Pons | pacs

Axial section

through mid-brain. (Schematic.) (Testut.) 1. Corpora quadrigemina. 2. Cerebral aqueduct. 3. Central gray stratum. 4. Interpeduncular space. 5. Sulcus lateralis. 6. Substantia nigra. 7. Red nucleus of tegmentum. 8. Oculomotor nerve, with 8’, its nucleus of origin. a. Lemniscus (in blue) with a’ the medial lemniscus and a" the lateral lemniscus. b. Medial longitudinal fasciculus. c. Raphé. d. Temporopontine fibers. e. Portion of medial lemniscus, which runs to the lentiform nucleus and insula. f. Cerebrospinal fibers. g. Frontopontine fibers.

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Pons •

Upper-level pons (Gray's illustration) - Ganzer Fall bei Radiopaedia

Hacking, C. Upper-level pons (Gray's illustration). Case study, Radiopaedia.org. (accessed on 01 Nov 2022) https://doi.org/10.53347/rID-81784 • CC by-nc-sa 3.0 (modified)

Pons •

Medial longitudinal fasciculus and associated defects (diagram) - Ganzer Fall bei Radiopaedia

Fahrenhorst-Jones, T. Medial longitudinal fasciculus and associated defects (diagram). Case study, Radiopaedia.org. (accessed on 01 Nov 2022) https://doi.org/10.53347/rID-151591 • CC by-nc-sa 3.0 (modified)

Radiopaedia • CC-by-nc-sa 3.0 • de

The pons (Varolii) is the middle portion of the three parts of the brainstem, sitting above the medulla and below the midbrain. It acts as a relay between the cerebellum and cerebral hemispheres.

Gross anatomy

The pons has a bulbous shape and has two main components - the basis pontis (basal/ventral part) and the pontine tegmentum (dorsal part).

The basis pontis consists of white matter tracts (e.g. anterior and lateral corticospinal, corticobulbar and corticopontine tracts) with transverse fibers contributing to the bulk of the pons.

The pontine tegmentum is continuous with the tegmentum of the medulla and the midbrain. It contains multiple white matter tracts (e.g. medial longitudinal fasciculus, medial lemniscus, lateral lemniscus, etc) and grey matter nuclei (e.g. cranial nerve nuclei). Within the dorsal tegmentum lie four cranial nerve nuclei:

trigeminal nerve (CN V): many motor, sensory and mesencephalic nuclei extending from the pons to the upper cervical cord
abducens nerve (CN VI): motor nucleus
facial nerve (CN VII): including superior salivary, motor and solitary tract nuclei
vestibulocochlear nerve (CN VIII): including vestibular and cochlear nuclei

Posteriorly, the pons is connected to the cerebellum by the middle cerebellar peduncle. Inferiorly the posterior surface of the pons is slightly depressed, forming the diamond-shaped rhomboid fossa which is the floor of the fourth ventricle.