First intraoperative Evoked Potential Monitor for neurosurgery

Product

This embedded system was designed to give neurosurgeons immediate feedback during surgery by directly measuring the signal carried by a sensory nerve. For example, during the resection of an acoustic neuroma (tumor growing on the auditory nerve), a click stimulus is provided to the patient, and the electrical waveshape generated as the signal jumps the successive synapse on the nerve is measured.

This prototype was used by the surgeons to guide their procedure, with dramatically improved success rates. Today, successors to this machine are part of the official recommended protocol for operating on such tumors.

What we provided

At the time this project was envisaged, nobody had ever tried to collect electrophysiological signals this small in an operating room. The facial nerve response, for example, is 0.1 microvolts peak-to-peak. Operating rooms tend to be electrically noisy, and the electocautery devices routinely used for cutting tissue use 500 volts of RF flowing directly through the patient. We designed and developed a realtime process that collected the data, performed the required mathematical filtering operations to remove extraneous noise, and displayed the results on a monitor within seconds of the data sampling.

We worked closely with the neurosurgeons to develop the machine, modifying the user interfaces to be able to more rapidly respond to situations that arose during surgery, and optimizing the mathematical operations in response to new sources of noise. The software was also written with full data integrity, so that if somebody tripped over the power cord during operation, not only was no data lost, but the program returned to the state it had been in before power was removed.