High-Convexity Tightness Predicts the Shunt Response in Idiopathic Normal Pressure Hydrocephalus

BACKGROUND AND PURPOSE: Although neuroimaging plays an important role in the diagnosis of idiopathic normal pressure hydrocephalus, its predictive value for response to shunt surgery has not been established. The purpose of the current study was to identify neuroimaging markers that predict the shunt response of idiopathic normal pressure hydrocephalus.

MATERIALS AND METHODS: Sixty patients with idiopathic normal pressure hydrocephalus underwent presurgical brain MR imaging and clinical evaluation before and 1 year after shunt surgery. The assessed MR imaging features included the Evans index, high-convexity tightness, Sylvian fissure dilation, callosal angle, focal enlargement of the cortical sulci, bumps in the lateral ventricular roof, and deep white matter and periventricular hyperintensities. The idiopathic normal pressure hydrocephalus grading scale total score was used as a primary clinical outcome measure. We used measures for individual symptoms (ie, the idiopathic normal pressure hydrocephalus grading scale subdomain scores, such as gait, cognitive, and urinary scores), the Timed Up and Go test, and the Mini-Mental State Examination as secondary clinical outcome measures. The relationships between presurgical neuroimaging features and postoperative clinical changes were investigated by using simple linear regression analysis. To identify the set of presurgical MR imaging features that best predict surgical outcomes, we performed multiple linear regression analysis by using a bidirectional stepwise method.

RESULTS: Simple linear regression analyses demonstrated that presurgical high-convexity tightness, callosal angle, and Sylvian fissure dilation were significantly associated with the 1-year changes in the clinical symptoms. A multiple linear regression analysis demonstrated that presurgical high-convexity tightness alone predicted the improvement of the clinical symptoms 1 year after surgery.

CONCLUSIONS: High-convexity tightness is a neuroimaging feature predictive of shunt response in idiopathic normal pressure hydrocephalus.