Cerebellum Flashcards
3 principle motor functions of cerebellum
Tone
Posture and balance
Co-ordination of movements
From which emrbyological precursor does cerebellum arise?
From metencerphalic portion of rhombencephalon
What are the three principle lobes of cerebellum
Anterior
Posterior
Flocullus
Function of flocculonodular lobe
Balance (most primitive) of head and eyes
Archicerebellum=
Floculonodular lobe
Paleocerebellum=
Anterior lobe
Function of anterior lobe of cerebellum?
Tone
Neocerebellum=
Posterior lobe
Function of posterior lobe
Co-ordination of movement
Which fissure divides anterior and posterior cerebellar lobes?
Primary fissure
Which fissure separates posterior lobe from floculonodular lobe
Posterolateral fissure
What is the name of the area of the cerebellum adjacent to the vermis?
Paravermal area/ Intermediate zone
What is the arrangement of the sensory homunculus of the cerebellum
In which portion of the cerebellum is the control of trunk and axial musculature found?
Vermal area
Where in the cerebellum is the control of the hands or feet?
Paravermal area
What are the two types of grey matter in the cerebellum?
Cerebellar cortex
Deep cerebellar nuclei
How can the afferent fibres to cerebellum be classified?
Those coming from alll portions of CNS - mossy fibres
Those coming from inferior olivary nucleus (olivocerebellar fibres- climbing fibres)
Spartans are climbing the olive tree to cerebellar cortex
Olivocerebellar fibres= climbing fibres
Spartans- contain aspartate
All fibres which enter cerebellum are
Exctitatory
Which neurotransmitters are released by mossy fibres?
Glutamate
Layers of cerebellar cortex
My
Personal
Garden
Molecular
Purkinje
Granular
With what must all fibres entering cerebllar cortex synapse before entering cortex?
Deep cerebellar nuclei
With what deeper structure do cells from the purkinje layer synapse?
Is this inhibitory or excitatory?
Deep cerebellar nuclei
Inhibitory (GABA)
With what do climbing fibres synape?
Dendrites of Purkinje cells in molecular layer of cerebellar cortex
Output from cerebellum is from which structures?
Deep cerebellar nuclei
With what layer of cortex do mossy fibres synapse?
Multiple dendrites with multiple granular cells
What happens to axons from the granular cell layer
Ascend to molecular layer and connects with millions of Purkinje cell dendrites as parallel fibres
Ratio of climbing fibre connections to Purkinje cells
1:1
Granular cells release which neurotransmitter?
Glutamate
What are the inhibitory cells of the granular layer of the cerebellar cortex?
What stimulates them?
Golgi cells (stimulated by parallel fibres of granular cells and directly by mossy cells)
Inhibitory to granular cells
What are the inhibitory cells of the molecular layer?
Basket and stellate cells
Function of stellate and basket cells
Inhibit Purkinje cells surrounding that activated by parallel fibres from the granular cell, dampens down background noise in effect.
Spinocerebellum=
Paleocerebellum
Archicerebellum=
Vestibulocerebellum
Neocerebelllum=
Cerebrocerebellum
What happens to fibres from vestibular system
Enters vestibular apparatus then cerebellum
Some enter cerebellum directly
Via which cerebellar peduncle do vestibulocerebellar fibres enter cerebellum?
Inferior cerebellar peduncle
What happens to fibres from the deep nucleus of floculonodular lobe?
Some return to vestibular apparatus (cerebellovestibular fibres)
Fibres from the vestibular apparatus descend as vestibulospinal tract
some interact with reticular nuclei and descend in reticulospinal tract
Some ascend from vestibular apparatus and influence CN3, 4, 6 as MLF
What is the function of the vestibulospinal tract
Extensor muscle tone
What is the deep nucleus of the floculonodular lobe?
Fastigial nucleus
Through which cerebellar peduncle does the dorsal spinocerebellar tract pass?
Ipsilateral inferior cerbellar peduncle
What is the nucleus of 2o spinocerebellar neurones?
Nucleus of Clark
How does proprioceptive information from upper limb enter cerbellum?
Cuneocerebellar pathway
How does ventral spinocerebellar pathway enter cerebellum?
Superior cerebellar peduncle then decussate again
Where do ventral spinocerebellar neurones decussate?
At level of spinal cord and again in the cerebellum
What additional information is carried by ventral spinocerebellar tract to cerebellum?
Carries information about descending corticospinal information
What is the most lateral deep cerebellar nuclei?
Dentate nucleus
What is the most medial deep cerebellar nuclei?
Fastigial
Deep cerebellar nuclei from lateral to medial
Don’t eat greasy food
Dentate
Emboliform
Globose
Fastigial
With which system is the fastigial nucleus intimately associated?
Vestibulocerebellar
With which system are the globose and emboliform nuclei associated?
Spinocerebellum
Dentate nucleus associated with which cerebellum
Cerebrocerebellum/neocerebellum
What are the interposed nuclei?
Globose and emboliform
What is the output of the interposed nuceli?
Spinocerebellar outflow:
Cerebellorubrothalamic fibres
Cerebellothalamic fibres
Cerrebellorubrospinal fibres
What is the output of neocerebellum?
Via dentate nucleus:
Dentorubrothalamic fibres
Dentothalamic fibres
What are the aminergic fibres of the cerebellum/
There are serotonin containing axons from the raphe nuclei of brainstem
Noradrenergive fibres from the locus coeruleus
What are the only excitatory cells in the cerebellar cortex?
Granule cells
Describe the cerebellar circuit
Excitatory input is derived from mossy and climbing fibres which are received by Purkinje cells directly and indirectly.
These are responsible for the inhibitory output of the cerebellar cortex
The excitatory input to the Purkinje cells is. modified by modulating interneurons
Deep cerebellar nuclei from medial to lateral
Fastigial
Globose
Emboliform
Dentate
FGED
What are the sources of input to the deep cerebellar nuclei
Excitatory input derived from fibres originating in cells outside the cerebellum (ponotcerebellar, spinocerebellar, olivocerebellar fibres)
Inhibitory input from fibres that arise from the Purkinje cells of cortex
Which of the deep cerebellar nuclei projects through the inferior cerebellar peduncle?
Fastigial nucleus-> brainstem
Remaining nuclei project to brainstem and cortex via thalamus through the superior peduncle
What are the main cerebellar afferents
Cortex
Spinal cord
Vestibular nerve
Describe corticocerebellar afferents
Cortical projections synapse with three structures prior to the cerebellum-
Pontine nuclei, inferior olivary nucleus, reticular formation
Corticopontocerebellar pathway
Originates from a large area of the cerebral cortex descends through the corona radiata and IC and terminates in pontine nuclei
The pontine nuclei cells give rise to mossy fibres that decussate to reach the opposite cerebellar hemisphere via the middle cerebellar peduncle
Cortico-olivocerebellar pathway
Large area of cerebral cortex descending to bilateral inferior olivary nuclei.
Cells of the olivary nuclei give rise to climbing fibres that cross the midline to enter the opposite cerebellar hemisphere via the inferior cerebellar peduncle
Cortico-reticulocerebellar pathway
Descends from cortex and terminates bilaterally in the reticular formation to give mossy fibres that enter the ipsilateral cerebellar hemisphere via the inferior and middle cerebellar peduncle
Which of the afferent cerebellar pathways is not bilateral
Corticopontocerebellar
Which of the afferent cerebellar pathways passes through the inferior cerebellar peduncle?
Cortico-olivocerebellar
Corticoreticulocerebellar
Which of the afferent cerebellar pathways passes through the middle cerebellar peduncle?
Corticopontocerebllear
Corticoreticulocerebellar
What are the three afferent spinocerebellar pathways?
Ventral spinocerebellar tract
Dorsal spinocerebellar
Cuneocerebellar
Ventral spinocerebellar
Originates in the ventral and intermediate gray matter of the spinal cord
Most decussate to enter the contralateral ventral spinocerebellar tract on the other side but some ascend ipsilaterally.
After ascending, the ventral spinocerebellar tract enters that cerebellum via the superior cerebellar peduncle, crosses the midline for a second time and terminates as mossy fibres in the ipsilateral cerebellar cortex
Carries mainly proprioceptive fibres from the lower limbs to the ipsilateral cerebellum
Ventral spinocerebellar tract function
Carries predominantly proprioceptive information from lower limbs to ipsilateral cerebellar hemisphere
Dorsal spinocerebellar tract
Originates in nucleus dorsalis (Clarke’s column)
Most fibres uncrossed
Ascends bilaterally in the ventrolateral region of the lateral funiculus
Enters the cerebellum via the inferior cerebellar peduncle and terminates as mossy fibres
Functionally this tract carries sensory information from one side of the body (trunk and lower. limbs) to the ipsilateral cerebellum
Dorsal spinocerebellar tract function
Carries sesnory (mainly proprioceptive) from one side of the body to the ipsilateral cerebellum.
Cuneocerebellar tract
Afferent cerebellar connection
Originates in the accessory cuneate nucleus of the medulla
Upper limb equivalent of dorsal spinocerebellar tract
Enters ipsilateral cerebellar hemisphere via the inferior cerebellar peduncle.
Transmits mainly proprioceptive information from upper limb and upper thorax
Cuneocerebellar tract function
Analagous to dorsal spinocerebellar tract
Proprioceptive information form upper limb and thorax
Vestibular afferents
Vestibular nerve fibres terminate in vestibular nucleus then send mossy fibres to the ipsilateral flocculonodular lobe via the inferior cerebellar peduncle
Efferent cerebellar connections
Entire output of the cerebellum is via the inhibitor Purkinje cells
Cells of the deep cerebellar nuclei constitute the entire efferent outflow syste,
These leave the cerebellum via the superior and inferior cerebellar peduncles to terminate in
Red nucleus
Thalamus
Vestibular complex
Reticular formation
Efferent fibres transmitted by superior cerebellar peduncle
Fibres passing to red nucleus and thalamus
Efferent fibres via inferior cerebellar peduncle
To vestibular and retiuclar formation
Describe efferents to red nucleus
Globose and emboliform nuclei send fibres through the superior cerebellar peduncle to contralateral red nucleus.
Which then projects fibres as the crossed rubrospinal tract
The function of rubrospinal tract
Infleunces flexor activity of the extremities
Which cerebellar nuclei send fibres to which red nucleus
Globose and emboliform to the contralateral red nucleus
Fibres from left emboliform/globose nuclei exert influence via rubrospinal tract on which side of body
Left
Contralateral red nucleus
Then crossed rubrospinal tract
Efferents from which cerebellar nuclei project to the thalamus
Dentate
(and some from globose and emboliform)
Via superior cerebellar peduncle
Contralateral thalamus
Coordination of which side of the body is influenced by the dentate nucleus?
Ipsilateral
Sends fibres via the thalamus to the contralateral primary motor cortex, the corticospinal tract of which projects to the same side as the dentate.
Which cerebellar nucleus sends efferent fibres to the vestibular complex
Fastigial nucleus
Descirbe efferent cerebellar fibres to the vestibular complex
Axons from the fastigial nucleus pass through inferior cerebellar peduncle to terminate on the lateral vestibular nucleus on both sides
Some Purkinje axons project directly onto the lateral vestibular nucleus.
Neurones of the lateral vestibular nucleus form the uncrossed descending vestibulospinal tract
Thus neurones from fastigial. nucleus facilitates ipsilateral extensor muscle tone.
Cerebellar efferents to the reticular formation
Fastigial nucleus axons pass through the inferior cerebellar peduncle to synapse with cells in the reticular formation on both sides.
The reticular formation descends as the reticulospinal tract which projects bilaterally to the spinal gray matter.
Fibres in superior cerebellar peduncle
Efferent fibres from globose, emboliform and dentate nuclei
Ventral spinocerebellar tract
Middle cerebellar peduncle fibres
Afferent pontocerebellar fibres from contralateralside
Inferior cerebellar peduncle fibres
Afferent fibres:
Dorsal spinocerebellar tract
Cuneocerebellar tract
Olivocerebellear tract
Vestibulocerebelar tract
Reticulocerebellar tract
Fastigial effernts to lateral vestibular nucleus and reticular formation
What is the general function of the cerebellum
Receives cortical proprioceptive input, spinal proprioceptive input and vestibular input vai mossy and climbing fibres which excite Purkinje cells
Purkinje cells inhibit deep cerebellar nuclei influence of descending motor pathways
To modulate motor output based on information about joint position
Vestibulocerebellum
Floculonodular lobe
Receives mossy fibres from ipsilateral vestibular nuclei and vestibular ganglion via inferior cerebellar peduncles
Also receives information from LGN, superior colliculi and striate cortex
Sends efferents via Fastigial nucleus-> inferior cerebellar peduncle-> vestibular nuclei
Function of vestibulocerebellum
Influences primary motor activity through its contacts with the vestibulospinal tract
Concerned with adjustment of axial muscle tone and maintenance of equilibrium
Role in eye movements, control and coordination of head and eye movements
Spinocerebellum
Vermis and intermediate part of cerebellar hemisphere
Somatosensory information from the dosral and ventral spinocerebellar tracts and auditory/visual/vestibular systems.
Two parts are composed of two separate output pathways
Vermis purkinje cells
Intermediate cerebellar hemispheric cells
Conrtols execution of movement and regulates muscle tone.
Function of vermis Purkinje cells in spinocerebellum
Vermis Purkinje cells-> Fastigial-> reticular formation, lateral vestibular nucleus and 1o motor cortex via relays in ventorlateral thalamus-> control of medial descending systems controlling axial and proximal musculature
Function of intermediate Purkinje cells in spinocerebellum
Sends axons to interposed nuclei (globose and emboliform) which project to rubrospinal and lateral corticospinal tracts
Responsible for control of the lateral descending systems which regulate appendicular muscles.
Cross twice so ipsilateral
Pontocerebellum
Large lateral regions of the cerebellar hemispheres
Input is from latera areas of contralateral cerebral cortex, especially parietal and frontal lobes via corticopontine fibres that enter the cerebellum through the middle cerebellar peduncle
Effernts project via dentate nuelcus to the ventrolateral nucleus of the thalamus to the primary motor cortex completing the corticopontinethalamocortical loop
Decussates in both cerebellar peduncle and corticospinal tract so it is ipsilateral.
Involved in precision in the conrtol of rapid limb movements and with tasks requiring fine dexterity.
Destructive lesions in the pontocerebellum
Can lead to movement disorders e.g. delay in initiation or termination of movement or involuntary tremor at the end of a movement.
Symptoms of cerebellar disease
HA
N+V
Gait disturbance
Vertigo
Midline structures in cerebellum
Anterior and posterior vermis
Flocculonodular lobe
Fastigial nuclei
Involved in equilibrium required during ambulation, maintenance of truncal posture and control of extra-ocular eye movements
Signs of midline cerebellar disease
Gait difficulty
Truncal ataxia
Abnormal head postures
Oculomotor dysfunction
Features of truncal instability 2o to cerbellar disease
May be manifested during walking by a tendency to fall towards the side of the lesion
While sitting patient may lean or fall to one side
Falling to left in cerebellar pathology
?Left sided lesions
Gait disturbance in cerebellar disease
Wider than normal base
Unsteadiness
Irregularity of steps
Lateral veering
Lateral lesions tend to cause the patient to veer towards the side of the lesion
Mild gait disturbance may be exacerbated by asking the patient to tandem walk.
Abnormal head postures in cerebellar disease
May be due to midline or lateral lesions
Can present as a head tilt or rotation
Primary disorders of gaze with cerbellar pathoology
Nystagmus
Ocular dysmetria
Nystagmus associated with midline cerebellar pathology
Gaze-evoked
Rebound
Optokinetic
Gaze evoked nystagmus
Fast saccade to laterally located target with slow movement back to mid-position
Rebound nystagmus
Type of gaze-evoked nystagmus that changes direction after sustained lateral gaze or refixation to the primary position
https://collections.lib.utah.edu/ark:/87278/s6089dz6
Optokinetic nystagmus
Non-pathological nystagmus which develops normally when an individual attempts to count the stripes on a rotating drum or moving cloth strip
In the presence of cerebellar disease, optokinetic nystagmus may become exaggerated, producing unusually large amplitudes of both the fast and slow components.
Ocular dysmetria
Conjugate overshoot of a target with voluntary saccades
Eyes appear to jerk back and forth because of repeated inaccuracies in saccadic movements intended to bring the target to the fovea.
Signs of lateral cerebellar disease
Involves lateral hemisphere, dentate and interposed nuclei
Hypotonia
Dysarthria
Limb ataxia
Intention tremor
Impaired check
Oculomotor disorders
Hypotonia in cerebellar disease
Seen in lateral cerebellar disease
Decreased resistance to passive movement of the limbs
May find an increased duration and amplitude of swing in patellar reflex (pendular cerebellar reflex), slower rate than clonus
Pendular cerebellar reflex
https://www.youtube.com/watch?v=_ff4FN8mGbc
Seen in the hypotonic lower limb in the context of cerebellar disorder
Should be distinguished from clonus which at occurs at a more rapid rate.
Dysarthria
Dysarthria of cerebellar disease is characterised by slow, laboured, slurred or garbled speech
Intact comprehension and grammar
Limb ataxia
Dysmetria and decomposition of movement
Dysmetria- error in trajectory and speed of movement, most easily demonstrated in the UE using a finger to nose test. Frequently patients with cerebellar disease will have past-pointing with over or undershoot when approaching the nose
Decomposition of movement involves errors in the sequence and speed of the component parts of the movement e.g. dysdiadochokinesia
Intention tremor
Irregular rhythmic interruption of voluntary movement that begins and increases as the patient approaches a target
Distinguished from rest tremor as it occurs on movement and from action tremor which is seen from beginning to end of the movement.
Impaired check
Wide excursion of a limb following the involuntary displacement of lib.
Oculomotor disorders with lateral hemispheric disease
Opsoclonus
Ocular flutter
Ocular bobbing
Ocular myoclonus
Opsoclonus
Constant, random, conjugate saccades of unequal amplitudes in all directions.
Frequently they are most marked immediately before and after a fixation
https://youtu.be/r1LQwWkaY9s?t=62
Constant, random, conjugate saccades of unequal amplitudes in all directions.
Frequently they are most marked immediately before and after a fixation
https://youtu.be/r1LQwWkaY9s?t=62
Opsoclonus
Ocular flutter
Rapid to and fro oscillations of the eyes
Abrupt in onset lasting only for seconds and disturbing vision for duration of episode
https://youtu.be/JV2z8bmTLHg?t=71
Rapid to and fro oscillations of the eyes
Abrupt in onset lasting only for seconds and disturbing vision for duration of episode
https://youtu.be/JV2z8bmTLHg?t=71
Ocular flutter
Ocular bobbing
Intermittent abrupt downward displacement of the eyes followed by a slow and synchronous return to primary position.
Relatively quick downward displacement is slower than the fast phase of nystagmus
Should be distinguished from downbeat nystagmus which is associated with cervicomedullary lesions.
Horizontal eye movements are typically paralysed
https://www.youtube.com/watch?v=YAUT15d1YBU
Intermittent abrupt downward displacement of the eyes followed by a slow and synchronous return to primary position.
Relatively quick downward displacement is slower than the fast phase of nystagmus
Should be distinguished from downbeat nystagmus which is associated with cervicomedullary lesions.
Horizontal eye movements are typically paralysed
Ocular bobbing
https://www.youtube.com/watch?v=YAUT15d1YBU
Ocular myoclonus
Rhythmic pendular oscillation of the eyes associated with synchronous oscillations of the palate
https://www.youtube.com/watch?v=OqZk5eeaL-U
Rhythmic pendular oscillation of the eyes associated with synchronous oscillations of the palate
https://www.youtube.com/watch?v=OqZk5eeaL-U
Oculopalatal myoclonus
This is a , usually vertical, pendular nystagmus associated with a synchronous rhythmic movement of the palate, developing months after a severe brain stem stroke. The stroke involves the dentato0rubro-olivary tract (Mollaret’s triangle). MRI can show hypertrophy of the inferior olivary nucleus in the medulla.
Hypertrophic olivary degeneration (HOD) is a rare condition characterized by a unique pattern of trans-synaptic degeneration. It is caused by a lesion in the triangle of Guillain and Mollaret, resulting in hypertrophy of the inferior olivary nucleus.
Palatal myoclonus, rhythmic involuntary movement of the soft palate, uvula, pharynx, larynx and upper extremity are classically described clinical features
Constituents of floculonodular lobe
Nodule
Inferior medullary velum
Flocullus
9 lobules of the vermis
LCCDFTPUN
Lingula
Central lobule
Culmen
Decline
Folium
Tuber
Pyramid
Uvula Nodule
Lingula (tongue)
Light blue- SCP.
Central lobule
Culmen (i.e. highest point)
Declive
Folium
Tuber
Pyramid
Uvula
Nodule
