonsils, the higher the risk)
                                                              • "Crowding" of posterior fossa with compression of CSF spaces
                                                              • Evaluate skull base, upper cervical spine
                                                                • Short clivus, craniovertebral junctioni (CVJ) assimilation anomalies common

                                                        IMAGING

                                                        • General Features

                                                          • Radiographic Findings

                                                            • CT Findings

                                                              • MR Findings

                                                                • Nonvascular Interventions

                                                                  • Imaging Recommendations

                                                                    DIFFERENTIAL DIAGNOSIS

                                                                      PATHOLOGY

                                                                      • General Features

                                                                        • Staging, Grading, & Classification

                                                                          • Gross Pathologic & Surgical Features

                                                                            • Microscopic Features

                                                                              CLINICAL ISSUES

                                                                              • Presentation

                                                                                • Demographics

                                                                                  • Natural History & Prognosis

                                                                                    • Treatment

                                                                                      DIAGNOSTIC CHECKLIST

                                                                                      • Consider

                                                                                        • Image Interpretation Pearls

                                                                                          Selected References

                                                                                          1. Alperin N et al: Imaging-Based Features of Headaches in Chiari Malformation Type I. Neurosurgery. ePub, 2015
                                                                                          2. Bond AE et al: Changes in cerebrospinal fluid flow assessed using intraoperative MRI during posterior fossa decompression for Chiari malformation. J Neurosurg. 1-8, 2015
                                                                                          3. Quon JL et al: Multimodal evaluation of CSF dynamics following extradural decompression for Chiari malformation Type I. J Neurosurg Spine. 1-9, 2015
                                                                                          4. Roller LA et al: Demographic confounders in volumetric MRI analysis: is the posterior fossa really small in the adult Chiari 1 malformation? AJR Am J Roentgenol. 204(4):835-41, 2015
                                                                                          5. Strahle J et al: Syrinx location and size according to etiology: identification of Chiari-associated syrinx. J Neurosurg Pediatr. 1-9, 2015
                                                                                          6. Godzik J et al: Relationship of syrinx size and tonsillar descent to spinal deformity in Chiari malformation Type I with associated syringomyelia. J Neurosurg Pediatr. 13(4):368-74, 2014
                                                                                          7. Lee S et al: Surgical outcome of Chiari I malformation in children: clinico-radiological factors and technical aspects. Childs Nerv Syst. 30(4):613-23, 2014
                                                                                          8. McVige JW et al: Imaging of Chiari type I malformation and syringohydromyelia. Neurol Clin. 32(1):95-126, 2014
                                                                                          9. Moore HE et al: Magnetic resonance imaging features of complex Chiari malformation variant of Chiari 1 malformation. Pediatr Radiol. 44(11):1403-11, 2014
                                                                                          10. Bollo RJ et al: Complex Chiari malformations in children: an analysis of preoperative risk factors for occipitocervical fusion. J Neurosurg Pediatr. 10(2):134-41, 2012
                                                                                          11. Hwang SW et al: Outcomes of Chiari I-associated scoliosis after intervention: a meta-analysis of the pediatric literature. Childs Nerv Syst. 28(8):1213-9, 2012
                                                                                          12. Brockmeyer DL: The complex Chiari: issues and management strategies. Neurol Sci. 32 Suppl 3:S345-7, 2011
                                                                                          13. Strahle J et al: Chiari malformation Type I and syrinx in children undergoing magnetic resonance imaging. J Neurosurg Pediatr. 8(2):205-13, 2011