FA 2010 ed page 395(neurology)

This forum made possible through the generous support of SDN members, donors, and sponsors. Thank you.
Does anyone understand the cerebellum input output diagram from page 395 neuro?

The purpose of the diagram is to explain why cerebellum lesions are ipsilateral.

Cerebellum provides contralateral out to the Cortex via SCP which via CST provides contralateral output to the body. Hence, contralateral of contralateral = ipsilateral.

That's what I learned from DIT.
 
That diagram is pretty jacked up. I've had to modify it.

You need to understand the following (if you draw out a quick diagram, it will make sense)

R motor cortex -> R pons -> decussate (pons) -> L MCP -> L cerebellum -> L SCP -> decussate (midbrain) -> R VA/VL -> R motor cortex

L spinal cord -> L ICP -> L cerebellum -> L SCP -> decussate (midbrain) -> R VA/VL -> R motor cortex

Cerebellar inputs
(1) Corticopontocerebellar pathway: Cortex projects to the ipsilateral pontine nuclei, which then decussate in the pons and project via the contralateral MCP (brachium pontis) to the contralateral cerebellum (intermediate and lateral zones). (So I believe that MCP arrow in FA is incorrect).

(2) Dorsal/ventral spinocerebellar and cuneocerebellar tracts: The cord projects to the ipsilateral cerebellum (median and lateral zones = spinocerebellum) via the ipsilateral ICP (restiform body).

Cerebellar output
(1) The cerebellum projects to the contralateral VA/VL and red nucleus via the ipsilateral SCP (brachium conjunctivum), which decussates in the midbrain. The VA/VL projects to the ipsilateral motor cortex.


These lesions give you an ipsilateral ataxia/intention tremor (explanations assume a L-sided ataxia)
(1) ICP
For example, Left ICP: input from the L body is not getting to the R cortex, which controls the L body
(2) MCP
For example, Left MCP: input from the R cortex is not getting to the L cerebellum, which projects to the R cortex, which controls the L body
(3) SCP before the decussation
For example, Left SCP before decussation: output from the L cerebellum is not getting to the R cortex, which controls the L body
(4) Cerebellum
For example, Left cerebellum: input from the R cortex (which controls the L body) is not being processed, and input from the L body is not being processed.

These lesions give you a contralateral ataxia/intention tremor
(1) Corticopontine tract
(2) Pontine nuclei
(3) SCP after decussation
 
Last edited by a moderator:
Top