title: MR venography in idiopathic intracranial hypertension: unappreciated and misunderstood.
abstract: BACKGROUND
  Venous sinus disease must be excluded before diagnosing idiopathic intracranial hypertension but is found only rarely in typical cases. Magnetic resonance venography (MRV) is the technique of choice for investigating this, and provides images that are diagnostic and easy to interpret. However, recent work using more invasive techniques has documented pressure gradients and stenoses in the lateral venous sinuses in many cases of idiopathic intracranial hypertension.
  
  
  OBJECTIVE
  To examine the reason for this discrepancy and to establish whether there are characteristic appearances on MRV in idiopathic intracranial hypertension that are routinely overlooked in clinical practice.
  
  
  METHODS
  MRVs from 20 patients with idiopathic intracranial hypertension were reviewed, unblinded, by two neuroradiologists, and their appearances rated for focal narrowings and signal gaps. A control group of 40 asymptomatic volunteers, matched for age and sex with the patient group, was recruited prospectively for MRV, and their scans rated in the same way.
  
  
  RESULTS
  The lateral sinuses presented a range of appearances with quite different distributions in the two groups (p<0.001). Bilateral lateral sinus flow gaps were seen in 13 of 20 patients with idiopathic intracranial hypertension and in none of 40 controls.
  
  
  CONCLUSIONS
  A historical failure to use normal healthy controls to establish the boundaries between imaging artefact, normal anatomical variant, and disease means that the pathological significance of the different appearances of the lateral sinuses on MRV has not so far been appreciated.
authors.affiliation: Department of Radiology, Box 219, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2QQ, UK. nick.higgins@addenbrookes.nhs.uk
authors.forename: J N P
authors.initials: JN
authors.lastname: Higgins
authors.forename: J H
authors.initials: JH
authors.lastname: Gillard
authors.forename: B K
authors.initials: BK
authors.lastname: Owler
authors.forename: K
authors.initials: K
authors.lastname: Harkness
authors.forename: J D
authors.initials: JD
authors.lastname: Pickard
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003251:Constriction, Pathologic / Q000175:diagnosis / Q000209:etiology; D003392:Cranial Sinuses / Q000473:pathology*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted; D019586:Intracranial Hypertension / Q000175:diagnosis / Q000209:etiology*; D020227:Lateral Sinus Thrombosis / Q000175:diagnosis* / Q000209:etiology; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D010690:Phlebography; D011446:Prospective Studies; D012016:Reference Values; D012680:Sensitivity and Specificity