Anatomy of the cerebellum

Question 1

Where is the cerebellum located?

Answer 1

Dorsal to the pons and medulla, occupying the posterior cranial fossa. Separated from the occipital lobes by the tentorium cerebelli.

Question 2

Name the three lobes of the cerebellum and their primary roles.

Answer 2

Anterior lobe: Regulates muscle tone.

Posterior lobe (largest): Coordinates voluntary movements.

Flocculonodular lobe: Maintains balance and posture (vestibular function).

Question 2

What are the primary functions of the cerebellum?

Answer 2

Maintenance of posture and balance (equilibrium).

Coordination of voluntary movements.

Regulation of muscle tone.

Motor learning and reflex modification.

Question 2

What are the three cerebellar peduncles and their main connections?

Answer 2

Inferior (Restiform body): Afferents (e.g., spinocerebellar, vestibulocerebellar); efferents (e.g., cerebellovestibular).

Middle: Afferents (corticopontocerebellar fibers).

Superior: Efferents (e.g., cerebellorubral, dentatothalamic tracts).

Question 3

What are the three phylogenetic divisions of the cerebellum?

Answer 3

Archicerebellum (oldest): Balance (flocculonodular lobe).

Paleocerebellum: Muscle tone and posture (vermis and paravermis).

Neocerebellum (newest): Motor coordination (cerebellar hemispheres).

Question 4

Name the three layers of the cerebellar cortex.

Answer 4

Molecular layer (outermost).

Purkinje cell layer.

Granular layer (innermost).

Question 5

List the four deep cerebellar nuclei and their functional associations.

Answer 5

Fastigial: Vestibular (axial muscles).

Globose & Emboliform (Interposed): Spinal (distal limbs).

Dentate: Cerebral (sequential movements).

Question 6

Which arteries supply the cerebellum?

Answer 6

Superior cerebellar artery (SCA).

Anterior inferior cerebellar artery (AICA).

Posterior inferior cerebellar artery (PICA).

Question 7

What are the key signs of cerebellar dysfunction?

Answer 7

Ataxia (incoordination).

Dysmetria (overshooting movements).

Nystagmus.

Hypotonia.

Dysdiadochokinesia (rapid alternating movement impairment)

Question 8

A patient presents with left-sided dysmetria, dysdiadochokinesia, and left-beating nystagmus. Where is the lesion likely located?

Answer 8

Left cerebellar hemisphere (cerebellar lesions produce ipsilateral signs).

Question 9

Which fissure separates the anterior and posterior lobes of the cerebellum?

Answer 9

The primary fissure (deepest fissure in the vermis).

Question 9

What is the clinical significance of the tonsillar lobes?

Answer 9

They overhang the foramen magnum; herniation (“tonsillar herniation”) can compress the medulla, causing respiratory failure.

Question 9

What is the “arbor vitae,” and where is it found?

Answer 9

he branching white matter pattern in the cerebellar core (medullary substance), resembling a tree.

Question 9

Which cerebellar zone controls axial muscles (neck, trunk, hips)?

Answer 9

The median (vermian) zone (projects to the fastigial nucleus).

Question 10

Which cerebellar tract carries proprioceptive input from the spinal cord?

Answer 10

Dorsal spinocerebellar tract (enters via the inferior peduncle).

Question 10

How do mossy fibers and climbing fibers differ in their cerebellar connections?

Answer 10

Mossy fibers: Synapse on granule cells (e.g., spinocerebellar/pontocerebellar tracts).

Climbing fibers: Directly synapse on Purkinje cells (e.g., olivocerebellar tract).

Question 10

What is unique about Purkinje cell axons?

Answer 10

They are the only efferent fibers from the cerebellar cortex (inhibit deep cerebellar nuclei).

Question 11

Which nucleus connects the cerebellum to the thalamus?

Answer 11

The dentate nucleus (via cerebellothalamic/dentatothalamic tract in the superior peduncle).

Question 12

What is the efferent pathway of the flocculonodular lobe (archicerebellum)?

Answer 12

Projects to the vestibular nuclei (via cerebellovestibular fibers in the inferior peduncle).

Question 13

Which spinal tracts send information to the paleocerebellum?

Answer 13

Dorsal and ventral spinocerebellar tracts (muscle tone/posture

Question 13

How does the neocerebellum communicate with the cerebral cortex?

Answer 13

Via pontocerebellar fibers (middle peduncle) → cerebellar hemispheres → dentate nucleus → thalamus → motor cortex.

Question 13

Name two inhibitory interneurons in the molecular layer.

Answer 13

Basket cells and stellate cells (both inhibit Purkinje cells).

Question 13

What role do glial cells play in the cerebellar cortex?

Answer 13

Support neurons; Bergmann glia guide Purkinje cell development and synaptic organization.

Question 14

Why does cerebellar damage cause intention tremor?

Answer 14

Due to disrupted error correction during movement (loss of Purkinje cell inhibition on motor pathways).

Question 14

How can cerebellar lesions cause slurred speech?

Answer 14

Poor coordination of orofacial muscles ("scanning dysarthria" from dentate nucleus dysfunction).

Question 14

What cerebellar symptoms can phenytoin (an antiepileptic) cause?

Answer 14

Ataxia, nystagmus, gait disturbances, and dysarthria (due to cerebellar Purkinje cell toxicity).

Question 14

Why do cerebellar lesions cause ipsilateral symptoms?

Answer 14

Efferent pathways double-cross (e.g., cortex → cerebellum → thalamus → cortex → contralateral spinal cord).

Question 15

What causes anterior vermis syndrome, and what are its symptoms?

Answer 15

Chronic alcohol abuse → truncal ataxia (staggering gait) and lower limb dystaxia.

Question 16

What is cerebellar hypoplasia?

Answer 16

Underdevelopment of the cerebellum, leading to lifelong motor coordination deficits.