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Skull base foramina and cranial nerves
Each skull base foramen "carries" a fixed nerve and vessel — foramen rotundum V2, ovale V3, spinosum the middle meningeal artery, and the jugular foramen nerves 9, 10 and 11 — so the lesion's location is explained by the combination of deficits.
Why it matters in the exam
Questions show a bone-window CT or an endoscopic image and ask what passes through the marked opening. Through the superior orbital fissure pass nerves 3, 4 and 6, the branches of V1 and the superior ophthalmic vein; inside the ring of Zinn pass nerve 3 in both its divisions, the nasociliary nerve and nerve 6, while outside it lie nerve 4, the frontal nerve, the lacrimal nerve and the vein. The optic canal carries the optic nerve and the ophthalmic artery. The inferior orbital fissure carries the infraorbital nerve (continuation of V2) and the zygomatic nerve. The vidian nerve runs in the pterygoid canal and is formed by the greater petrosal nerve (parasympathetic, from nerve 7) and the deep petrosal nerve (sympathetic); it leads to the petrous carotid artery and serves as a landmark in the endonasal approach.
In the internal auditory canal, at its fundus, a horizontal crest and a vertical crest (Bill's bar) divide four quadrants: nerve 7 anterosuperior, the cochlear nerve anteroinferior, and the superior and inferior vestibular nerves posteriorly. In the jugular foramen the neural (anteromedial) part carries nerve 9 and the inferior petrosal sinus, and the vascular part carries nerves 10 and 11 and the continuation of the sigmoid sinus into the jugular vein. The auricular branch of the vagus (Arnold) supplies the ear canal — hence coughing when cleaning the ear — and the tympanic branch of nerve 9 (Jacobson) goes to the middle ear. In Vernet syndrome injury to nerves 9, 10 and 11 indicates a jugular foramen lesion, and added nerve 12 involvement points below the skull base. In uncal herniation nerve 3, which runs between the posterior cerebral artery and the superior cerebellar artery, is compressed against the tentorial edge — the pupil dilates first.
Key points
- Rotundum V2, ovale V3, spinosum middle meningeal artery.
- Ring of Zinn: 3, nasociliary, 6; nerve 4 outside it.
- Auditory canal: 7 anterosuperior, cochlear anteroinferior.
- Jugular foramen: 9, 10, 11.
- Vidian: greater and deep petrosal — landmark to the carotid.
Summary table
| Opening | Main contents | Exam point |
|---|---|---|
| Optic canal | Nerve 2, ophthalmic artery | Does not pass through the superior fissure |
| Superior orbital fissure | 3, 4, 6, V1 branches, superior ophthalmic vein | Inside the ring of Zinn: 3, nasociliary, 6 |
| Foramen rotundum / ovale / spinosum | V2 / V3 / middle meningeal artery | Temporal fracture — epidural bleed |
| Internal auditory canal | 7, 8, labyrinthine artery | Nerve 7 anterosuperior |
| Jugular foramen | 9, 10, 11, sigmoid and inferior petrosal sinuses | Vernet syndrome |
| Hypoglossal canal / stylomastoid foramen | 12 / 7 on leaving the skull | Tongue deviates to the injured side |
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Sources
- Rhoton's Cranial Anatomy and Surgical Approaches (Neurosurgery supplement), 2003 — The orbit; The temporal bone and internal acoustic meatus; The jugular foramen
- Gray's Anatomy: The Anatomical Basis of Clinical Practice, 42nd edition (2020) — Cranial cavity and skull base
- Youmans and Winn Neurological Surgery, 8th edition (2022) — Surgical anatomy of the skull base
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.