Motor Control - Constraints on Motor Control

Primary vs secondary impairments

primary: paresis, spasticity

secondary: structural and functional changes in muscles and joints

Impairments of the motor system

-strength

-tone

-coordination

Strength definition

ability to generate enough tension in a mm for posture and movement

Muscles have

-musculoskeletal properties

-neural aspects of strength

Weakness

inability to recruit and/or modulate motor neurons (and generate torque)

What are the neural aspects of strength

# of motor units, type of motor units recruited, discharge frequency

Paralysis/plegia

inability or difficulty recruiting MU

Paresis

mild or partial loss of muscle activity

RX for weakness

muscle activation

-NMES

-biofeedback

-reflexes

What type of weaknesses do you have with LMN syndrome?

-flaccid weakness

-fibrillation

-fasciculations

Fibrillation

individual skeletal muscle twitches (esp denervated muscle that produce a spontaneous action potential)

Fasciculations

involuntary muscle twitch of a group of muscle fibers caused by overactive or hyperirritable peripheral nerve

Between fasciculations and fibrillations, what can you ONLY see on an EMG?

fibrillations

What is the purpose of muscle tone?

- postural support

- readiness for movement

- joint stability

- shock absorption

- reflexive adjustments

Intervention for the treatment of paresis

-biofeedback

-electrical stimulation

-strength training

-task oriented training

Muscle tone

a muscles resistance to passive stretch

Impairment to Pyramidal system leads to what?

motor weakness

What structures are included in the pyramidal system?

Primary motor cortex and corticospinal tracts

Cortical spinal tracts makes sure

alpha motor neurons are appropriately stimulated or inhibited

Impairments to Extrapyramidal system lead to what?

abnormal muscle tone

What structures are within the extra pyramidal system?

Cerebellum and basal ganglia

What system regulates gamma motor neurons?

Extra pyramidal

Hypertonia

increased resistance to passive motion

Rigidity

heightened resistance to possible movement of the limb

-cogwheel--bidirectional

-lead pipe

Spasticity

velocity dependent resistance to passive motion

-usually unidirectional

What are the mechanisms that cause Spasticity?

-decreased threshold of a stretch reflex and/or

-hyper excitability of alpha motor neurons (loss of descending inhibitory input, post synaptic denervation super sensitivity

-changes in viscoelastic properties and excitability

Consequences of spasticity?

-clonus

-abnormal synergies/loss of isolated movements

-weakness

What is clonus?

Repetitive stretch reflex discharges

What are abnormal synergies and when do they occur?

Mass movement patterns to a stimulus or can be a voluntary movement or both

Describe an UE flexor synergy

Scapular retraction, GH ABD & ER, elbow flexion and supination

Describe an UE extension synergy

Scapular protraction, GH ADD & IR, elbow extension, and pronation

Describe a LE flexor synergy

Hip flexion, ABD, ER, knee flexion, DV, toe extension

Describe LE extensor synergy

Hip extension, ADD, IR, knee extension, PF, toe flexion

Examination of abnormal muscle tone

-modified ashworth scale

-DTRs

-pendulum test

-PROM---what do you feel?

-babinski

How can spasticity be helpful?

A hemiplegic can you their LE spasticity (increased tone) as the stability needed to walk if they are weak

Intervention for spasticity

-stretching (but once they contract the muscles they go straight back to their "normal")

-splinting, bracing, casting (stronger research for casting to increase ROM)

-muscle re ed (handling)

-positioning (bed, wheel chair)

-heat (relaxation)

-cold (inhibition)

-sensory modalities: icing, vibration, approximation

*weaker research for sensory interventions

General pharmacological intervention for spasticity

baclofen (GABA agonist; decreases neuroneal firing)

Local pharmacological intervention for spasticity

-phenol

-botulinum toxin A (acts presynaptically at nerve terminals; prevents release of acetylcholine)

What is the cause of cog wheel rigidity?l

Lack of dopamine

What is athetosis?

Constant writing movements

What is chorea movements?

Writing dance like movements

What is Dystonia?

Syndrome dominated by sudden and sustained muscle contraction

What are factors that determine coordination?

Appropriate timing, reaction time, sequencing, correct amount of force, accuracy

What is incoordination a result from?

Sequencing problems, abnormal synergies, co-activation, inappropriate timing, and systematic

What are structure in the brain controls coordination?

Cerebellum

What are some conditions that have lack of coordination?

Dysmetria, dysdiachokinesia, and dysarthria

What is dysmetria

inability to control the distance, power, and speed of a muscular action (overshooting/undershooting)

What is dysdiachokinesia?

inability to perform rapid alternating movements

What is dysarthria?

Speech disorder that affects all aspects of speech

What is a tremor?

Involuntary oscillatory movement resulting from alternative contractions of opposing muscle groups

What anatomical structures cause a resting tremor?

basal ganglia

What anatomical structures cause an intention tremor?

cerebellum

What are associated movements?

Unintentional movement of one limb during voluntary movement

When do "facial contortions" occur?

When the body is exerting a lot of force

When does a "shoulder shrug" occur?

When the load on the UE is too great

When does "sticking your tongue out occur"

When writing or doing complex task

What is raimiste's phenomenon?

Reaction that occurs in hemiplegia, where resistance to hip movement in one limb causes the same movement in the affected limb