Communication difficulties are caused by motor and/or cognitive impairment in people with Parkinson’s disease, a review study highlights.
An interdisciplinary approach to assess changes in patients’ daily communications may help detect and monitor motor and cognitive symptoms in this population.
The review, “Communication impairment in Parkinson’s disease: Impact of motor and cognitive symptoms on speech and language,” was published in the journal Brain and Language.
While the clinical diagnosis of Parkinson’s disease is based on the presence of characteristic motor symptoms like tremor, slowness of movement, and rigidity, cognitive impairment is a significant non-motor symptom of the disease.
Up to 90 percent of all Parkinson’s patients have impaired communication, which may develop in the early or late stages of the disease. These deficits have a great impact in patients’ quality of life and can lead to social isolation and depression.
Communication deficits in Parkinson’s patients include changes in voice and speech acoustics, comprehension and production of language, verbal fluency, the use of action verbs, and speech pauses. These deficits have the potential to be used as linguistic biomarkers of the disease.
However, the contribution of motor and cognitive deficits toward impairment in each of those areas of communication, along with the appropriate tools to assess them, are still unclear.
Researchers conducted a PubMed database search using the terms “Parkinson’s” and “language,” “speech,” “acoustics,” “voice,” “pause,” and “communication.” All studies that met the team’s criteria were reviewed to evaluate the relative roles of motor and cognitive impairment in Parkinson’s communication impairment.
Changes in voice and speech acoustic, such as decreased loudness, monotone speech, and impaired articulation, appear to be associated with motor impairment, including slowness and rigidity of the vocal apparatus.
Linguistic deficits, such as production and comprehension of complex grammar and syntax language, are more likely to be caused by cognitive impairment than motor dysfunction. Also, studies have shown that language processing is associated with attention and executive function and working memory.
However, the frequency of those deficits in Parkinson’s patients without dementia is still unclear, and no well-established tools to measure patients’ grammatical complexity are available. Thus, future development of objective measures may help identify these deficits and determine whether they occur early in the disease to make them useful markers.
While verbal fluency is one of the most tested communication skills in Parkinson’s patients, so far results have not been consistent, suggesting that verbal fluency may be “a less sensitive marker of language impairment in [Parkinson’s disease], or that other confounders need to be examined,” researchers wrote.
Parkinson’s patients show consistent difficulties in using action verbs, which appear to be more associated with motor dysfunction than with cognitive deficits. One of the possible explanations for this deficit is that the process of storing the meaning of a word that describes an action uses the same brain regions as the process of learning and executing actions, which also is impaired in these patients.
“…action verb deficits could thus be contrasted with grammar and syntax deficits (i.e. markers of cognitive function), to develop symptom-specific linguistic markers for improved disease monitoring,” researchers wrote.
The authors also found that the increased frequency of speech pauses in Parkinson’s patients is likely to be affected by both motor and cognitive impairment. Because it also is increased in other neurodegenerative diseases, further research is necessary to identify Parkinson’s-specific pausing patterns and develop appropriate assessment tools.
Parkinson’s patients also may have subtle comprehension and processing deficits of non-verbal and emotional aspects of communication, such as difficulties in recognizing affective tones in speech and/or emotional faces and gestures. Additional knowledge about how these deficits affect communication in Parkinson’s patients is necessary.
“With improved characterization of speech and language deficits, it may be possible to develop markers specific for motor and non-motor symptoms of PD,” researchers wrote.
They noted these potential communication markers should be studied further in the context of daily communication, and that mobile technology and automated speech analysis approaches may be powerful tools that can be used in patients’ daily life.