Cerebellum

Question 1

Mention differences between cerebrum & cerebellum

Answer 1

1. Cerebellum is not involved in sensory perception
2. Cerebellar lesion does not lead to paralysis
3. Cerebellum body representation is ipsilateral
4. The body is represented in vermis and intermediate part of cerebellar hemisphere in 2 maps in upper map of ant lobe, ipsilateral & upside down, but lower map (post lobe) ipsilateral & upright. Audio-visual represntation is bilateral upright

Question 2

Describe output of spinocerebellum

Answer 2

1. From vermis through fastigial nucleus to brainstem
2. From intermediate zone of cerebellar hemisphere through interposed nuclei to a)VA & VL nuclei of thalamus then to cerebral cortex, b) several midline structures if thalamus then to BG and reticular formation and red nucleus.

Question 3

Describe output of cerebrocerebellum

Answer 3

Projected to dentate nucleus to VA & VL nuclei of thalamus then to cerebral cortex

Question 4

Mossy circuit is concerned with….., its effect on Purkinje cell results in….

Answer 4

Well learned movement
Single spike AP

Question 5

Describe effect of climbing fibers on Purkinje

Answer 5

Act directly on Purkinje fibers to modify their sensitivity
1. In overshooting they increase Purkinje cell sensitivity (rapid inhibition of DNCS) inhibiting the overshooting.
2. In undershooting they decrease Purkinje cell sensitivty (delay inhibitory effect) thus inhibit undershooting
They condition Purkinje cells, and cause complex multipeaked AP

Question 6

Mention functions of vestibulo-cerebellum

Answer 6

Equilibrium & body posture
Control eye movements (vestibulo-occular reflex)

Question 7

Mention functions of spinocerebellum

Answer 7

Servo-comparator function
Control of ballistic movements (Mossy)
Damping function

Question 8

Mention the input of spino-cerebellum of servo-comparator function

Answer 8

1. Information from motor cortex & red nucleus about the intended sequential plan of movement
2. Feedback from body about what actual movement results
3. Efference copy of actual motor control signals that reach anterior motor neurons

Question 9

Mention the output of spino-cerebellum of servo-comparator function

Answer 9

1. Back to cerebral cortex through thalamic relay nuclei
2. To lower part of red nucleus (rubrospinal t.)
3. Brainstem areas which give rise to medial brainstem pathways

Question 10

List functions of cerebrocerebellum

Answer 10

1. Planning of sequential movements
2. Predictive function
3. Timing function for sequential movements
4. Extra motor predictive function for visual & auditory phenomena progression

Question 11

Mention effect of cerebellum on muscls tone

Answer 11

Excitatory to stretch reflex

Question 12

Mention the 2 main manifestations of cerebellar lesions

Answer 12

1. Hypotonia
2. Motor ataxia

Question 13

Desfine symptoms of motor ataxia

Answer 13

Dysmetria, dysartheria, dysdiadokokinesia, decomposition of movement, disturbed gait, intention temors, cerebellar nystagmus, rebound.

Question 14

Decomposition of movement is tested for by…..test

Answer 14

Heel-knee test

Question 15

Lesion of vestibulocerebellum leads to ….&…..

Answer 15

Titubation
Drunken gait

Question 16

Neocerebellar lesion leads to ….. gait

Answer 16

Zigzag-like

Question 17

Gait in case of LL monopelgia is….., while in case of paraplegia is…..

Answer 17

Spastic gait (circumduction)
Sissoring gait

Question 18

Site & grade of medulloblastoma

Answer 18

Cerebellum/dorsal brain stem
Grade VI

Question 19

Describe gross picture of medulloblastoma

Answer 19

Mostly arise in vermis, as pink/grey friable mass that fill 4th ventricle. In cerebellar hemispheres they tend to be more firm & circumscribed & generally of desmoplastic/nodular variant. Small foci of necrosis may be grossly evident but extensive necrosis is rare.

Question 20

Describe microscopic picture of medulloblastoma

Answer 20

Variants: classic, desmplastic/nodular, medulloblastoma with extensive nodulatrity, large cell/anaplastic
Classic form shows densely packed small round cells with mild to moderate nuclear pleomorphism & high mitotic count. May show Homer-Wright rosettes (primitive tumour cells surrounding central neuropil)