Spasmodic Dysphonia (SD) is a chronic voice disorder that originates in the nervous system, affecting the muscles of the larynx, or voice box. This condition is characterized by involuntary movements, known as spasms, that interfere with the normal vibration of the vocal folds during speech. These spasms prevent the vocal folds from functioning smoothly, leading to a distinct and often debilitating change in the voice’s quality. The resulting sound is a direct consequence of this neurological interference with the delicate process of voice production. This neurological disruption makes communication challenging and often highly effortful for the speaker.
General Auditory Impressions of Spasmodic Dysphonia
The overarching auditory impression of Spasmodic Dysphonia is a voice that sounds effortful and irregular, conveying a sense of physical struggle to the listener. This is because the neurological spasms disrupt the steady flow of air and the consistent closure of the vocal folds necessary for smooth phonation. The voice is frequently described as “choppy” or “interrupted,” as the involuntary muscle movements cause sudden breaks or irregularities in the sound.
Listeners often perceive a voice affected by SD as unstable, sometimes exhibiting a tremor or a shaky quality during sustained vowels or connected speech. The irregularity of the spasms means that the severity of the vocal disturbance can fluctuate even within a single sentence. For the person speaking, the experience is commonly characterized as an intense effort to push sound out, feeling as though the voice is being forcibly stopped or released. This irregularity distinguishes SD from other voice disorders that might involve a steady hoarseness or a fixed change in vocal tone.
Adductor Spasmodic Dysphonia: The Strained and Staccato Voice
Adductor Spasmodic Dysphonia (ADSD) is the most prevalent form of the disorder, defined by a strained, choked, or squeezed quality. In this type, involuntary spasms cause the vocal folds to clamp shut suddenly and forcefully (hyperadduction), often occurring when producing voiced sounds. This excessive closure results in a voice that sounds as though the speaker is being physically strangled or is pushing a heavy weight while attempting to speak.
The spasms cause abrupt interruptions, leading to a clipped or “staccato” pattern of speech, especially noticeable on words beginning with a vowel sound. Since the folds slam together too tightly, the sound produced is often higher in pitch and sounds tense. The strain is most apparent during vowel production and connected speech, where the voice is required to sustain continuous vibration.
This hyperadduction momentarily stops the airflow, causing “voice arrests,” which are sudden periods of silence. These arrests fragment the flow of speech, making the voice difficult to understand, particularly when the speaker is fatigued or stressed. This form of SD specifically targets the adductor muscles, primarily the thyroarytenoid muscles, which bring the vocal folds together.
Abductor and Mixed Spasmodic Dysphonia: Breathy Gaps and Complexity
Abductor Spasmodic Dysphonia (ABSD)
Abductor Spasmodic Dysphonia (ABSD) presents an auditory profile characterized by breathiness, weakness, and sudden drops in volume. The spasms cause the vocal folds to open inappropriately (abduct), resulting in the premature escape of air during speech. This uncontrolled air release creates a whispery or breathy sound, especially at the beginning of words starting with voiceless consonants like /h/ or /s/. The inappropriate opening causes distinct, voiceless gaps or breaks in the flow of speech, rather than the strained arrests heard in ADSD. The voice may suddenly become a weak whisper or disappear entirely, leading listeners to perceive a voice that is airy and weak.
Mixed Spasmodic Dysphonia (MSD)
Mixed Spasmodic Dysphonia (MSD) incorporates the auditory features of both adductor and abductor types, resulting in a highly complex and variable sound. A speaker with MSD may exhibit periods of strained, choked phonation interspersed with moments of breathy, whispery gaps within the same utterance. This combination makes the voice sound profoundly irregular and unpredictable, often shifting rapidly between the two distinct qualities. This mixed presentation occurs because the neurological signals affect both the adductor and abductor laryngeal muscles. The complexity of the sound reflects the dual nature of the underlying muscular spasms.
Contextual Variations in Voice Production
The distinct sounds of Spasmodic Dysphonia are not constant, as the severity of the spasms is heavily influenced by the speaker’s emotional and physical state, as well as the context of the speech. For many individuals, the voice may sound nearly or entirely normal during non-speech activities such as laughing, crying, coughing, or sneezing. This phenomenon demonstrates that the vocal apparatus itself is functionally intact, and the disorder is specific to the neurological control of speech.
The characteristics of the SD voice often diminish or temporarily disappear during activities like singing, speaking at an unusually high pitch, or whispering. These actions utilize different neural pathways or laryngeal muscle recruitment patterns that bypass the neurological trigger for the spasms. The temporary relief in these contexts provides a practical way for speakers to experience their voice without the interference of spasms.
Conversely, certain conditions are known to exacerbate the spasms and worsen the auditory quality of the voice, making the strained or breathy interruptions more frequent and severe. Stress, fatigue, anxiety, and speaking on the telephone are commonly reported triggers that intensify the vocal effort. The variability across different contexts highlights the neurological and situational sensitivity of Spasmodic Dysphonia.