About half of all PD patients have difficulty speaking. The difficulty ranges in severity from minor to moderate in most patients, and marked in about 10%. Minor difficulties may be barely perceptible to most listeners and not at all perceptible to the patient. Minor difficulties in speaking are best appreciated over the telephone: the phone filters out many high frequencies and makes your speech less audible. Marked difficulties are usually associated with difficulty in swallowing and breathing.
The muscles used in speaking are shared, in part, by the muscles used in swallowing and breathing, and when one set is severely affected it is likely the other sets will also be affected. Speech can be divided into voice, the act and the mechanics of speaking, and language, the content of speech. PD mainly affects voice. Strokes of the left-side of the brain, PD dementia (Lewy body dementia), and Alzheimer’s disease, all affect language. The qualities of voice affected by PD are: loudness, tone (the vocal “equivalent” of the shades of a particular color, like the different shades of blue or red or yellow), and pitch (the vocal equivalent of the intensity, the bright-ness or darkness, of a particular shade of color).
For most PD patients, voice difficulty manifests as a decrease in loudness, tone, and pitch. Your voice may be described as low, monotonous, and unvarying. Voice difficulty in PD, like difficulty moving, arises because the muscles involved in speaking are affected: they become rigid, they move slowly and incompletely. These muscles and the structures they affect include the nose, lips, tongue, cheeks, soft and hard palates, back of the throat or pharynx, vocal cords, and the muscles of the chest wall including the diaphragm and the intercostal muscles.
Your vocal cords are muscles; their configuration results from an in-folding of a membrane stretched across the larynx, or voice box. The cords vibrate, modulating the flow of air coming from your lungs. The frequency at which your cords vibrate deter-mines the pitch of your voice; females have a higher frequency than males, and thus higher-pitched voices. Three problems related to the vocal cords can occur in PD:
First, your cords may not close completely. This can be seen by examining the cords through an instrument called a laryngoscope. If your cords don’t close completely, your voice becomes low and muffled. In some patients, collagen may be injected into each cord to “bulk it up,” resulting in more complete closure.
Second, your vocal cords may close too tightly. This can also be seen through a laryngoscope. If your cords close too tightly, your voice, while initially loud, fades quickly, and has a “reedy” or “breathy” quality. In some patients the cords close too tightly because of scarring, and in some because of dystonia, called spasmodic dystonia, which can be helped by Botox injections into the vocal cords. In Parkinson-like conditions such as multiple system atrophy, the cords may close completely. Such closure is heralded by a shrill, high-pitched sound called strider. This is a medical emergency because, if not treated, air will be unable to enter your lungs from your nose and throat.
Third, and most common, the vocal cords may not vibrate as rapidly and may fatigue easily. This is responsible, in part, for the low, monotonous voice common in PD patients.
Your lungs also play a role in the quality of your voice. Housed in your chest wall cavity, your lungs are protected by the bony structure of your rib cage and further enclosed by a double-walled sac called the pleura. Your intercostal muscles work to expand and contract your chest cavity as you breathe, allowing air into your lungs through your trachea and bronchial tubes. In PD, your intercostal muscles become rigid, which can result in your breathing faster—up to 20 breaths or more per minute. This faster rate of breathing, called hyperventilation, results in a decrease in the carbon dioxide tension and in the buffering capacity of your blood, leading to a feeling of shortness of breath or suffocation, which fatigues you and heightens anxiety.
If you are unable to take a deep breath, you cannot speak loudly. To illustrate this, hold your breath and try to speak loudly. Your voice, initially loud, quickly fades. As disorders of the vocal cords are difficult to treat, I emphasize improving the other muscles involved in speaking. The regimen I teach is one that can be easily carried out by anyone, anywhere.
First, place a helium-quality balloon between your lips, tightening and toning the lip muscles. Slowly blow up the balloon, tightening and toning your cheek, throat, and intercostal muscles. Do this 30 times a day when your anti-Parkinson drugs are working and your muscles are working efficiently.
Therapists who treat PD are usually familiar with or trained in the Lee Silverman Voice Therapy (LSVT). LSVT emphasized voice training by strengthening the muscles used in speaking; similar to training an opera singer to sing louder. At the Muhammad Ali Parkinson Center (MAPC), patients are taught to speak louder and more clearly.