An optical, surgical instrument that is passed through the brain substance, via a burr holeA small hole, usually about 15 to 20mm in diameter, which is drilled through the skull, using either a hand-held bit and... in the skull, and into the ventriclesThe brain is not an entirely solid organ. There are chambers within the brain, referred to as ventricles or, more correc... of the brain. Abnormal tissues may be biopsied (sampled), internal channels may be created to by-pass obstructions, or shuntA shunt shifts one object, or volume of fluid (or gas or electrical current), from one place to another. In the context ... tubing may be positioned – or sometimes removed.