Neurological Voice Disorders - Causes, Types, Assessment, And Treatment
Author: Roselyn Mathew, Reg. CASLPO, Speech-Language Pathologist
Date: Wednesday, May 14, 2025
Table of Contents
Causes of neurological disorders
Infections
Trauma
Genetic
Degenerative disorders
Developmental disorders
Types of Neurological Voice Disorders
Spastic voice disorders
Flaccid voice disorders
Hyperkinetic voice disorders
Hypokinetic voice disorders
Ataxic voice disorders
Differences between neurological voice disorders and psychogenic voice disorders
Speech therapy
Pharmacological treatment
Surgery
Assistive devices
Neurological voice disorders are voice disorders that are caused due to any damage in the nervous system. This may affect the pitch, quality, volume of the voice and may also result in an increase in the vocal effort to produce speech. These disorders not only reduce a person’s ability to speak clearly but can also significantly affect their quality of life, self-esteem, and social interaction.
According to the definition given by Duffy in 2013 “Neurological voice disorders are conditions resulting from dysfunction in the central or peripheral nervous system, which disrupts the normal control of muscles responsible for phonation and voice modulation.”
Neurological disorders can be congenital, which means they can be present since birth, or acquired, meaning they can be caused in the later periods of life.
Causes of neurological disorders
Some of the common causes of neurological disorders are:
Infections
Infections can be caused by bacteria, viruses or parasites. Some examples are Meningitis and Encephalitis.
Trauma
Injuries on the head, throat or spinal cord can cause neurological voice disorders.
Genetic
Genetic disorders like muscular dystrophy or Huntington’s disease might result in voice disorders.
Degenerative disorders
Conditions like Parkinson’s disease, Multiple Sclerosis etc. can lead to voice impairments.
Developmental disorders
Weakness or incoordination of the muscles due to disorders like Cerebral Palsy can lead to voice impairments.
Types of Neurological Voice Disorders
Neurological voice disorders can be classified into different types based on different factors. One common type of classification based on the nature of the motor abnormality was given by Darley, Aronson, and Brown. The different types of neurological voice disorders based on this classification are:
Spastic voice disorders
These occur when there is excessive muscle tone and stiffness which generally happens due to bilateral upper motor neuron damage. Examples of spastic voice disorders are Primary Lateral Sclerosis, Amyotrophic Lateral Sclerosis (ALS) in the early stages and bilateral stroke.
Voice impairments
Voice impairments observed in spastic voice disorders are:
Harsh, strained-strangled voice quality due to excessive tension in the muscles
Monopitch and monoloudness, which means that there is lack of inflections in speech and a lack of change in the volume of speech
Low pitch with pitch breaks
The rate of speech is reduced
Speech is more effortful
Due to the effort in speaking, people generally experience an increased vocal fatigue even after speaking for a few minutes
Frequent voice arrests or spasms
Hypernasality due to velopharyngeal dysfunction
Flaccid voice disorders
These are caused because of weakness or paralysis due to damage to the lower motor neurons or neuromuscular junctions. Common conditions that cause flaccid voice disorders are vocal fold paralysis and brainstem stroke.
Some of the common issues observed in the voice are:
Weak, breathy phonation which often sounds like a whisper
Hoarseness in voice
The range of pitch variation and loudness is less
Diplophonia, which is, having 2 voices that is heard at the same time while speaking
Nasal emission and hypernasality due to weakness of the muscles in the soft palate
Rapid tiredness due to effort put to have loud and clear speech
Hyperkinetic voice disorders
Hyperkinetic voice disorders are voice disorders that are caused by excessive, involuntary muscle activity. These muscle activities can cause disruptions in the common speech patterns. Some of the main causes of hyperkinetic voice disorders are conditions like spasmodic dysphonia, dystonia, Tardive dyskinesia and Huntington’s disease.
Voice impairments observed in this type of voice disorder are:
Sudden changes in loudness and pitch which are involuntary
Tremors in voice which can be clearly observed during sustained phonation. For example, when the person is asked to say /ah/ for a period, like 10 seconds, the voice produced would be shaky and might have pitch and volume changes which is usually rapid
The voice might sound strained and can also sound breathy
Unpredictable vocal spasms and the person might feel their throat tightening and relaxing while speaking
Voice may worsen with emotional stress or fatigue
Intermittent voice breaks
Hypokinetic voice disorders
In this type of voice disorder, there is reduced movement and muscle rigidity. This is usually caused due to any impairments in the Basal Ganglia. The most common cause which can result in hypokinetic voice disorder is Parkinson’s Disease.
Common characteristics observed in this type of voice disorder are:
Monotone voice with limited pitch variability
Breathy, weak voice quality which sounds like whispering
Imprecise articulation which affects the speech intelligibility and clarity
Reduced stress and speech intonation/inflections
Difficulty in initiating speech due to the reduction of voluntary movements of muscles involved in speech
Speech would be short, consisting mostly of phrases due to difficulties in breathing
Festination of speech is observed, which is an increase in the rate of speech as the speech keeps progressing. There is also a reduction in the clarity of speech.
Loudness is significantly reduced
Ataxic voice disorders
Ataxic voice disorders are caused due to inadequate coordination of the speech muscles. This is mostly due to impairments in the cerebellum, which is responsible for balance and coordination. The most common conditions which may cause ataxic voice disorder is Cerebellar Ataxia.
Common issues in voice observed are:
Breakdowns in enunciation that are irregular
Consonant production is imprecise
The person speaks by stressing all the syllables of words equally without any variations. This is called scanning of speech.
Unsteady pitch and tremor-like instability
Excessive loudness variations
Prolonged pauses which might be irregular
Differences between neurological voice disorders and psychogenic voice disorders
Psychogenic voice disorders are voice disorders that are caused by psychological or emotional stress. As the issues in voice in neurological voice disorders can be very similar to psychogenic voice disorders, it would be beneficial to understand the differences between them. Two of the main differences between them are:
The onset of psychogenic disorders is generally very sudden and is often after a mentally traumatic or emotionally stressful event, whereas the onset of neurological voice disorders is generally gradual except for physical injuries or trauma.
The degree of severity of the symptoms shown are inconsistent in psychogenic voice disorders but are fairly consistent in neurological voice disorders.
Assessment
Assessment is usually done by a team of professionals which mainly consists of General physician, Neurologist, ENT specialist and Speech Language Pathologist.
An initial assessment may be done by a general physician who would refer the person for neurological evaluation. A Neurologist would examine the person to assess neurological conditions. The person might undergo different tests like MRI, CT scan etc. so that the Neurologist can have a better understanding of the condition. ENT specialists assess the vocal folds and the other structures in the throat using methods like Laryngoscopy or Videostroboscopy. Speech Language Pathologists assess the voice, speech and other communication issues faced by the person by using different tests and/or software.
Treatment
Treatment, like assessment, usually involves a team of professionals. The various treatment options are:
Speech therapy
In speech therapy, different approaches are used to improve voice quality, pitch, volume, reduce vocal effort and to improve clarity of speech.
Pharmacological treatment
Certain methods, like injecting Botox, drugs to relax muscles that are excessively tight, drugs to increase muscle coordination and control are used to treat impairments in muscle movements.
Surgery
Surgery is sometimes required to repair nerve damage. Based on the neurological severity and degree, vocal folds can be placed closer to the middle position to increase quality of voice production.
Assistive devices
Assistive devices that can be used are:
Voice amplifiers
Voice amplifiers are used in situations where the vocal output of a person is low in volume. Voice amplifiers can be used to boost the volume of the voice. Some people use voice amplifiers only when they are outside home to be heard above the background noise and some others, whose voice is significantly low in volume use them all the time.
AAC devices
AAC devices (Augmentative and Alternative Communication Devices) are devices that can be used to enhance speech or completely replace speech. They are generally used when a person has significant issues in speaking.
Apps and devices to generate speech
There are certain apps that could convert text to speech and certain device to generate speech based on hand or mouth movements. These devices are sometimes used temporarily as a mean to communicate while the person is recovering or used permanently as an alternative to speaking.
Conclusion
Neurological voice disorders are voice disorders that happen due to damage in the nervous system. It may be present since birth or can occur in the later years of life. There are different causes for neurological voice disorders. Neurological voice disorders can be classified based on different factors. Assessment and treatment of these voice disorders are typically done by a team of professionals.
To speak with a psychotherapist or one of the speech-language pathologists at Well Said: Toronto Speech Therapy, schedule an initial consultation by clicking the link below or calling (647) 795-5277.
