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Dysarthria
DIAGNOSIS OF DYSARTHRIA
Dysarthria- A motor speech disorder that results from abnormalities in speed, strength, range, steadiness, tone, or accuracy of movements. It can affect the control of the respiratory, phonatory, resonatory, articulatory, and prosodic aspects of speech production. Central or peripheral nervous system abnormalities are responsible for the deficits. The most frequent results are weakness, spasicity, involuntary movements, incoordination or excessive, reduced and variable muscle tone.
Types of Dysarthria
FLACCID DYSARTHRIA-
Produced by injury to the lower motor neurons (cranial nerves) involved in speech. The effects depend upon which cranial nerves are damaged. See Cranial Nerve Exam to determine how to test if the cranial nerves are intact or damaged.
Nonspeech characteristics- Weakness and faciculations may be present.
Nonspeech Oral Mechanism
This may reveal lesions of cranial nerves V, VII, IX, X, XI, and XII. All or some of these nerves can be affected. The affects depend on which nerves are affected.
Speech affects:
Trigeminal Nerve (V) Lesion- This is rarely the only cranial nerve involved in flaccid dysarthria. The effects on speech can be seen during conversation, reading and alternate motion rates (AMRS). AMRs include repetition of /pa/, /ta/, /ka/, and /pataka/. Slowness for /pa/ would be greather than /ta/ or /ka/. A bilaterally weak jaw can produce difficult with bilabials, labiodental, lingualdental, lingual alveolar articulation as well as some glides and liquids. Speech may also be slowed.
Facial nerve (VII) Lesion- Poor biabial closure can occur so that AMRs are mismatched for /pa/, /ta/, and /ka/ with slowness for /pa/. Distortions may occur on bilabials (/p/, /m/, /b/) as well as /w/,/f/, and /v/.
Glossopharyngeal Nerve ( IX) Lesion- This nerve is rarely damaged in isolation due to the close proximity with the vagus nerve (X). Speech deficits are associated more with cranial nerve X.
Vagus Nerve ( X) Lesion- Unilateral pharyngeal branch lesion leads to mild to moderate hypernasality and nasal emission during pressure consonants. Hypernasality can be severe if weakness is bilateral.
Speech may be breathy, hoarse, reduced in loudess, have diplophonia, reduced pitch or pitch breaks if the lesion is below the pharyngeal branch but including the superior and recurrent laryngeal branches.
There can be an inability to alter pitch if the superior laryngeal nerve is damaged, sparing the pharygeal and recurrent laryngeal nerves.
Unilateral recurrent larngeal nerve lesions that spare the superior laryngeal nerve and pharyngeal branch cause a breathy-hoarse vocal quality, decreased loudness and sometimes diplophonia and pitch breaks. Bilateral wakness or paralysis causes inhalatory stridor.
Accessory Nerve Lesions- Respiration, phonation and resonance can be indirectly affeted.
Hypoglossal Nerve (XII) Lesion- The most apparent speech characteristic is imprecise articulation. Difficulty with the tip or back of the tongue may occur with bilateral lingual weakness. The phonemes most disrupted are “s”, “sh”, “ch”, “r”, and “l”. Velars (/d/, /t/) can also be difficult to produce. For AMRs /pa/ should be normal, while /ta/ and /ka/ would be imprecise and slow.
SPASTIC DYSARTHRIA-
The is produced by upper motor neuron lesions with amage to the direct activation pathway. Damage leads to increased tone and spasticity. Reflexes are diminished at first and then hyperactive. This dysarthria is not described by listing the cranial nerves and characteristics associated with their abnormal function. Spastic dysarthria is associated with impaired movement patterns, not weakness to individual muscles. It is usually associated with all components of the speech system.
Non speech Oral Mechanism:
Dysphagia and drooling are common. At rest the nasolabial folds may be smoothed or flattened. The face can be weak bilaterally. The tongue is usually symmetric, but range of motion and strength can be weak. AMRs are often slow and reduced range of motion. However, AMRs are generally in rhythm. The palate is usually symmetric, but may move slwly or minimally on phonation. Jaw strength is normal. Frequently, there is pseudobulbar affect which is excessive laughing or crying with no apparent reason.
Speech Affects:
The main characteristics are slowness, reduced range of movement, and excessive muscle tone or spasticity. Speech can consist of excess and equal stress and slow rate. Imprecise consonants, distorted vowels, and hypernasality are common. Also monopitch, monoloudness, reduced stress, and short phrases can occur. Furthermore low pitch, harshness, strained-strangled voice, and pitch breaks are characteristic.
ATAXIC DYSARTHRIA-
The is associated with damage to the cerebellar circut, which controls smooth movement and coordination. Damage leads to incoordination and reduced muscle tone. It can affect the respiratory, phonatory, resonatory and articualtion levels of speech, but it’s most evident in articulation and prosody. It is typically a bilateral or generalized cerebelar lesion.
Nonspeech chacteristics- Difficulty standing and walking are common and stance is usually broad based. Hypotonia can also occur. Dysmetria is also common. This is the inability to control range of motion such as overshooting or undershooting targets.
Nonspeech Oral Mechanism
Examination of the oral mechanism is often normal in ataxic dysarthria. Nonspeech AMRs of the tongue, jaw, and lips may often be irregular
Speech Affects:
Speech AMRs are abnormal in rate, rhythm and precision. Irregular AMRs are a distinctive feature of ataxic dysarthria. The individual muscles are not necessarily affected. The difficulty is in coordination of movement patterns.
Characteristics include irregular articulatory breakdowns, vowel distortions, excess and equal stress on all syllables and words. Also characteristic is prolonged phonemes, prolonged intervals, slow rate, hashness, monopitch, and monoloudness.
Voice tremors, abnormal resonance, intermittent hyponasality, and explosive loudness may also occur but are less common.
Speech is especially slurred and patients may report that they sound like they have been drinking.
HYPOKINETIC DYSARTHRIA
A lesion to the basal ganglia can result in hypokinetic dysarthria. Damage results in failure to inhibit involunary movement (“too little movement”). Voice, articulation and prosody are most affected. Parkinson’s Disease is the prototype, but not the only disease associated with hypokinetic dysarthria.
Nonspeech characteristics- Cogwheel rigidity is frequent in which there is resistance of the limbs to passive stretch whiich has a jerky character. There may also be a resting tremor, rigidity, bradykinesia (delays or false starts at the beginning of movement), and a loss of postural reflexes.
Nonspeech oral mechanism- expressionless face (“masked”), infrequent blinking and swallowing, tremor of the jaw or lips, and slowly initiated AMRs of the jaw, lips and tongue.
Speech Affects:
Rapid, accelerated, and sometimes blurred speech AMRs are distinctive. Range and force of movements are reduced.Voice is hoarse, rough, tremulous and/or breathy. Some individuals also have syllable repetitions, shortened syllables, and excessive pauses.
Characteristics also include monopitch and monoloudness. Pallilalia, or the compulsive repetition of syllables, is sometimes present. Many individuals also have low vocal volume.
Respiratory deficiency is also frequent and can affect speech. The individual may have reduced vital capacity or irregular breathing patterns. he individual may also be unable to produce speech at the beginning of exhalation, reducing the amount of speech the individual is able to produce.
HYPERKINETIC DYSARTHRIA
This is from a lesion to the basal ganglia as well. It is primarily associated with involuntary movement (“too much movement”) and it may be unilateral or bilateral damage.
Nonspeech characteristics-Abnormal involuntary movement that can occur at rest, static postures, or voluntary movement.
Dyskinesia- a general term for anormal involuntary movements
Orofacial dyskinesias- involuntary orofacial movements
Akathisia- inner sense of restlessness that manifests as an inability to sit still
Myoclonus- brief, involuntary twitching of a muscle or group of muscles
Tics- a sudden, repetitive, stereotyped motor movement involving discrete muscle groups
Chorea- Involuntary rapid, nonstereotypic, random, purposeless movement. It is seen in Huntington’s chorea.
Ballismus- an involuntary movement of the proximal limb musculature, manifested in jerking, flinging movement of the extremity.
Athetosis- Slow, purposeless movemnts that flow into one another
Dystonia- sustained muscle contractions cause twisting adn repetivie movements or abnormal postures
Spasm- a general description for muscle spasms; tonic spasms are prolonged and continuous; clonic spasms are repetitive, rapid in onset, and brief in duration.
Tremor- an unintentional, rythmic muscle movement involving movements of one or more parts of the body.
Speech Affects:
Voice can be harsh, strained or strangled and excess loudness variations. Voice stoppages associated with dystonia can occur. Irregular articulatory breakdown and hypernasality are common.
MIXED DYSARTHRIA
Mixed dysarthrias are common. The characteristics depend on whether the upper or lower motor neurons remain most intact. For example, if the upper motor neurons remain intact initially, the voice will sound harsh. However, if the lower motor neurons are more affected than the voice may sound breathy. It can result from more than one neurologic events or the occurance of two or more diseases such as a stroke and Parkinson’s Disease.
Amyotropic Lateral Sclerosis is a degenerative disease that results in a mixed dysarthria. There are both upper and lower motor neuron signs and thus is classically associated with mixed spastic-flaccid dysarthria.
Go to our dysarthria treatment page for information on improving speech for patients with dysarthria.
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