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posterior commissure

caudal commissure

A rounded band of white fibres crosses the midline on the dorsal aspect of the upper end of the cerebral aqueduct: the posterior commissure. Most of its fibres originate in the nucleus of the posterior commissure, the nucleus of Darkschewitsch, which lies in the central grey substance at the upper end of the aqueduct in front of the oculomotor nucleus; some are probably derived from the posterior part of the thalamus and from the superior colliculus, while others are believed to continue downward into the medial longitudinal fasciculus. Its fibres acquire their medullary sheaths early, although their connections have not been definitely determined. Functionally it interconnects the pretectal nuclei and is important in the bilateral pupillary light reflex, mediating the consensual response.

Rounded band of white fibers crossing the middle line on the dorsal aspect of the upper end of the cerebral aqueduct. It is important in the bilateral pupillary light reflex. Its fibers acquire their medullary sheaths early, but their connections have not been definitely determined. Most of them have their origin in a nucleus, the nucleus of the posterior commissure (nucleus of Darkschewitsch), which lies in the central gray substance of the upper end of the cerebral aqueduct, in front of the nucleus of the oculomotor nerve. Some are probably derived from the posterior part of the thalamus and from the superior colliculus, whereas others are believed to be continued downward into the medial longitudinal fasciculus. The posterior commissure interconnects the pretectal nuclei, mediating the consensual pupillary light reflex[WP]. Diencephalic tract which is located in the vicinity of the dorsal diencephalon and mesencephalon and connects the pretectal nuclei. From Neuroanatomy of the Zebrafish Brain[ZFA].

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ประเภท Nerve
ระบบของร่างกาย Nervous
โครงสร้างหลัก commissure of diencephalon
ชื่อภาษาละติน caudal commissure
FMA ID 62072

Frequently Asked Questions

What is the posterior commissure?

The posterior commissure is a bundle of white matter fibers crossing the midline at the upper end of the cerebral aqueduct (aqueduct of Sylvius), at the junction of the midbrain and diencephalon. It connects homologous structures on both sides of the brain.

What is the anatomical location of the posterior commissure?

The posterior commissure is located at the junction of the midbrain tegmentum and the diencephalon, just dorsal to the cerebral aqueduct where it opens into the third ventricle, in the region of the pineal body.

What is the most important clinical function of the posterior commissure?

The posterior commissure is critically important for the bilateral pupillary light reflex. It carries fibers from the pretectal nuclei to the Edinger-Westphal nuclei on both sides, allowing light in one eye to constrict both pupils (direct and consensual responses).

What nuclei are associated with the posterior commissure?

The posterior commissure originates from fibers in the nucleus of Darkschewitsch (Darkschewitsch nucleus) and the interstitial nucleus of Cajal, both located in the rostral midbrain. These nuclei are involved in vertical eye movements and the pupillary light reflex pathway.

How does a lesion of the posterior commissure affect the eyes?

Damage to the posterior commissure, as can occur with pineal region tumors or dorsal midbrain lesions (Parinaud syndrome), causes loss of the upgaze reflex, loss of the pupillary light reflex, and convergence-retraction nystagmus—a classic set of findings.

References

  1. Foundational Model of Anatomy — FMA:62072 Reference anatomy ontology (University of Washington)
  2. UBERON — UBERON:0000936 Cross-species anatomy ontology (EMBL-EBI Ontology Lookup Service)
  3. Wikipedia — posterior commissure Encyclopedia article (verified cross-reference)

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Educational Disclaimer

This content is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider for medical decisions.

Data sources: Terminologia Anatomica, Foundational Model of Anatomy, Wikidata.