Dysarthria with ALS
|
Progressive bulbar palsy (PBP) is a motor neuron disease that primarily affects LMNs supplied by cranial nerves (Duffy, 2005, p.112). This syndrome is dominated by LMN weakness of cranial nerve muscles and UMN signs in the bulbar muscles may or may not be present (Duffy, 2005, p.276). Thus, PBP can be viewed as ALS without limb involvement (p.276). When it is confined to LMNs, PBP is associated with flaccid, instead of mixed dysarthria (p.276).
Unlike most other dysarthria types, flaccid dysarthrias sometimes reflect involvement of only one single muscle group or speech subsystem (Duffy, 2005, p.109). However, they can also involve several subsystems and muscle groups in various combinations (p.109).
DAB identified three clusters of abnormal speech characteristics in flaccid dysarthrias (Duffy, 2005, p.133).
Phonatory incompetence
due to incompetent laryngeal valve:
· breathiness, short phrases, audible inspiration
due to weakness of velopharyngeal valve
· hypernasality, imprecise consonants, nasal emissions, short phrases
Phonatory-prosodic insufficiency:
due to hypotonia in laryngeal muscles:
· harsh voice, monoloudness, monopitch
The most deviant speech characteristics encountered in flaccid dysarthria include:
Primary lateral sclerosis (PLS) is a motor neuron disease (MND) that affects UMNs only (Duffy, 2005, p.146). It is manifest by corticospinal and/or corticobulbar tract signs without LMN involvement (p.146). When dysarthria and dysphagia are the primary manifestations in PLS, the disorder may be referred to as progressive pseudobulbar palsy (p.146). Clinical motor findings are limited to descending UMN tracts, thus, it can be assumed that the type of dysarthria is usually spastic (Duffy, 2005, p.146).
In spastic dysarthria, damage usually involves the direct and indirect motor pathway of the central nervous system (Duffy, 2005, p.143). It may manifest in any or all of the respiratory, phonatory, resonatory and articulatory components of speech, and is usually not confined to a single area (p.143). Thus, the involvement of multiple speech systems explains why intelligibility is so frequently affected (p.150). Its characteristics are due to the combined effects of weakness and spasticity, which slows down movement and reduces its range and force (p.143). The clinical features of spastic dysarthria reflect the effects of excessive muscle tone and weakness on speech (p.143).
The components of the speech system most prominently involved
(Darley, Aronson & Brown; Duffy, 2005, p.151).
The most distinctive features associated with spastic dysarthria include the following:
(Duffy, 2005, p.418)
The characteristic speech of people with ALS has been classified as a mixed dysarthria (Duffy, 2005). A review of the description of speech characteristics reveals that, as in most dysarthrias, speakers with ALS demonstrate impairments in all components of the speech mechanism. The following outline describes these impairments at each level of the mechanism:
Respiratory Function
Many of the perceptual features associated with dysarthria in ALS are present in both spastic and flaccid dysarthria. For example, imprecise consonants, hypernasality, and harsh voice quality are found in both types of dysarthrias. Other features are found either in spastic or flaccid dysarthria. For example, low pitch, reduced stress and strained-strangled voice quality are found in spastic dysarthria, and audible inspiration and nasal emission are found in flaccid dysarthria as well as ALS. With the progression of the disorder, the contributions of each type of dysarthria may change (Yorkston et al., 2010). For instance, as the individual’s neuromuscular system becomes increasingly weaker, the symptoms associated with the flaccid dysarthria usually become more apparent. According to Yorkston et al. (2010), the stages of functional limitations in dysarthria for ALS are as follows: (1) No detectable speech disorder, (2) obvious speech disorder with intelligible speech, (3) reduction in speech intelligibility, (4) natural speech supplemented with augmentative communication approaches, (5) no useful speech.
In terms of the oral mechanism, abnormalities are usually bilateral and generally consistent with those encountered in people with flaccid or spastic dysarthria of any etiology (Duffy, 2005). When conducting an oral mechanism exam, speakers with spastic-flaccid ALS frequently exhibit excessive weakness of the tongue and the lips (Yorkston et al., 2010). Changes in tongue function may also include reductions in range and velocity of movement, changes in tongue strength and changes in size, shape, position and histopathological characteristics. Finally, these patients may have an audible reflexive dry swallow.
References:
Duffy, J. R. (2005). Motor Speech Disorders . St. Louis: Elsevier Mosby.
Yorkston, K. M., Beukelman, D. R., Strand, E. A., & Hakel, S. (2010). Management of motor speech disorders in children and adults. Austin: Pro-Ed.
Unlike most other dysarthria types, flaccid dysarthrias sometimes reflect involvement of only one single muscle group or speech subsystem (Duffy, 2005, p.109). However, they can also involve several subsystems and muscle groups in various combinations (p.109).
DAB identified three clusters of abnormal speech characteristics in flaccid dysarthrias (Duffy, 2005, p.133).
Phonatory incompetence
due to incompetent laryngeal valve:
· breathiness, short phrases, audible inspiration
due to weakness of velopharyngeal valve
· hypernasality, imprecise consonants, nasal emissions, short phrases
Phonatory-prosodic insufficiency:
due to hypotonia in laryngeal muscles:
· harsh voice, monoloudness, monopitch
The most deviant speech characteristics encountered in flaccid dysarthria include:
- hypernasality
- breathiness (continuous)
- diplophonia
- audible inspiration (stridor)
- nasal emission (audible)
- short phrases
- rapid deterioration and recovery with rest
- speaking on inhalation
Primary lateral sclerosis (PLS) is a motor neuron disease (MND) that affects UMNs only (Duffy, 2005, p.146). It is manifest by corticospinal and/or corticobulbar tract signs without LMN involvement (p.146). When dysarthria and dysphagia are the primary manifestations in PLS, the disorder may be referred to as progressive pseudobulbar palsy (p.146). Clinical motor findings are limited to descending UMN tracts, thus, it can be assumed that the type of dysarthria is usually spastic (Duffy, 2005, p.146).
In spastic dysarthria, damage usually involves the direct and indirect motor pathway of the central nervous system (Duffy, 2005, p.143). It may manifest in any or all of the respiratory, phonatory, resonatory and articulatory components of speech, and is usually not confined to a single area (p.143). Thus, the involvement of multiple speech systems explains why intelligibility is so frequently affected (p.150). Its characteristics are due to the combined effects of weakness and spasticity, which slows down movement and reduces its range and force (p.143). The clinical features of spastic dysarthria reflect the effects of excessive muscle tone and weakness on speech (p.143).
The components of the speech system most prominently involved
(Darley, Aronson & Brown; Duffy, 2005, p.151).
- Prosodic excess: excess and equal stress and slow rate- most likely the result of slowness of individual and repetitive movements (p.151).
- Articulatory-resonatory incompetence leading to imprecise consonants, distorted vowels and hypernasality due to reduced range and force of articulatory movements (p.151)
- Prosodic insufficiency including monopitch, monoloudness, reduced stress and short phrases- most likely the result of decreased range of movement (p.151).
- Phonatory stenosis such as low pitch, harshness, strained-strangled voice, pitch breaks, short phrases and slow rate. These features may be related to laryngeal hypertonus, slowness of movement and inefficient valving at the velopharyngeal and articulatory valves (p.151).
The most distinctive features associated with spastic dysarthria include the following:
(Duffy, 2005, p.418)
- Tight, strained-strangled voice
- Low pitch
- Harshness
- Slow rate
- Slow regular AMRs
- Pitch breaks
The characteristic speech of people with ALS has been classified as a mixed dysarthria (Duffy, 2005). A review of the description of speech characteristics reveals that, as in most dysarthrias, speakers with ALS demonstrate impairments in all components of the speech mechanism. The following outline describes these impairments at each level of the mechanism:
Respiratory Function
- Limitations in vital capacity are associated with changes in maximum phonation time.
- Poor respiratory support exaggerates the oral movement problems of people with bulbar symptoms and contributes to vocal changes in people with spinal symptoms.
- Spastic presentation → phonatory stenosis resulting in elevated laryngeal resistance, reduced exhalatory force and a strained, hoarse vocal quality.
- Flaccid presentation → vocal fold weakness resulting in breathy voice and reduced loudness.
- Inadequate velopharyngeal closure results in hypernasality and nasal emission.
- Tongue and lip weakness → articulatory deficit and distorted vowels
Many of the perceptual features associated with dysarthria in ALS are present in both spastic and flaccid dysarthria. For example, imprecise consonants, hypernasality, and harsh voice quality are found in both types of dysarthrias. Other features are found either in spastic or flaccid dysarthria. For example, low pitch, reduced stress and strained-strangled voice quality are found in spastic dysarthria, and audible inspiration and nasal emission are found in flaccid dysarthria as well as ALS. With the progression of the disorder, the contributions of each type of dysarthria may change (Yorkston et al., 2010). For instance, as the individual’s neuromuscular system becomes increasingly weaker, the symptoms associated with the flaccid dysarthria usually become more apparent. According to Yorkston et al. (2010), the stages of functional limitations in dysarthria for ALS are as follows: (1) No detectable speech disorder, (2) obvious speech disorder with intelligible speech, (3) reduction in speech intelligibility, (4) natural speech supplemented with augmentative communication approaches, (5) no useful speech.
In terms of the oral mechanism, abnormalities are usually bilateral and generally consistent with those encountered in people with flaccid or spastic dysarthria of any etiology (Duffy, 2005). When conducting an oral mechanism exam, speakers with spastic-flaccid ALS frequently exhibit excessive weakness of the tongue and the lips (Yorkston et al., 2010). Changes in tongue function may also include reductions in range and velocity of movement, changes in tongue strength and changes in size, shape, position and histopathological characteristics. Finally, these patients may have an audible reflexive dry swallow.
References:
Duffy, J. R. (2005). Motor Speech Disorders . St. Louis: Elsevier Mosby.
Yorkston, K. M., Beukelman, D. R., Strand, E. A., & Hakel, S. (2010). Management of motor speech disorders in children and adults. Austin: Pro-Ed.