Cerebellar Dysfunction

Coordinate timing of movement
Maintain posture and balance
Predicting and Learning Movements
Cognitive and Emotional Processing

planning and timing of sequential movements
conscious assessment of movement errors

vermis - trunk and prox extremities
intermediate zone - distal extremities
integration of sensory input with motor commands to produce adaptive motor coordination

postural control and vestibulo-ocular reflexes

global
not necessarily by lobe because vascular supply goes all the way around

motor learning and error correction
this helps to adapt and fine tune motor control

activity patterns of upper motor neurons to make movements more adaptie and accurate

muscle activation across multiple joints
in anticipation or adjustment during movement

inputs recieved from parietal and supplementary motor area/pre-motor cortex
Basal Ganglia controls pattern of motor recruitment (what muscles)
Cerebellum controls timing and coordination (when)
Together produce motor program sent to the motor cortex

able to isolate movement, timing is off
less accurate, trajectory is off
exaggerated movements, increased variability

control is driven by a sensory prediction of error (feedforward)
errors are partially corrected each time (feedback)
correction collect until error reduced and "internal model" is updated (adaptation)
as control improves, shift from feedback to feedforward
Practice and repetition -> neuroplasticity -> internal model of the task -> changes in motor behavior

Individual Constraints: Structural and Functional (height, weight, attention)
Task Constraints: demands of the task itself (chair height, AD)
Environmental Constraints: weather, lighting, sound

Vascular Pathologies (*PICA*, AICA, SCA)
Tumors
Degenerative Diseases
Toxins #alc
*Demyelinating Disorders*
*Trauma*
Genetic Disorders

2-10% of strokes
PICA>SCA>AICA
Mean age 60-70, and 2/3 are men
Motor control and cognition

increased postural sway
hypermetric reactive balance responses
impaired anticipatory postural control
postural tremor (even at rest)
Ataxic Gait: step timing off

impaired gaze stability with head movements (VOR)

Impaired motor refinement
reduced timing and control of movement

Impaired skill acquisition and motor learning
Increased motor variability
feedforward and feedback impaired
Impaired error detection and abiity to correct/adapt

variable BOS
increased double limb stance time
increased variability in timing, length and direction of step
increased variability in timing and execution of joints
decreased speed, stability, and efficiency

impaired sensorimotor integration
impaired gaze stabilization
inaccurate movement

reduced/conflicting sensory inputs

reweighting of sensory inputs

vision and proprioception

impaired perception of visual and sensory inputs
impacts estimate of limb inertia resulting in dysmetria
adaptability and precision are impaired (excessive variability)
deficits increase with multi joint vs single joint movement
exaggerated/prolonged muscle activation and reaction times
-adding and AD will usually make things worse!

impaired sequence recognition
impaired predictive timing

with auditory and visual feedback removed, ppl can walk with each leg either moving at the same or different speeds

speed of adaptation recorded

adaptation deficits increase as severity of ataxia increases
typically people can adapt pretty fast

Dysmetria
Dysdiadochokinesia
Intention Tremor
Decomposition of Movement

hyper/hypo
error in movement accuracy

impaired ability to perform rapid alternating movements

tremor mainly in the hand or arm with voluntary active movement

movements are broken down into component parts and completed in sequence vs one smooth multicomponent movement

task complexity

feedforward

predictive
updating

Nystagmus
Dysmetric Saccades
Saccadic Breakdown with Smooth Pursuit
Delayed Vestibular Ocular Reflex

rhythmical involuntary rapid eye movement at rest and during eccentric gaze

Impaired accuracy or target location of the eyes
over or undershooting target with oscillating correction

inability to produce a smooth accurate eye movement to track a moving target

impaired gaze stabilization during head turns

Scale of Assessment and Rating of Ataxia (SARA)
International Cooperative Ataxia Rating Scale (ICARS)

assessment of impact of ataxia at the activity and BS&F levels
eight subscales: gait, balance, speech disturbance, dysmetria
0-40 (higher is worse)
<14 at 7 days post stroke onset predicted good functional outcome at 3 mos

<= 8: Independent in Gait no AD
<= 11.5: Independent with Cane
<= 12.5: Independent with Walker
<= 10: min dependence
<= 14.25: mod dependence
>= 23: total dependence

used primarily with hereditary ataxias
assessment of impact of ataxia at the activity and BS&F levels
19 items with 4 subscales: postural and gait disturbances, Limb Ataxia, Dysarthria, Oculomotor Disorders
0-100 (higher is worse)
MDC = 11.58