In her mid-seventies, Mrs. Adell Jones noticed her husband becoming more hard of hearing over two to three years. She ponders out loud to me, “Perhaps I am the one having trouble and perhaps post-nasal drip is ruining my voice.” She also concedes, “Not only is my voice weak, but I am having some difficulty speaking. I have given up talking to my friends on the phone. My voice is too unsteady for them to understand me. The more I talk, the more my voice fades.”
While she is telling me her story, I notice that her voice is cracking and jumping up to higher pitches. Some of her words are not articulated clearly. She can only make a sound at her regular speaking pitch for about eight seconds on one breath. She has problems both above and below her speech line. I begin my examination in her mouth and I notice that the left half of her tongue has begun to shrink in size. She also has poor control of her tongue and the left side is weaker when she sticks it out. I can see that she has indications of a neurologic problem that involves not only her voice but also her speech.
I place the endoscope into her nose and part of my neurologic examination of the larynx always includes the palate, since the Xth cranial nerve supplies the muscles along the side of the throat and the palate as well as the larynx. The left side of her palate is weak and does not elevate when she makes sounds such as /p/, /t/, or /k/. Air escapes out through her nose on these sounds, although it is difficult to hear since her voice is so weak. As I move the endoscope into the throat, I ask her to make a high-pitched sound and the left side of her throat does not contract. Finally, when I look at the vocal cords, the left vocal cord is not moving and the muscle within the vocal cord has atrophied.
A nerve paralysis can be an indication of an injury and consequently of a tumor anywhere along the path of the nerve between the brain and the vocal cords.
Whenever one vocal cord is paralyzed and there is no obvious reason for the paralysis, one of the considerations is that a tumor may be putting pressure on the recurrent laryngeal nerve. Additionally, whenever there is a neurologic problem in the larynx, the examiner needs to assess the other cranial nerves in the vicinity. As the cranial nerves wind their way from the brain to the muscles that they control, they are sometimes close to each other and in some locations far apart. If more than one cranial nerve has a problem, the astute examiner will look in the location where the cranial nerves are near to each other.
In Mrs. Jones, I find weakness of the left side of her throat and palate suggesting that the Xth cranial nerve, which supplies the pharynx, palate and vocal cords, is not working at all on her left side. When I add in the finding of the left-sided tongue weakness, indicating at least a partial paralysis of the XIIth cranial nerve, I know that both of these cranial nerves (X and XII) pass right next to each other as they exit the skull. This clue makes the base of the skull the most likely location to find Mrs. Jones’s problem. Before dealing with her vocal cord weakness, I obtain an MRI scan of her skull base. I find a tumor compressing the Xth and XIIth cranial nerves in this location.
On the left side, the Xth cranial nerve follows a rather convoluted path. After it leaves the skull it passes all the way down to the heart and around the aorta, the main blood vessel leaving the heart. Consequently, the Xth cranial nerve can become weak if pressure is put on it from a dilation of the vessels of the heart, from tumors in the lung, or from tumors of the thyroid gland.
What you learned
- A paralyzed vocal cord with no obvious local cause should prompt a search for a tumor along the entire path of the recurrent laryngeal nerve — from the skull base down to the aorta.
- When multiple cranial nerves are involved, the examiner should look where those nerves travel close together — in Mrs. Jones’s case, both cranial nerves X and XII converge at the base of the skull.
- The laryngologic examination is also a neurologic examination: palate, pharynx, tongue, and vocal cord movement all give information about which cranial nerves are functioning.
- Tongue atrophy (wasting) on one side is a sign of XIIth cranial nerve (hypoglossal) dysfunction — a clue that points away from the larynx and toward a distant lesion.