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Foramina of the Skull
Clinical Relevance
There are foramina in the skull through which multiple vital neurological and vascular
structures pass. Knowledge of the 'normal' route structures take through the foramen
is relevant as it provides the ability to differentiate structures on imaging from
potential pathology (e.g. tumours, bleed). Furthermore, combining the clinical
presentation and the arrangement of structures within a foramen can be crucial in
identifying the underlying cause and location of pathology.
Below are some examples of the route that structures take through the foramen and
some of the clinical manifestations of pathology due to the underlying anatomy.
INJURIES
Severe head injuries involving the anterior cranial fossa can result in the olfactory
bulb being torn from the olfactory nerves. Head injuries can often present with few
symptoms and can be difficult to identify without imaging. A patient presenting with
torn olfactory nerves (CN I) would have lost the ability to smell (anosmia), providing a
clue that the injury was located in the anterior cranial fossa.
INTERNAL ACOUSTIC MEATUS
Cranial nerves VII (facial) and VIII (vestibulocochlear) and their branches pass
through the internal acoustic meatus in order to exit the cranial cavity. The nerves
(and branches) positions are most constant in the lateral portion of the meatus which
is divided into superior and inferior portions by a horizontal ridge (Figure 1).
Foramina of the Skull
Figure 1. Schematic diagram depicting a right internal acoustic meatus and in
which order structures pass through the foramen.
Superior: Facial and superior vestibular nerve (facial nerve is situated anteriorly)

Facial nerve is separated laterally to the superior vestibular nerve by a vertical
ridge of bone from the temporal bone (Bill's bar)
Inferior: Cochlear and inferior vestibular nerve (cochlear nerve is situated anteriorly)
Clinical relevance:
A common type of brain tumour, an acoustic neuroma, most often arises in the
posterior aspect of the internal acoustic meatus.
Due to the underlying anatomy:

Vestibular nerves are most likely to be damaged (compressed), resulting in
problems with balance

Facial nerve innervation (to the muscles of expression and parotid gland
(etc...)) will be preserved

Cochlear nerve innervation will be preserved (no loss of hearing)
Foramina of the Skull
If undetected an acoustic neuroma will continue to grow and will eventually cause
damage to the facial and cochlear nerves.
INTERNAL CAROTID ARTERY
The internal carotid artery enters the middle cranial fossa of the cranial cavity by the
carotid canal found in the temporal bone anterior to the jugular foramen. Shown in
Figure 2, the canal ascends vertically and then bends to open superior to the
foramen lacerum (which is filled with cartilage).
The internal artery then enters the cavernous sinus (a large venous plexus) and
continues to travel anteriorly along the skull surface towards the optic canal (Figure
3). Within the cavernous sinus the abducent (CN VI) nerve is also found.
Clinical relevance:
Cavernous sinus thrombosis or internal carotid artery can compress and damage the
abducent nerve (CN VI)

Loss of innervation to the superior oblique muscle of the eye

The affected eye rotates medially causing blurred vision - a subtle clinical sign
for a potentially life threatening issue
Foramina of the Skull
Figure 2. The path of the internal carotid artery into the cranial cavity and
the relevant anatomical relations.
Figure 3. Coronal view of the internal carotid artery within the
cavernous sinus.
Foramina of the Skull