Cranial Foramina Overview

Overview

This lecture covers the main cranial foramina, which nerves and vessels pass through them, and mnemonics to remember their locations and contents for exams.

Olfactory and Optic Foramina

• The olfactory (CN I) nerve passes through the cribriform plate; remember "crib" for "cribriform."
• The optic nerve (CN II) passes through the optic canal leading into the orbit.

Superior Orbital Fissure and Associated Nerves

• The superior orbital fissure is located underneath a cranial process and carries multiple nerves and vessels.
• Oculomotor (CN III), trochlear (CN IV), and abducent (CN VI) nerves pass through; these control eye movement.
• The three branches of the ophthalmic nerve (frontal, lacrimal, nasociliary) also pass through here.

Diagonal Row Foramina: Rotundum, Ovale, Spinosum

• The foramen rotundum carries the maxillary branch of the trigeminal nerve (CN V2).
• The foramen ovale carries the mandibular branch of the trigeminal nerve (CN V3).
• Use "Rule Out Syphilis" or "Rot Max" and "Real Man Ovaltine" to remember the order and contents.
• The foramen spinosum transmits the middle meningeal artery, not a cranial nerve.

Foramen Lacerum and Carotid Canal

• The foramen lacerum is filled with cartilage at birth and doesn't transmit major structures.
• The carotid canal (near lacerum) transmits the internal carotid artery.

Internal Acoustic Meatus, Stylomastoid Foramen, and Facial Nerve

• Internal acoustic meatus carries facial (CN VII) and vestibulocochlear (CN VIII) nerves.
• Facial nerve exits the skull at the stylomastoid foramen, between the styloid and mastoid processes.

Jugular Foramen and Hypoglossal Canal

• Jugular foramen transmits cranial nerves IX (glossopharyngeal), X (vagus), and XI (accessory).
• Cranial nerves with "X" in their number (9, 10, 11) go through the jugular foramen.
• The condylar canal carries only a small vein, not a cranial nerve.
• Hypoglossal canal, found below and under the condyles, transmits the hypoglossal nerve (CN XII).

Foramen Magnum

• The foramen magnum is the largest hole at the skull base and is easily identifiable.

Key Terms & Definitions

• Cribriform Plate — perforated part of ethmoid bone transmitting olfactory nerve fibers.
• Optic Canal — passage for optic nerve (CN II) to the orbit.
• Superior Orbital Fissure — opening transmitting nerves and vessels for eye movement.
• Foramen Rotundum — passage for maxillary branch (V2) of trigeminal nerve.
• Foramen Ovale — passage for mandibular branch (V3) of trigeminal nerve.
• Foramen Spinosum — passage for middle meningeal vessels.
• Foramen Lacerum — cartilage-filled space, not a functional passage for major structures.
• Internal Acoustic Meatus — canal for facial and vestibulocochlear nerves.
• Jugular Foramen — exit for cranial nerves IX, X, XI.
• Hypoglossal Canal — passage for hypoglossal nerve (CN XII).
• Foramen Magnum — main opening at the skull base.

Action Items / Next Steps

• Review skull diagrams to visually locate each foramen and their associated nerves and vessels.
• Memorize mnemonics for foramina-nerves relationships before the next exam.