OBJECTIVE: In the case of ventriculomegaly in the elderly, it is often difficult to differentiate between communicating chronic hydrocephalus (CCH) and brain atrophy. The aim of this study is to describe the MRI criteria of CCH, defined by a symptomatic patient with ventriculomegaly and that improved after shunt placement. MATERIALS AND METHODS: Magnetic resonance imaging was prospectively evaluated in 90 patients with ventriculomegaly. Patients were classified into three groups: patients without clinical signs of CCH (control, n = 47), patients with CCH treated by shunt placement with clinical improvement (responders, n = 36), and patients with CCH treated using a shunt without clinical improvement (nonresponders, n = 7). MRI parameters of the two groups of interest (responders vs. controls) were compared. RESULTS: Compared with controls, Evans' index (p = 0.029), ventricular area (p < 0.01), and volume (p = 0.0001) were higher in the responders. In this group, the callosal angle was smaller (p = 0.0001) and the aqueductal stroke volume (SVa) of CSF was higher (p = 0.0001) than in controls. On the ROC curves, the optimal cut-off values for differentiating between responders and controls were a ventricular area >33.5 cm(2), a callosal angle <90.8 degrees and a SVa > 136.5 muL/R-R. In multivariate analysis, responders remained associated with SVa and callosal angle, with a c-statistic of 0.90 (95%CI, 0.83-0.98). CONCLUSION: On suspicion of CCH, a large ventricular area, a small callosal angle, and an increased aqueductal stroke volume are important MRI arguments that can be associated with the clinical evaluation and dynamic testing of CSF to confirm the indication for a shunt.