Five years ago, at age 75, Peter McDash was found to have a thyroid cancer. His voice was normal at that time. He underwent radiation therapy and then surgery to treat the cancer and his voice was still normal immediately after surgery. Twenty-four hours later his voice became weak, higher pitched and he lost his vocal durability. Since then, he cannot compete with any background noise, such as in a restaurant, and that is a significant problem for a talkative person in a talkative family. He initially sought help from several doctors. One doctor told him that one of his vocal cords was not moving but he should live with it. Another doctor told him that perhaps his thick secretions were straining his vocal cords. He became skeptical that anything could be done to restore his voice, so he has just got along since then without any treatment. Peter’s son-in-law previously had a successful voice surgery and finally persuaded Peter to come for a visit.
On first listen, Peter sounds like a frail, 80 year old man with his voice thin and high in pitch, yet he plays tennis every day, suggesting he may not be as frail as he sounds. Thus, there is an incongruity in Peter’s story; he sounds frail, but he is not truly frail. After beginning the endoscopic exam, my first impression is that Peter’s right vocal cord is in a position near the midline and not moving, while the left vocal cord opens and closes. Most physicians would agree that he has a paralyzed vocal cord. That may even be exactly what his first doctor said.
Merriam-Webster defines paralysis in two different ways: complete or partial loss of function, or loss of the ability to move. Peter does have a paralysis by this definition. One vocal cord is not moving open and closed when he breathes or speaks, while the other cord retains its opening and closing motions. The injured vocal cord appears (superficially) to be fixed in position.
He sounds frail, but he is not truly frail.
Why Did He Lose His Voice?
The main nerve that supplies the majority of the muscles of the voice box is called the recurrent laryngeal nerve (RLN). Due to something that happens when we are still not much larger than a ping-pong ball in a uterus, both recurrent laryngeal nerves (left and right) leave the brain, head to the chest and pass around a blood vessel before coming back up to the larynx. On the right side, this U-turn takes place under the collar bone, but on the left side, the U-turn is at the level of the heart.
These long RLNs pass a lot of important structures on their way to the vocal cords: the carotid artery, the windpipe (trachea), the swallowing tube (esophagus), the neck vertebrae, the lungs, the heart and the thyroid gland. If a tumor grows from one of these organs or if a surgeon works on one of these structures, there is the potential for injury to the RLN by stretching or by injuring the nerve’s blood supply. If you pull on the cable to your telephone hard enough, you may lose the connection inside the cable. Even when the surgeon just pulls the RLN aside to get where he is going, the RLN can be injured to the point where less signal passes through the nerve.
An interruption of a signal going to a muscle results in a reduced movement of the muscle supplied by that nerve. No signal to a muscle means no movement in that muscle. Each RLN supplies several muscles including muscles that open as well as muscles that close the vocal cord. When the RLN is injured, the movements required for breathing (abduction) and for making sound (adduction) are often injured simultaneously.
Why didn’t Peter get hoarse until several days after surgery? In a long surgery, under general anesthesia, there may be a tube in the windpipe for several hours. It can cause swelling of the vocal folds, so both vocal cords may be swollen enough that with one RLN injured, the vocal fold still working can close against the swollen, immobile vocal cord and make a reasonable sound. As the swelling subsides, the opening between the vocal cords becomes larger and Peter loses his voice because he leaks air through this enlarging gap.
Why Did His Voice Come Back?
If the nerve injury is very mild, a reconnection may occur within a few days or weeks. The reconnections will be appropriate in quantity and the nerve fibers will reconnect with their original muscles. The voice is restored to normal and visible movement is restored to normal.
In anything more than a mild injury, which is the case with Peter, the nerve fibers regrow back through the injured nerve trunk over three to four months and reconnect to the vocal cord muscles. While the nerve fibers have an incredibly strong propensity to find a muscle to connect to, they are indiscriminate or not very choosy. The fibers will hook up to any muscle they encounter that needs a connection. A lot of the connections in the larynx become mixed up because all of the injured muscles are releasing nerve attractants. Some of the fibers programmed in the brain to open the vocal cords inadvertently connect to the muscle that tightens (TA) or closes (LCA) the vocal cord. Some of the fibers meant to close the vocal cord find their way to the muscle that opens (PCA) the vocal cord.
With this random reconnection, all of the muscles initially supplied by the RLN may be reinnervated in new proportions or new degrees after the nerve reconnections are complete. Each muscle may receive appropriate as well as conflicting or inappropriate stimulation when the individual wants to make a sound, breathe, or swallow. The vocal cord ends up moving to the middle of the road position with all this stimulation and just stays put — visibly paralyzed, but not without innervation. The innervation is just continuous rather than intermittently appropriate.
Several months after his injury, Peter’s reinnervation fixed his right vocal cord near the midline and his left vocal cord learned to actually cross the midline. Peter’s vocal cords could again nearly close. He could set them vibrating and his voice returned. Yet hoarseness remains because there is still an air leak or an asymmetric vibration. Watching the video in slow motion, the paralyzed side is weak enough that it actually gets blown slightly sideways by air pressure during sound production. A gap opens at the back of the vocal folds. Air leaks along the entire length of the cord, adding a huskiness to his voice and causing him to get out of breath quicker with talking.
Unknowingly, Peter tries to compensate. The CT muscle that stretches the vocal cord and puts him into falsetto is supplied by a different nerve (the superior laryngeal nerve or SLN), so is probably uninjured. Peter’s CT muscles stretch his vocal cords to try to tension the right side, holding the right cord tight. This supports his weak right vocal cord, but one consequence is that his pitch rises. He is actually speaking in a falsetto voice all the time in order to minimize the gap between his vocal folds. This is the reason for the “frail, elderly man” quality to his voice.
A Scope Is Not a Scope
When Peter’s general otolaryngologist looked, he announced that one cord was paralyzed but that the vocal cords were coming together. However, his otolaryngologist likely only viewed the vocal cords from one perspective — directly above and probably far away, blurry, for a very brief period of time, at a single pitch and not recorded for review.
I move the scope closer for a detailed look, until I can align the scope more nearly parallel to the axis of the vocal cords and begin to appreciate the actual thickness of the vocal folds. In cross section, his weaker (paretic) vocal cord is very different in appearance than from above. The paretic cord resembles a linguine noodle in diameter when compared to his healthy cord, which resembles a biceps on a body builder. If I am not certain about a difference in size between the TA muscles, I have Peter sniff in. Sniffing opens the vocal cords to the fullest extent and pulls them to a long, drawn out position. In this position, his injured cord is less than half as thick as his healthy cord.
With only one side injured, I can watch and compare the normal side with the injured side. The good cord opens with inspiration and it partially closes with expiration. On the injured side, the vocal process is fixed in position, but the middle of the vocal cord is sucked inward during inspiration (Bernoulli effect) and bows outward during expiration. This injured side is passively reacting to changes in air pressure, while the healthy side is actually tensing lightly during inspiration. Because his paretic side does not help resist the outflow of air, his lungs do not retain as much air. The alveoli start collapsing as they empty too completely. The limitation in his tennis game that he attributes to aging is at least partially due to his weak vocal cord not keeping his lungs full.
In surgery I placed a plastic shim inside Peter’s weak and atrophic right vocal cord — a surgery called medialization laryngoplasty or thyroplasty type I. The shim accomplishes two things. It provides bulk to the paretic side so that in cross section, the paralyzed side more nearly resembles the good side in terms of mass. The paretic cord can now maintain tension without the CT muscle pulling on it. The implant also fixed the cord in a good position so that his weak LCA muscle doesn’t have to hold up against the stronger left side.
The Outcome
Meeting Peter the day after surgery, he told me that when he phoned his daughter after the surgery, she was convinced that she was talking to her brother, not her father. Peter’s voice had dropped in pitch. He no longer sounded like a “little old man.” He also noted that he could drink without being so careful. His weak vocal cord had not just been impairing his conversation at the café, it had been impairing his pleasure of drinking. In retrospect, he realizes that he was choking on liquids more often than he realized. It had just become second nature for him to drink slowly and carefully, so it had not occurred to him to relate this to his nerve injury.
He also found out that he was less winded when he walked. When breathing out, his glottis could partially close now keeping more air in his lung. Lastly, he said that he could speak louder and longer. He didn’t realize that his presenting complaint of hoarseness was actually way down on his list of what he would appreciate by a restoration of his glottic valve. Being less out of breath, not choking so frequently, speaking louder, restoring a more masculine voice, a clearer vocal quality and improved volume all came with supporting his weak vocal cord.
Details you may see during endoscopy that represent the “hidden” problems of RLN paresis:
- Squeeze of the supraglottis — the false vocal cords squeeze as a compensation for true vocal cord weakness.
- Air leak from a gap between the cords — best visualized at low pitches which removes the CT muscle compensation.
- A difference in thickness of the vocal cords represents atrophy of the denervated TA muscle.
- A tense vocal cord will oscillate about its axis. A weak vocal cord will oscillate lateral to its axis.
- On a close exam, fasciculations of the TA muscle may be seen, supporting the diagnosis of denervation.
- During respiration, the Bernoulli effect may in-draw the weak vocal cord.
What you learned
- The recurrent laryngeal nerve (RLN) makes a long U-turn through the chest before returning to the larynx, passing the thyroid, carotid, lungs and heart — all of which can injure it during surgery.
- When the RLN is injured, both the opening (PCA) and closing (TA, LCA) muscles lose their signal simultaneously; the cord stops moving and air leaks through the resulting gap.
- Nerve regrowth is indiscriminate — fibers reconnect to whichever muscle is available, often crossing to opposing muscles. The cord ends up “frozen” not from lack of signal but from competing signals.
- The CT muscle (supplied by the superior laryngeal nerve, usually uninjured) compensates by stretching the cord tight, raising pitch into falsetto — producing the thin, frail voice quality.
- Medialization laryngoplasty (thyroplasty type I) places an implant to bulk up and support the paretic cord, restoring not just voice but breathing efficiency, swallowing safety, and vocal endurance.
- A single-sided RLN injury is very forgiving; injuring the nerve on the opposite side is a life-altering event.