The diagnosis of dysarthria is based upon complete assessment of five characteristics: respiration, phonation, resonance, articulation, and prosody (Table 10-2). Standardized articulation protocols are more commonly used with children to determine whether the child is exhibiting a disorder of articulation or phonologic processes. This is not the case in the adult population. The Frenchay Dysarthria Assessment (11) is one commonly used protocol in the adult population. The Assessment of Intelligibility of Dysarthric Speech (AIDS) (29) is another.

While there are a few standardized articulation protocols that may be used with adults, they are infrequently used in deference to a “speech sample” that is both tape recorded and transcribed and possibly videotaped in order to provide the patient with visual feedback of his or her own communication skills. As mentioned earlier, the combination of speech AMRs and SMRs and speech intelligibility for verbal production of basic needs/wants words, phrases, sentences, and paragraph levels are assessed. The most commonly used paragraphs are presented
in Figure 10-1. Both paragraphs contain a fair sampling of all phonemes and phoneme combinations in the English language. In addition to having the patient read these passages, speech intelligibility is perceptually rated in open context conversation. Some individuals may not be able to see or read; therefore, accommodating the individual’s abilities and needs is essential in order to determine the patient’s baseline level and current status and assess for confirmatory signs.

There are seven types of dysarthria that are dependent upon the location of the lesion (8). These are as follows:

Flaccid dysarthria is caused by a lesion in the lower motor neuron or final common pathway, resulting in weakness, paresis, paralysis, hypotonia, and atrophy. The presence of fasciculations is a confirmatory sign.

Unilateral upper motor neuron dysarthria is caused by a unilateral lesion located in the upper motor neuron. Speech intelligibility is impacted by location of weakness and compounded by discoordination. Speech will sound slurred, slow, and thick. Oral dysphagia is frequently a concomitant problem.

In spastic dysarthria, the lesion occurs in the upper motor neuron bilaterally and results in spastic, tight muscles. All five speech characteristics are affected. Often, short phrases are produced in a low monopitch. Resonance is hypernasal. A strain-strangled vocal cry or pseudobulbar cry is frequently seen. Hallmark signs include spasticity; weak, slow, reduced range of motion; degenerative conditions; slow and effortful articulation; appear to be speaking against resistance; fatigue; hypernasality; dysphagia; drooling; and emotional lability.

Ataxic dysarthria is typically noted when there is a cerebellar or brainstem lesion. Coordination and integration are affected. To the untrained ear, this speech disorder sounds much like “drunken speech.” Excessive loudness and unequal stress are features.

Hypokinetic dysarthria typically results from a lesion in the basal ganglia. Reduced range and amplitude of movement are exhibited. Speech articulation sounds are blurred, and voice is quiet. Patients typically benefit from use of prosodic cues such as a metronome and compensatory strategies that enable improved vocal intensity.

Hyperkinetic dysarthria also occurs in a basal ganglia lesion. Excessive, uncontrollable movement, involuntary hyperkinesias, and chorea are exhibited. Vocal quality is typically hypernasal, harsh, and loud in intensity. Speech articulation is characterized by inconsistent articulatory breakdown; there is no pattern. Dyskinesias are further broken down into nine types: hyperkinesia, myoclonus, tic, chorea, ballism, athetosis, dystonia, spasm, and tremor. Hyperkinetic dysarthria is not amenable to a specific dysarthria treatment unless the underlying movement disorder is medicated. Speech therapy services are beneficial to individuals and their family or caregivers initially and for a brief duration to provide education and counseling.

Mixed dysarthria lesions are, as the name implies, mixed or diffuse. This can be seen in traumatic brain injury (TBI), closed head injury (CHI), multiple sclerosis (MS), and amyotrophic lateral sclerosis (ALS). Therapy techniques are highly individualized and based upon which component contributes most to unintelligibility.

In anarthria, the lesions are typically in the cortex and cerebellum. If a patient’s mutism is related to a single lesion, it is likely brainstem. Patients are often speechless due to loss of neuromuscular control over the speech mechanism.

Apraxia is an impairment in motor programming and is not due to weakness or paralysis of structures. Traditional characteristics include phonemic errors, perseverative and anticipatory misarticulations, and inconsistent articulatory approximations. Errors vary with increased complexity. For example, an individual may have little difficulty producing automatic speech phrases or overlearned passages or songs but increased difficulty for novel verbal productions. The patient will usually exhibit awareness of misarticulations and a great deal of frustration. Because of this frustration, the focus of therapy is initially generally placed on getting the message out and later on fine tuning the use of compensatory strategies such as slow rate, even stress, and even spacing between words.

When determining whether a person has apraxia or dysarthria, the first characteristic to which attention must be paid is the patient’s struggle or “articulatory groping” as speech is attempted. The SLP will have previously noted on the OME whether the patient demonstrated “articulatory groping” when attempting various oral postures upon command (e.g., grimacing when asked to open the mouth, lingual extension when asked to puff up the cheeks, squinting when asked to demonstrate pursing the lips and blowing). If no asymmetry or weakness is demonstrated on OME and no effortful struggle is apparent when performing volitional oral postures, verbal apraxia may be present. Phonemic substitutions are quite commonly exhibited in verbal apraxia, even if no effortful articulatory groping is demonstrated when volitionally producing various oral postures for the OME. For example, an individual may say “The clog jumped off the cliff” or “The dog jumped off the diff” when asked to read “The dog jumped off the cliff.” Individuals with verbal apraxia will likely exhibit difficulty repeating words of increasing length (e.g., back, backhand, backhanded; increase, increasing, increasingly). Difficulty will be exhibited for multisyllabic words. They will often report, “I know the word, I just can’t say it.” They may well exhibit no difficulty when reading a printed paragraph aloud and then an inordinate amount of difficulty during conversation.

Differentiating between apraxia and dysarthria is fundamental in order to initiate the correct treatment approach. Excessive repetition and practice are essential treatment techniques for verbal apraxia; whereas, they would be ineffective and inappropriate for some types of dysarthria (e.g., mixed flaccid-spastic dysarthria seen in ALS or flaccid dysarthria seen with myasthenia gravis). Figure 10-2 illustrates basic considerations for diagnostic differentiation of dysarthria and apraxia.