Cerebellar Disorders Flashcards
what are 4 theories of cerebellar function?
1- comparator
2- compensator
3- feedforward control
4- motor learning
what is the comparator theory of cerebellar function?
error correcting mechanism
Sensory information from evolving movement and motor output are compared
if it doesn’t match the cerebellar will provide corrective feedback
what is the compensator theory of cerebellar function?
rather than providing corrections to ongoing movement the cerebellum is assumed to perform predictive compensatory modifications of reflexes in preparation for movement
what is feedforward control theory of cerebellar function?
programs or models of voluntary movement skills based on a memory of previous sensory input and motor output.
If the cerebellum is damaged movement is then graded by long delay sensor feedback loops through the cerebrum just as in learning a new skill and incoordination will result.
what is the motor learning theory of cerebellar function?
through trial and error and cognition
what does damage to the cerebellum cause?
The cerebellum is not necessary to basic elements of perception or movement.
Rather, damage to the cerebellum disrupts the spatial accuracy and temporal coordination of movement.
It impairs balance and reduces muscle tone.
It also markedly impairs motor learning and certain cognitive functions.
what is the flocculonodular lobe/vestibulocerebellum (archicerebellum)?
receives input directly from vestibular afferents (SCC and otolith) controlling balance and eye movements.
Disruption of these projections impair an individual’s ability to use vestibular information to control eye movements during head rotation and movements of the limbs and body during standing and walking.
what is the spinocerebelum (paleocerebellum)?
receives visual, auditory, and vestibular inputs as well as somatic sensory input from the head and proximal parts of the body
It functions to control proximal muscles of the body and limbs.
It governs posture and locomotion as well as gaze.
Pathways cross x2- ipsilateral deficits
what is the cerebrocerebellum (neocerebellum)?
its output is mediated by the dentate nucleus, which projects to motor, premotor and prefrontal cortices.
It is intimately involved in planning and menial rehearsal of complex motor actions and in the conscious assessment of movement errors.
Many motor acts are made up of multiple components, each of which is initiated before the preceding one is completed.
Lesions disrupt timing of various components, which appear to take place sequentially rather than being coordinated smoothly–> decomposition of movement
what are symptoms of cerebellar damage ?
hypotonia
-pendular reflexes
ataxia
- delay in initiating movement
- dysmetria- errors in the range of movement
- dysdiadochokinesia- can’t sustain a regular rhythm nor produce an even amount of force
- decomposition of movement- errors in the relative timing of the components of complex multi-joint movements
- intentional tremors
balance
-postural tremors and a delay in the automatic postural adjustments
gait disturbances- staggering gait resembling someone intoxicated
- decrease in arm swing
- can’t walk in straight line
- uneven step length
- increase or decrease BOS
- decrease rhythm of gait
- can’t adjust to changes in surface
speech- melodic quality of speech is changed- dysarthric
gaze evoked nystagmus
what are types of disorders to the cerebellum?
CVA
TBI
degeneration
tumors
when cerebellar testing, what are non equilibrium coordination tests?
alternate or reciprocal motion- the ability to quickly reverse movement from agonist to antagonist
finger to nose
finger to finger
alternate finger to nose, finger to finger
finger opposition
alternate supination/pronation
patting (hand)
tapping (foot)
heel to knee to toe (shin slides)
what is the loss of ability to alternate motion called ?
adiadochokinesia
what is impaired ability to alternate motion called?
dysdiadochokinesia
what is synergy of movement?
ability to perform movement achieved by muscle groups acting together
