Dysarthria
Encyclopedia
Dysarthria is a motor speech disorder
resulting from neurological injury
of the motor component of the motor-speech system and is characterized by poor articulation of phonemes (cf.
aphasia
: a disorder of the content of language). Any of the speech subsystems (respiration
, phonation
, resonance
, prosody
, and articulation
) can be affected, leading to impairments in intelligibility, audibility, naturalness, and efficiency of vocal communication.
Neurological injury due to damage in the central or peripheral nervous system may result in weakness, paralysis, or a lack of coordination of the motor-speech system, producing dysarthria. These effects in turn hinder control over the tongue, throat, lips or lungs for example; swallowing problems (dysphagia
) are also often present.
The term dysarthria does not include speech disorders from structural abnormalities, such as cleft palate, and must not be confused with apraxia
, which refers to problems in the planning and programming aspect of the motor-speech system.
Cranial nerves
that control these muscles include the trigeminal nerve
's motor branch (V), the facial nerve
(VII), the glossopharyngeal nerve
(IX), the vagus nerve
(X), and the hypoglossal nerve
(XII).
(resulting from bilateral damage to the upper motor neuron
), flaccid (resulting from bilateral or unilateral damage to the lower motor neuron
), ataxic (resulting from damage to cerebellum), unilateral upper motor neuron
(presenting milder symptoms than bilateral UMN damage), hyperkinetic and hypokinetic (resulting from damage to parts of the basal ganglia
, such as in Huntington's disease or Parkinsonism
), and the mixed dysarthrias (where symptoms of more than one type of dysarthria are present). The majority of dysarthric patients are diagnosed as having 'mixed' dysarthria, as neural damage resulting in dysarthria is rarely contained to one part of the nervous system — for example, multiple strokes, traumatic brain injury
, and some kinds of degenerative illnesses (such as amyotrophic lateral sclerosis
) usually damage many different sectors of the nervous system.
Dysarthria may affect a single system; however, it is more commonly reflected in multiple motor-speech systems. The etiology, degree of neuropathy, existence of co-morbidities, and the individual's response all play a role in the effect the disorder has on the individual's quality of life. Severity ranges from occasional articulation difficulties to verbal speech that is completely unintelligible.
Individuals with dysarthria may experience challenges in the following:
Examples of specific observations include a continuous breathy voice, irregular breakdown of articulation, monopitch, distorted vowels, word flow without pauses, and hypernasality.
, ALS
, Huntington's Disease, Niemann Pick disease, Ataxia
etc.), traumatic brain injury, or thrombotic or embolic stroke. These result in lesions to key areas of the brain involved in planning, executing, or regulating motor operations in skeletal muscles (i.e. muscles of the limbs), including muscles of the head and neck (dysfunction of which characterises dysarthria). These can result in dysfunction, or failure of: the motor or somatosensory cortex of the brain, corticobulbar pathways, the cerebellum, basal nuclei (consisting of the putamen, globus pallidus, caudate nucleus, substantia nigra etc.), brainstem (from which the cranial nerves originate), or the neuro-muscular junction (in diseases such as Myasthenia Gravis
) which block the nervous system's ability to activate motor units and effect correct range and strength of movements.
Causes:
, right hemisphere brain damage, etc.), intensity (loudness of the voice, affected e.g. in hypokinetic dysarthrias such as in Parkinson's), resonance (ability to alter the vocal tract and resonating spaces for correct speech sounds) and phonation (control of the vocal folds for appropriate voice quality and valving of the airway). These treatments have usually involved exercises to increase strength and control over articulator muscles (which may be flaccid and weak, or overly tight and difficult to move), and using alternate speaking techniques to increase speaker intelligibility (how well someone's speech is understood by peers).
More recent techniques based on the principles of motor learning (PML), such as LSVT (Lee Silverman Voice Treatment
) speech therapy and specifically LSVT may improve voice and speech function in PD. For Parkinson's, aim to retrain speech skills through building new generalised motor programs, and attach great importance to regular practice, through peer/partner support and self-management. Regularity of practice, and when to practice, are the main issues in PML treatments, as they may determine the likelihood of generalization of new motor skills, and therefore how effective a treatment is.
Augmentative and Alternative Communication
(AAC) devices that make coping with a dysarthria easier include speech synthesis
and text-based telephones. These allow people who are unintelligible, or may be in the later stages of a progressive illness, to continue to be able to communicate without the need for fully intelligible speech.
Motor speech disorders
Motor speech disorders are a class of speech disorder that disturb the body's natural ability to speak. These disturbances vary in their etiology based on the integrity and integration of cognitive, neuromuscular, and musculoskeletal activities...
resulting from neurological injury
Brain damage
"Brain damage" or "brain injury" is the destruction or degeneration of brain cells. Brain injuries occur due to a wide range of internal and external factors...
of the motor component of the motor-speech system and is characterized by poor articulation of phonemes (cf.
Cf.
cf., an abbreviation for the Latin word confer , literally meaning "bring together", is used to refer to other material or ideas which may provide similar or different information or arguments. It is mainly used in scholarly contexts, such as in academic or legal texts...
aphasia
Aphasia
Aphasia is an impairment of language ability. This class of language disorder ranges from having difficulty remembering words to being completely unable to speak, read, or write....
: a disorder of the content of language). Any of the speech subsystems (respiration
Respiratory system
The respiratory system is the anatomical system of an organism that introduces respiratory gases to the interior and performs gas exchange. In humans and other mammals, the anatomical features of the respiratory system include airways, lungs, and the respiratory muscles...
, phonation
Phonation
Phonation has slightly different meanings depending on the subfield of phonetics. Among some phoneticians, phonation is the process by which the vocal folds produce certain sounds through quasi-periodic vibration. This is the definition used among those who study laryngeal anatomy and physiology...
, resonance
Resonance
In physics, resonance is the tendency of a system to oscillate at a greater amplitude at some frequencies than at others. These are known as the system's resonant frequencies...
, prosody
Prosody (linguistics)
In linguistics, prosody is the rhythm, stress, and intonation of speech. Prosody may reflect various features of the speaker or the utterance: the emotional state of the speaker; the form of the utterance ; the presence of irony or sarcasm; emphasis, contrast, and focus; or other elements of...
, and articulation
Manner of articulation
In linguistics, manner of articulation describes how the tongue, lips, jaw, and other speech organs are involved in making a sound. Often the concept is only used for the production of consonants, even though the movement of the articulars will also greatly alter the resonant properties of the...
) can be affected, leading to impairments in intelligibility, audibility, naturalness, and efficiency of vocal communication.
Neurological injury due to damage in the central or peripheral nervous system may result in weakness, paralysis, or a lack of coordination of the motor-speech system, producing dysarthria. These effects in turn hinder control over the tongue, throat, lips or lungs for example; swallowing problems (dysphagia
Dysphagia
Dysphagia is the medical term for the symptom of difficulty in swallowing. Although classified under "symptoms and signs" in ICD-10, the term is sometimes used as a condition in its own right. Sufferers are sometimes unaware of their dysphagia....
) are also often present.
The term dysarthria does not include speech disorders from structural abnormalities, such as cleft palate, and must not be confused with apraxia
Apraxia
Apraxia is a disorder caused by damage to specific areas of the cerebrum. Apraxia is characterized by loss of the ability to execute or carry out learned purposeful movements, despite having the desire and the physical ability to perform the movements...
, which refers to problems in the planning and programming aspect of the motor-speech system.
Cranial nerves
Cranial nerves
Cranial nerves are nerves that emerge directly from the brain, in contrast to spinal nerves, which emerge from segments of the spinal cord. In humans, there are traditionally twelve pairs of cranial nerves...
that control these muscles include the trigeminal nerve
Trigeminal nerve
The trigeminal nerve contains both sensory and motor fibres. It is responsible for sensation in the face and certain motor functions such as biting, chewing, and swallowing. Sensory information from the face and body is processed by parallel pathways in the central nervous system...
's motor branch (V), the facial nerve
Facial nerve
The facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity...
(VII), the glossopharyngeal nerve
Glossopharyngeal nerve
The glossopharyngeal nerve is the ninth of twelve pairs of cranial nerves . It exits the brainstem out from the sides of the upper medulla, just rostral to the vagus nerve...
(IX), the vagus nerve
Vagus nerve
The vagus nerve , also called pneumogastric nerve or cranial nerve X, is the tenth of twelve paired cranial nerves...
(X), and the hypoglossal nerve
Hypoglossal nerve
The hypoglossal nerve is the twelfth cranial nerve , leading to the tongue. The nerve arises from the hypoglossal nucleus and emerges from the medulla oblongata in the preolivary sulcus separating the olive and the pyramid. It then passes through the hypoglossal canal...
(XII).
Classification
Dysarthrias are classified in multiple ways based on the presentation of symptoms. Specific dysarthrias include spasticSpastic
The word spastic is used differently depending on location which has led to some controversy and misunderstanding. Derived via Latin from the Greek spastikos , the word originally referred to a change in muscles affected by the medical condition spasticity, which is seen in spastic diplegia and...
(resulting from bilateral damage to the upper motor neuron
Upper motor neuron
Upper motor neurons are motor neurons that originate in the motor region of the cerebral cortex or the brain stem and carry motor information down to the final common pathway, that is, any motor neurons that are not directly responsible for stimulating the target muscle...
), flaccid (resulting from bilateral or unilateral damage to the lower motor neuron
Lower motor neuron
Lower motor neurons are the motor neurons connecting the brainstem and spinal cord to muscle fibers, bringing the nerve impulses from the upper motor neurons out to the muscles...
), ataxic (resulting from damage to cerebellum), unilateral upper motor neuron
Upper motor neuron
Upper motor neurons are motor neurons that originate in the motor region of the cerebral cortex or the brain stem and carry motor information down to the final common pathway, that is, any motor neurons that are not directly responsible for stimulating the target muscle...
(presenting milder symptoms than bilateral UMN damage), hyperkinetic and hypokinetic (resulting from damage to parts of the basal ganglia
Basal ganglia
The basal ganglia are a group of nuclei of varied origin in the brains of vertebrates that act as a cohesive functional unit. They are situated at the base of the forebrain and are strongly connected with the cerebral cortex, thalamus and other brain areas...
, such as in Huntington's disease or Parkinsonism
Parkinsonism
Parkinsonism is a neurological syndrome characterized by tremor, hypokinesia, rigidity, and postural instability. The underlying causes of parkinsonism are numerous, and diagnosis can be complex...
), and the mixed dysarthrias (where symptoms of more than one type of dysarthria are present). The majority of dysarthric patients are diagnosed as having 'mixed' dysarthria, as neural damage resulting in dysarthria is rarely contained to one part of the nervous system — for example, multiple strokes, traumatic brain injury
Traumatic brain injury
Traumatic brain injury , also known as intracranial injury, occurs when an external force traumatically injures the brain. TBI can be classified based on severity, mechanism , or other features...
, and some kinds of degenerative illnesses (such as amyotrophic lateral sclerosis
Amyotrophic lateral sclerosis
Amyotrophic lateral sclerosis , also referred to as Lou Gehrig's disease, is a form of motor neuron disease caused by the degeneration of upper and lower neurons, located in the ventral horn of the spinal cord and the cortical neurons that provide their efferent input...
) usually damage many different sectors of the nervous system.
Dysarthria may affect a single system; however, it is more commonly reflected in multiple motor-speech systems. The etiology, degree of neuropathy, existence of co-morbidities, and the individual's response all play a role in the effect the disorder has on the individual's quality of life. Severity ranges from occasional articulation difficulties to verbal speech that is completely unintelligible.
Individuals with dysarthria may experience challenges in the following:
- Timing
- Vocal quality
- Pitch
- Volume
- Breath control
- Speed
- Strength
- Steadiness
- Range
- Tone
Examples of specific observations include a continuous breathy voice, irregular breakdown of articulation, monopitch, distorted vowels, word flow without pauses, and hypernasality.
Causes
The causes of dysarthria can be many, including toxic, metabolic, degenerative diseases (such as ParkinsonismParkinsonism
Parkinsonism is a neurological syndrome characterized by tremor, hypokinesia, rigidity, and postural instability. The underlying causes of parkinsonism are numerous, and diagnosis can be complex...
, ALS
Amyotrophic lateral sclerosis
Amyotrophic lateral sclerosis , also referred to as Lou Gehrig's disease, is a form of motor neuron disease caused by the degeneration of upper and lower neurons, located in the ventral horn of the spinal cord and the cortical neurons that provide their efferent input...
, Huntington's Disease, Niemann Pick disease, Ataxia
Ataxia
Ataxia is a neurological sign and symptom that consists of gross lack of coordination of muscle movements. Ataxia is a non-specific clinical manifestation implying dysfunction of the parts of the nervous system that coordinate movement, such as the cerebellum...
etc.), traumatic brain injury, or thrombotic or embolic stroke. These result in lesions to key areas of the brain involved in planning, executing, or regulating motor operations in skeletal muscles (i.e. muscles of the limbs), including muscles of the head and neck (dysfunction of which characterises dysarthria). These can result in dysfunction, or failure of: the motor or somatosensory cortex of the brain, corticobulbar pathways, the cerebellum, basal nuclei (consisting of the putamen, globus pallidus, caudate nucleus, substantia nigra etc.), brainstem (from which the cranial nerves originate), or the neuro-muscular junction (in diseases such as Myasthenia Gravis
Myasthenia gravis
Myasthenia gravis is an autoimmune neuromuscular disease leading to fluctuating muscle weakness and fatiguability...
) which block the nervous system's ability to activate motor units and effect correct range and strength of movements.
Causes:
- Brain tumor
- Cerebral palsy
- Guillain-Barre syndrome
- Head injury
- Hypothermia
- Lyme disease
- Multiple sclerosis
- Parkinson's disease
- Wilson's disease
- Intercranial Hypertension (formerly known as Pseudotumor Cerebri)
- Tay-Sachs, and Late Onset Tay-Sachs (LOTS), disease
Treatment
Articulation problems resulting from dysarthria are treated by speech language pathologists, using a variety of techniques. Techniques used depend on the effect the dysarthria has on control of the articulators. Traditional treatments target the correction of deficits in rate (of articulation), prosody (appropriate emphasis and inflection, affected e.g. by apraxia of speechApraxia of speech
Apraxia of Speech is a motor speech disorder affecting an individual's ability to translate conscious speech plans into motor plans and is caused by illness or injury in adults. Like other apraxias, it only affects volitional movement patterns...
, right hemisphere brain damage, etc.), intensity (loudness of the voice, affected e.g. in hypokinetic dysarthrias such as in Parkinson's), resonance (ability to alter the vocal tract and resonating spaces for correct speech sounds) and phonation (control of the vocal folds for appropriate voice quality and valving of the airway). These treatments have usually involved exercises to increase strength and control over articulator muscles (which may be flaccid and weak, or overly tight and difficult to move), and using alternate speaking techniques to increase speaker intelligibility (how well someone's speech is understood by peers).
More recent techniques based on the principles of motor learning (PML), such as LSVT (Lee Silverman Voice Treatment
Lee Silverman voice treatment
The Lee Silverman voice treatment is one of the most widely practiced treatment for speech disorders associated with Parkinson's disease . It focuses on increasing vocal loudness and has an intensive approach of one month. Speech therapy and specifically LSVT may improve voice and speech function...
) speech therapy and specifically LSVT may improve voice and speech function in PD. For Parkinson's, aim to retrain speech skills through building new generalised motor programs, and attach great importance to regular practice, through peer/partner support and self-management. Regularity of practice, and when to practice, are the main issues in PML treatments, as they may determine the likelihood of generalization of new motor skills, and therefore how effective a treatment is.
Augmentative and Alternative Communication
Augmentative and alternative communication
Augmentative and alternative communication is an umbrella term that encompasses the communication methods used to supplement or replace speech or writing for those with impairments in the production or comprehension of spoken or written language...
(AAC) devices that make coping with a dysarthria easier include speech synthesis
Speech synthesis
Speech synthesis is the artificial production of human speech. A computer system used for this purpose is called a speech synthesizer, and can be implemented in software or hardware...
and text-based telephones. These allow people who are unintelligible, or may be in the later stages of a progressive illness, to continue to be able to communicate without the need for fully intelligible speech.