Value of quantitative MRI biomarkers (Evans' index, aqueductal flow rate, and apparent diffusion coefficient) in idiopathic normal pressure hydrocephalus

Abstract

Purpose:To define the value of Evans' index (EI), aqueductal flow rate (FR), and apparent diffusion coefficient (ADC) in the diagnosis of normal pressure hydrocephalus (NPH) and to assess the ability of these markers preoperatively to predict shunt response. To shed some light as to the mechanisms responsible for the symptoms of NPH. Materials and Methods:Preoperative EI, FR, and ADC readings in nine cases of clinically diagnosed NPH were compared with those of age-and gender-matched controls. Similar pre-and postoperative readings of responders and nonresponders were subsequently compared. Results:Compared with the controls, all measurements were statistically significant except for peak systolic flow rate (pSfr), which was near statistical significance. Comparison of pre-and postoperative readings of responders and nonresponders revealed a decrease in ADC in all responders (P ϭ 0.032). Subdural hemorrhage was found in all nonresponders (P ϭ 0.012). Conclusion:For patients presenting with signs and symptoms of NPH, readings on MRI greater than 0.3, 10 mL/ min, Ϫ9.0 mL/min, and 10.65 ϫ 10 Ϫ4 mm 2 /s for EI, peak diastolic flow rate (pDfr), pSfr, and ADC, respectively, add further weight to the diagnosis. The strong correlation between shunt response and ADC decline support our hypothesis that water accumulation in the cerebrum is the major cause for the symptoms of NPH. The presence of subdural hemorrhage in all nonresponders raises suspicion of decreased compliance as the other major cause.

Reversed aqueductal cerebrospinal fluid net flow in idiopathic normal pressure hydrocephalus

“…Ng et al 12 also found similar result with us using this method. When peak velocities of the two phases were compared, that of diastole (V peak-d ) increased significantly in iNPH patients, whereas the difference of peak velocity in systole (V peak-s ) was not significant between the two groups.…”

In vivo viscoelastic properties of the brain in normal pressure hydrocephalus

“…In this respect, other quantitative MRI methods might support the analysis of MRE wave data by, for example, providing information about fiber alignment or tissue perfusion. One important structure-sensitive imaging method is diffusion MRI, which has revealed an increased water accumulation in PV tissue of patients with NPH via the alternative egress of CSF via extracellular spaces (33,34). Future studies should combine different quantitative MRI methods to assemble a more complete picture of the microstructural changes in cerebral tissue in NPH.…”

The pulsating brain: A review of experimental and clinical studies of intracranial pulsatility

“…Flow rate, or mean flow, is the average flow in one direction (or for unidirectional flow, average flow above the mean) and is related to stroke volume, except that flow rate is affected by heart rate; to rough approximation, stroke volume and flow rate are related by stroke volume = flow rate/heart rate/2. While not as commonly used a measure as stroke volume, it has been used by various groups for diagnostic [59,60] and prognostic [61-64] applications in HC.…”