Where is the foramen lacerum located?
The foramen lacerum serves as a pathway communicating between the internal and external skull bases.
- At the internal skull base, it belongs to the middle cranial fossa (Fossa cranii media). This fossa is bounded anteriorly by the lesser wings of the sphenoid bone (Alae minores) and the prechiasmatic sulcus (Sulcus prechiasmaticus). The posterior boundary runs along the superior border of the petrous part of the temporal bone (Margo superior partis petrosae) or the groove for the superior petrosal sinus, and along the midline by the dorsum sellae (Dorsum sellae).
- At the external skull base (Basis cranii externa), the opening is viewed from the inferior (basal) norma. On a dry skull, it appears as a slit located at the posteromedial margin of the greater wing of the sphenoid bone and the petrous part of the temporal bone.
Structural features in the living human
The anatomical appearance of the foramen lacerum varies depending on the state of the skull:
- On a macerated (dry) skull, it is clearly visible as a gap or opening.
- In a living skull, the region of the foramen lacerum is not a free opening. It is filled with a permanent synchondrosis that forms the sphenopetrosal fissure (Fissura sphenopetrosa).
What passes through the foramen lacerum?
Important vascular and neural structures pass through this region:
- Internal carotid artery (Arteria carotis interna) — after passing through the carotid canal of the petrous part of the temporal bone (Pars petrosa) and navigating its S-shaped bends, the artery exits through the foramen lacerum into the cranial cavity. From there, it enters the carotid sulcus on the body of the sphenoid bone.
- Greater and lesser petrosal nerves (Nervi petrosi major et minor). Additionally, the middle cranial fossa communicates with the facial nerve canal and tympanic canaliculus via the hiatuses for these nerves (Hiatus canalis nervi petrosi majoris/minoris).
- Glossopharyngeal nerve (cranial nerve IX) — also passes through this opening.
Topography and adjacent structures
The external skull base around the foramen lacerum essentially "receives" the exit and entrance apertures of all major canals of the temporal bone. Adjacent structures include:
- Carotid canal (Canalis caroticus) — its external aperture lies nearby, from which the internal carotid artery heads toward the foramen lacerum.
- Foramen ovale (Foramen ovale) — located on the greater wing of the sphenoid bone, transmitting the mandibular nerve and an accessory branch of the middle meningeal artery.
- Foramen spinosum (Foramen spinosum) — also located on the greater wing, transmitting the middle meningeal artery, vein, and a branch of the mandibular nerve.