Reduced Thalamic NAA in Idiopathic Normal Pressure Hydrocephalus A Controlled 1H -MRS Study of Frontal Deep White Matter and the Thalamus Using Absolute Quantification
Résumé
Introduction Patients with idiopathic normal pressure hydrocephalus (INPH) frequently have a reduction of cerebral blood flow in the subcortical frontal lobe/basal ganglia/thalamic areas. With magnetic resonance spectroscopy the metabolism in the brain can be examined. The aim of this study was to investigate if there was a compromised metabolism in the thalamus and in the subcortical frontal areas in INPH patients. This was done by measuring total creatine (tCr), myo-inositol (mIns), total choline (tCho), N-acetylaspartate (NAA), total N-acetylaspartate (tNA), glutamate (Glu), and lactate (Lac) levels. A comparison was made with healthy individuals (HI). Subjects and Methods Sixteen patients (9 M, 7 F, mean age 74 years, range 49-83) diagnosed as INPH and 15 HI (9 M, 6 F, mean age 74 years, range 62-89) were examined. 1H-MRS (1.5 T, PRESS, TE/TR 30/3000 ms, VOI 2.5-3 ml) was performed in frontal deep white matter and in the thalamus. Absolute quantification with internal water as a reference was used. Results INPH patients had lower NAA (p=0.02) and lower tNA (p=0.05) concentrations in the thalamus compared to HI. NAA and tNA in the frontal deep white matter (FDWM) did not differ between patients and HI. The absolute metabolic concentrations of tCr, mIns tCho, tNA, Lac and Cr ratios in FDWM and in the thalamus were similar in INPH patients and HI. Conclusion Reduced thalamic NAA and tNA in INPH patients suggests a compromised metabolic neuronal function in these regions. Thus, the thalamus might have an important role in the pathogenesis of INPH.
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