Anterior Cranial Fossa : anatomy and clinical anatomy

 

Anterior Cranial Fossa

Boundaries:

Anteriorly and laterally: by the inner surface of the frontal bone.

Median part of the posterior boundary: by the body of the sphenoid.

Lateral part of the posterior boundary: by the sharp posterior border of the lesser wing of the sphenoid.

The floor is formed by:

The lateral part of the floor is formed by the cerebral surface of the orbital parts of the frontal bone (forming the roof of the orbital cavity) and the lesser wings of the sphenoid bone.

The median area of the floor is formed by the cribriform plate of the ethmoid bone (forming the roof of the nasal cavity) and the anterior aspects of the body of the sphenoid.

 

Contents:

The frontal lobes of the brain,

The olfactory bulbs and tracts, and

The anterior cerebral arteries.

 

Foramina:

The cribriform plate of the ethmoid, through which the olfactory nerves (cranial nerve I) pass.

Anterior ethmoidal foramen – through which the anterior ethmoidal artery, nerve, and vein pass.

Posterior ethmoidal foramen – through which the posterior ethmoidal artery, nerve, and vein pass.

Foramen caecum: it transmits a small emissary vein, known as the emissary vein of the foramen caecum, that connects the superior sagittal sinus and the veins of the nasal cavity.

 

Other important features:

Crista galli: The crista galli is situated at the midline of the skull, between the two cribriform plates of the ethmoid bone. The falx cerebri attaches to the crista galli, which lodges the superior sagittal sinus.

Jugum sphenoidale: The jugum sphenoidale, also known as the sphenoidal crest, is a ridge-like elevation located on the superior surface of the body of the sphenoid bone. It attaches to the tentorium cerebelli, a fold of dura mater that separates the cerebrum from the cerebellum, along its posterior edge.

Sulcus chiasmatis: The sulcus chiasmatis, also known as the optic groove or optic sulcus, is a shallow depression on the superior surface of the body of the sphenoid bone, located just posterior to the jugum sphenoidale. It lodges the optic chiasma.

Anterior clinoid process: It is a small, pointed process of the lesser wing of the sphenoid that extends anteriorly and medially from the body of the sphenoid bone. It serves as the attachment point for the anterior part of the tentorium cerebelli.

Which anatomical structures damage in fracture of the anterior cranial fossa ?

Sinuses: Fractures here can involve the frontal sinus, potentially leading to CSF leakage and sinusitis. It may also damage the ethmoidal and sphenoidal sinuses and be accompanied by bleeding from the nose or mouth.

Artery Tears: Tears in branches of the anterior cerebral arteries may result in intracranial hemorrhage or ischemic stroke affecting the frontal lobes.

Vein Tears: Damage to the superior sagittal sinus can cause venous hemorrhage and increased intracranial pressure.

Nerve Damage: Injury to the olfactory nerves (cranial nerve I) may result in anosmia, while damage to nearby structures can affect cognitive and emotional functions.

Foramen Damage: The cribriform plate of the ethmoid is the thinnest part of the anterior cranial fossa and is therefore most likely to fracture. There are two major consequences of a cribriform plate fracture:

Anosmia – loss of the sense of smell due to damage to the olfactory nerve fibers that run through the cribriform plate of the ethmoid bone.

CSF rhinorrhea – the leakage of cerebrospinal fluid into the nasal cavity due to a tear in the meningeal coverings of the brain by a fractured bone fragment.

Meningitis: Infection of the nasal cavity may pass into the meninges, causing meningitis.

Brain Damage: Fractures in this region can cause contusions or lacerations in the frontal lobes, leading to cognitive deficits, personality changes, or motor dysfunction.

Primary optic atrophy and blindness: Fracture of the optic canal.

Subconjunctival hemorrhage, which is associated with fractures involving the roof of the orbit.

A black eye does not always indicate a fracture of the anterior cranial fossa; direct contusion of the soft tissues may produce a black eye deep to the aponeurotic layer of the scalp.