People with SD initially notice either a gradual or sudden onset of difficulty in speaking. They may hear breaks in their voices during production of certain words or speech sounds, breathy-sounding pauses on certain words or sounds, or a tremulous shaking of the voice. They may feel that talking requires more effort than before. Often people say that their voices sound as if they “have a cold or laryngitis.” The symptoms of SD can vary from mild to severe. A person's voice can sound strained, tight, strangled, breathy, or whispery. The spasms often interrupt the sound, squeezing their voice to nothing or dropping it to a whisper. Stress does not cause SD, but it can worsen the spasms.
Adductor Spasmodic Dysphonia
SD is generally catergorized into two primary forms: adductor spasmodic dysphonia (AdSD) and abductor spasmodic dysphonia (AbSD). Adductor SD, the most common form, affects approximately 80–90% of people with SD. In this type, spasms, usually in the thyroarytenoid muscle (TA), force the vocal folds together in adduction, or closing. AdSD may also affect the lateral cricoarytenoid muscle (LCA) or interarytenoid (IA). These spasms occur particularly on “voiced” speech sounds.
Examples of “voiced” sounds that cause problems for people with adductor SD include the vowel sounds in the words "eat," "back," "in," "I," "olives," or "nest."
If the voice cuts out, or breaks when the voiced sound is at the beginning of the word, as in “eels,” the speaker often strains over the spasm to get the word started. If the troubling vowel occurs in the middle of the word, the voice often breaks the word in two.
For example, the word “lawn” would come out as “la---awn.” When the voiced vowel is at the end of the word, such as “pleasingly,” the word terminates earlier than it should, causing the speaker to sound as if he or she is swallowing words. The speaker usually has no effort or disruption with the non-voiced vowels and unvoiced consonants. However, since most words and sentences contain voiced sounds, an adductor voice can be very hard to understand as the spasms continuously interrupt the flow of speech.
In very severe cases of AD, the speaker may need to use extreme effort to produce any voice at all since vowels occur frequently in speech. People with AdSD often complain of having to struggle to speak.
Abductor Spasmodic Dysphonia
AbSD, a less common form, occurs in approximately 10–20 percent of cases and results from spasms when the posterior cricoarytenoid muscles (PCA) abducts, or opens, the vocal folds. AbSD causes problems with the production of “voiceless” speech sounds, which normally sound “airy” or “breathy” when produced.
Examples of “voiceless” speech sounds are: “f” as in funny, “k” as in kite or cat, “t” as in top
“h” as in hello, “th” as in thank you, and “s” as in master
In AbSD, the spasms in the abductor muscles cause the vocal folds to remain open for a longer duration than should normally occur on these sound combinations. This results in the voice taking longer to complete the voiceless sounds, which makes the speaker sound “breathy.” For example, a person with AbSD might produce the word “he” as “h……….he.” The symptoms of AbSD can occur on any voiceless sound at the beginning, middle, or end of the word.
As with AdSD, the symptoms in AbSD can range from mild to severe. Significant overall breathiness or a whispered voice quality may occur in people with a very severe form of the disorder where breaks occur on every voiceless consonant. Because people with AbSD expend too much air as they produce sound, they often describe feeling winded or out-of-breath during speaking.
Subtypes of Spasmodic Dysphonia
While most people with spasmodic dysphonia fall into these two categories, researchers have identified several subtypes. A person may have a mixed form with symptoms of both AdSD and AbSD. Some people with SD also have a tremor in their voice. Typically, tremor affects muscle groups outside of the larynx and can cause the voice to sound “shaky” or “quivery.” Like adductor and abductor spasmodic dysphonia, the symptoms of vocal tremor can range from mild (infrequent, periodic tremor) to severe (affecting all voicing and singing). A very severe tremor with significant shaking can even cause the voice to cut out, sounding similar to the voice breaks in AdSD. In addition, sometimes treatment of the SD symptoms reveals a co-existing underlying tremor.
Muscle Tension Dysphonia
SD may also be accompanied by or misdiagnosed as muscle tension dysphonia (MTD), which is sometimes also referred to as a “hyperfunctional” voice. Although the MTD voice sounds tight or strained and sometimes similar to AdSD, MTD is considered a functional condition rather than a neurological one. MTD occurs when the speaker exerts too much pressure or effort on the laryngeal muscles. In some cases, people with AdSD may try to hold their vocal folds tighter in an attempt to control them. This compensatory mechanism can result in the person developing a variant of MTD on top of the SD.
Examples of Symptom Provoking Sentences
During an evaluation by a healthcare professional, a specific series of voicing and speaking tasks may be used to determine the type of SD.
People with AdSD will have more difficult with sentences with voiced sound such as these:
- Albert eats eggs every Easter
- We mow our lawn all year long
- Early one morning a man and a woman were ambling along a one mile lane
Whereas people with AbSD will find these sentences with voiceless sounds more challenging:
- Harry hit the hammer hard
- She sells seashells by the seashore
- The puppy bit the tape
Other parts of the evaluation may include reciting numbers, singing, laughing and shouting.