Cerebellum - Lecture 13

What is the main role of the cerebellum?

Coordination of skeletal muscle action with the cerebral cortex and basal ganglia.

How does the cerebellum help ongoing motor activity?

It modifies motor neuron activity to provide error correction.

What other functions does the cerebellum support?

Posture, balance, muscle tone, and motor memory.

What are examples of motor memory activities?

Bicycle riding and dancing.

What does the term cerebellum mean?

Little brain.

Where is the cerebellum located?

Posteriorly.

What connects the cerebellum to the brainstem?

The cerebellar peduncles.

What is the function of the superior cerebellar peduncle?

Efferents to the red nucleus and thalamus.

What is the function of the middle cerebellar peduncle?

Afferents from the pons and cortex.

What is the function of the inferior cerebellar peduncle?

Connections to and from the vestibular nuclei.

What does an afferent pathway carry?

Input toward a structure.

What does an efferent pathway carry?

Output away from a structure.

What are folia?

Folds that increase the surface area of cerebellar gray matter.

What percentage of the neocortex does the cerebellar surface area represent in humans ?

80%.

What percentage is represented in non-human primates?

33%.

What higher-level functions might the cerebellum help support?

Language and abstract reasoning.

How might the cerebellum contribute to conceptual movements?

By helping coordinate mental processes, such as rearranging a movement plan.

What is the function of the lateral cerebellum?

Motor planning.

What is the function of the intermediate cerebellum?

Muscle regulation of distal extremities.

What is the function of the medial cerebellum (vermis)?

Control of the trunk and proximal extremities.

What is the function of the flocculonodular lobe?

Balance and vestibular/vision coordination.

What are the three cerebellar cortex layers from superficial to deep?

Molecular layer, Purkinje cell layer, and granule cell layer.

What characterizes the molecular layer?

Low density of cellular nuclei; contains inhibitory stellate and basket cells.

What characterizes the Purkinje cell layer?

Large multipolar neurons whose axons project to the deep cerebellar nuclei.

What is the neurotransmission effect of Purkinje cells?

Inhibitory.

What characterizes the granule cell layer?

High density of cellular nuclei; contains excitatory granule cells and inhibitory Golgi cells.

What are the two main input fiber types to the cerebellum?

Mossy fibers and climbing fibers.

What are mossy fibers?

The primary input to the cerebellum.

Where do mossy fibers originate?

Cerebral cortex, spinal cord, and vestibular system.

Are mossy fibers excitatory or inhibitory?

Excitatory.

Which cells receive excitatory input from mossy fibers?

Granule cells, deep cerebellar nuclei, and Golgi cells.

How do climbing fibers project in the cerebellum?

They send excitatory branches to the deep cerebellar nuclei and to Purkinje cells in the molecular layer.

Are climbing fiber inputs excitatory or inhibitory?

Excitatory.

Why are climbing fibers visually compared to ivy?

They wrap around Purkinje cell projections.

What is the only descending pathway from the cerebellar cortex?

Purkinje cells.

What signal do Purkinje cells send to the deep cerebellar nuclei?

An inhibitory signal.

Which cerebellar cells are excitatory?

Granule cells.

Which cerebellar cortical cells are inhibitory?

Stellate cells, basket cells, Golgi cells, and Purkinje cells.

Which cerebellar layer contains stellate and basket cells?

Molecular layer.

Which cerebellar layer contains Purkinje neurons?

Purkinje cell layer.

Which cerebellar layer contains granule and Golgi cells?

Granule cell layer.

What is the effect of granule cells?

Excitatory.

What is the effect of Golgi cells?

Inhibitory.

What is the effect of stellate and basket cells?

Inhibitory.

What is the effect of Purkinje cells on deep cerebellar nuclei?

Inhibitory.

Which two input fibers provide excitatory signals to the cerebellum?

Mossy fibers and climbing fibers.

What is the most common manifestation of cerebellar dysfunction?

Ataxia.

What is ataxia?

Unsteady gait.

What causes of cerebellar dysfunction are listed ?

Toxicity, genetic disorders, and trauma.

Which toxic substances are associated with cerebellar dysfunction?

Alcohol, lithium, and some anticonvulsants.

Which genetic disorders are associated with cerebellar dysfunction?

Spinocerebellar ataxia and Friedreich's ataxia.

What can cause traumatic cerebellar injury?

Stroke and accidents.

What is hypotonia?

Decreased muscle tone.

What condition is described in relation to causing infant hypotonia?

Cerebral palsy

What is nystagmus?

Lateral movement of the eyes.

Damage to which structure is associated with nystagmus?

The flocculus.

What function of the flocculus is related to nystagmus?

Neural integration for gaze-holding.

What structural change is seen in alcoholic cerebellar degeneration?

Increased space between folia.

What symptoms are associated with alcoholic cerebellar degeneration?

Moderate ataxia, unsteady gait, difficulty standing, and a positive Romberg sign.

What is a positive Romberg sign ?

Loss of balance when the eyes are closed.

What is typically preserved in the alcoholic cerebellar degeneration case described?

Normal speech, eye function, alertness, and mental status.

What characterizes alcoholic cerebellar degeneration?

A chronic, slowly progressive condition localized to the cerebellum.

What is Dandy-Walker syndrome?

A rare genetic disorder involving a poorly developed cerebellum and an enlarged fourth ventricle.

What causes the hydrocephalus described in Dandy-Walker syndrome?

Enlargement of the fourth ventricle.

What are infant symptoms of Dandy-Walker syndrome?

Rapidly increasing head circumference, bulging fontanelle, irritability, vomiting, and poor feeding.

What symptoms may occur in older children with Dandy-Walker syndrome?

Balance difficulties, impaired coordination, poor fine motor control, and diplopia.

How is Dandy-Walker syndrome managed?

Ventriculoperitoneal shunt.

Which three arteries supply the cerebellum?

Superior cerebellar artery (SCA), anterior inferior cerebellar artery (AICA), and posterior inferior cerebellar artery (PICA).

Why can cerebellar artery problems cause brainstem symptoms?

These arteries also supply the cerebellar peduncles and brainstem.

Which cerebellar artery is associated with the most common and largest cerebellar infarcts in the slides?

PICA.

What symptoms are associated with PICA infarction?

Sudden spinning dizziness, ipsilateral gait ataxia, truncal instability, and posterior headache with nausea or vomiting.

What dangerous complications can occur with large PICA infarcts?

Obstructive hydrocephalus and foramen magnum herniation.

Which artery affects the anterior inferior cerebellum, flocculus, and middle cerebellar peduncle?

AICA.

What are the characteristic symptoms of AICA infarction?

Facial palsy, deafness, and contralateral loss of pain and temperature.

How does AICA infarction differ from lateral medullary syndrome?

It resembles lateral medullary syndrome but does not affect cranial nerves IX and X.

What is the most common cause of SCA infarction

Embolism.

What are the most common symptoms of SCA infarction?

Gait and limb ataxia with dysarthria.

What other symptoms may occur with SCA infarction?

Headache and vertigo, less commonly than in PICA territory.

What additional symptoms may occur if SCA infarction affects the upper pontine and midbrain tegmentum?

Contralateral pain and temperature impairment of the face and limbs

contralateral CN IV paresis

ipsilateral involuntary movements

Horner's syndrome.

What are the three signs of Horner's syndrome listed in the slides?

Miosis, ptosis, and anhidrosis.