title: Improvement after cerebrospinal fluid drainage is related to levels of N-acetyl-aspartate in idiopathic normal pressure hydrocephalus.
abstract: OBJECTIVE
  This study uses proton magnetic resonance spectroscopy to investigate whether or not idiopathic normal pressure hydrocephalus is associated with neuronal dysfunction or ischemia in the brain. We evaluate whether or not proton magnetic resonance spectroscopy is useful for predicting improvement after long-term external lumbar drainage (ELD) of cerebrospinal fluid.
  
  
  METHODS
  Eighteen patients (mean age, 73 yr; six women) and 10 matching controls participated. Participants were characterized by clinical features, cognitive and motor function tests, and cerebrospinal fluid hydrodynamics (patients only). Signals from N-acetyl-aspartate (NAA), choline, lactate, and creatine (Cr) (reference) were sampled once in controls and twice in patients (before and after a 3-day ELD of approximately 135 mL/24 h) by proton magnetic resonance spectroscopy (1.5 T) from a 7.2-mL volume in the frontal white matter. Improvement was defined by video recordings of the patients' gait.
  
  
  RESULTS
  Sixteen patients finished the ELD (one patient had meningitis, and one patient had catheter insertion failure) with a mean drain volume of 395 mL. NAA/Cr ratios were lower in patients than in controls (1.60 versus 1.84, P = 0.02), but no difference was found for choline/Cr ratios. No lactate signals were detected. Fifty percent of patients improved after ELD. They had higher NAA/Cr ratios than nonimproved patients (1.70 versus 1.51, P = 0.01), but no differences were found in choline/Cr ratios or drain volume.
  
  
  CONCLUSIONS
  NAA/Cr ratios were decreased in patients with idiopathic normal pressure hydrocephalus, which is consistent with neuronal dysfunction in the frontal white matter. Improved patients had NAA/Cr ratios close to normal, indicating that enough functional neurons are a prerequisite for the cerebrospinal fluid drainage to have an effect.
authors.affiliation: Department of Clinical Neuroscience, Center for Biomedical Engineering and Physics, Umeå University, Umeå, Sweden. niklas.lenfeldt@neuro.umu.se
authors.forename: Niklas
authors.initials: N
authors.lastname: Lenfeldt
authors.forename: Jon
authors.initials: J
authors.lastname: Hauksson
authors.forename: Richard
authors.initials: R
authors.lastname: Birgander
authors.forename: Anders
authors.initials: A
authors.lastname: Eklund
authors.forename: Jan
authors.initials: J
authors.lastname: Malm
mesh_terms: D000368:Aged; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D002557:Cerebrospinal Fluid Shunts / Q000379:methods*; D005260:Female; D006801:Humans; D006850:Hydrocephalus, Normal Pressure / Q000378:metabolism* / Q000601:surgery*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D011522:Protons
chemical_list: D011522:Protons; D001224:Aspartic Acid; C000179:N-acetylaspartate