Figure 1a. Dura-arachnoid pachymeningeal enhancement. (a) Diagram illustrates dura-arachnoid enhancement, which occurs adjacent to the inner table of the skull; in the falx within the interhemispheric fissure; and also in the tentorium between the cerebellum, vermis, and occipital lobes. Pure dural enhancement, without pial or subarachnoid involvement, will not fill in the sulci or basilar cisterns. (b) Postoperative coronal gadolinium-enhanced T1-weighted MR image of a patient in whom a shunt catheter had been placed in the high right parietal region (arrow) demonstrates diffuse and relatively thin dura-arachnoid enhancement along the inner table of the skull and in the dural reflections of the falx and tentorium (arrowheads). There are bilateral subdural fluid collections, larger on the right (*).