Today we are talking about Motor Speech disorders. A motor speech disorder can be described as the difficulty with the control of muscles of structures that help us produce speech (Kent, 2000). This involves muscles that control structures such as the lips, jaw, vocal chords (voice-box), the larynx (which houses the voice-box) as well as the respiratory system which helps us breathe (Kent, 2000). There are 2 types of motor speech disorders namely Dysarthria and Apraxia of speech (Kent, 2000).
Apraxia of speech is a neurological disorder that is characterised by the difficulty with planning, coordinating and sequencing muscles for speech production and is often marked by reduced speech speed and disruptions in prosody. Prosody or (prosodic features) refers to the pitch, intonation, stress, rhythm, and voice quality. (Iuzzini-Seigel, 2021)(Krishner, 2020). Apraxia of speech can either be acquired or present from birth, this when a child presents with Childhood Apraxia of Speech (CAOS). Acquired Apraxia of speech is caused by damage to the parts of the brain that are involved in speaking thus leading to any of speech abilities, it may result from a CVA, traumatic brain injury, dementia, tumour, or damage to brain tissue that will affect the motor strip in the left hemisphere (Kent, 2020).
Symptoms and Signs of Apraxia of Speech
Inconsistent articulation or phonological errors - such substitutions, additions and syllable deletions. E.g ‘nana’ for banana. The same articulation errors will not always be present in their speech.
Groping sounds - the tongue and articulators extra effort to produce sounds.
They may present with issues related to automatic speech - the use of everyday, commonly known words or phrases. Greetings - such as ‘hello’ and ‘goodbye’
In severe cases of brain injury/attrition of tissue/scarred tissue, speech may not be present at all (ASHA, n.d)
Dysarthria, on the other hand, is a motor speech disorder due to a neurological injury that involves damage to the muscles responsible for producing speech (Perotta, 2020). It is characterised by muscle weakness leading to difficulty with articulation, breathing, phonation, resonance, prosody thus affecting how intelligibile a person is and ultimately affecting communication (Perotta, 2020).
Symptoms and Signs of Dysarthria
There are many types of Dysarthrias and they all present differently.
Flaccid dysarthria is due to the damage to the lower motor neuron and has the following symptoms:
Spastic dysarthria is casued by upper motor neuron damage and has the following symptoms:
Ataxic dysarthria is due to damage to the cerebellum and has the following symptoms:
Damage to basal ganglia results in 2 types of dysarthrias namely hyperkinetic and hypokinetic types of dysarthria:
Hypokinetic: altered voice loudness and pitch – weak and softer voice. Monotone speech but at a fast pace. Imprecise consonant production.
Hyperkinetic: pitch and loudness is affected. Effortful speech, struggle to produce words, unintended interruptions in speech, vowel production difficulty.
A mixed dysarthria is due to damage in many areas resulting in a combination of symptoms of different types of dysarthrias.
