Glossary term:

Burr hole

A small hole, usually about 15 to 20mm in diameter, which is drilled through the skull, using either a hand-held bit and brace or, more often these days, an electrically or pneumatically powered drill. Several different types of neurosurgical procedures can be carried out through a burr hole, including placement of shunt catheters and passage of a ventriculoscope.