New Techniques in Vocal Cord Surgery Sparing the Voice
It is hard to believe that the source of the purest, sweetest singing voice is two small folds of tissue drubbing together at high speed in the middle of the throat, that even the most delicate aria is born of pressure and force. The vocal cords move together and apart in a wave, from bottom to top. Repeat this contact 100 to 1,000 times a second and you have a voice that can produce exquisitely varied sounds. But too much strain can leave flaws in this delicate system, and when bumps, cysts, or cancers arise in the vocal cords, they carry the threat that a patient may lose one of the most valuable tools for communication.
Innovations in vocal cord surgery have helped improve the chances of eliminating some of these problems without losing the voice.Better Access
Vocal cord surgery of the larynx lends itself to minimally invasive techniques, though the organ is just far enough from the mouth to have created logistical problems for early physicians trying to view and manipulate it. Improvements in laryngoscopes and the use of microscopes and endoscopic instruments have made it easier to access the vocal cords. Over the past 25 years or so, endoscopic surgery has replaced open surgery in a large number of laryngeal cancer cases. The surgeon views the vocal cords through a microscope and removes cancerous tissue with specially elongated instruments and Even with improvements in instrumentation, surgery generally has been viewed as less desirable than radiation in the treatment of early vocal cord cancer. Both have high cure rates, but radiation is thought to result in less damage to vocal cords. The goal of vocal cord surgery is to preserve the normal tissue since this is the primary voice source. So radiation treatment for early cancer is conceptually flawed because it targets both the normal and cancerous vocal cords indiscriminately.
Zeitels believes the poor voice outcomes of surgery are not necessary in many cases. "What we learned about cancer patients in the early '90s is that their management was frequently not done with the optimum amount of precision," he said. "Often the approach consisted of overtreatment." Part of the uncertainty lay in not knowing the depth of the tumor in the tissue. Cancer excisions confined to the superficial layers of the folds were much less damaging to the voice than those including the underlying muscle and vocal ligament, which may compromise the ability of the folds to close. Zeitels developed the technique of infusion, in which liquid is injected into the subepithelial tissue; if the tumor rises, it has not yet invaded the ligament and musculature. He found that many early cancers were shallow and required less tissue removal.
The latest study gathered vocal outcome data for a group of 32 patients undergoing phonosurgery for early cancer of the vocal cords. Infusion showed that nearly half needed only superficial resections. Of the others, nine required reconstruction, which involved lipoinjection or a Gore-Tex implant to fill out the folds. All of the patients are free of cancer without radiation or open surgery, and most achieved conversationally normal voices after the surgery.Occupational Hazards
Singers and vocal performers put a stress on their vocal cords akin to the physical exertion of a marathon runner. With their vocal folds vibrating at full volume for long periods of time, singers and orators often develop bumps, polyps, and rough surfaces on the tissues. These lesions can damage the voice that for many is also a livelihood. Though surgical removal is possible, there is a chance that any excision will permanently alter the voice. Zeitels set out to study this patient population more systematically. "There's often not a lot of science to the surgical management of vocal performers," Zeitels said. Until this recent study, there was little data to determine the success of surgical management in vocalists.
Using an approach called stroboscopy, the surgeon can assess the vibratory function of the vocal cords. A strobe light creates the illusion of slowing down the rapidly vibrating cords and allows the observer to watch them move together and apart. Voice outcomes of the surgeries in both studies were evaluated by Robert Hillman, HMS associate professor of otology and laryngology and a voice scientist who leads the voice lab at MEEI. Hillman's group primarily tested two general metrics of the voice: acoustic measures such as loudness, pitch, and regularity of tone, and aerodynamic measures--how much air the person must push from the lungs to get the vocal cords to vibrate.
In the cancer patient group, many of the measures taken before surgery were abnormal but showed significant improvement after the procedure and some voice therapy. For the group of 185 singers and performers, Hillman said, the voice measurements were trickier. The metrics of normal and abnormal ranges are designed for the general population, not the exacting standards of a performer. "It's not surprising that the measures we used to indicate a range of normal limits may not be as sensitive in this group," he said. "It's like making physical measurements in a group of athletes." However, the team did find that the few abnormal measures improved after surgery, and eight of the 24 objective measures showed statistical improvements across the group. The surgery did not cause any measures to drop below the normal range, and nearly all the patients thought their voices had improved. The study helps bring some data to a patient population that often approaches treatment with trepidation, unsure if the outcome is worth the risk of worsening the voice.
Zeitels believes that the two studies, though very different in type of patient, represent a convergence of surgical approaches. His team found that "when we managed the cancer patient with the precision that you manage the performer, we could enhance the voice outcome without sacrificing oncologic efficacy." Similarly, while singers were often managed with finesse, past approaches to their treatment lacked the systematic decision-making of surgical oncology.
Singers, like athletes, offer a model for studying how different behaviors affect the vocal cords: a musical-theater singer who belts out Broadway numbers is creating a different kind of stress than an opera singer. "If you can understand how these individuals function, you can master restoring most other voices," Zeitels said. He has found that singers can often perform with long-term trauma because their activity has induced more elastic normal tissue to compensate--their vocal cords even appear larger. The team has a partnership with Robert Langer, an HMS senior lecturer on surgery at Children's Hospital and the Kenneth J. Germeshausen professor of chemical and biomedical engineering at MIT, to develop biomaterials that could be used to reconstruct this elastic tissue. The trick, Zeitels said, is to find a material that does not degrade and is pliable, since stiffness is the cause of the majority of hoarseness. Zeitels believes that maintaining or even supplementing the healthy tissue may become just as important in vocal surgery as removing the abnormalities.