Bipolar coagulation is more precise as the current travels between 2 electrical contacts which also act as tissue grasping forceps. The laser is a tool that was in vogue among neurosurgeons during the early 1980's. It was touted to be superior for many procedures but was bulky, expensive and cumbersome compared to more conventional techniques. The laser is continues to be used in more limited circumstances and is most helpful when debulking large tumors, particularly in the posterior fossa, where the tumor is firm or hard and tumor movement must be minimized because of the risk to adjacent tissues. The laser is also used for tissue fenestration during endoscopic procedures but may not provide any advantages over conventional cautery via the same approach.
Ultrasonic liquefaction is the decomposition of tumor by direct application of an ultrasonic probe.
The ultrasonic energy breaks up the interstitial cellular matrix permitting suction of tumor tissue from the operative field. This instrument may be referred to as the CUSA or the ultrasonic surgical aspirator. Suction and irrigation, as well as a probe for transmission of ultrasonic energy, are usually included in the tip of this hand held instrument. I hope this has provided you with an overview of the most important technical aspects of neurosurgery.