The Ommaya reservoir

How the Ommaya reservoir works: To insert an Ommaya reservoir, the physician drills a burr hole and inserts the device's catheter through the patient's nondominant frontal lobe into the lateral ventricle. The reservoir, which has a self-sealing silicone injection dome, rests over the burr hole under a scalp flap. This creates a slight, soft bulge on the scalp about the size of a quarter. Usually, drugs are injected into the dome with a syringe.