Motor Speech Disorders In Adults And Their Types

Written by: Roselyn Mathew / Medical Rehabilitation / May 24, 2022 / 7 minutes read

Motor speech disorders are a class of disorders where there is weakness or incoordination of the muscles that are required for speech due to a neurological damage. The signals sent by the brain are not transmitted adequately or appropriately to the muscles. 

"...incoordination of the muscles that are required for speech due to a neurological damage."

Causes of Motor Speech Disorders

Some of the common causes are:

• Stroke

• Brain tumors

• Brain injury due to accident or surgical trauma

• Side effects of certain medications used for sedation or for treating seizures

• Neurodegenerative disorders like Parkinson’s disease, dementia, Huntington’s disease etc.

Type of Motor Speech Disorders

There are 2 types of motor speech disorders seen in adults which are apraxia of speech and dysarthria.

Apraxia of Speech

Apraxia of speech is a motor speech disorder where the transmission of electric signals by the brain are not sent to the appropriate muscles. Due to this a person with apraxia have difficulty moving their lips, jaw or tongue in the required manner to say a sound.

Symptoms of Apraxia of Speech

• There are distortions or substitutions seen in the speech sounds. The person might either say a word in a different way or might say a similar word which has a different meaning. For eg. instead of saying ‘night’, they might say ‘nime’ or ‘might’.

• Groping movements in the lips, tongue or jaw, where the person tries to approximate their position for speaking.

• Delay in giving a response or initiating speech.

• Difficulty in transitioning from one sound to another

• Giving sound stress to a different sound in the word or giving equal stress to all sounds in a word.

• Having a pause between sounds in a word

• Difficulty saying longer words compared to shorter words

• Difficulty in imitating a sound or word

• Errors made are inconsistent. The person might make a different error instead of the previous error while repeating a word.

Dysarthria

Dysarthria is a motor speech disorder where the neutral transmissions are made by the brain to the appropriate muscle but the transmission strength is inadequate. There is weakness or in-coordination of the muscles due to this.

Types Of Dysarthria

• Spastic Dysarthria

  • In spastic dysarthria, the muscle tone has tightness and restricted movements. There is damage in the brain and spinal cord. The reflexes are abnormal. Speech appears to be strained and strangled.

• Flaccid Dysarthria

  • In this, the damage is in the cranial or spinal nerves. There is predominant weakness in muscles. Muscle tone is low and the reflexes are diminished. Speech appears to be weak, has hypernasality and nasal emissions, breathiness and imprecise production of sounds. There is also reduced loudness while speaking. Due to nasal emissions, the person might speak in phrases or short sentences.

• Ataxic Dysarthria

  • In ataxia dysarthria, the cerebellum is damaged. The cerebellum is responsible for coordination and for transmitting sensory information. The speech appears ‘drunken’. There are also difficulties seen in coordinating breathing and speaking. Speech is unintelligible especially with a faster rate of speech. The person might also bite their cheek or tongue while speaking. There can be shallow inhalations and reduced exhalation control. The sound stress might be explosive and loudness and pitch keep varying. There can also be irregular duration or same duration of pauses between words or sounds. Most of the time the sounds are excessively and equally stressed.

• Hyperkinetic Dysarthria

  • Hyperkinetic dysarthria is caused due to the damage in the basal ganglia which is responsible for voluntary motor movements, procedural learning and habit learning along with a few other functions. There is an abnormal muscle tone. According to ASHA, the other characteristics seen are slurred or slow speech, shaky voice or having tremors in voice, shortness of breath or tiredness while speaking, having muscle spasms and tremors and having an involuntary jerking or flailing movement. There can also be strained and strangled voice.

• Hypokinetic Dysarthria

  • In this, the lesion is in the other areas of the basal ganglia which are responsible for cognition and involuntary motor movements. A well-known disorder of hypokinetic dysarthria is Parkinson’s disease. Some characteristics seen are a quiet and monotonous speech, stuttered speech, trouble in initiating words, rigidity in the facial muscles, no variations in pitch and volume of speech and a faster speaking rate. There would also be cognitive impairments which affects the content of the speech as well. Resting tremors, that is, tremors when not moving are also observed. Tremors are also heard in voice especially when a sound is prolonged. Voice is low pitched and hoarse.

• Unilateral Upper Motor Neuron Dysarthria

  • This is the least severe type of dysarthria. The recovery rate is much quicker than the other types of dysarthria. Here, the damage is in a specific group of nerves called the upper motor neuron, which are responsible for movement. The symptoms are similar to spastic dysarthria but milder and only one side of the face is affected. Therefore, speech is more intelligible.

• Mixed dysarthria

  • It is the most common type of dysarthria. Here, the person has more than one type of dysarthria due to neurological damage in multiple areas of the brain. The symptoms therefore vary depending on each type.

Conclusion

Motor speech disorders affect speech and communication. Since they are of different types and severities, an assessment and a tailored treatment by a speech language pathologist is essential for maintaining communication.

To speak with 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.