detailed anatomy of cerebellum

1. - Dr. Gourav D. Thakre

2.  Introduction
 External Features
 Subdivisions Of Cerebellum
 Cytoarchitecture / Histology
 Connections Of Cerebellum
 Intrinsic Cerebellar Circuitry
 Cerebellar Peduncles
 Development Of Cerebellum
 Blood Supply
 Functions
 Applied Anatomy

3. Introduction
 Cerebellum (Latin) - little brain
 Weight- 150 gm
 Location- post. Cranial fossa
 Connected with brainstem
by 3 peduncles
 Imp function of maintenance
of posture, tone , coordination
of voluntary motor activity.

4. External Features
 Parts – hemispheres
vermis- superior
inferior
 Surfaces
 Notches
 Fissures- horizontal
Posterolateral
Fissura prima

5. Subdivisions Of Cerebellum
A. Anatomical subdivisions
B. Morphological subdivisions
C. Functional subdivisions

6. Anatomical Subdivisions
Primary fissure
Anterior lobe
corpus of
cerebellum
Posterior lobe
Posterolateral fissure Flocculonodular lobe

8.  Some neuroscientist map out cerebellum by Ten
Roman numericals

9. Morphological Subdivisions
 Archicerebellum / vestibular cerebellum
 Paleocerebellum / spinal cerebellum
 Neocerebellum / cerebro-pontine cerebellum

10.  Archicerebellum / vestibular cerebellum
 First to appear
 Aquatic vertebrates
 Flocculonodular lobe& lingula
 Maintenance of equilibrium, tone & posture of Trunk
muscles
 Paleocerebellum / spinal cerebellum
 Next to Archicerebellum in evolution
 Terrestrial vertebrates
 Anterior lobe except lingula, pyramid & uvula
 Muscle tone and posture &crude movements of limbs

11.  Neocerebellum / cerebro-pontine cerebellum
 Developmentally last
 Max. development in mammals
 Rest of the cerebellum
 Smooth performance of the skilled acts by
coordination of movements

12. Functional Subdivisions
 Corpus cerebelli (cerebellum except flocculo-nodular lobe)
 Vermal / median
 Nucleus fastigii
 Movement of the trunk & extensor muscle tone
 Pair of Para-vermal / intermediate
 Nucleus interpositus ( globosus , emboliformis)
 Flexor muscle tone
 Pair of hemisphere/ lateral zones
 Nucleus dentatus
 Distal limb muscles for skillful prehensile act.

13. Spinocerebellum:
Vermis
Intermediate hem
Cerebrocerebellum:
Lateral hem.
Spinocerebellum:
IVth vent Vermis
Intermediate hem
Cerebrocerebellum:
Lateral hem.
Floculo-nodular lobe

14. Cytoarchitecture / Histology
 Outer gray matter / cerebellar cortex
 Inner white matter
 Intracerebellar nuclei
 Fissures
 Folia
 Arbor vitae cerebelli

15. Cerebellar Cortex
 Uniform thought/ homotypical
 3 layers
a) Outer molecular layer
b) intermediate Purkinje cell layer
c) Inner granular layer

16. The molecular layer
 300-400 μm thick
 sparse population of neurones, dendritic arborizations,
non-myelinated axons & radial fibres of neuroglial cells
 stellate neurones (superficially)
short processes ,
axons arborise with dendritic
spines of purkinje cells
 basket cells (deeper)
small in size, little cytoplasm
& extensive processes axon
runs transversely parallel to
cortex & rt. Angle to longitudinal axis of folia
synapse with >500 Purkinje cell

17.  Purkinje cell dendritic trees
 Climbing fibres
 Radiating branches from large epithelial (Bergmann)
glial cells give off processes -surround all neuronal
elements, except at the synapses.
 At the surface of the cerebellum their conical
expansions join to form an external limiting
membrane.

18. Purkinje cell layer
 large, pear-shaped somata
 smaller somata of epithelial (Bergmann) glial cells.
 Clumps of granule cells and occasional Golgi cells
penetrate between the Purkinje cell somata.

19.  Dendrites synapse with
 Collaterals from basket cells
 Axons of granule cells
 Climbing fibers
 Axon pass through
granular layer into white
matter
i.e to intracerebellar nuclei
 Sole output from cerebellar cortex
 Inhibitory to the intracerebellar nuclei
 Individual Purkinje cells are separated by 50 μm transversely
& 50-100 μm longitudinally.
 Their somata measure 50-70 μm vertically & 30-35 μm
transversely
 total number of dendritic spines per Purkinje neurone
180,000.

20. Granular Layer
 100 μm thick in the fissures and 400-500 μm on foliar
summits
 2.7 million granular neurones per cubic millimetre
 3000 granule cells for each Purkinje cell.
 granule cell - 5-8 μm in diameter
 3 to 5 short dendrites- end in claw-like terminals
within the synaptic glomeruli
 Axon bifurcates at a “T” junction , branches runs
parallel to long axis of folium (Parallel fibers)
 Also contains few larger Golgi cells , dendrites ramify
in molecular layer

21. Intrinsic neurons of cortex
 5 types- Purkinje cells, granule cells , basket and
stellate cells, Golgi cells
 All are inhibitory except granule cells.

22. synaptic glomerulus

23.  A rosette of mossy fiber in centre ( pre-synaptic
element)
 Claw like dendritic expansions of granule cells
envelops rosette ( post synaptic element)
 Axon terminals of golgi cells come in contact with
granule cell dendrites as pre-synaptic elements

24. Cerebellar Nuclei
 On each side- 4 nuclei
 Lat.- med.
A. Dentate nucleus
B. Emboliform nucleus
C. Globose nucleus
D. Fastigial nucleus Fastigial nucleus
Cerebellar cortex Globose nucleus
Emboliform nucleus
Dentate nucleus
medullary center

25. Dentate nucleus
 Most prominent
 Largest in primates
 Nucleus of neocerebellum
 Crumpled bag shape, hilum facing anteromedially
 Interior filled with white matter
 Fibers mainly forms superior cerebellar peduncle
 Dentorubral(red nucleus- spinal cord), dentothalamic
fibers( ventral lateral nucleus of thalamus- cerebral
cortex)

26. Emboliform nucleus
 Oval, medial to dentate nucleus
 Nucleus of paleocerebellum
 Red nucleus through sup. Cerebellar peduncle
 Red nucleus spinal cord (rubrospinal tract)
 Flexor muscle tone
Globose nucleus
 Rounded
 Between emboliform & fastigial nucleus
 Similar connection as emboliform nucleus
 Globose & Emboliform nucleus collectively called
nucleus interpositus

27. Fastigial nucleus
 Near midline in vermis, close to roof of 4th ventricle
 Nucleus of archicerebellum
 Afferents from flocculonodular lobe
 Efferents to vestibular & reticular nuclei
 Extensor muscle tone

28. Connections Of Cerebellum
 Afferent fibers- cerebral cortex, spinal cord,
vestibular apparatus
 Also from red nucleus, tectum of midbrain
 Cortex- cortico-ponto-cerebellar
cerebro-olivo-cerebellar
cerebro-reticulo-cerebellar pathways
 Spinal cord- post. Spinocerebellar
ant. Spinocerebellar
cuneocerebellar tracts
 Afferent mainly enters through inferior & middle
peduncles

29. Two types of fibers
 Climbing fibers
 Originate in inf. Olivary nucleus
 Collateral to intracerebellar nucleus
 Monosynaptic contact with purkinje cell.
 Mossy fibers
 Ends by forming 30-40 rosette
 Synapse with dendrites of granule cells & axons of
golgi cells
 Forms cerebellar glomerulus.
 Both fibers are excitatory to the purkinje cells
 All afferent fibers are mossy except olivocerebellar &
parolivocerebellar

30.  Efferent fibers- to the red nucleus, thalamus,
vestibular complex & reticular formation
 Entirely from axons of purkinje cells .
 Fibers from dentate, emboliform & globose nuclei-
sup. Cerebellar peduncle
 Fastigial nucleus- inf. Cerebellar peduncle

31. Intrinsic Cerebellar Circuitry
 Feed forward inhibition
 Neural sharpening- row of excited purkinje cells is
surrounded by zone of inhibition at periphery.

32. Cerebellar Peduncles

33. Inferior cerebellar peduncle
Afferent fibers
 Posterior spinocerebellar fibers- ipsilateral thorasic
nucleus (Clarke’s column)
 Olivocerebellar – opposite inf. Olivary nucleus
 Parolivocerebellar fibers- opposite medial & dorsal
accessory olivary nucleus
 Cuneocerebellar- ipsilateral cuneate nucleus
 Anterior external arcuate fibers- arcuate nuclei of both
sides
 Vestibulocerebellar- primarily from vestibular nerve.
Secondary from medial & inf. Vestibular nuclei
 Reticulocerebellar- lateral & paramedian reticular nuclei
of medulla oblongeta

34. Efferent fibers
 Cerebellovestibular fibers- ipsilateral
flocculonodular lobe & fastigial nuclei of both sides
 Cerebelloreticular fibers- fastigial nuclei of both
sides to pontine & medullary reticular formation
 Cerebello-olivary fibers- to inf. Olivary nucleus

35. Middle cerebellar peduncle
Afferents
 Pontocerebellar fibers- forms the bulk of peduncle,
from pontine nuclei to opposite neocerebellar cortex.
(cortico-ponto-cerebellar pathway)
 Reticulocerebellar fibers- reticular formation to
ipsilateral vermal region of cerebellum
 Seratogenic fibers- from raphe nuclei of pons.
No efferent fibers

36. Superior cerebellar peduncle
Afferent fibers
 Anterior spinocerebellar tract
 Tectocerebellar fibers- tectum of midbrain (sup. &
inf. Colliculi of both sides)
 Trigeminocerebellar fibers- sup. Sensory & spinal
nuclei of trigeminal nerve
 Ceruleocerebellar fibers- noradrenergic fibers from
locus ceruleus
 Hypothalamocerebellar fibers- cholinergic fibers
from hypothalamus

37. Efferent fibers
 Cerebellorubral- globose & emboliform nuclei to
contralateral red nucleus
 Dentatorubral & dentatothalamic fibers- dentate
nucleus to opposite red nucleus & thalamus
 Cerebello-olivary fibers- dentate nucleus to opposite
inf.olivary nucleus
 Cerebelloreticular fibers-nucleus fastigius to
reticular nucleus.

38. Development Of Cerebellum
 The cerebellum develops from the rhombic lip, the
dorsal part of the alar plate of the metencephalon
 Two rounded swellings develop which at first project
partly into the ventricle forming the rudimentary
cerebellar hemispheres

39.  With growth, a number of transverse grooves appear on
the dorsal aspects of the cerebellar rudiment(precursors
of the numerous fissures )

40.  early in cerebellar development a layer of cells derived
exclusively from the metencephalic rhombic lip
 cerebellum has an intraventricular portion (cells
proliferating from the ventricular zone) and an
extraventricular portion (cells proliferating from the
external germinative layer) during development
 Before the end of the third month the main mass of the
cerebellum is extraventricular.

41. Four stages in the histogenesis of the
cerebellar cortex and the cerebellar nuclei
 Purkinje cells and cells of the cerebellar nuclei are produced by
the ventricular epithelium and are in the process of migration to
their future positions. The cells of the superficial matrix (the
external granular layer) take their origin from the ventricular
epithelium at the caudal pole of the cerebellar anlage and
migrate rostrally over its surface.

42.  After migration the Purkinje cells constitute a
multicellular layer beneath the external granular layer.
Cell production in the ventricular epithelium has
stopped. The remaining cells transform into
ependymal cells.

43.  Granule cells are produced by the external granular
layer and migrate inwards through the Purkinje cell
layer to their position in the granular layer. Purkinje
cells spread into a monolayer.

44.  Adult position of cortical and nuclear neurones.

45. Blood Supply

46.  Cerebellar veins arranged in 2 groups- superior & inferior
 Sup. Cerebellar vein  partly in straight sinus & great cerebral
vein, partly in transverse & superior petrosal sinus
 Inf. Cerebellar vein  sigmoid, inferior petrosal, occipital
sinus

47. Functions
 ANTICIPATORY FUNCTION
The vermis of the cerebellum is involved in taking
anticipatory action
 POSTURAL FIXATION
The posterolateral region of the cerebellum is required to
prevent oscillation of distal limb parts caused by the
viscoelastic properties of the muscles in response to
sudden movements
 MOTOR LEARNING
when a novel motor skill is being learned, the
olivocerebellar climbing fibre system becomes active when
errors are made. The inferior olivary complex appears to be
involved in correction
 HIGHER FUNCTIONS

48. Applied Anatomy
 Are usually vascular, may be traumatic or tumour.
 Manifestations of unilateral cerebellar lesions :
1-ipsilateral incoordination of (U.L) arm = intention tremors :
it is a terminal tremors at the end of movement as in
touching nose or button the shirt.
2-Or ipsilateral cerebellar ataxia affects (L.L.) leg, causing
wide-based unsteady gait.
 Manifestations of bilateral cerebellar lesions (caused
by alcoholic intoxication, hypothyrodism, cerebellar
degeneration & multiple sclerosis) :
1-dysarthria : slowness & slurring of speech.
2-Incoordination of both arms.= intention tremors.

49. 3-Cerebellar ataxia : intermittent jerky movements or
staggering , wide-based, unsteady gait.
4-Nystagmus : is a very common feature of multiple sclerosis.
It is due to impairment coordination of eye movements /so,
incoordination of eye movements occurs and eyes exhibit a
to-and-fro motion.
 Combination of nystagmus+ dysarthria + intension
tremors constitutes Chacot’triad, which is highly
diagnostic of the disease.

50.  For purpose of localization, cerebellum can be
viewed as a saggitally-oriented structure
containing 3 zones on each side:
 Midline
 Intermediate
 Lateral

51.  Midline zone
 Consists of the anterior and posterior parts of the
vermis, fastigial nucleus and associated input and
output projections
 concerned with posture, locomotion, position of head
relative to trunk, control of EOM’s
 Cerebellar signs resulting from midline cerebellar
disease
 disorders of stance/gait, truncal postural disturbances, rotated
postures of the head, disturbances of eye movements
 Rhomberg Test
 Tests of gait- tandem, toe + heel walking, walking
backward
 Hop on each foot

52.  Intermediate zone
 Consists of paravermal region of cerebellum and
interposed nuclei (emboliform, globose)
 concerned with control of velocity, force and pattern of
muscle activity
 Clinical disorders related to disease of this zone not
clearly delineated

53.  Lateral zone
 cerebellar hemisphere and dentate nucleus on each side
 concerned with the planning of movement in
connection with neurons in the Rolandic region of the
cerebral cortex (fine, skilled)
 Lesions result in abnormalities of skilled voluntary
movements: hypotonia, dysarthria, dysmetria,
dysdiadochokinesia, excessive rebound, impaired check,
kinetic and static tremors, past-pointing
 Finger-to-nose test
 Rapidly alternating movements
 Heel-to-shin test

54.  Hypotonia
 Ataxia
 Dysarthria
 Tremor
 Ocular Motor Dysfunction
 Depending on extent, an individual may have one
symptom or a combination
 In all cases, symptoms from unilateral damage appear on
the side ipsilateral to the injury
 Ascending spinocerebellar pathways are uncrossed and
descending corticoopontocerebellar fibers are crossed; thus
motor deficits from cerebellar damage are ipsilateral to the
lesion whereas motor deficits from damage to motor areas
of the cerebral cortex are contralateral to the lesion

55.  postural instability
 delayed initiation and termination of motor actions
 inability to perform continuous, repetitive movements
 errors in smoothness and direction of a movement
 lack of coordingation or synergy of movement, especially
complex movements
 lack of motor plasticity or learning

57. Cerebellar Medulloblastoma
 Cerebellar tumors on
vermis
 - Truncal Ataxia
 - Frequent Falling
 The child in this picture:
- would not try to stand
unsupported
- would not let go of the bed
rail if she was stood on
the floor.