Apraxia of Speech Vs. Dysarthria- Key Differences
Speech disorders can be divided into different categories. If we talk about Motor Speech Disorders, there can be two main types of Motor Speech Disorders named as:
1. Apraxia (of Speech)
&
2. Dysarthria
Apraxia of speech (AOS)
Apraxia of speech is characterized by brain’s inability to program movements of the tongue, lips and larynx i.e. voice box that are involved in the production of sequence of speech sounds. It is related to the difficulty in planning, sequencing and coordinating speech related muscles. It can be both developmental or acquired which means it can either be present when the baby is born or can be acquired later in life.
Apraxia of speech occurs when the neural pathway between brain and speech related muscles is obscured or damaged. People with Apraxia of speech feel difficulty reaching out for words. They know what they want to say and are even able to write it down correctly, it is just that their brain is unable to send correct information for producing speech. It does not happen due to the damaged or weakened muscles relevant to speech. Apraxia occurs due to lesion in the central nervous system and never in the peripheral nervous system. It occurs due to the lesions in the cerebrum region especially The tone of muscles is not affected in Apraxia. People in apraxia when speaking make different errors when talking spontaneously and different errors when making a learned speech.
Mild form of Apraxia of speech is harder to diagnose as they share a wide variety of speech problems including incorrect pronunciation of words and irregularities in rhythm, speed and flow of speech. However, severe cases of Apraxia can be diagnosed easily as symptoms are quite easy to be noted such as substitution, groping or reaching for words in a laborious manner, distorted sound movements, repetition and unpredictability in pronunciation and addition errors.
Apraxia of speech can be treated by speech and occupational therapy. In the treatment for apraxia of speech, the focus is on improving the programming, sequencing and coordination of movement of speech muscles (Forrest, 2003).
Dysarthria
Dysarthria is a motor speech disorder which occurs due to the damaged, weakened or paralyzed muscles that are involved in speech resulting slurred speech. It results from the neurological lesion in the central nervous system of the brain. The injury might be due to brain tumor, Parkinson’s disease which is 70% to 100% comorbid with Dysarthria.
Just like Apraxia, it can be both developmental or acquired. Unlike Apraxia, Dysarthria results either due to the lesion in central nervous system (i.e. Spastic Dysarthria) or in the peripheral nervous system (i.e. Flaccid Dysarthria). Dysarthria also causes difficulty in swallowing food which is termed as Dysphagia.
Dysarthria, unlike Apraxia, is an error in the transmission rather than the planning or programming of speech. The tone of muscles is disrupted in Dysarthria as the movement of lips, tongue and other speech muscles involved is all affected. People with Dysarthria can have difficulty in almost all aspects of speech such as articulation, phonation, respiration, resonance and prosody.
Treatment of Dysarthria involves treating underlying neurological cause. As compared to adults, children have better prognosis of Dysarthria. The main focus in treating Dysarthria is to slowing down the speech rate, enhance their speech intelligibility, strengthening mouth, lips and throat muscles movement, making respiration better and family therapy (Caruso & Strand, 1999). Severe form of dysarthria involves alternative forms of communication.
