Preoperative prognostic value of MRI findings in 108 patients with idiopathic normal pressure hydrocephalus

Abstract

Background and purpose: MR imaging is used in the diagnostic evaluation of patients with idiopathic normal pressure hydrocephalus. The aim of this study was to describe the prevalence of several imaging features and their prognostic use in the selection of shunt candidates with idiopathic normal pressure hydrocephalus.

Materials and methods: Preoperative MR imaging scans of the brain were retrospectively evaluated in 108 patients with idiopathic normal pressure hydrocephalus who had undergone a standardized, clinical evaluation before and 12 months after shunt surgery. The MR imaging features investigated were the Evans index, callosal angle, narrow sulci at the high convexity, dilation of the Sylvian fissure, diameters of the third ventricle and temporal horns, disproportionately enlarged subarachnoid space hydrocephalus, flow void through the aqueduct, focal bulging of the roof of the lateral ventricles, deep white matter hyperintensities, periventricular hyperintensities, and focal widening of sulci and aqueductal stenosis.

Results: In logistic regression models, with shunt outcome as a dependent variable, the ORs for the independent variables, callosal angle, disproportionately enlarged subarachnoid space hydrocephalus, and temporal horns, were significant (P < .05), both in univariate analyses and when adjusted for age, sex, and previous stroke.

Conclusions: A small callosal angle, wide temporal horns, and occurrence of disproportionately enlarged subarachnoid space hydrocephalus are common in patients with idiopathic normal pressure hydrocephalus and were significant predictors of a positive shunt outcome. These noninvasive and easily assessed radiologic markers could aid in the selection of candidates for shunt surgery.

Fig 1.

Nine different patients with iNPH. A, Evans index = x/y. B, Callosal angle. C, Narrow medial sulci and 2 focally dilated sulci on the left side. D, DESH. E, A flow void in the aqueduct and fourth ventricle graded as 2. In addition, a flow void in the foramina of Monro. F, Large diameter of the third ventricle. G, Dilated temporal horns. H, DWMH graded as 3 in a patient who also has PVH. I, PVH graded as 2.

Fig 2.

T1-weighted 3D images of a patient with iNPH. A and B, Coronal images illustrate the different heights of the Sylvian fissure that can be achieved depending on the angulation of the section. B, The Sylvian fissure ordinal. C, Sagittal image with orientation lines represented by the coronal images A and B.

Fig 3.

Two patients with focal bulging of the roof of the lateral ventricles. Sagittal images include the most cranial portions of the lateral ventricles. A, T2-weighted image. B, T1-weighted image.

Fig 4.

Forest plot with sex-adjusted odds ratios for all imaging features. OR with a 95% CI of 1-SD increase for continuous variables and a 1-U increase for dichotomous and ordinal variables. An arrow indicates that the confidence interval extends beyond the range of the plot. The Sylvian fissure ordinal is the ordinal scale 0–2; the Sylvian fissure height is measured in millimeters. The asterisk indicates P < .05.