By Paul Blanchet, Ph.D., CCC-SLP, Department of Communication Disorders & Sciences, State University of New York at Fredonia
blanchet@fredonia.edu
Parkinson’s disease (PD) is a degenerative disorder of the brain affecting control of movement. This disease occurs in approximately one percent of the U.S. population over 50 years of age, with approximately 40,000 new cases reported each year. The incidence of Parkinson’s disease increases sharply after 64 years of age, as the peak of incidence is 75-84 years of age1. Parkinson’s disease is often divided into subgroups based on the causes and associated symptoms. The term “idiopathic” or “primary” Parkinson’s disease is generally used when the cause of the disease cannot be identified. “Secondary parkinsonism” includes a number of disorders with “parkinsonian” features which have an identifiable cause, such as toxicity, infections, certain drugs, traumatic brain injury, or cerebral vascular accidents (i.e., strokes). “Parkinsonism-plus” syndromes are conditions that include symptoms of PD as part of the clinical profile, such as progressive supranuclear palsy.
The motor (i.e., movement) symptoms present in PD result from a loss of dopamine-producing neurons in areas of the brain such as the basal ganglia, substantia nigra, and brainstem. In some cases, dopamine content has been found at autopsy to be one tenth of normal levels2. The basal ganglia, through connections with other areas of the brain, are believed to influence the direction, speed, and force of voluntary movements. This, of course, would include speech, which can be thought of as “movement made audible!”
A neurologist’s diagnosis of Parkinson’s disease is usually based on the presence of tremor (especially of the hands), muscle rigidity, akinesia (i.e., lack of movement), and postural instability. The acronym TRAP (Tremor, Rigidity, Akinesia, and Postural Instability) is often used as a mnemonic for the motor symptoms of Parkinson’s disease. Bradykinesia, a less extreme form of akinesia, refers to slowness of volitional movements. Other signs of Parkinson’s disease include stooped posture, reduced arm swing, micrographia (i.e., small hand writing), and masked facial expression. This type of facial expression results from rigidity of the facial muscles, although these patients are sometimes mischaracterized as “angry’ or “depressed.” In addition, approximately 15% of all Parkinson’s disease patients meet the criteria for dementia3. This usually occurs during the latter stages of the disease.
It has been estimated that 60-80% of PD patients will develop speech deficits as the disease progresses4, although a relatively small percentage of these individuals receive speech services. Communication disorders often begin with reduced loudness and progress to more severe functional limitations characterized by changes in speech rate, articulatory precision (i.e., how clearly sounds and words are pronounced), and intelligibility. Individuals with Parkinson’s disease often exhibit dysarthria, which actually refers to a group of speech disorders usually resulting from neurological damage (e.g., degenerative diseases, stroke, traumatic brain injury, etc.). Dysarthria is typically characterized by some degree of weakness, slowness, incoordination, or change in the tone of the speech muscles.
The perceptual features of the type of dysarthria usually exhibited by PD patients (i.e., hypokinetic dysarthria) may include reduced vocal loudness, difficulty changing their vocal pitch and/or loudness, fast or fluctuating speech rate, short rushes of speech, and imprecise consonant articulation (i.e., pronunciation). Inappropriate or excessively long pauses may result from bradykinesia. These speech rate difficulties are a distinctive feature of hypokinetic dysarthria. Syllables are often rapid or accelerated, and some PD patients report that their speech sounds “jumbled” or that they are “stuttering.” As a speech-language pathologist who does stutter, I must say that I have observed “stutter-like” disfluencies in many speakers with PD, in addition to low loudness levels. These two aspects of speech are often addressed in speech therapy with PD patients, which often results in significant improvements in the communicative functioning of these individuals.
REFERENCES
- Yorkston, K. M., Beukelman, D. R., Strand, E. A., & Bell, K. R. (2000). Management of motor speech disorders in children and adults (2nd ed.). Austin, TX: Pro-Ed.
- Darley, F. L., Aronson, A. E., & Brown, J. R. (1975). Motor speech disorders. Philadelphia: W. B. Saunders, Co.
- Levin, B. E., Tomer, R., & Rey, G. J. (1992). Cognitive impairments in Parkinson’s disease. Neurologic Clinics, 10 (2), 471-481.
- Adams, S. G. (1994). Accelerating speech in a case of hypokinetic dysarthria: Descriptions and treatment. In J. Till, K. Yorkston, & D. Beukelman (Eds.), Motor speech disorders: Advances in assessment and treatment (pp. 213-228). Baltimore: Paul H. Brookes Publishing Co.
Paul Blanchet is an Assistant Professor in the Department of Communication Disorders and Sciences at SUNY Fredonia. He earned his B.A. from SUNY Fredonia, his M.S. from Northeast Louisiana University, and his Ph.D. from Louisiana State University. Dr. Blanchet’s primary interests are neurogenic speech disorders and fluency disorders, being as person who stutters himself.