title: Can MR measurement of intracranial hydrodynamics and compliance differentiate which patient with idiopathic normal pressure hydrocephalus will improve following shunt insertion?
abstract: BACKGROUND
  Between 10 and 90% of patients with normal pressure hydrocephalus (NPH) treated with a shunt will improve but they risk significant morbidity/mortality from this procedure. NPH is treated hydrodynamically and it has been assumed that a hydrodynamic difference must exist to differentiate which patient will respond. The purpose of this study is to see whether MRI hydrodynamics can differentiate which patients will improve post shunting.
  
  
  METHODS
  Thirty-two patients with NPH underwent MRI with flow quantification measuring the degree of ventricular enlargement, sulcal compression, white matter disease, total blood inflow, sagittal sinus outflow, aqueduct stroke volume, relative compliance ratio and arteriovenous delay. Patients were followed up after shunt insertion to gauge the degree of improvement and were compared with 12 age-matched controls and 12 patients with Alzheimer's disease.
  
  
  RESULTS
  63% of patients improved with insertion. The responders were identical to the non-responders in all variables. The NPH patients were significantly different to the controls (e.g. Total blood inflow reduced 20%, sagittal sinus outflow reduced 35%, aqueduct stroke volume increased 210%, relative compliance ratio reduced 60% and arteriovenous delay reduced 57% with p = 0.007, 0.03, 0.04, 0.0002 and 0.0003 respectively. The patient's with Alzheimer's disease values were midway between the NPH and control patients.
  
  
  CONCLUSIONS
  Significant hydrodynamic differences were noted between NPH and controls but these were unable to differentiate the responders from non-responders. The hydrodynamics of Alzheimer's disease makes exclusion of comorbidity from this disease difficult.
authors.affiliation: Department of Medical Imaging, John Hunter Hospital, Newcastle, Australia. grant.bateman@hnehealth.nsw.gov.au
authors.forename: G A
authors.initials: GA
authors.lastname: Bateman
authors.forename: A M
authors.initials: AM
authors.lastname: Loiselle
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001783:Blood Flow Velocity / Q000502:physiology; D002552:Cerebral Ventricles / Q000473:pathology / Q000503:physiopathology; D002557:Cerebrospinal Fluid Shunts; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003187:Compliance; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006850:Hydrocephalus, Normal Pressure / Q000473:pathology / Q000503:physiopathology* / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008297:Male; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D016896:Treatment Outcome