The Cerebellum
Anatomy of
the Cerebellum
2 hemispheres
with vermis in between
Very folded cerebellar cortex
Underlying white
matter & deep nuclei
Deep nuclei are
the output pathway
Massive cerebellar peduncles (axon bundles to and from cerebellum)
connecting to brainstem
Primitive Cerebellum in Blue
Evolution of
Cerebellum
Oldest part is
the flocculonodular lobe - it gets input from the
vestibular system (Vestibulocerebellar path)
Next: the region
around the vermis gets proprioceptive
& cutaneous input via spinal cord (spinocerebellar tr.)
Most recent
region the hemispheres- get input from cortex via the pons
(corticopontocerebellar path)
All input goes to
cerebellar cortex; all output is from the deep cerebellar nuclei
Loop-like
feedback to each of those sources of input
Mode of Functioning
Totally
unconscious
Computer-like
feedback loops
Moment-to-moment
adjustments
Ipsilateral in its control (right side of cerebellum related to
movements of right side of body)
Cerebellum
Is Needed For:
Fluid
coordination of movements
Synergy/cooperation
between muscles
Precise timing
& targeting of
movements
Appropriate force
& muscle tone
Cerebellum is
storing these details during motor learning
Automatic
adjustments to changing conditions & to maintain balance
Symptoms of Cerebellar Damage
Asynergia - loss of fluid coordination & cooperation
between muscles; movements jerky & disjointed
Dysmetria - poor targeting of movement; over- or under-reach
Cant do finger
to nose test
Intention tremor
while targeting movements (see clip)
Dysarthria/Dysphonia - slurred, uncoordinated speech & speech volume
Lateral lesion-
affects ipsilateral limbs
Symptoms
of Cerebellar Damage
Disturbed balance
(cant balance on 1 foot; walk heel-to-toe)
Gait ataxia
wide-based, staggering walk, may shuffle,veer
to side, may fall
Poor muscle tone
(hypotonia)
Adiadochokinesia/Dysdiadochokinesia - cant rapidly alternate movements http://www.neuroexam.com/36.html
Nystagmus-jerky, oscillating eye movements (see dbnystag. clip)
Midline lesion
most likely to cause gait, posture, balance problems - Romberg test http://www.neuroexam.com/37.html
Test for Dysdiadochokinesia
Medulloblastoma
A cerebellar tumor usually originating in the vermis, which then presses down on the brainstem
Accounts
for ~1 in 20 brain tumors (1 in 5 in kids). 2/3 cases occur before age of 15 (median age = 5-6)
Symptoms:
Falling, nausea & vomiting, double vision,
headache, eventually trouble moving. If its located on midline child will tend
to fall forward or backward
Other Causes of Cerebellar
Damage
Strokes or tumors
affecting cerebellum
Demyelination due to MS
Genetically based
degenerative disorders (e.g. Friedrichs ataxia caused by degeneration of spinocerebellar tracts)
Alcoholic
cerebellar atrophy. Cerebellum can also be damaged by some
anticonvulsants or chemotherapy.