Cerebellum Flashcards
Superior cerebellar peduncles
Connects to rostrum pons
Contains mostly efferent fibers
Middle cerebellar peduncles
Connects to pons
Contains mostly afferent fibers from cerebral cortex
Inferior cerebellar peduncles
Connects to caudal pons/rostrum medulla
Coattails mostly afferent fibers for BS and SC
Contains efferent to vestibular nuclei and RF in brainstem
Cerebellum function
Detects movement that deviates from the intended cortical command
Contributes to motor planning
Smoothly coordinates ongoing movements and posture by comparing the intended movement w/ actual movement
Cerebellum receives sensor input from
SC cerebellar tracts
- muscle spindles
- GTOs
- joint and cutaneous receptors
- vestibular apparatus
Integrates this sensory info and adjusts movement as necessary
Cerebellum - three main functions
Synergy of movement
Maintenance of upright posture
Maintenance of tone (during muscle contraction)
Other cerebellum functions
Speech articulation
Respiratory movement
Motor learning
Possibly higher order cognitive processes
Lateral cerebellar hemispheres
Motor planning for extreme ties
Lateral corticospinal tract
Intermediate cerebellar hemisphere (B/n lat and vermis)
Distal limb coordination
Lateral corticospinal tract, rubrospinal tract
Vermis and flocculonodular lobe
Proximal limb and trunk coordination — anterior corticospinal tract, reticulospinal tract, vestibulospinal tract, tectospinal tract
Balance and vestibulo-ocular reflexes — medial longitudinal fascicles
Cerebellar lesions result in
Ataxia — uncoordinated movements
Input to cerebellar cortex
Mossy fibers (excitatory) Climbing fibers (excitatory)
Synapse directly or indirectly onto purkinje cells
-input to cerebellar cortex also have collateral fibers that synapse on deep cerebellar nuclie
Output from cerebellar cortex
Purkinje fibers (inhibitory)
Project to the deep cerebellar nuclei and/or vestibular nuclei (excitatory)
On/off center for cerebellar output
Deep cerebellar nuclei
Deep cerebellar nuclei - lateral to medial
Don’t eat greasy foods
Debate
Emboliform
Global economic
Fastigial
Denate cerebellar nucleus
Deep
Input from lateral hemisphere
Emboliform cerebellar nuclei
Deep
Input from intermediate hemisphere
Globase cerebellar nuclei
Deep
Input from intermediate hemisphere
Fastigial cerebellar nuclei
Deep
Input from vermis
Vestibular nuclei
Function in some ways like deep cerebellar nuclei
Input form inferior vermis and flocculonodular lobe
Why do cerebellar lesions cause ipilateral deficits?
Pathways from cerebellum that influence the lateral motor systems and periphery are double crossed
Lesions of the vermis don’t cause unilateral deficits because
Medial motor systems influence bilateral proximal trunk musculature
Cerebellar input
From virtually all areas of cerebral cortex
Many sensory modalities
BS nuclei
SC
Vestibular nuclie, RF nuclei, inferior Oliver’s nucleus
Corticopontine fibers
Fibers traveling from the cerebral cortex to the cerebellum
Synapse in pons, then are called pronto cerebellar fibers
Spinocerebellar pathways
Unconscious proprioception of limb movements
- dorsal spinocerebellar tract (LE)
- cuneocerebllar tract (UE)
Unconscious information regarding activity of spinal interneurons as well as spinal reflex circuit
- ventral spinocerebellar tract (LE)
- rostrum spinocerebellar tract (UE)
Each cerebellar hemisphere receives inform from
Ipsilateral limbs
Inputs either don’t cross or are double crossed
Cerebellar somatotopy
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Cerebellar lesions
- Ataxia
- Midline lesions
- Lesion lateral to vermis
Cerebellar lesion- ataxia
Ipsilateral to side of lesion
Disordered contractions of agonist and antagonist muscles and lack of normal coordination between movements at different joints
Movements have irregular, wavering course that consists of continuous overshooting and over correcting
Cerebellar lesion- midline lesions
Unsteady gait and eye movement abnormalities
Cerebellar lesion- lesions lateral to vermis
Limb ataxia
Three classic signs of cerebellar damage
Ataxia
Nystagmus
(Intention) tremor (with movement)
Cerebellar damage also involves
Dysrhythmia (abnormal timing)
Dysdiadochokinesia (ab rapid alternating movement)
Dysmetria (ab distance trajectory)
Other possible S/S of cerebellar damage
Vertigo N/V Unsteadiness Slurred speech HA -side of lesion
Abnormalities in other systems can confound the cerebellar exam
UMN - slow, clumsy movement of extreme tiers
LMN- weakness, test requiring little strength can be helpful
Basal ganglia - slow clumsy momvements and or gait unsteadiness
Sensory ataxia - severe loss of position sense (dorsal column/sensory nerves)- should improve w/ visual feedback
Truncal ataxia
Lesion of vermis
Wide based, unsteady, drunk like gait
Severe cases: may also have problems sitting up w/out support
Bilateral disorder affects medial motor systems - fall or sway toward side of lesion
Appendicular ataxia
Lesion of intermediate or lateral cerebellum
Uncoordinated movement of extreme ties
Intention tremor - irregular oscillating movements in multiple planes through trajectory when attempting to move limb toward a target
Lesion of vermis and both cerebellar hemisphere
Exhibit truncal and appendicular ataxia
Ipsilateral localization of ataxia
Lesion of cerebellar hemispheres cause ipsilateral ataxia of extremeties
False localization of ataxia
Can be caused by lesion outside cerebellar cortex that involve cerebellar input or output pathways
Testing for appendicular ataxia
Finger- nose- finger test
-watch for dysmetria and dysrhythmia
Rapid hand movements, foot patting, precision finger tap, rapid alternating movements, overshoot
Testing for truncal ataxia
Tandem gait (heal-to-toe-gait) -pt will tend to fall/sway to side of lesion if it extends slightly into cerebellar hemisphere
Romberg test
-note increased sway or fall
Vasculature
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S/s of cerebellar artery infarcts
Limb ataxia Unsteady gait Nystagmus Vertigo N/V HA
SCA and PICA infarct - cerebellum
Most common
SCA infarct cerebellum
Ipsilateral ataxia w/ little/no BS signs
Mostly involves cerebellum itself and usually spares the lateral BS
PICA infarct cerebellum
Ipsilateral ataxia w/ nystagmus, vertigo, N/V
Involves inf cerebellar peduncle and vestibular nuclei
Also can see signs of lateral medullary (Wallenberg) sysndrome
AICA infarct - cerebellum
Supplies internal auditory artery
Unilateral hearing loss
What can mimic S/S of cerebellar infarcts?
Infarcts to lateral pons or medulla because of cerebellar peduncles and vestibular nuclei involvement
What happens if the cerebellum swells?
Can cause hydrocephalus because of compression of the fourth ventricle, as well as compression of vital brainstem structures, and subsequent herniation
