Robert Blue

Journal of Undergraduate Research
Volume 2, Issue 6 - March 2001

Struggling to Speak: An Overview of Parkinsonian Speech

INTRODUCTION

Symptoms of Parkinson's Disease

Parkinson's disease; idiopathic parkinsonism; paralysis agitans: three names for an incurable degenerative disorder first described in 1817 by the man whose name it bears. When James Parkinson first wrote his "Essay on the Shaking Palsy", he probably would have never guessed that as far as extrinsic characteristics of Parkinsonism are concerned, he had already observed most of what would be known about it for the next two centuries. Although strides are being made to understand its basis, it is not currently know how the disease is contracted.

As discovered by James Parkinson, there is a triad of defining symptoms: rigidity, tremor, and bradykinesia. The ratchet rigidity of Parkinsonism means that there is a resistance to passive movement. Technically not a symptom but an objective sign of the disease that can be observed by someone giving an examination, this resistance is also known as cogwheel rigidity (Duvoisin, 23). A patient suffering from this condition may have muscles that are in a constant state of flex even when they should be relaxed while not in use.

Commonly thought of as the defining characteristic, tremor apparently does not appear in up to 25% of Parkinsonian patients (PDF-Symptoms). This resting tremor occurs in various places over the body and typically occurs when a muscle is at rest. It is often called a "pill-rolling" tremor because when affecting the hand, the patient appears to be rolling an invisible pill (Duvoisin, 21).

Bradykinesia, or slowness of movement, is the third symptom found in Parkinsonian patients. Bradykinesia is not a secondary symptom of rigidity: the limbs most affected by rigidity may still move freely. Parkinsonian bradykinesia is often characterized by a difficulty in initiating movements (PDF-Symptoms), but may include a slowness to perform fine motor movements and trouble with repetitive movements (Parkinson Glossary).

This triad of symptoms is what is mostly used to diagnose Parkinsonism, but beyond rigidity, tremor, and bradykinesia, there are a number of secondary symptoms potentially occurring with Parkinsonism. Some of these symptoms include poor balance, problems walking, constipation, and many others.

Models for the Neurological Basis of Parkinsonism

Presented here is a model currently used to explain the rigidity of Parkinsonism. Although it is incomplete for modeling tremor, it is sufficient for speech production because tremor is only present at rest. For people not suffering from Parkinson's disease, the cortex develops a plan for movement, sending an excitatory signal to the striatum (the caudate nucleus and the putamen). In turn, the striatum sends an inhibitory message to the globus palladus, which inhibits the subthalamic nucleus. This sends an excitatory message both back to the substantia nigra and to the globus palladus, which then inhibits the thalamus, also inhibited by the substantia nigra. The cortex is then stimulated by the thalamus, and it is then free to send the motor program into action. The substantia nigra also produces dopamine, which is both excitatory and inhibitory for the striatum and apparently controls the inhibition of the subthalamic nucleus through the globus palladus (Huber, 11 - 12).

Figure 1. Current model for the rigidity of Parkinsonism.

However, Parkinsonism results from a breakdown of the substantia nigra (Duvoisin, 2). It appears that the pigment neromelanin is useful in the production of dopamine. The implication of this is that the inhibition of the striatum on the globus palladus is no longer controlled and we ultimately have ratchet rigidity due to over-inhibition of the thalamus by the subthalamic nuclei.

Research on General Language Concerns

Turning now to the recent research in the field, we see certain trends, the first of which is the number of papers dealing generally with language. From these papers, we learn a number of things regarding aspects of language for the Parkinsonian patient.

The most frequent vocal tract disorders found in patients with Parkinson's Disease include breathiness, hoarseness, roughness, and tremulousness, occurring in approximately 89% of Parkinsonian patients (Longemann et al, 1978). Fourty-nine percent of the patients also suffered from lingual and labial articulatory disorders. In another study, similar results show that 89.5% of the patients tested were perceived to have some form of laryngeal dysfunction (Murdoch et al, 1997). This study went a step beyond considering the group entirely homogeneous and came up with four subgroups of patients. One subgroup had breathy speech, but few other characteristics, whereas another had this same quality along with a higher pitch of voice and a lower volume. A third group had a reduced speech volume with little else detectable. Yet another group had very little detectably wrong.

Another study found Parkinsonian patients to have smaller rib cage volume, but larger abdominal volume than their healthy counterparts (Hertrich & Ackermann, 1993). These patients also produced fewer words per breath than their healthy counterparts. Not only is the breathing rate per word higher, but there is also a phenomenon of increased silent hesitation time (Illes et al, 1988). Parkinsonian patients also include fewer interjections and modalizations than non-Parkinsonian subjects. Long-duration silent hesitations and prevalant open class phrases in Parkinsonian speech were also found (Illes et al, 1989).

Other research that has been done on general research includes work done regarding the change of speech after neurosurgery. Language change regarding higher language functions was found to be most prevalent in left or multiple thalamotomy and mixed procedures (Darley et al, 1975).

Articulatory Concerns

Moving beyond the general language features, a number of papers have been written regarding articulation problems. When repeating syllables beyond about three cycles per second, Parkinsonian patients do not displace their lips as widely as people not suffering from Parkinsonism (Ackermann et al, 1993). From the same study it was found that Parkinsonian patients perform articulation tasks at six hertz that non-Parkinsonian subjects can do at eight. Apparently, below approximately five hertz, Parkinsonian patients perform normally, but at faster rates, the displacement of the lips is smaller than normal (Caligiuri, 1989).

Other papers dealing with articulation included tests of movement or control of digit or orofacial movements. Parkinsonian patients produce significantly smaller lip movements for stressed syllables (Forrest & Weismer, 1995). It has also been found that Parkinsonian subjects demonstrate smaller peak rate of force change than controls (Gentil et al, 1999). As far as syllable repetition rates and forefinger tapping rates are concerned, they are significantly slower for Parkinsonian patients (Gurd et al, 1998).

We must ask the question, however, if these differences are truly far off from non-Parkinsonian speech. As far as reaction time, sentence duration, and syllable repetition rate are concerned, Parkinsonian subjects may be slightly off from "normal", but they are not as far as people suffering from Huntington's disease (Ludlow et al, 1987). Apparently, Parkinsonian subjects usually have at most very mild dysarthria (Svensson et al, 1993)&endash; they differ only slightly from normal in production of sequences of homogeneous and heterogeneous syllables (Ho et al, 1998).

Parkinsonism and Prosody

Prosody, the melodic qualities of speech, has also been characterized for the Parkinsonian patient. The two major deficiencies in prosody lie with pitch measures and pause measures (Darkins, Fromkin, and Benson). It appears to be the variation in pitch of single words such as distinctions between noun and verb homophony. However, we must also question just how different these are from "normal". A study by Hertrich and Ackermann comparing Parkinsonism to Huntington's Disease concluded that Parkinsonian patients were not as far off as the Huntington's group on measures of pitch or strength of accent.

Another major characteristic of Parkinsonian prosody is a diminished speech volume. Fox and Ramig found that the speech of Parkinsonian patients is approximately 2.00 - 4.00 dB SPL less than average for non-Parkinsonian subjects. Another study by Ho et al shows that although these patients are not able to automatically correct for volume when background noise is present, they can produce louder speech when directly asked to do so (1999).

Other Research on Parkinsonian Speech

Although most of the papers on Parkinsonian speech can be summed up in these categories, there is some research being done outside of these realms. One such study conducted by Lieberman et al found that voice onset time (VOT) was highly correlated with deficits in syntax comprehension. Another study by McNamara et al found that Parkinsonian subjects produced fewer words on average than normal, but make few errors while correcting only twenty-five percent of these.

One paper brought forth a theme relating to volume regulation&endash;specifically, it discussed a sensory speech disorder. Scott, Caird, and Williams concluded in this study that Parkinsonian subjects were less able to appreciate tone and facial expression. Although further study would be required to verify this, it does appear from this study that Parkinsonian patients may have trouble producing and responding to both facial and verbal prosody.

CONCLUSION

The three major trends in Parkinsonian research include the study of general language concerns, of articulation concerns, and of prosodic concerns. This is probably due to how the motor impairments affect the speech of a person suffering from Parkinsonism. We see from the research that there is little cognitive impairment of these patients, but a distinct trouble communicating.

Although research on this elusive disease is far from being complete, we can definitely see some potential avenues for future research inherent in these papers. Specifically, the study of perception problems of patients with Parkinsonism is one possible area of continuation of research. Many researchers have prematurely ruled this possibility out before searching for other causes. Whatever research is done in the future, it can be guaranteed that research will be performed and knowledge will be gained.

REFERENCES

Ackermann, H, Konczak, J, & Hertrich, I. (1997). The Temporal Control of Repetitive Articulatory Movements in Parkinson's disease. Brain and Language, 56(2).

Caligiuri, MP. (1989). The Influence of Speaking Rate on Articulatory Hypokinesia in Parkinsonian Dysarthria. Brain and Language, 36(3).

Darkins, AW, Fromkin, VA, & Benson, DF. (1988). A Characterization of the Prosodic Loss in Parkinson's Disease. Brain and Language, 34(2).

Darley, FL, Brown, JR, & Swesnon, WM. (1975). Language Changes after Neurosurgery for Parkinsonism. Brain and Language, 2(1).

Duvoisin, RC, & Sage, J. (1996). Parkinson's Disease: a Guide For Patient and Family. (4th ed). Philadelphia, PA: Lippincott-Raven Publishers.

Forrest, K, & Weismer, G. (1995). Dynamic Aspects of Lower Lip Movement in Parkinsonian and Neurologically Normal Geriatric Speakers' Production of Stress. Journal of Speech, Language, and Hearing Research, 38.

Fox, CM, & Ramig, LO. (1997). Vocal Sound Pressure Level and Self-Perception of Speech and Voice in Men and Women with Idiopathic Parkinson Disease. American Journal of Speech-Language Pathology, 6(2).

Gentil, M, Perrin, S, Tournier, C, & Pollak, P. (1999). Lip, tongue and forefinger force control in Parkinson's disease. Clinical Linguistics and Phonetics, 13(1).

Gurd, JM, Bessell, N, Watson, I, & Coleman, J. (1998). Motor speech versus digit control in Parkinson's disease: a cognitive neuropsychology investigation. Clinical Linguistics and Phonetics, 12(5).

Hertrich, I, & Ackermann, H. (1993). Acoustic analysis of speech prosody in Huntington's and Parkinson's disease: a preliminary report. Clinical Linguistics and Phonetics, 7(4).

Ho, AK, Bradshaw, JL, Cunnington, R, Phillips, JG, & Iansek, R. (1998). Sequence Heterogeneity in Parkinsonian Speech. Brain and Language, 64(1).

Ho, AK, Bradshaw, JL, Iansek, R, & Alfredson, R. (1999). Speech volume regulation in Parkinson's disease: effects of implicit cues and explicit instructions. Neuropsychologia, 37(13).

Huber, SJ, & Cummings, JL. (1992). Parkinson's Disease: Neurobehavioral Aspects. New York, NY: Oxford University Press, Inc.

Illes, J, Metter, EJ, Hanson, WR, & Iritani, S. (1988). Language Production in Parkinson's Disease: Acoustic and Linguistic Considerations. Brain and Language, 33(1).

Illes, J. (1989). Neurolinguistic Features of Spontaneous Language Production Dissociate Three Forms of Neurodegenerative Disease: Alzheimer's, Huntington's, and Parkinson's. Brain and Language, 37(3).

Lieberman, P, Kako, E, Friedman, J, Tajchman, G, Feldman, LS, & Jiminez, EB. (1992). Speech Production, Syntax Comprehension, and Cognitive Deficits in Parkinson's Disease. Brain and Language, 43(2).

Logemann, JA, Fisher, HB, Boshes, B, & Blonsky, ER. (1978). Frequency and cooccurrence of vocal tract dysfunctions in the speech of a large sample of Parkinson patients. Journal of speech and hearing disorders, 43.

Ludlow, CL, Connor, NP, & Bassich, CJ. (1987). Speech Timing in Parkinson's and Huntington's Disease. Brain and Language, 32(2).

McNamara, P, Obler, LK, Au, R, Durso, R, & Albert, ML. (1992). Speech Monitoring Skills in Alzheimer's Disease, Parkinson's Disease, and Normal Aging. Brain and Language, 42(1).

Murdoch, BE, Manning, CY, Theodoros, DG, & Thompson, EC. (1997). Laryngeal and phonatory dysfunction in Parkinson's disease. Clinical Linguistics and Phonetics, 11(3).

A Parkinson Glossary. http://www.chebucto.ns.ca/Health/NSPF/glossary.html.

PDF--Symptoms. http://www.pdf.org/aboutdisease/overview/symptoms.html.

Scott, S, Caird, F, & Williams, B. (1984). Evidence for an apparent sensory speech disorder in Parkinson's disease. Journal of Neurology, Neurosurgery, and Psychiatry, 47.

Solomon, NP, & Hixton, TJ. (1993). Speech Breathing in Parkinson's Disease. Journal of Speech, Language, and Hearing Research, 36.

Svensson, P, Henningson, C, & Karlsson, S. (1993). Speech motor control in Parkinson's disease: a comparison between a clinical assessment protocol and a quantitative analysis of mandibular movements. Folia Phoniatrica, 45(4).

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