title: MR differential diagnosis of normal-pressure hydrocephalus and Alzheimer disease: significance of perihippocampal fissures.
abstract: OBJECTIVE
  In the older patient with dilated ventricles, it is often difficult to differentiate normal pressure hydrocephalus (NPH) from cerebral atrophy caused by Alzheimer disease (AD). This study was undertaken to see if dilatation of the perihippocampal fissures (PHFs) could be used as a distinguishing characteristic of these two disorders.
  
  
  METHODS
  MR images of 17 patients with AD were compared with those from an equal number of patients with NPH who improved after ventriculoperitoneal shunting. The PHFs, lateral ventricles, third ventricle, and temporal horns were graded subjectively. Objective, computer-aided volumetric measurements of the PHFs and lateral ventricles were obtained. The preshunt images of the NPH patients were evaluated.
  
  
  RESULTS
  Significant differences between the two groups were found for the PHFs and lateral ventricles by both the subjective and objective methods, with a high degree of correlation between the two methods.
  
  
  CONCLUSIONS
  The degree of dilatation of PHFs appears to be a sensitive and specific marker for differentiating AD from NPH by both subjective and objective means, with a very small overlap between the two groups. This observation may have relevance in day-to-day practice.
authors.affiliation: Department of Radiology, New York University Medical Center, New York, USA.
authors.forename: A I
authors.initials: AI
authors.lastname: Holodny
authors.forename: R
authors.initials: R
authors.lastname: Waxman
authors.forename: A E
authors.initials: AE
authors.lastname: George
authors.forename: H
authors.initials: H
authors.lastname: Rusinek
authors.forename: A J
authors.initials: AJ
authors.lastname: Kalnin
authors.forename: M
authors.initials: M
authors.lastname: de Leon
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000175:diagnosis*; D002552:Cerebral Ventricles / Q000473:pathology; D003937:Diagnosis, Differential; D005260:Female; D006624:Hippocampus / Q000473:pathology*; D006801:Humans; D006850:Hydrocephalus, Normal Pressure / Q000175:diagnosis*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity