Spasmodic dysphonia

Spasmodic Dysphonia, also known as Spastic Dysphonia, is a chronic neurological voice disorder characterized by involuntary spasms of the muscles of the larynx, or voice box. These spasms cause a person's voice to be interrupted during speech, resulting in a distinct and often debilitating change in voice quality.

It is now understood to be a form of focal dystonia, a type of neurological movement disorder that affects a specific muscle or group of muscles. In this case, the dystonia affects the muscles that control the vocal cords. The brain sends incorrect signals to these muscles, causing them to contract involuntarily during speech. It is important to note that spasmodic dysphonia is a neurological condition, not a psychological or psychiatric disorder.

Types of Spasmodic Dysphonia

The disorder is classified into two primary types based on which laryngeal muscles are affected.

1. Adductor Spasmodic Dysphonia (ADSD)

This is the most common form. It is caused by involuntary spasms of the adductor muscles, which are responsible for closing the vocal cords.

• Mechanism: The spasms cause the vocal cords to slam together and stiffen, making it difficult for sound to pass through.
• Voice Quality: The voice sounds strained, tight, choked, strangled, or full of effort. Speech may be choppy, with words being cut off. The effort to speak can be physically exhausting for the individual.

2. Abductor Spasmodic Dysphonia (ABSD)

This form is less common. It is caused by spasms of the abductor muscles, which are responsible for opening the vocal cords.

• Mechanism: The spasms cause the vocal cords to pull apart, allowing air to leak out from the lungs during speech.
• Voice Quality: The voice sounds weak, breathy, or whispery. The individual may run out of air quickly while trying to speak.

Some individuals may have Mixed Spasmodic Dysphonia, which involves symptoms of both types.

A key characteristic of the disorder is that the spasms typically occur only during connected speech. Many individuals find they can laugh, cry, or sing with a relatively normal voice.

Diagnosis

Diagnosing spasmodic dysphonia can be challenging and is often delayed because it can be mistaken for other voice problems. A definitive diagnosis is typically made by a multidisciplinary team, including:

• An Otolaryngologist (ENT), particularly a Laryngologist who specializes in the voice box.
• A Speech-Language Pathologist specializing in voice disorders.
• A Neurologist.

The diagnostic process includes a detailed patient history, a voice evaluation, and a visual examination of the larynx using a laryngoscope. During this procedure, the specialist can observe the vocal cords in action as the patient speaks, allowing them to see the characteristic involuntary spasms.

Treatment

While there is no cure for spasmodic dysphonia, several treatments are highly effective at managing the symptoms and improving voice quality.

• Botulinum Toxin (Botox) Injections: This is the gold-standard treatment. A very small amount of Botox is injected directly into the affected laryngeal muscles. The Botox temporarily weakens the overactive muscles, reducing or eliminating the spasms.
  • For ADSD, the injection is made into the adductor (closing) muscles.
  • For ABSD, the injection is made into an abductor (opening) muscle. The effects are temporary, and the injections must be repeated, typically every 3 to 6 months, to maintain the voice improvement.
• Voice Therapy: While speech therapy cannot cure the underlying neurological problem, it is a crucial part of management. A speech-language pathologist can help patients reduce compensatory strain, learn strategies to manage their voice more effectively, and maximize their vocal function between Botox treatments.
• Surgical Options: Several surgical procedures that involve cutting or altering the nerves to the vocal cords exist. However, their results are variable, and they carry risks of permanent side effects, so they are generally reserved for specific cases where Botox treatment is not an option.