title: Alteration of disc vacuum contents during prolonged supine positioning: evaluation with MR image.
abstract: METHODS
  Consecutive study.
  
  
  OBJECTIVE
  To investigate the changes of disc signal in intradiscal vacuum phenomenon during prolonged supine MR imaging.
  
  
  BACKGROUND
  Increased T2 signal on MR imaging in intravertebral vacuum cleft during prolonged supine positioning has been described, but no sequential observation of the intervertebral discal signal change in intervertebral disc vacuum.
  
  
  METHODS
  Six women and 4 men (age range, 49-89 years; mean, 77 years) with low back pain and more than one level of intradiscal vacuum phenomenon underwent MR examinations at 0 minute, 1 hour, and 2 hours while remaining continuously supine. We recorded the original T2 signal intensity in the vacuum disc and subsequent alterations in the disc signals; they were scored 0 for signal void, 1 for equivocal or mild fluid intensity, or 2 for fluid signal intensity.
  
  
  RESULTS
  Vacuum phenomena affected 31 of 60 intervertebral discs (T11-T12 to L5-S1). In 9 patients, the signal intensity of the vacuum content progressively replaced by hyperintense fluid occurred in 25 discs (81%) after prolonged supine positioning, mostly from L3 to S1 levels. The location of fluid signal was central in 20 discs (65%), anterior in 4 (13%), and posterior in 1 (3%). Signal intensity was unchanged in 6 discs (19%). Fluid signal intensity was linear shape in 9 discs (29%), homogeneous in 5 (16%), and mixed in 11 (35%). Overall scores were 8, 26, and 38 at 0, 71, and 161 minutes, respectively.
  
  
  CONCLUSIONS
  After prolonged supine positioning, fluid-like signal could be identified among the intradiscal vacuum by using T2 MR images. This in vivo observation suggested the possible pathway of fluid diffusion from surrounding tissues into degenerative discs.
authors.affiliation: Department of Medical Imaging, Taipei Medical University Hospital, Taipei, Taiwan.
authors.forename: Hung-Jung
authors.initials: HJ
authors.lastname: Wang
authors.forename: Bang-Bin
authors.initials: BB
authors.lastname: Chen
authors.forename: Chih-Wei
authors.initials: CW
authors.lastname: Yu
authors.forename: Chao-Yu
authors.initials: CY
authors.lastname: Hsu
authors.forename: Tiffany Ting-Fang
authors.initials: TT
authors.lastname: Shih
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001826:Body Fluids / Q000378:metabolism*; D004058:Diffusion; D015299:Discitis / Q000000981:diagnostic imaging / Q000378:metabolism; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000000981:diagnostic imaging / Q000378:metabolism*; D017116:Low Back Pain / Q000000981:diagnostic imaging / Q000378:metabolism*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009584:Nitrogen / Q000378:metabolism*; D011859:Radiography; D016683:Supine Position / Q000502:physiology*; D013997:Time Factors; D014618:Vacuum
chemical_list: D009584:Nitrogen