title: Kinematic magnetic resonance imaging of a thoracic spinal extradural arachnoid cyst: an alternative suggestion for exacerbation of symptoms during straining.
abstract: METHODS
  A case study of an extradural arachnoid cyst using kinematic magnetic resonance imaging.
  
  
  OBJECTIVE
  To access the dynamic and pathologic changes of an extradural subarachnoid cyst during straining by kinematic magnetic resonance imaging and to clarify the pathomechanism of a fluctuation in symptoms.
  
  
  BACKGROUND
  Extradural arachnoid cysts of the spine are an uncommon cause of myelopathy secondary to spinal cord compression; however, the precise mechanism of cord compression and subsequent symptoms remain unclear.
  
  
  METHODS
  A 31-year-old female presented with severe left lower thoracic back pain and leg stiffness, which were exacerbated by coughing and straining. She was diagnosed with an extradural subarachnoid cyst by magnetic resonance imaging. Kinematic magnetic resonance imaging was carried out to assess the dynamic change of the extradural cyst and to demonstrate the mechanism causing her chest pain and leg stiffness during straining.
  
  
  RESULTS
  Kinematic magnetic resonance imaging demonstrated that the cyst wall was compressed, and the size of extradural cyst was decreased for several seconds during straining. Furthermore, the ring of cerebrospinal fluid was gradually compressed circumferentially. After surgery, the patient experienced complete relief of symptoms. Postoperative kinematic magnetic resonance imaging revealed good decompressive results had been obtained, and the ring of cerebrospinal fluid was preserved even when the patient strained for a few minutes.
  
  
  CONCLUSIONS
  Kinematic magnetic resonance imaging study demonstrated that pressure changes which occur in the extradural space as well as in the arachnoid cyst might cause spinal cord compression and result in intermittent exacerbation of symptoms.
authors.affiliation: Department of Orthopedic Surgery, Kobe University Graduate School of Medicine, Kobe City, Japan. doita@med.kobe-u.ac.jp
authors.forename: Minoru
authors.initials: M
authors.lastname: Doita
authors.forename: Kotaro
authors.initials: K
authors.lastname: Nishida
authors.forename: Jyuichi
authors.initials: J
authors.lastname: Miura
authors.forename: Toru
authors.initials: T
authors.lastname: Takada
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kurosaka
authors.forename: Masahiko
authors.initials: M
authors.lastname: Fujii
mesh_terms: D000328:Adult; D016080:Arachnoid Cysts / Q000150:complications* / Q000175:diagnosis* / Q000503:physiopathology; D001696:Biomechanical Phenomena; D004824:Epidural Space; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D009192:Myelography; D013117:Spinal Cord Compression / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology*; D014057:Tomography, X-Ray Computed; D014636:Valsalva Maneuver