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CHAPTER 8
Chapter Overview
Hypokinetic dysarthria is caused by any process that damages the basal ganglia
(extrapyramidal system). It is manifested in any or all of the respiratory, phonatory,
resonatory, and articulatory levels of speech, being most evident in voice, articulation,
and prosody. Speech characteristics reflect rigidity, reduced force and range of
movement, and slow but sometimes fast repetitive movements of speech. It is unique in
that it is the only dysarthria in which increased rate of speech may be one of the
symptoms, and it is the only dysarthria in which the vast majority of cases share the
same causative factor, parkinsonism. Hypokinetic means “less motion” and is often
confused with hypotonia, which means decreased muscle tone. Patients with
parkinsonism often have increased muscle tone. Characteristics of parkinsonism include
a distinctive collection of symptoms, including resting tremor, bradykinesia, rigidity,
spasticity, akinesia, and disturbances of postural reflexes. Parkinsonism is caused by
dysfunction of the basal ganglia, which includes the caudate nucleus, globus pallidus,
and the putamen. The caudate nucleus and putamen are made of many of the same
types of neurons, are functionally related, and together are known as the striatum. To
function properly the basal ganglia depend on the balanced interaction of several
Causes of hypokinetic dysarthria include idiopathic Parkinson’s disease, neuroleptic-
induced parkinsonism, postencephalitic parkinsonism, traumatic head injury, toxic metal
poisoning, and stroke. Speech characteristics of hypokinetic dysarthria are usually quite
distinctive, with errors of prosody and articulation being the most noticeable. The
individual may give the impression that the sequencing and placement of their
articulatory movements are fairly accurate but range is greatly restricted. It may seem
that their speech movements are compressed and abbreviated. Most speech
characteristics are a result of bradykinesia, akinesia, and muscle rigidity, with tremulous
tumors noted in severe cases. Errors of prosody involve monopitch, reduced stress, and
monoloudness as the most prominent, with inappropriate silences, increased rate, and
short rushes of speech also noted. Articulation is characterized by imprecise consonants,
repeated phonemes, and palilalia.
Motor Speech Disorders, Second Edition
ii
Phonatory errors include harsh or breathy voice quality, aphonia, and low pitch.
Respiration difficulties are noted in some patients, including breathing rates that are
faster than normal or paradoxical movements of the muscles of exhalation and
inhalation. Most individuals will not have significant deficits of resonance, but mild
hypernasality may be noted in some cases.
Key evaluation tasks for hypokinetic dysarthria include conversational speech and
reading, speech alternate motion rates, and vowel prolongations. Treatments can be
divided into three categories – pharmacologic, surgical, and behavioral. Pharmacologic
treatments include replacing dopamine in the striatum with use of L-dopa treatments or
decreasing the amount of acetylcholine activity in the striatum with anticholinergic drugs.
The effectiveness of these treatments is well established; however, minor to quite
serious side effects can result. Surgical treatments involve ablative procedures
(thalamotomy and pallidotomy) or deep brain stimulation. Ablative procedures are not
used frequently in modern days. Stem-cell implantation research has been conducted,
Study Questions and Answers
1. Define hypokinetic dysarthria in your own words.
2. What are the characteristic symptoms of parkinsonism?
3. Describe how the substantia nigra and the striatum are involved in the
cause of parkinsonism.
4. What is L-dopa?
5. What can be the adverse side effects of L-dopa treatment?
6. What is postencephalitic parkinsonism?
7. About what percentage of individuals with idiopathic Parkinson’s disease
eventually have dementia?
8. What is the most common phonation deficit in individuals with hypokinetic
dysarthria?
9. Describe two rate control treatment tasks for individuals with increased rate
of speech.
10. Describe two treatment tasks for reducing the harsh or breathy vocal quality
that is so common in hypokinetic dysarthria.
