Dysarthria and Motor Speech Disorders Flashcards
Motor speech disorders
Resulting from neurological impairments affecting the motor planning, programming or execution of speech
Apraxia of Speech
Impacts the retrieval, activation and sequencing of motor plans for speech
Dysarthria
Impacts the execution of movements for speech
Motor Skills involved in Speech Production
Phonation - phonatory system Resonation - velar-pharyngeal system Articulation - articulatory system Respiration - respiratory system Controlled by the cerebral cortex (primary motor cortex), other control centres (cerebellum, basal ganglia)
3 Levels of the Motor System
Strategy - cerebral cortex and basal ganglia
Tactics - Motor cortex and cerebellum
Execution - brainstem and spinal cord
Use of sensory info
important for determining starting position of the muscles
Sensory info during = important for adapting planning and execution of movement
Frontal lobes in Motor Planning
Prefrontal Cortex - planning of movements
Premotor cortex - organises motor sequences
Primary motor cortex - produces specific movements
Motor Cortex Representation
Part of the body to be moved
Spatial location where the movement is directed
Movement’s function
Corticospinal motor pathway
(30% of fibres)
- travels from cortex to spine
- controls voluntary movements of the skeletal muscles
- activates spinal motor neurons
Originate from the upper 2/3 of PMC, premotor cortex, sensory cortex
Corticobulbar motor pathway
(70% of fibres)
- travels from cortex to brainstem
- controls the facial and associated muscles
- activates cranial nerve nuclei in brainstem (UMN)
Originate from the lower 1/3 of the PMC and adjacent area
Controls the skeletal muscles of head and face via cranial nerve
Corticospinal Tract
Motor cortex - contralateral organisation to output and input
Majority of corticospinal axons cross midline in the medulla to innervate contralateral spinal output nuclei
Upper Motor Neuron Damage
Weakness, increased tone, hyperreflexia (overactive reflexes)
Lower Motor Neuron Damage
Flaccidity, severe weakness, atrophy of muscle, hyporeflexia (underactive/absent), fasciculations (twitch)
Cranial Nerve Nuclei
Found in the brainstem
Can be connected to several related nerves
LMN nuclei - innervated by the UMN of the corticobulbar tracts
Majority receive bilateral innervation (safety)
- Both L and R nerves in pair are innervated by crainal nerves in L and R hem; except lower facial nerve (VII), hypoglossal nerve (XII)
Cranial Nerves Specific for Speech/Swallowing
CN V - Trigeminal CN VII - Facial CN IX - Glossopharyngeal CN X - Vagus CN XII - Hypoglossal
Testing Muscle Function
Symmetry Muscle bulk (signs of wasting, atrophy) Muscle tone - hypotonia - hypertonia Muscle strength Reflexes - hyper/hyporeflexia Coordination
Ipsilateral
innervates the same side
Contralateral
Innervates the opposite side
Unilateral
Innervates one side only
Bilateral
Innervates both sides
Decussation - Corticospinal tract
Majority decussate midline in medulla to innervate contralateral spinal output nuclei
Become two lateral corticospinal tracts to innervate contralateral side
Nerves that don’t cross = anterior corticospinal tracts, innervate ipsilateral side
Decussation - Corticobulbar Tract
Do no decussate
except:
CN I - optic nerve & CN IV - trocholear
CN VII - facial & CN XII - hypoglossal
Basal Ganglia
Collection of subcortical nuclei within forebrain
Receives input from cortex (neocortex, limbic cortex), midbrain (substatia nigra)
Sends output to motor cortex and substantia nigra
Basal Ganglia Structure
- Caudate nucleus
- Putamen
- Globus Pallidua
Subthalamic nucleus, substatia nigra and red nucleus are functionally related to BG
Circuitry of Basal Ganglia
Caudate and putamen - major input nuclei to basal ganglia; integrates sensorimotor info
Caudate and putament connect with the substantia nigra
Substantia nigra and globus pallidus are the major output nuclei
Volume hypothesis
Internal globus pallidus = volume dial
Projects into thalamus, projects into motor cortex
Direct pathway into Basal Ganglia
Amplifies force of movement
Increases cortical activity
- can see abnormal, violent, involuntary movements
- hyperkinetic
Indirect Pathway into Basal Ganglia
Reduces force of movement
Reduces cortical activity
- diminished, reduced, small, slow movements
- hypokinetic
Basal Ganglia Function - Speech
Roles in speech execution and motor programming (between formulator and articulator)
Involved in the specification of individual movements
- sets force, range, rate of movement
- involved in specifying volume, speed, stress etc involved in motor program dependent on context/communicative intent
Impairments - Basal Ganglia
Hyperkinetic symptoms - excessive involuntary movements (Huntington’s Disease)
Hypokinetic symptoms - paucity of movement (Parkinson’s Disease)
Parkinson’s Disease - Symptoms
Motor tremors, rigidity, loss of balance/coordination, difficulty moving
Resting tremor
Bradykinesia (slowness in initiating/performing movement)
Reduced postural reflexes
Hypokinetic dysarthria
Decrease in non-verbal communication
Parkinson’s Disease - Pathology
Destruction of neurons that produce dopamine in substatia nigra
Parkinson’s Disease - Executive Function
20% will develop frank dementia
Often associated with Lewy Body dementia
Subtle cognitive impairments common (esp executive difficulties)
Huntington’s Disease - Symptoms
Involuntary movements
- chorea (writhing of body, facial grimacing)
Cognitive decline
Psychiatric features
Huntington’s Disease - Pathology
Cell loss in the caudate nucleus
- lesser degree in putament, globus pallidus and cortex
Autosomal dominant condition
Huntington’s Disease - Speech
Hyperkinetic dysarthria - inappropriate silences, intermittent breathiness, hypernasality, loudness variations and imprecise articulations; lingual chorea (vocal tics)
Huntington’s Disease - Cognitive and Language
Impaired delayed recall of info Impaired memory Poor cognitive flexibility and abstration Impaired attention and concentration Slowed thought process
Language difficulties could be a result of more general cognitive difficulties;
loss of convo initiative
reduced syntactic structure
reduced verbal fluency
Cerebellum
Sequencing, timing, fine motor control of movement
Cerebellar Lesions
Ataxia - uncoordinated and inaccurate movements
Dysmetria - overshoot/undershoot target
Cerebellum Structure
Separated into two hemispheres by the vermis Lobes: - Vestibulocerebellum - Spinocerebellum - Cerebrocerebellum
Cerebellum - Motor Functions
Regulation of motor planning and control of movements (reaching and acquiring targets)
Refinement and amplification of movement online
Motor programming role - parameters for executrion
Cerebellum - planning
Receives info from the motor cortex about intended movement
- determines order of muscular contractions, timing, ranges and force
- info from vestibular system to maintain posture, balance, refine movement
Info is sent back to primary motor cortex after modification
Cerebellar Damage
Ipsilateral signs Incoordination of the limbs Ataxia Reduced fine motor control Wide based gait Dysarthria Difficulty performing rapid alternating movements incoordination of thought
Ataxia - Articulation
Breakdown in motor organisation and control
= slowness and inaccuracy in range, force, timing, direction of articulatory movements
