Ventriculostomy is a neurosurgical procedure that involves creating a hole ("ostomy") within a cerebral ventricle for drainage. It is done by surgically penetrating the skull, dura mater, and brain such that the ventricle of the brain is accessed. When catheter drainage is temporary, it is commonly referred to as an external ventricular drain, or EVD. When catheter drainage is permanent, it is usually referred to as a shunt. There are many catheter-based ventricular shunts that are named for where they terminate, for example, a ventriculo-peritoneal shunt terminates in the peritoneal cavity, a ventriculoatrial shunt terminates within the atrium of the heart, etc. The most common entry point on the skull is called Kocher's point, which is measured 11 cm posterior to the nasion and 3 cm lateral to midline. EVD ventriculostomy is done primarily to monitor the intracranial pressure as well as to drain CSF (primarily) or blood to relieve pressure from the CNS.
Strictly speaking, "ventriculotomy" does not require the use of tubing. For example, a "third ventriculostomy" is a neurosurgical procedure that creates a hole in the floor of the third ventricule and usually has no indwelling objects.
Other types ventriculostomy include ventriculocisternostomy developed by the Norwegian doctor Arne Torkildsen.