The callosal angle measured on MRI as a predictor of outcome in idiopathic normal-pressure hydrocephalus

Object. Different neuroimaging biomarkers have been studied to find a tool for prediction of response to CSF shunting in idiopathic normal-pressure hydrocephalus (iNPH). The callosal angle (CA) has been described as useful in discriminating iNPH from ventricular dilation secondary to atrophy. However, the usefulness of the CA as a prognostic tool for the selection of shunt candidates among patients with iNPH is unclear. The aim of this study was to compare the CA in shunt responders with that in nonresponders and clarify whether the CA can serve as a predictor of the outcome. Methods. Preoperative MRI brain scans were evaluated in 109 patients who had undergone shunt surgery for iNPH during 2006-2010. Multiplanar reconstruction was performed interactively to obtain a coronal image through the posterior commissure, perpendicular to the anterior-posterior commissure plane. The CA was measured as the angle between the lateral ventricles on the coronal image. The patients were examined clinically before surgery and at 12 months postoperatively. Results. Shunt responders had a significantly smaller mean preoperative CA compared with nonresponders: 59 degrees (95% CI 56 degrees-63 degrees) versus 68 degrees (95% CI 61 degrees-75 degrees) (p < 0.05). A CA cutoff value of 63 degrees showed the best prognostic accuracy. Conclusions. The preoperative CA is smaller in patients whose condition improves after shunt surgery and may be a useful tool in the selection of shunt candidates among patients with iNPH.