Role of computerized tomographic cisternography in idiopathic normal pressure hydrocephalus

We prospectively evaluate the role of computerized tomographic cisternography (CTC) in idiopathic normal pressure hydrocephalus (iNPH).

The cerebrospinal fluid kinetics of 70 patients who passed the entry criteria for the Study of iNPH on Neurological Improvement (SINPHONI) and underwent insertion of a shunt were studied.

Stasis of the contrast medium at the lateral ventricles over 24 h (positive ventricular stasis) was observed in 60 patients and at the Sylvian fissure or parietal sulci over 48 h (positive surface stasis) in 59 patients. Sixty patients showed a good response to shunt insertion. The sensitivities of CTC findings at the lateral ventricles and brain surface for shunt effectiveness were 81.7 and 86.7%, respectively; however, the specificities were 20 and 0%. Among the 60 patients who showed a good response to the shunt, 49 had positive surface stasis. Positive ventricular stasis was observed in 52 of the 60 patients, and both findings were observed in 44 patients. Three patients who responded to the shunt had negative stasis in both sites. The 11 patients who had negative surface stasis had significantly lower (p < 0.05) preoperative iNPH grading scale-R scores than the 49 patients with positive surface stasis; these patients were considered to be in an early stage of iNPH.

CTC did not provide additional diagnostic value for predicting the shunt response among patients selected using SINPHONI criteria. We suggest that factors other than disturbances in CSF circulation may be related to the pathogenesis of iNPH.