Cranionavigator combining a high-speed drill and a navigation system for skull base surgery--technical note.

Drilling of the skull base bone without damaging the important inside structures and with the correct orientation is very difficult even with the help of the anatomical landmarks. Monitoring of the location and direction of the drill tip and indications of the removed part of the bone during the drilling procedure enhances safety and achieves less invasive neurosurgery. We have developed a novel cranionavigator by combining a high-speed drill with a neurosurgical navigation system. To reduce the positional error to less than 1.5 mm, the position sensor (magnetic field sensor) must be attached 5 cm from the metallic fan portion of the drill and the sensor kept at least 10 cm away from the operating microscope. Simulation studies with the cranionavigator using two dried skulls and three cadaver heads were performed before clinical application. Clinically, this surgical instrument was used in four patients with the skull base tumor. The cranionavigator helped to safely drill the skull base bone in a shorter time by dynamic and real-time display of the precise operating site and extent of bone drilling on the preoperative computed tomography scans or magnetic resonance images. The cranionavigator is a very helpful instrument for skull base surgery in the hands of neurosurgeons with extensive expertise and anatomical knowledge.