What is spasmodic dysphonia?

When you suffer from spasmodic dysphonia there is a problem with the learned skill of speaking. The
cells in the brain where the learned controls of the vocal chords muscles situate, are damaged.
The muscles that open or close the vocal chords in a smooth and controlled way, are receiving
scrambled signals. The signals that are being sent to the voice muscles normally do not operate like an on or off
switch. The activation of the muscles that close or open the vocal chords goes normally in a very
smooth and controlled way.

The brake is busted

All the muscles in your body receive two signals at the same time. You can compare it to your
car’s gas pedal and the brake. They receive an activation signal accompanied by an slow down
signal. If the activation signal is stronger then the slow down signal, the muscle contracts. The
more slow down signal there is, the less the muscle contracts.

On or off

When you suffer from spasmodic dysphonia there is a problem with the brain cells that produce
the slow-down signal. The muscles do not operate in a smooth way anymore, but they contract
like an on-off switch. It is like pressing the gas pedal fully down fast with your foot, while your
brake is not functioning anymore. And then releasing it in an instant. Your car will move in a very
jerky way. It is all or nothing.

All or nothing

This is exactly the problem with the muscles that move your vocal chords.
They go all the way open or all the way shut.


Spasmodic dysphonia neurological based?

SD is formally classified as a movement disorder, one of the focal dystonias, and is also known as laryngeal dystonia.  Supporting evidence that SD is a neurological disorder includes:

  •  SD may co-occur with other neurological movement disorders such as blepharospasm (excessive eye blinking and involuntary forced eye closure), tardive dyskinesia (involuntary and repetitious movement of muscles of the face, tongue, body, arms and legs), oromandibular dystonia (involuntary movements of the jaw muscles, lips and tongue), torticollis (involuntary movements of the neck muscles), or tremor (rhythmic, quivering muscle movements).
  • Spasmodic dysphonia runs in some families and is thought to be inherited. Research has identified a possible gene on chromosome 9 that may contribute to the spasmodic dysphonia that is common to certain families.

Histological examination of the nerve to the vocal cords in patients with SD demonstrates that the percentage of abnormally thin nerve fibers was higher than in normal controls
Functional MRI signal is reduced in sensorimotor cortices associated with movement of the affected body part in laryngeal dystonia, supporting a dystonic basis for this voice disorder

Spasmodic dysphonia causes

The exact cause of spasmodic dysphonia (SD) is unknown.[1] According to the National Institute on Deafness and Other Communication Disorders, “research has revealed increasing evidence that most cases of spasmodic dysphonia are in fact neurogenic or having to do with the nervous system (brain and nerves).”[2]

SD is a neurological disorder rather than a disorder of the larynx, and as in other forms of dystonia, interventions at the end organ (i.e., larynx) have not offered a definitive cure, only symptomatic relief. The pathophysiology underlying dystonia is becoming better understood as a result of discoveries about genetically based forms of the disorder, and this approach is the most promising avenue to a long-term solution.

Neurological cause or psychogenic?

The National Institute of Neurological Disorders and Stroke (NINDS) and the American Academy of Neurology (AAN) classify SD as a neurological disorder. However, because the voice can sound normal or near normal at times, some practitioners believe it to be psychogenic, that is, originating in the affected person’s mind rather than from a physical cause.

No medical organizations or groups take this position. A comparison of SD patients compared with vocal fold paralysis (VFP) patients found that 41.7% of the SD patients met the DSM-IV criteria for psychiatric comorbidity compared with 19.5% of the VFP group.

However, another study found the opposite, with SD patients having significantly less psychiatric comorbidity compared to VFP patients: “The prevalence of major psychiatric cases varied considerably among the groups, from a low of seven percent (1/14) for spasmodic dysphonia, to 29.4 percent (5/17) for functional dysphonia, to a high of 63.6 percent (7/11) for vocal cord paralysis.”

A review in the journal Swiss Medicine Weekly states that “Psychogenic causes, a ‘psychological disequilibrium’, and an increased tension of the laryngeal muscles are presumed to be one end of the spectrum of possible factors leading to the development of the disorder”.

Alternatively, many investigators into the condition feel that the psychiatric comorbidity associated with voice disorders is a result of the social isolation and anxiety that patients with these conditions feel as a consequence of their difficulty with speech, as opposed to the cause of their dysfluency. The opinion that SD is psychogenic is not upheld by experts in the scientific community