Ventricular Temperatures in Idiopathic Normal Pressure Hydrocephalus (iNPH) Measured with DWI-based MR Thermometry

The brain produces intense heat as a result of cerebral metabolism and cerebral blood flow, and the generated heat is removed mainly through circulation of the intracranial blood vessels and cerebrospinal fluid (CSF). Because magnetic resonance (MR) images are constructed from analysis of the spin of various molecules, the diffusion coefficient can be used as a parameter that reflects the temperature of water molecules. We used diffusion-weighted imaging (DWI)-based MR imaging to measure the temperature of the CSF around the lateral ventricles in patients with idiopathic normal pressure hydrocephalus (iNPH).

Our study included 33 cases of iNPH (Group N, mean age, 75.1 years) and 40 age-matched controls (Group C, mean age, 74.5 years). We calculated CSF temperature in the ventricular domain using the conversion formula to evaluate the feasibility of iNPH study.

The mean temperatures were significantly higher in Group N (37.6°C ± 0.4°C) than Group C (36.7°C ± 0.5°C; P < 0.01). The cut-off value of 37.2°C (more than the mean + 2 standard deviations [SD] of the values in Group C) showed sensitivity of 72.4% and specificity of 77.5% for distinguishing the 2 groups. We confirmed improved CSF temperature in the lateral ventricles in all patients examined both before and after shunting.

Elevated ventricular temperatures in patients with iNPH (Group N) may represent a disturbance in heat balance. Our results showed that thermometry using DWI-based MR imaging can help in the noninvasive and consistent evaluation of CSF temperature and may thus provide a useful supplementary brain biomarker for iNPH.