The foramen lacerum is term used to describe a triangular opening present at the base of the skull, situated in the middle cranial fossa between the top section of petrous temporal, the sphenoid, and the basilar section of occipital.
The foramen lacerum is bordered on the front by the sphenoid bone’s body at the junction of pterygoid process and greater wing, while the posterior border is formed by the petrous apex. The basilar section of the occipital bone forms the medial border of the foramen lacerum. The opening measures around 7 mm breadthwise and about 9 mm lengthwise. The term lacerum is Latin and means lacerated piercing.
The foramen lacerum is full of connective tissue. It allows the passage emissary veins commencing from the cavernous sinus as well as the tiny meningeal branches belonging to the ascending pharyngeal artery. The internal carotid artery runs along the upper surface of the foramen lacerum but does not cross it.
Foramen lacerum- Functions
The foramen lacerum is located antero-medial with relation to the carotid canal. It fills up with cartilage after the child is born.
- Before the greater petrosal nerve attaches with the pterygoid canal nerve, it passes across the foramen lacerum. The pterygoid canal itself contains the greater petrosal nerve and the deep petrosal nerve, the latter of which carries sympathetic fibers while the former transmits parasympathetic fibers to the mucous membranes, blood vessels, lacrimal glands, and salivary glands, from the autonomic nervous system.
- The internal carotid artery runs onwards from the carotid canal located at the bottom section of the skull, emerges and continues superiorly to the foramen lacerum before exiting the carotid canal. This artery does not traverse through or cross via the foramen lacerum. The part of the internal carotid artery which passes over the superior surface of the foramen lacerum is referred to as the lacerum segment. The pterygoid canal nerve, the pterygoid canal artery, and certain venous drainage systems traverse across the foramen lacerum.
- The ascending pharyngeal artery is a branch of the external carotid artery. One of its terminal or last branches also traverses across the foramen lacerum. The ascending pharyngeal artery is considered as one of the 3 available ‘meningeal branches’ belonging to this vessel.
- The foramen lacerum also acts as a route via which the nasopharyngeal carcinoma can get entry into the cavernous sinus and affect the nerves of the cranium.
- The foramen lacerum also allows the passage of certain emissary nerves. They join the intracranial cavernous sinus to the extracranial pterygoid plexus and facilitate an unrestricted access for infection.