To identify features on magnetic resonance imaging (MRI) scans that are associated with unstable intracranial pressure (ICP) and outcome after CSF shunting in patients with NPH, we reviewed MRI scans of 17 patients who had continuous ICP monitoring performed prior to ventriculo-peritoneal shunt insertion. We evaluated the association between periventricular/deep white matter lesion burden, focal impingement of the corpus callosum, aqueductal CSF flow void, and B-waves with outcome after shunting. The change in neurological function between pre- and post CSF shunting evaluation was scored according to a standard scale (range -3 or +3). Patients were divided into those with clinical improvement (score > 0) or without improvement (score < or = 0) after shunt surgery. Focal impingement of the corpus callosum was more frequent in patients who improved after CSF shunting compared to those without improvement (8 of 13 vs 0 of 4, p = 0.05). Patients with focal impingement of corpus callosum had more B-wave time than those without impingement (60.5% vs 24.7%, p = 0.02). Focal impingement of corpus callosum on MRI may be associated with unstable intracranial pressure in patients with NPH and may be useful in identifying patients who will benefit from CSF shunting.