November 9, 2007

New, less-invasive approach eases cochlear implant surgery

Featured Image

Robert Labadie, M.D., Ph.D., left, adjusts the new cochlear implant of patient Rodney Poling. (photo by Neil Brake)

New, less-invasive approach eases cochlear implant surgery

Treating deafness might just get a little easier.

Robert Labadie, M.D., Ph.D., and his colleagues at Vanderbilt University Medical Center have come up with an image-guided, minimally invasive approach to cochlear implant surgery they believe will make it faster, less invasive and more precise.

This spring they received a $3 million, four-year grant from the National Institute on Deafness and Other Communication Disorders to test their hypothesis.

“We envision such a minimally invasive technique to become the LASIK procedure of the ear,” said Labadie, associate professor of Otolaryngology and Biomedical Engineering.

In order to accurately implant an electrode in the cochlea without damaging the critical facial nerve, surgeons currently have to excavate a large section of bone from the lateral skull base, a process that takes approximately two hours to complete in the operating room with patients under general anesthesia.

Labadie said that with his group's software and frame design, surgeons will be able to plan a specific trajectory by putting anchors into the skull, and then having a customized frame built to guide a drill along a safe path from the lateral skull base to the cochlea.

This process may reduce operating time from hours to minutes, and could eliminate the need for general anesthesia, he said.

Labadie's partner in the Vanderbilt Department of Electrical Engineering and Computer Science, J. Michael Fitzpatrick, Ph.D., has written software that automatically identifies the anchor positions.

Others in the department, Benoit Dawant, Ph.D., and Rui Li, have developed planning software that allows the surgeon to identify an entry point in the skull, and then verify a path to the cochlea that does not injure any vital anatomy such as the facial nerve. To do this, the surgeon can “fly” down the proposed trajectory in the CT scan, looking at adjacent structures as they pass by.

Jack Noble, a former Vanderbilt undergrad now pursuing his Ph.D. here, has automated the planning software using an atlas-based method developed by Dawant for neurosurgical applications.

The surgeon need only verify that this automated path is safe before ordering the frame. Information is sent electronically to a manufacturing company, which makes the frame using rapid-prototyping with a turnaround time of 48 hours. After the frame is mounted to anchors in the patient's skull, a drill is inserted through it and guided down the planned trajectory.

Jason Mitchell, a machinist in the Vanderbilt Department of Mechanical Engineering, is co-inventor of another innovation, the Posi-Seat anchor driver, which allows surgeons to place bone-implanted anchors more securely.

During the first two years of the grant, the team will be validating the accuracy of drill guidance on patients who are undergoing the traditional wide-field surgery. Wendy Lipscomb is the research nurse coordinator.

Three other centers — the University of North Carolina at Chapel Hill, University of Texas Southwestern, and Case Western Reserve University — will join the study this fall. The researchers anticipate performing the first percutaneous cochlear implant surgery in April 2009.

Labadie estimates that the time required for this new procedure will initially be on the order of one hour, and that it will ultimately be performed outside the operating room.

“Currently the patient needs to recover for two to three weeks before we can activate the device, but with our design the patient could activate the device the same day,” Labadie said.