title: Flexion-extension cervical spine MRI in children with skeletal dysplasia:  is it safe and effective?
abstract: BACKGROUND
  Skeletal dysplasias may be associated with cervical spinal instability or stenosis. Cervical spine flexion-extension plain radiographs in children with skeletal dysplasia are difficult to interpret. The purpose of this study was to review the indications, efficacy, and safety of performing flexion-extension magnetic resonance imaging (MRI) under sedation/anesthesia in these children.
  
  
  METHODS
  Retrospective, Institutional Review Board-approved review of 31 children with skeletal dysplasia who underwent 38 cervical spine flexion-extension MRI studies under sedation/anesthesia. Indications included abnormal neurological examination, suspected instability, stenosis, or inconclusive findings on flexion-extension radiographs. Studies were performed by the radiology technologist as directed by the radiologist with an anesthesiologist present. MRI was evaluated for odontoid hypoplasia, os odontoideum, cerebrospinal fluid effacement, cord compression, spinal cord changes, cervical canal narrowing in the neutral, flexion, and extension positions. Neurological examinations were recorded before and after MRI to assess safety.
  
  
  RESULTS
  The average age at MRI was 3 years, 2 months. In 6 patients whose plain radiographs showed C1-C2 or subaxial instability, flexion-extension MRI showed no cord compression. Nine patients with inconclusive plain radiographs had abnormal MRI findings. An os odontoideum not seen on plain radiographs was diagnosed in 3 patients on flexion-extension MRI. On the basis of the MRI findings, 14 patients underwent surgery, 9/14 had increased cord compression in flexion or extension compared with neutral, and observation was continued in 17 others. Patients who underwent surgery had significant cord compression on MRI. There were no significant changes in the neurological examinations after MRI.
  
  
  CONCLUSIONS
  Cervical spine flexion-extension MRI under sedation/anesthesia in children with skeletal dysplasia is safe under adequate supervision and is necessary to guide accurate medical and surgical decision making. Flexion-extension MRI is useful for identifying dynamic changes in canal diameter resulting in cord compression not seen on plain radiographs, and it is also useful for identifying patients with suspected plain film instability who may not have stenosis or cord compression on MRI.
  
  
  METHODS
  Level IV-retrospective case series.
authors.affiliation: Department of Orthopaedics, Nemours/Alfred I. duPont Hospital for Children, Wilmington, DE 19889, USA. wmackenz@nemours.org
authors.forename: William G
authors.initials: WG
authors.lastname: Mackenzie
authors.forename: Arjun A
authors.initials: AA
authors.lastname: Dhawale
authors.forename: Matthew M
authors.initials: MM
authors.lastname: Demczko
authors.forename: Colleen
authors.initials: C
authors.lastname: Ditro
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Rogers
authors.forename: Michael B
authors.initials: MB
authors.lastname: Bober
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Campbell
authors.forename: Leslie E
authors.initials: LE
authors.lastname: Grissom
mesh_terms: D001848:Bone Diseases, Developmental / Q000175:diagnosis*; D002574:Cervical Vertebrae; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008279:Magnetic Resonance Imaging / Q000009:adverse effects / Q000379:methods*; D008297:Male; D056888:Patient Positioning / Q000009:adverse effects / Q000379:methods; D012189:Retrospective Studies; D013122:Spinal Diseases / Q000175:diagnosis*