The Cranial Foramina

Original Author: Smrithi Santhosh
Last Updated: March 29, 2018
Revisions: 8
Print this page

A foramen (pl. foramina) is an opening that allows the passage of structures from one region to another.

In the skull base, there are numerous foramina that transmit cranial nerves, blood vessels and other structures – these are collectively referred to as the cranial foramina.

In this article, we shall look at some of the major cranial foramina, and the structures that pass through them.

Cranial Nerve Foramina

The foramina of the skull are most commonly considered in the context of the cranial nerves. In this section, we will discuss the foramina that transmit cranial nerves.

Figure 1 – Superior view of the skull base showing the foramina and which cranial nerves pass through them.

Cribriform Foramina

The cribriform foramina refer to numerous perforations in the cribriform plate of the ethmoid bone. They connect the anterior cranial fossa with the nasal cavity.

These foramina allow the passage of axons of the olfactory nerve from the olfactory epithelium of the nose into the anterior cranial fossa where they communicate with the olfactory bulb.

Optic Canal and Foramen

The optic canal permits the passage of the optic nerve (CN II) and the ophthalmic artery into the bony orbit.

It is bounded medially by the body of the sphenoid, and laterally by the lesser wing of the sphenoid bone

Superior Orbital Fissure

The superior orbital fissure is a cleft that opens anteriorly into the orbit, and enables communication between the cavernous sinus and the apex of the orbit

It is bordered superiorly by the lesser wing and inferiorly by the greater wing of the sphenoid bone.

It transmits several structures that are listed below (from superior to inferior):

  • Lacrimal nerve
  • Frontal nerve – branch of ophthalmic nerve of trigeminal nerve (CN V)
  • Superior ophthalmic vein
  • Trochlear nerve (CN IV)
  • Superior division of the Oculomotor nerve (CN III)
  • Nasociliary nerve – branch of ophthalmic nerve of trigeminal nerve (CN V)
  • Inferior division of the Oculomotor nerve (CN III)
  • Abducens nerve (CN VI)
  • A branch of the Inferior ophthalmic vein

Fig 2 – Foramina and bony landmarks of the sphenoid wings and pterygoid process.

Foramen Rotundum

The foramen rotundum is located at the base of the greater wing of the sphenoid, inferior to the superior orbital fissure.

It provides a connection between the middle cranial fossa and the pterygopalatine fossa. The maxillary nerve (branch of the trigeminal nerve, CN V) passes through this foramen.

Foramen Ovale

The foramen ovale is another opening located at the base of the greater wing of the sphenoid.

It is positioned posterolaterally to the foramen rotundum within the middle cranial fossa. It conducts the mandibular nerve (branch of the trigeminal nerve, CN V) and the accessory meningeal artery.

Internal Acoustic Meatus

The internal acoustic meatus is a bony passage located within the petrous part of the temporal bone.

The canal connects the posterior cranial fossa and the inner ear, transporting neurovascular structures to the auditory and vestibular apparatus. The facial and vestibulocochlear nerves pass through the internal acoustic meatus, alongside the vestibular ganglion and labyrinthine artery.

Jugular Foramen

The jugular foramen is formed anteriorly by the petrous part of the temporal bone and posteriorly by the occipital bone.

It can be considered as three separate compartments with their respective contents:

  • Anterior – contains the inferior petrosal sinus (a dural venous sinus).
  • Middle – transmits the glossopharyngeal nerve, vagus nerve and cranial part of the accessory nerve.
  • Posterior – contains the sigmoid sinus, and transmits meningeal branches of occipital and ascending pharyngeal arteries.

Fig 3 – The bony landmarks and foramina of the posterior cranial fossa.

Hypoglossal Canal – CN XII

The hypoglossal canal is located in the occipital bone, through which the hypoglossal nerve (CN XII) passes to exit the posterior cranial fossa.

Other Foramina

Foramen Magnum

The foramen magnum is the largest of the cranial foramina.

It lies in the occipital bone within the posterior cranial fossa, and allows the passage of the medulla and meninges, the vertebral arteries, the anterior and posterior spinal arteries and the dural veins.

The spinal division of the accessory nerve ascends through the foramen magnum to join the cranial division. Once combined, the completed nerve exits through the jugular foramen as described above.

Foramen Spinosum

The foramen spinosum is located within the middle cranial fossa, laterally to the foramen ovale.

It allows the passage of the middle meningeal artery, the middle meningeal vein and the meningeal branch of CN V3.

Summary

ForamenStructures ConductedCranial FossaCranial Bone
Cribriform foramina in cribriform plate
  • Olfactory nerve (CN I)
  • Anterior ethmoidal nerves
Anterior cranial fossaEthmoid bone
Optic canal
  • Optic nerve (CN II)
  • Ophthalmic artery
Middle cranial fossaSphenoid bone
Superior orbital fissure
  • Lacrimal nerve
  • Frontal nerve- branch of ophthalmic nerve of trigeminal nerve (CN V)
  • Superior ophthalmic vein
  • Trochlear nerve (CN IV)
  • Superior division of the oculomotor nerve (CN III)
  • Nasociliary nerve- branch of ophthalmic nerve (CN V1)
  • Inferior division of the oculomotor nerve (CN III)
  • Abducens nerve (CN VI)
  • A branch of the Inferior ophthalmic vein
Middle cranial fossaSphenoid bone
Foramen rotundum
  •  Maxillary branch of trigeminal nerve (CN V)
Middle cranial fossaSphenoid bone
Foramen ovale
  • Mandibular branch of trigeminal nerve (CN V)
Middle cranial fossaSphenoid bone
Foramen spinosum
  • Middle meningeal artery
  • Middle meningeal vein
  • Meningeal branch of CN V3
Middle cranial fossaSphenoid bone
Internal acoustic meatus
  • Facial nerve (CN VII)
  • Vestibulocochlear nerve (CN VIII)
  • Vestibular ganglion
  • Labyrinthine artery
Middle cranial fossaPetrous part of temporal bone
Jugular foramen
  • Glossopharyngeal nerve (CN IX)
  • Vagus nerve (CN X)
  • Spinal accessory nerve (CN XI)
  • Jugular bulb
  • Inferior petrosal and sigmoid sinuses
Posterior cranial fossaAnterior aspect: Petrous portion of the temporal

Posterior aspect: Occipital bone

Hypoglossal canal
  • Hypoglossal nerve (CN XII)
Posterior cranial fossaOccipital bone
Foramen magnum
  • Vertebral arteries
  • Medulla and meninges
  • CN XI (spinal division)
  • Dural veins
  • Anterior and posterior spinal arteries
Posterior cranial fossaOccipital bone

 

Edit This Article

Rate This Article

19

Average Rating:

Quiz

Question 1 / 3
The optic canal lies within which bone?
Report question
Report Question

Quiz

Question 2 / 3
Which structure passes through foramen rotundum?
Report question
Report Question

Quiz

Question 3 / 3
Which of the following structures is NOT conducted by foramen spinosum?
Report question
Report Question

Results

Load 3d model