title: Qualitative grading of severity of lumbar spinal stenosis based on the morphology of the dural sac on magnetic resonance images.
abstract: METHODS
  Retrospective radiologic study on a prospective patient cohort.
  
  
  OBJECTIVE
  To devise a qualitative grading of lumbar spinal stenosis (LSS), study its reliability and clinical relevance.
  
  
  BACKGROUND
  Radiologic stenosis is assessed commonly by measuring dural sac cross-sectional area (DSCA). Great variation is observed though in surfaces recorded between symptomatic and asymptomatic individuals.
  
  
  METHODS
  We describe a 7-grade classification based on the morphology of the dural sac as observed on T2 axial magnetic resonance images based on the rootlet/cerebrospinal fluid ratio. Grades A and B show cerebrospinal fluid presence while grades C and D show none at all. The grading was applied to magnetic resonance images of 95 subjects divided in 3 groups as follows: 37 symptomatic LSS surgically treated patients; 31 symptomatic LSS conservatively treated patients (average follow-up, 2.5 and 3.1 years); and 27 low back pain (LBP) sufferers. DSCA was also digitally measured. We studied intra- and interobserver reliability, distribution of grades, relation between morphologic grading and DSCA, as well relation between grades, DSCA, and Oswestry Disability Index.
  
  
  RESULTS
  Average intra- and interobserver agreement was substantial and moderate, respectively (k = 0.65 and 0.44), whereas they were substantial for physicians working in the study originating unit. Surgical patients had the smallest DSCA. A larger proportion of C and D grades was observed in the surgical group. Surface measurements resulted in overdiagnosis of stenosis in 35 patients and under diagnosis in 12. No relation could be found between stenosis grade or DSCA and baseline Oswestry Disability Index or surgical result. C and D grade patients were more likely to fail conservative treatment, whereas grades A and B were less likely to warrant surgery.
  
  
  CONCLUSIONS
  The grading defines stenosis in different subjects than surface measurements alone. Since it mainly considers impingement of neural tissue it might be a more appropriate clinical and research tool as well as carrying a prognostic value.
authors.affiliation: Department of Orthopedics, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Avenue Pierre-Decker 4, Lausanne, Switzerland. cschizas@hotmail.com
authors.forename: Constantin
authors.initials: C
authors.lastname: Schizas
authors.forename: Nicolas
authors.initials: N
authors.lastname: Theumann
authors.forename: Alexandre
authors.initials: A
authors.lastname: Burn
authors.forename: Rosamond
authors.initials: R
authors.lastname: Tansey
authors.forename: Douglas
authors.initials: D
authors.lastname: Wardlaw
authors.forename: Francis W
authors.initials: FW
authors.lastname: Smith
authors.forename: Gerit
authors.initials: G
authors.lastname: Kulik
mesh_terms: D000368:Aged; D015331:Cohort Studies; D004388:Dura Mater / Q000473:pathology* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000473:pathology* / Q000503:physiopathology; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013115:Spinal Canal / Q000473:pathology* / Q000503:physiopathology; D013130:Spinal Stenosis / Q000175:diagnosis* / Q000473:pathology*