Dysarthria : A Brief
Dysarthria is a motor speech disorder resulting from neurological injury of the motor component of the motor–speech system and is characterized by poor articulation of phonemes. In other words, it is a condition in which problems effectively occur with the muscles that help produce speech, often making it very difficult to pronounce words. It is unrelated to problems with understanding language (that is, dysphasia or aphasia), although a person can have both. Any of the speech subsystems (respiration, phonation, resonance, prosody, and articulation) can be affected, leading to impairments in intelligibility, audibility, naturalness, and efficiency of vocal communication. Dysarthria that has progressed to a total loss of speech is referred to as anarthria. The term dysarthria is from New Latin, dys- "dysfunctional, impaired" and arthr- "joint, vocal articulation".
Neurological injury due to damage in the central or peripheral nervous system may result in weakness, paralysis, or a lack of coordination of the motor–speech system, producing dysarthria.These effects in turn hinder control over the tongue, throat, lips or lungs; for example, swallowing problems (dysphagia) are also often present in those with dysarthria. Cranial nerves that control the muscles relevant to dysarthria include the trigeminal nerve's motor branch (V), the facial nerve (VII), the glossopharyngeal nerve (IX), the vagus nerve (X), and the hypoglossal nerve (XII).
Dysarthria does not include speech disorders from structural abnormalities, such as cleft palate and must not be confused with apraxia of speech, which refers to problems in the planning and programming aspect of the motor–speech system. Just as the term "articulation" can mean either "speech" or "joint movement", so is the combining form of arthr- the same in the terms "dysarthria", "dysarthrosis", and "arthropathy"; the term "dysarthria" is conventionally reserved for the speech problem and is not used to refer to arthropathy, whereas "dysarthrosis" has both senses but usually refers to arthropathy.
There are many potential causes of dysarthria. They include toxic, metabolic, degenerative diseases, traumatic brain injury, or thrombotic or embolic stroke.
Degenerative diseases include parkinsonism, amyotrophic lateral sclerosis (ALS), multiple sclerosis, Huntington's disease, Niemann-Pick disease, and Friedreich's ataxia.
Toxic and metabolic conditions include: Wilson's disease, hypoxic encephalopathy such as in drowning, and central pontine myelinolysis.
These result in lesions to key areas of the brain involved in planning, executing, or regulating motor operations in skeletal muscles (i.e. muscles of the limbs), including muscles of the head and neck (dysfunction of which characterises dysarthria). These can result in dysfunction, or failure of: the motor or somatosensory cortex of the brain, corticobulbar pathways, the cerebellum, basal nuclei (consisting of the putamen, globus pallidus, caudate nucleus, substantia nigra etc.), brainstem (from which the cranial nerves originate), or the neuromuscular junction (in diseases such as myasthenia gravis) which block the nervous system's ability to activate motor units and effect correct range and strength of movements.
Causes include Brain tumor, Cerebral palsy, Guillain–Barré syndrome, Hypothermia, Lyme disease, Stroke, Idiopathic intracranial hypertension (formerly known as pseudotumor cerebri), Tay–Sachs disease, and late-onset Tay–Sachs disease (LOTS)