Proton MR spectroscopy and white matter hyperintensities in idiopathic normal pressure hydrocephalus and other dementias

Abstract

The differentiation of idiopathic normal-pressure hydrocephalus (INPH) from other types of dementia is a clinical challenge. The aim of this prospective study was to evaluate the role of proton MR spectroscopy (MRS) and white matter hyperintensities (WMH) in the diagnosis of INPH, predicting response to therapy and differentiating INPH from other dementias. The study included 18 patients with INPH (Group 1), 11 patients with other types of dementia (Group 2) and 20 control patients (Group 3). The value of WMH scores and MRS findings in diagnosis, evaluation of response to therapy and in the differentiation of INPH from other dementias was statistically evaluated. The level of statistical significance was set at p<0.05 (Kruskal-Wallis and Mann-Whitney U-test). In both Groups 1 and 2, N-acetylaspartate (NAA)/choline-NAA/creatine ratios were significantly less than in the control group (p<0.05). The WMH and MRS findings of Groups 1 and 2 demonstrated no statistically significant correlation (p>0.05). No correlation was found between the outcome of shunt operations and WMH and MRS findings (p>0.05). In conclusion, neither WMH nor MRS were useful in differentiating INPH from other types of dementia. WMH and MRS showed no additional benefit in identifying INPH patients who will better respond to shunt therapy.

Figure 1

Representative (a) axial, (b) sagittal T₁ weighted and (c) coronal T₂ weighted MR spectroscopy images. The black rectangles indicate the region of interest for MR spectroscopy. To achieve a reproducible position, the voxels were placed in the same regions in all patients and controls.

Figure 2

Scoring of the white matter hyperintensities (WMH) in axial T₂ weighted images of three patients: (a) Grade 1, (b) Grade 3 and (c) Grade 4 (case with vascular dementia). Cases in (a, b) were diagnosed as idiopathic normal pressure hydrocephalus.

Figure 3

Proton MR spectra in (a, b) a patient with idiopathic normal pressure hydrocephalus and (c) the control. N-acetylaspartate (NAA), choline (cho) and creatine peaks are observed in (a). The NAA/Cho ratio (1.51, b) in this patient was decreased compared with the control (1.67, c).