After ventricular catheterization magnetic resonance (MR) imaging very often demonstrates a focal area of high signal along the drain track which corresponds to parenchymal oedema. This high signal seemed to be more pronounced when the frontal area was catheterized than when the junctional parieto-temporo-occipital parenchyma (or trigonal area) was catheterized. In order to confirm this impression, we prospectively studied 41 consecutive patients with normal-pressure hydrocephalus in whom both of these brain regions were catheterized for intracranial pressure monitoring. Each patient was evaluated by serial MR. The extent of the MR hypersignal induced by both catheterizations was computed from digitized MR masks. The extent of the MR high signal area was significantly greater when the frontal area was catheterized compared to the trigonal area suggesting that the frontal area could be more prone to injury.