Neuroscience Week 4: Cerebellar pathways

Question 1

MCP AKA

Answer 1

The middle cerebellar peduncle

Question 2

ICP AKA

Answer 2

The inferior cerebellar peduncle

Question 3

SCP AKA

Answer 3

superior cerebellar peduncle

Question 4

The middle cerebellar peduncle afferent/efferent?

Answer 4

• Is an afferent pathway into the cerebellum.
• It encompasses fibers that originate from pontine nuclei.

Question 5

The inferior cerebellar peduncle afferent/efferent?

Answer 5

• Is an afferent pathway into the cerebellum.
• it receives fibers from throughout the brainstem and spinal cord.

Question 6

The superior cerebellar peduncle afferent/efferent?

Answer 6

Sends efferent fibers out of the cerebellum.

Question 7

The anterior spinocerebellar tract exception

Answer 7

enters the cerebellum through the superior cerebellar peduncle, which defies this peduncle’s role as an outflow pathway.

Question 8

enters the cerebellum through the superior cerebellar peduncle, which defies this peduncle’s role as an outflow pathway

Answer 8

The Anterior spinocerebellar tract

Question 9

Select midline cerebellar tracts exception

Answer 9

• exit the cerebellum through the inferior cerebellar peduncle, which defies this peduncle’s role as an inflow pathway.

Question 10

Key fiber tracts of the MCP comprises

Answer 10

corticopontocerebellar fibers, which are critical for the modulation of movement.

Question 11

Key fiber tracts of the ICP are the

Answer 11

spinocerebellar tracts and the olivocerebellar fibers (known as climbing fibers)

Question 12

Spinocerebellar pathways

Answer 12

• Three of the four spinocerebellar pathways enter the cerebellum through the inferior cerebellar peduncle: the posterior spinocerebellar tract, cuneocerebellar tract, and rostral spinocerebellar tract.
• The fourth spinocerebellar tract, the anterior spinocerebellar tract, defies the general organization of cerebellar inflow and enters the cerebellum through the superior cerebellar peduncle.

Question 13

Brainstem pathways that enter the cerebellum (other than the climbing fibers)

Answer 13

and enter through the inferior cerebellar peduncle are: the reticulo- and trigeminocerebellar fibers, and fibers from the vestibular nucleus and nerve, itself.

Question 14

Pathways that exit the cerebellum through superior cerebellar peduncle are the

Answer 14

• dentatorubal and dentatothalamic tracts, which project rostrally; the dentatoreticular tract, which projects caudally; and fibers from the globose and emboliform nuclei, which reach the region of the red nucleus responsible for the rubrospinal tract.

Question 15

Pathways that exit the cerebellum through superior cerebellar peduncle are the

Answer 15

dentatorubal and dentatothalamic tracts, which project rostrally; the dentatoreticular tract, which projects caudally; and fibers from the globose and emboliform nuclei, which reach the region of the red nucleus responsible for the rubrospinal tract.

Question 16

THE CORTICOPONTOCEREBELLAR PATHWAY: The clinical application of this pathway comes in the analysis of

Answer 16

cerebellar deficits

Question 17

Cerebellar injuries cause ipsilateral/contralateral deficits

Answer 17

Cerebellar injuries cause ipsilateral deficits.

Question 18

If a person has a cerebellar deficit (for instance, incoordination) due to brainstem injury,

Answer 18

then either the ipsilateral cerebellum or a portion of this pathway (somewhere along its course) is affected

Question 19

If the area of injury localizes contralateral to the side of the body that is affected, think of a

Answer 19

corticopontocerebellar pathway lesion

Question 20

corticopontocerebellar pathway originates in

Answer 20

The bulk of the pathway originates in the primary motor and sensory cortices; we exclude the lesser contributions from more wide-reaching brain regions.

Question 21

corticopontocerebellar pathway fiber count as compared to the corticospinal tract

Answer 21

Nearly 20 million fibers are dedicated to the corticopontocerebellar pathway, whereas only 1 million fibers are dedicated to the corticospinal tract.

Question 22

The corticopontocerebellar fibers first descend to the

Answer 22

pontine nuclei, where they make their primary synapse.

Question 23

corticopontocerebellar fibers make their primary synapse in the

Answer 23

pontine nuclei

Question 24

The pontine nuclei project across

Answer 24

midline through the MCP into the contralateral cerebellar cortex

Question 25

The cerebellar cortex projects to the

Answer 25

dentate nucleus, which lies deep within the cerebellum

Question 26

The dentate projects fibers out of the

Answer 26

cerebellum through the superior cerebellar peduncle, which cross midline within the midbrain, inferior to the red nucleus, to synapse in the ventrolateral nucleus of the thalamus and also in the red nucleus.

Question 27

The red nucleus projections typically originate from the

Answer 27

globose and emboliform nuclei, which lie medial to the dentate nucleus, whereas the thalamic projections typically originate from the dentate nucleus.

Question 28

The thalamus projects back to the

Answer 28

primary motor strip to complete the corticopontocerebellar pathway.

Question 29

corticopontocerebellar fibers originate from?

Answer 29

motor/sensory cortices

Question 30

Corticopontocerebellar pathway overview

Answer 30

* The bulk of the corticopontocerebellar fibers originate from the primary motor/sensory cortices * The corticopontocerebellar fibers first descend to the pontine nuclei, where they make their primary synapse. * The pontine nuclei project across midline through the MCP into the contralateral cerebellar cortex. * The cerebellar cortex projects to the dentate nucleus, which lies deep within the cerebellum. * The dentate projects fibers out of the cerebellum through the superior cerebellar peduncle, which cross midline within the midbrain, inferior to the red nucleus, to synapse in the ventrolateral nucleus of the thalamus and also in the red nucleus. * The red nucleus projections typically originate from the globose and emboliform nuclei, which lie medial to the dentate nucleus, whereas the thalamic projections typically originate from the dentate nucleus. * The thalamus projects back to the primary motor strip to complete the corticopontocerebellar pathway.

Question 31

Show arterial supply of the cerebellum

Answer 31

PICAs perfuse the inferior cerebellum AICAs perfuse the mid-lateral cerebellum SCAs perfuse the superior cerebellum.

Question 32

Identify arteries

Answer 32

* Paired vertebral arteries derive the basilar artery, which branches into the paired posterior cerebral arteries. * The posterior inferior cerebellar arteries (PICAs) emerge from the vertebral arteries. * At the base of the basilar artery, paired anterior inferior cerebellar arteries (AICAs) emerge. * At the upper portion of the basilar artery, the paired superior cerebellar arteries (SCAs) emerge.

Question 33

Identify cerebellum

Answer 33

* We draw one of the saddle-shaped cerebellar hemispheres b/c the unfolded schematic of the cerebellum, which is so commonly used to represent the cerebellum, places the flocculonodular lobe at the bottom of the diagram, and we need to appreciate that the flocculonodular lobe actually lies in anterior, mid-cerebellar position. * Above the fourth ventricle, we find the lingula: the slender vermian tip of the anterior cerebellar lobe. * The lingula combines with the flocculonodular lobe to form the vestibulocerebellum. * The cerebellar tonsils are a paired, midline structure that is an important aspect of a common neurologic condition, Chiari malformation

Question 34

Chiari Malformation: Type 2

Answer 34

In Type 2 Chiari Malformation (aka Arnold-Chiari malformation), the cerebellum and brainstem protrude into the foramen magnum; the cerebellar vermis may be absent, and it typically accompanies a myelomeningocele (a form of spina bifida). The cerebellar tonsils are a paired, midline structure that is an important aspect of a common neurologic condition, Chiari malformation.