Cultural Considerations for Dysarthria Treatment

Introduction

In the field of Speech-Language Pathology, clinicians are faced with assessing, diagnosing, and treating a wide variety of communication, cognition, and swallowing disorders stemming from an extensive array of etiologies.  Similarly, the populations being served are continuously growing and expanding, with numerous cultural and linguistic backgrounds represented on client and patient caseloads. When serving clients of diverse backgrounds, clinicians need to exhibit cultural responsiveness to come to an accurate diagnosis and subsequently form the meaningful, individualized, and effective treatment plans required for successful and beneficial practice. Similarly, when serving a patient from a linguistically diverse background, a clinician must exhibit knowledge of potential differences in the technical aspects of language, as well as potential biases inherent in assessment and treatment tools. The clinician must also be aware of how their cultural background can potentially influence how they perceive a patient's presentation of communicative characteristics. For clinicians assessing and treating dysarthria, the need for cultural responsiveness is no less critical. Clinicians must consider how current theoretical models of dysarthria have been derived and whether or not they can or should be applied across all patients. It merits inquiry as to whether or not the condition will have the same linguistic and perceptual effects on the speech of linguistically diverse patients as on English-speaking patients. It also warrants a clinician's consideration to contemplate and reflect on how their own background and views of typical and atypical speech might influence a culturally diverse patient's assessment. Research in the field regarding the effects of dysarthria on languages other than English is in the early stages compared to research on dysarthria in English-speaking patients. As more research is conducted with participants of varied backgrounds, clinicians and the theoretical models they work from can become better informed and prepared to serve their diverse array of clients competently.

What is Dysarthria?

Dysarthria is a neurogenic motor speech disorder that results in impairment to the motor execution of speech. This impairment often results from damage to the central and/or peripheral nervous system that impedes the successful transmission of neuronal signals to the muscles used for speech. Such damage can occur following stroke, brain injury, other physical injury, and as a part of a variety of progressive degenerative diseases such as Parkinson's, Multiple Sclerosis, Cerebral Palsy, and Amyotrophic Lateral Sclerosis (ALS). 

Dysarthria Types and Characteristics (As Described by Current English-Based Models)

Overall, seven distinct types of dysarthria have been identified based on their neural etiology and site of lesion or damage. Each type is associated with damage to a specific neuroanatomical location, leading to various impairments in fine and gross motor and muscle control and movement execution. Each type of dysarthria can affect a person's speech in terms of strength, speed, range, tone, or accuracy of movement and may affect respiration, phonation, resonance, articulation, & prosody. Difficulty involving impaired respiration and breath support can lead to impaired vocal qualities, such as strained or strangled voice, harshness, monopitch, and pitch breaks. Impairment of resonance and velopharyngeal function can cause hypernasality, hyponasality, and audible nasal air emission. Impairment during articulation can lead to imprecise consonant production, distortion of consonants and vowels, and irregular articulatory breakdowns. Clinicians use the known perceptual speech characteristics and other neurological and physical signs to determine a correct diagnosis and plan appropriate treatment plans.

By and large, the characteristics involved in any dysarthria will likely impact a patient's overall intelligibility, which can lead to a variety of activity and participation limitations, potential social isolation, and other social-emotional difficulties. According to current English-based model regarding dysarthria diagnosis, a significant impact on speech intelligibility is imprecise consonant production. Imprecise consonant production and/or irregular articulatory breakdowns are features of many dysarthrias. Therefore, these features will play a large part in how a clinician perceptually assesses patient intelligibility.  

Multicultural Considerations for Diagnosis

The previously discussed model of dysarthria differential diagnosis was developed using English and is mainly based on English. Similarly, there is currently a lack of assessment and treatment materials for most languages spoken across the world. As the populations that Speech-Language Pathologists work with continue to expand, it becomes more imperative to consider whether this standard English-based theoretical model can be generalized and applied across all languages. Exploration on whether articulatory difficulties seen so commonly in English-speaking patients, such as consonant imprecision and irregular breakdowns, will have the same linguistic effects and impact in the speech of linguistically diverse patients is warranted. Speech sounds, stress, and intonation patterns vary across languages, so it should not be assumed that English- based research is always appropriate to apply when other languages are affected. Research in this area is in the beginning stage; therefore, the following information and discussion are not exhaustive. This page serves as an ongoing discussion and continuously developing space for information regarding how dysarthria manifests in the speech of those who speak languages other than English. As the effects of dysarthria are examined in more languages, the working clinical and theoretical model for assessment, diagnosis, and treatment can become more comprehensive, and clinicians will be better informed. 

The Universality of Dysarthria 

Studies Regarding the Commonalities of Dysarthric Speech Characteristics Across Languages

Dysarthric Bengali Speech: A Neurolinguistic Study

In this 2008 cross-sectional observational study, Chakraborty and colleagues examined the effects of dysarthria on the speech of 66 Bengali speakers. They aimed to examine how the patients' dysarthria affected speech across the domains of respiration, phonation, articulation, resonance, and prosody. The patients' speech was analyzed using perceptual analysis of a nine-sentence conversationally-read text that included all Bengali consonant and vowel phonemes. Their speech was assessed using 24 parameters grouped into their respective speech domains. Parameters assessed included: imprecise consonants, distorted vowels, prolonged phonemes, forced inhalation/exhalation, audible inspiration, vocal tremor, monoloudness, alternate loudness, loudness decay, excessive loudness, strained voice, breathy voice, hoarse voice, aspiration, reduced stress, excess or equal stress, slow rate, variable rate, increased rate, short rushes, inappropriate silences, irregular articulatory breakdowns, hypernasality, and nasal emission. Using statistical analysis, the parameters were used to classify dysarthria type and determine which speech irregularities were most prominent in each type. The study found that, like in English studies, imprecise consonants were one of the most prominent speech irregularities occurring across patients. A further breakdown of perceptual speech characteristics of dysarthric Bengali speech is provided below.

• Flaccid Dysarthria: hypernasality (80%), imprecise consonants (70%), prolonged phonemes (40%), breathy and strained quality (40%), reduced stress (40%).

  • Differential Diagnosis: Hypernasality and breathy voice could distinguish flaccid dysarthria from other types. 

• Spastic Dysarthria: strained voice (74%), monoloudness (60%), imprecise consonants (67%), prolonged phonemes (27%), reduced stress (54%), slow rate (47%), hypernasality (40%).

  • Differential Diagnosis: Strained voice is more prominent in spastic dysarthria than other types except hyperkinetic. However, strained voice accompanied by monoloudness can distinguish spastic from hyperkinetic because monoloudness was much less prevalent in hyperkinetic.

• Hypokinetic Dysarthria: monoloudness and strained voice (50%), reduced stress (50%), slow rate, and increase in overall rate (25%).

  • Differential Diagnosis: These characteristics resembled those found in spastic dysarthria except hypernasality, which did not occur in hypokinetic, and increase in overall rate, which did not occur in the spastic type.

• Hyperkinetic Dysarthria: Imprecise consonants (89%), strained voice (78%), vocal tremor (56%), monoloudness (34%), reduced stress (56%), slow rate (45%), irregular articulatory breaks (34%), hypernasality (34%).

  • Differential Diagnosis: Vocal tremor is likely to be present in hyperkinetic rather than hypokinetic and can serve as a distinguishing feature. 

• Ataxic Dysarthria: Excess/equal stress and irregular articulatory breakdown (63%), short rushes, variable rate, and reduced stress (25%).

  • Differential Diagnosis: The high prevalence of excess/equal stress can distinguish ataxic dysarthria from other types. 

Overall, the study points to more similarities than differences in how dysarthria could potentially affect the speech and intelligibility of a Bengali-speaking patient as compared to the English-based models. The Bengali speakers with dysarthria also had difficulties across speech parameters, with a high incidence of imprecise consonants affecting intelligibility. The article also offers a closer look at potential clues to a more specific differential diagnosis breakdown for Bengali speakers with dysarthria (see above). However, clinicians should consider that these differential diagnosis findings are based on a 66 speaker sample and may not necessarily apply to all Bengali speakers. However, these results could potentially serve as a comparative reference to English-based tools.  

Studies of Chinese Speakers with Dysarthria: Informing Theoretical Models

In a 2010 review study, Whitehill examined and synthesized the results of existing studies on dysarthria in Chinese speakers. The review looked at studies on either Mandarin or Cantonese speakers with dysarthria stemming from either Parkinson's disease or Cerebral Palsy. Ultimately, the study results are compared with those of studies involving English speakers with dysarthria. The author notes that since Chinese is tonal and phonologically very different than English, the study provides a unique opportunity to determine if there are universal aspects to dysarthria across languages. Similarly, since tonal languages make up nearly 70% of the world's languages, it highlights the need to determine how linguistically and culturally appropriate models of diagnosis and treatment are for diverse populations.

The author details four studies regarding the dysarthrias of Cantonese or Mandarin speakers with Cerebral Palsy. Across the studies, patients were found to have several dysarthric manifestations similar to English-speaking patients with Cerebral Palsy. Regarding segmental and tonal errors, similarly to English-speakers, Cantonese speakers showed the most impaired accuracy in initial consonants, followed by final consonants and vowels, resulting from difficulties with articulatory, velopharyngeal, and laryngeal control (articulation, resonance, and phonation). These similarities were also seen with Cantonese speakers regarding single-word intelligibility. In a study of Mandarin speakers with Cerebral Palsy, similarities to English speakers with dysarthria of the same etiology were found regarding vowels retaining intelligibility and marked difficulty with the contrast between aspirated and unaspirated consonants. Also, similarly to studies of English speakers, Mandarin speakers with dysarthria had difficulties controlling the timing and spatial control of their articulators.    

The author also reviews four studies regarding hypokinetic dysarthria of Cantonese speakers with Parkinson's disease. Again, the studies found similarities between dysarthria characteristics of Cantonese speakers and English speakers. Like English speakers, the Cantonese speakers were found to have difficulties with pitch and loudness variation, imprecise consonants, and vocal quality. In studies examining the effects of Lee Silverman Voice Treatment (LSVT) on Cantonese speakers with Parkinson's disease, like English speakers, the participants gained increased vocal intensity and pitch range and showed a significant decrease in monotonicity. This improvement, however, did not lead to improved accuracy in lexical tone in the tonal language. Overall, the author concludes that Chinese speakers with dysarthria tend to exhibit the same speech errors as most English-speaking patients with dysarthria.

This study contributes to the hypothesis that there are similarities in how dysarthria affects speech across languages. However, clinicians should note that the studies reviewed here focused on patients with either Cerebral Palsy or Parkinson's disease. Thus, the similarities seen cannot necessarily be applied to other etiologies leading to different types of dysarthria. Clinicians should also be aware and informed regarding the tonal nature of Chinese languages. Cantonese and Mandarin have different lexical tonal systems, which can be impacted by dysarthria. Although tone in the Chinese languages was affected by dysarthria in manners similar to English speakers (monotonicity), this does not necessarily mean that the impact on a patient's speech will be identical to that of an English-speaking patient. For example, even when monotonicity was improved via LSVT, there was not a subsequent improvement in improved lexical accuracy within the tonal language. The language-specific effects of dysarthria on these tonal languages are still being investigated, and clinicians should be aware of this when drawing clinical conclusions.

Other Considerations

• Clinicians should always consider how their personal, cultural, and linguistic background potentially influences their assessment, diagnosis, and treatment of dysarthria. Even the presence of a dialect can affect our perception of altered intelligibility and impaired speech characteristics. 

• A clinician's standard for typical speech can influence the assessment of culturally and linguistically diverse patients, including English speakers with non-mainstream dialects. 

• Research in the field is beginning to look at the effect of dialects on the perception of speech intelligibility. A dissertation study by Stallworth (2012) explored whether dialectical differences in the dysarthric speech of African American and Caucasian Americans affected the perception of intelligibility and comprehensibility, as well as views of acceptability. The study found that perceptual raters tended to give higher ratings to speakers of their own ethnicity.

• Differences in cultural views on disability and healing can also affect dysarthria treatment. Many clinicians will come from a medical model of disability and American Individualistic background. Due to these biases, clinicians may inherently see dysarthria as a disability or problem that needs to be fixed for the patient to be independent. Patients with other cultural backgrounds may have a very different view of dysarthria. Some cultures view the effects of aging or health conditions to be spiritual rather than a medical impairment. A patient could view their dysarthria as a gift rather than a disability. 

• Exhibiting cultural responsiveness in clinical assessment and treatment of dysarthria can lead to a treatment plan that accurately reflects a patient's needs and goals, respecting their cultural identity.

Contributed by Candice Harrell, Spring 2014