DEAR MAYO CLINIC:

About a year ago I started having problems with my voice. After many tests, my doctor diagnosed me with muscle tension dysphonia. But after nine months of speech therapy with no improvement, I'm not sure about the diagnosis. My grandmother had ALS. Could my voice problems be a symptom of this?

ANSWER:

This is a complicated question because voice problems have a wide array of causes. Voice changes can be an early sign of some neurologic disorders, such as amyotrophic lateral sclerosis (ALS). But the problems you're experiencing could also be the result of muscle tension dysphonia, or another voice box (larynx) disorder, and a different treatment approach may be in order.

It's not uncommon for voice changes to be one of the earliest signs of ALS. Typically, the voice problems caused by ALS involve increased muscle tension (spasticity) of the vocal folds that causes the voice to sound strained and tight. It usually begins with a hoarse or raspy quality to the voice that progresses slowly and continuously to a more strained voice quality.

But with ALS, having voice problems as the only sign of the disease for more than nine months is very unlikely. Those who experience voice changes as the first sign of ALS have what's known as bulbar-onset ALS. Most people with this type of ALS begin to notice other signs of the disease soon after voice problems begin. Other common bulbar-onset ALS signs may include tongue and lip weakness, air coming through the nose during speech that causes the voice to have a nasal quality, mildly slurred speech and difficulty swallowing.

If you haven't experienced any other signs or symptoms, or if you've seen some improvement in your voice quality, even if it's been only mild or temporary, then it's unlikely that ALS is the underlying cause of your voice problems.

Your diagnosis of muscle tension dysphonia may be accurate, but it's a difficult diagnosis because different clinicians define muscle tension dysphonia in different ways. Basically, the condition involves the muscles of the larynx being tight or tense, resulting in a strained or tight voice quality. There are several causes of muscle tension dysphonia, and accurately determining which one is the source of your symptoms is key because effective treatment depends on identifying the underlying cause.

One way people develop muscle tension dysphonia is when the vocal folds themselves are weak and don't come together completely. This causes air escape and a hoarse breathy voice, often called hypophonia. To compensate for this, people sometimes squeeze the tissue just above the vocal folds (sometimes called the false folds). This can cause a tight, strained sounding voice.

Another way people can develop muscle tension dysphonia is following a period of typical laryngitis, where the voice is hoarse due to some inflammation or swelling of the vocal folds. People sometimes compensate by "pushing" through it to get voice. The brain can actually habituate this so that the person continues to use extra muscle tension even when the vocal folds are healthy again. Voice therapy with a speech pathologist can be very effective for this problem.

In some cases, the problem is caused by muscle spasms that force the vocal folds closed, causing a tight strained vocal quality that is sometimes mistaken for muscle tension dysphonia. This is called adductor spasmodic dysphonia. Another type of spasmodic dysphonia is abductor spasmodic dysphonia, in which spasms open the vocal folds, allowing extra air to escape during speech. Spasmodic dysphonia often can be effectively treated with periodic injections of botulinum toxin (Botox) that reduce the muscle spasms, allowing the vocal folds to open and close properly.

Because you haven't seen improvement in your condition, I recommend you seek another evaluation with an otolaryngologist (a physician who specializes in ear, nose and throat disorders) who has experience working with people who have voice disorders. If possible, find one who works in partnership with a speech pathologist. This team of specialists would be best suited to effectively evaluate your situation, provide an accurate diagnosis and work with you to develop an appropriate treatment plan.

-- Edythe Strand, Ph.D., Speech Pathology, Mayo Clinic, Rochester, Minn.

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