Flaccid Dysarthria Flashcards
Overview of Flaccid Dysarthria
Perceptually distinct
Caused by injury or disease of one or more spinal or cranial nerves.
Involves only a single muscle group or speech subsystem
Primary distinguishing deviant characteristics include
- Muscle weakness
- Reduced muscle tone
Primary Characteristics
Weakness Hypotonia Diminished reflexes Atrophy Fasciculations
Weakness
Stems from damage to the motor unit at any point (could be the cranial or spinal nerve cells, the nerves leading to muscle, or the neuromuscular junction).
Paralysis could result if motor unit disease inactivates all other LMN input.
Paresis results if some input to the muscle remains viable.
Hypotonia and Reduced Reflexes
Hypotonia is reduced muscle tone, and is characterized by floppiness of muscle and reduced resistance to passive movement.
Atrophy
Atrophy means to loose bulk. This occurs here when cranial or spinal nerve cell bodies, nerves, or fibers are involved, resulting in the eventual atrophy of the muscle.
Atrophy is almost always associated with significant weakness.
Fasciculations and Fibrillations
Fasciculations are visible, arrhythmic, isolated twitches in resting muscles resulting from spontaneous motor unit discharges in response to nerve degeneration or irritation.
Fibrillations are invisible, spontaneous, independent contractions of individual muscle fibers that reflect slow and repetitive action potentials.
These may develop when motor neuron cell bodies and/or their axons are damaged.
Progressive Weakness with Use
Rapid weakening of muscles with use followed by recovery with rest can occur when disease affects the neuromuscular junction.
Myasthenia Gravis is an example of neuromuscular junction disease.
Myasthenia Gravis
Most common neuromuscular junction disease.
First signs include:
- Weakness of eye muscles
- Difficulty swallowing
- Slurred speech
The following are often affected and become weak:
- Eye and eyelid movement control muscles
- Facial expressions
- Chewing
- Talking
- Swallowing
- Breathing
- Neck/limb movements
Etiologies
Flaccid dysarthrias can result from anything that causes damage to the motor unit.
- Congenital
- Demyelinating
- Degenerative
- Infectious/Inflammatory
- Metabolic
- Neoplastic
- Traumatic
- Vascular
Degenerative Diseases
Motor neuron diseases are a group of disorders that involve degeneration of motor neurons.
ALS
Kennedy’s Disease
Amyotrophic Lateral Sclerosis (ALS)
The most common motor neuron disease.
Affects the bulbar, limb, and respiratory muscles.
Kennedy’s Disease (aka Spinobulbar Muscular Atrophy)
The most common adult-onset spinal muscle atrophy, often mistaken for ALS.
Affects only males, usually after 30.
Characterized by:
- Gynecomastia (excessive breast size)
- Muscle cramps and twitches
- Limb-girdle muscle weakness
- Bulbar involvement
Trauma
Surgery in the brainstem, head, neck, or upper chest can injure or permanently damage cranial nerves used for speech.
- Most common cause of vocal fold paralysis.
- Nerve damage can result from stretching, cutting, compression, or disruption of blood supply.
CHI, skull injuries, and neck injuries can cause flaccid dysarthria due to the trauma to the cranial or cervical nerves.
Muscle Disease / Muscular Dystrophies
Muscular dystrophies are genetic skeletal muscle diseases associated with muscle fiber degeneration and replacement with fatty, fibrous connective tissue, resulting in inability of muscles to contract normally.
Articulation, phonation, resonance, swallowing, and respiration can be affected.
- Characteristics would include hoarsness, reduced pitch variability, reduced rate and loudness, hypernasality.
- Oculopharyngeal Muscular Dystrophy
- Myotonic Muscular Dystrophy
Oculopharyngeal Muscular Dsytrophy
- A muscle disease
- Emerges in middle age
- Ptosis, dysphagia, and dysarthria
Myotonic Muscular Dystrophy
- Autosomal dominant inherited muscle disease
- Most common form of muscular dystrophy in adults
- Affects muscles’ normal contracting processes.
Vascular Disorders
Any brainstem stroke that affects the nuclei of speech cranial nerves can lead to flaccid dysarthria.
Some specific vascular disorders, like Wallenberg’s Syndrome, are also associated with flaccid dysarthria.
