Cerebellum Flashcards
Where is the cerebellum found?
Posterior cranial fossa
What is the name given to the part of the cerebellum that lies along the midline?
Vermis
What divides the vermis and more lateral parts of the cerebellum into the anterior and posterior lobe?
Primary fissure
What is the flocculus? What does it help form?
Small lobe of the cerebellum at the posterior border of the middle cerebellar peduncle
Forms part of the roof of the 4th ventricle (flocculonodular lobe)
Describe the main blood supply to the cerebellum.
Supplied by 3 main arteries:
- Superior cerebellar artery
- Anterior inferior cerebellar artery
- Posterior inferior cerebellar artery (most common site of an infarct in the posterior circulation)
Describe the microanatomy of the cerebellum. (3 distinct layers; what is found in each)
- Outer molecular layer: pale with mostly axons and only a few cells
- Middle layer: single row of Purkinje cells
- Inner layer: granule layer - thick and contains vast numbers of granule cells
Where are the cerebellar input fibres located?
Middle cerebellar peduncle - input fibres from the contralateral cerebral cortex and cranial nerves
Inferior cerebellar peduncle - input fibres from the spinal cord
Where are the cerebellar output fibres located?
Superior cerebellar peduncle
Describe the course of the dorsal/posterior spinocerebellar tract in the body.
This is a column of relay neuron cell bodies within the medial gray matter within the spinal cord in layer VII, specifically between T1-L3
- These neurons then send axons up the spinal cord
- Project ipsilaterally to medial zones of the cerebellum through the inferior cerebellar peduncle
Carries information from proprioceptors (joints, muscle spindles, golgi apparatus)
Describe the course of the ventral/anterior spinocerebellar tract in the body.
- Some neurons of the ventral spinocerebellar tract form synapses with neurons in layer VII of L4-S3
- Most of these fibres cross over to the contralateral lateral funiculus via the anterior white commissure and through the superior cerebellar peduncle
- The fibres then often cross over again within the cerebellum to end on the ipsilateral side. (globose and emboliform nuclei)
- -> tract is sometimes termed the “double-crosser.”
Carries information about the state of reflexes in the spinal cord
(cerebellar signs are always on the same side as the lesion)
What are the deep cerebellar nuclei?
nuclei that lie in the white matter below the cortex through which all input/output to the cerebellar cortex pass
medial -> lateral: Fastigial nucleus; Globose nucleus; Emboliform nucleus; Dentate nucleus
Which parts of the cerebellar cortex are connected to each deep cerebellar nucleus?
Vermis -> Fastigial nucleus
Anterior lobe -> Globose and Emboliform nuclei
Hemispheres -> Dentate nucleus
(Flocculonodular connects to the lateral vestibular nuclei of the pons)
What is the role of the cerebellum in relation to movement?
Helps the motor cortex produce accurate and smooth movements
- modulates + refines motor cortex commands
What are signs of cerebellar damage?
Clumsiness
Abnormal fatigue
Instability
*extraocular eye msucles are particularly affected
What would happen if the deep nuclei were damaged?
Usually the cerebellum exhibits neuronal plasticity meaning that recovery after damage is possible
However, if the deep nuclei are damaged then there will be persistent disability
What are the functional zones of the cerebellum called and what parts of the cerebellum are they comprised of?
- Vestibulocerebellum - comprised of flocculonodular lobe, connected to the lateral vestibular nucleus
- Spinocerebellum - comprised of the vermis, anterior lobes, fastigial nucleus, globose and emboliform nucleus
- Cerebrocerebellum - comprised of the posterior lobe (cerebellar hemisphere) connected to dentate nucleus
What is the role of the vestibulocerebellum?
Coordinates head + eye movements (stability of gaze)
Balance of head on the body - via the medial vestibulospinal tract
Balance of body on the ground - via the lateral vestibulospinal tract
What is responsible for sending motor commands to the head and neck?
Medial longitudinal fasciculus
Medial vestibulospinal tract
What is the role of the spinocerebellum?
Controls locomotion and limb coordination
Sends motor commands down the reticulospinal tract –> coordinate postural and locomotor movements
What is the role of the cerebrocerebellum?
coordinates movement initiated by the motor cortex
speech, voluntary movement of head + arms, hand-eye coordination
What part of the cerebellar cortex and which deep nuclei forms the neocerebellum?
Cerebellar cortex: cerebellar hemispheres
deep nucleus: dentate
Describe the input and output of the neocerebellum.
Input: from the cerebral cortex via the middle cerebellar peduncle
Output: to the motor (VL) thalamus via the superior cerebellar peduncle
What is flocculonodular syndrome and how does it often occur?
Little control of axial muscles - wide based ataxic gait, reeling and swaying, and there is a tendency to fall to the side of the lesion, can also have nystagmus
In severe cases –> cannot sit or stand without falling
Commonly occurs in young children with medulloblastoma in the 4th ventricle (wall)
What is anterior lobe syndrome and how does it often occur?
Characterised by incoordination of the limbs
Ataxia/ataxic gait
Hypotonia
Reflexes may be depressed or pendular (UMN lesion)
It is often seen in alcoholics (malnutrition + lack fo vitamin b) and also associated with damage to the spinocerebellum
What is neocerebellar syndrome and how does it often occur?
Loss of hand-eye coordination
Dysmetria (inaccuracy of reaching with intention tremor)
Dysdiadochokinesis (DDK = irregular performance of rapid, alternating movements of hands)
Kinetic tremor
Loss of good speech/slurred speech (loss of coordination of muscles involved in speech production)
Causes: stroke, tumour, trauma, degenerative diseases
What are the signs of a cerebellar stroke?
- Headache, vertigo, nausea + vomiting
- onset is sudden + severe - Eye changes
- usually affects on eye + contributes to vertigo
- nystagmus
- ptosis (drooping eyelid)
- miosis (constricted pupil) - Dysarthria + dysphagia
- dysarthria = motor disorder of speech, weakening the muscles of the mouth, face and resp system
- speech may be slurred, monotonous, hoarse, may be some drooling
- dysphagia = difficulty chewing/swallowing - incoordination of muscles of throat + oesophagus - Ataxia
- loss of balance + coordination while walking - Arm weakness + incoordination
- usually only in one arm
