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Pontocerebellar fibers

The pontocerebellar fibers are the second-order neuron fibers of the corticopontocerebellar tracts that cross to the other side of the pons and run within the middle cerebellar peduncles, from the pons to the contralateral cerebellum.[1] They arise from the pontine nuclei as the second part of the corticopontocerebellar tract (the first part being the corticopontine fibers which synapse in the pontine nuclei), and decussate (cross-over) in the pons before passing through the middle cerebellar peduncles to reach and terminate in the contralateral posterior lobe of the cerebellum (neocerebellum). It is part of a pathway involved in the coordination of voluntary movements.[2]

The middle cerebellar peduncle consists entirely of pontocerebellar fibers and is the largest pathway of the cerebellum.[2]

Anatomy

The fibers are horizontally oriented, forming bundles which pass dorsally through the pons among the pontine nuclei and interweave with the perpendicularly oriented corticospinal fibers.[2]

Termination

The pontocerebellar fibers terminate throughout the cerebellar cortex except the flocculonodular lobe in an arrangement corresponding to the cortical origin of the pathway: efferents of the primary motor cortex project to the vermis and paravermal zone; efferents of the premotor, somatosensory, and association cortex project to the cerebellar hemisphere cortex. Additionally, the fibers also issue collaterals to the dentate nucleus.[2]

Pathway

The entire pathway begins and ends in the cerebral cortex, and its entire course is the following:[2]

(Motor and sensory areas of) cerebral cortex → corticopontine fibers → (ipsilateral) nuclei pontis (synapse) → pontocerebellar fibers (decussation within pons) → middle cerebellar peduncle → (contralateral) (cerebellar cortex and (collaterals) dentate nucleus of) posterior lobe of cerebellum (synapse) → cerebellothalamic tract → superior cerebellar peduncle → mesencephalon (midbrain) (decussation of tract at level of inferior colliculus) → (ipsilateral) (ventral lateral nucleus of) thalamus → (ipsilateral) motor (cerebral) cortex (predominately premotor cortex and primary motor cortex)

Clinical significance

Damage to the pontocerebellar fibers (or pontine nuclei) will result in contralateral ataxia: due to the double decussation of the pathway along its entire course, it terminates in the motor cortex of the same cerebral hemisphere in which it began; the motor lateral corticospinal tract then decussates once during its descent to control movement of the opposite side of the body.[2]

References

  1. ^ Rahman, Masum; Tadi, Prasanna (2024). "Neuroanatomy, Pons". StatPearls. StatPearls Publishing. Retrieved 11 August 2024.
  2. ^ a b c d e f Patestas, Maria A.; Gartner, Leslie P. (2016). A Textbook of Neuroanatomy (2nd ed.). Hoboken, New Jersey: Wiley-Blackwell. pp. 109–110, 113, 116, 292, 295–296. ISBN 978-1-118-67746-9.