Fossa Cranii Anterior: Structure, Function & Diseases

The anterior cranial fossa corresponds to the anterior cranial fossa and contains the olfactory bulb (bulbus olfactorius) and the frontal lobe (lobus frontalis) of the cerebrum. In addition, the anterior cranial fossa has four openings through which blood vessels and nerves pass.

What is the anterior cranial fossa?

Anatomy refers to the anterior cranial fossa as the anterior fossa, which lies in front of the middle cranial fossa and the posterior cranial fossa. They all belong to the base of the skull (basis cranii interna). The frontal bone (Os frontale), ethmoid bone (Os ethmoidale) and the small sphenoid wing participate in the formation of the anterior cranial fossa. The latter represents a part of the sphenoid bone (Os sphenoidale) and is accordingly also known under the Latin name Ala minor ossis sphenoidalis. The anterior fossa contains the olfactory bulb (bulbus olfactorius) and the frontal lobe (lobus frontalis), which is part of the cerebrum. Usually, anatomy does not include the olfactory bulb in the telencephalon because the olfactory bulb is very different from the cortex in terms of its functioning and tasks.

Anatomy and structure

In the fossa cranii anterior lies the frontal area of cerebrum. Its convolutions (gyri) and folds (sulci) are reflected in the impressiones digitatae and juga cerebralia of the bone. Four openings are located in the fossa cranii anterior. The caecum ossis frontalis foramen is a blind opening in the frontal bone. In children, the emissary vein runs through this part of the anterior fossa. It connects various other blood vessels of the head. However, as development progresses, the foramen caecum closes in most cases. A second opening in the anterior cranial fossa is formed by the ethmoidal anterior foramen, which is located at the border of the ethmoid and sphenoid bones. The anterior ethmoidal artery (anterior ethmoidal artery) and the anterior ethmoidal nerve are located in the depression. The posterior ethmoidal foramen forms another opening in the anterior cranial fossa. Analogous to the anterior ethmoidal foramen, it contains the posterior ethmoidal artery, which branches from the ophthalmic artery, and the posterior ethmoidal nerve. The ethmoidal plate (lamina cribrosa or lamina horizontalis) has other openings and depressions, which anatomy also counts as part of the fossa cranii anterior. The olfactory filaments (fila olfactoria), which transmit olfactory stimuli to the olfactory brain, run through them.

Function and tasks

The frontal lobe belongs to the cerebrum (telencephalon) or neocortex. The lobe includes the motor cortex, whose task is to control movement, and the prefrontal cortex. The latter participates in numerous cognitive processes, including planning and controlling actions and anticipating action outcomes, working memory processes, and problem solving. The anterior fossa also contains the olfactory bulb (bulbus olfactorius), which participates in olfactory perception. The anterior ethmoidal artery supplies blood to ethmoidal cells (cellulae ethmoidales) in the paranasal sinuses. Anatomy divides ethmoidal cells into three types according to their location (anteriores, mediae, and posteriores), with the anterior ethmoidal artery responsible for the anterior ethmoidal cellulae and the mediae ethmoidal cellulae. In addition, the ramus meningealis branches off from the artery. In medicine, this branch is also known as the anterior meningeal artery because it leads to the hard meninges (dura mater). The nasal branch (ramus nasales) serves to supply the septum and the lateral wall of the nasal cavity. Subsequently, the terminal branch of the anterior ethmoidal artery runs to the bridge of the nose. The anterior ethmoidal nerve, which like the anterior ethmoidal artery passes through the ethmoidal foramen, is part of the nasociliary nerve. It is composed of sensory fibers and innervates the nasal tip and wings, the lateral wall of the nasal cavity, and the anterior portion of the septum. The fibers of the anterior ethmoidal nerve terminate there at the cells of the mucosa. The posterior ethmoidal nerve is also composed of sensory fibers and supplies the sphenoid sinuses, which are part of the paranasal sinuses. In addition, the posterior ethmoidal nerve is responsible for the sensory supply of the posterior ethmoidal cells (cellulae ethmoidales posteriores).The blood supply to these cells is provided by the posterior ethmoidal artery, which, like the anterior ethmoidal artery, also supplies parts of the dura mater. In addition, the blood vessel supplies cells of the nasal cavity mucosa.

Diseases

Damage to the anterior cranial fossa often results from injury, for example, as a result of an accident involving the head. This may involve damage to the structures located in the anterior fossa. Various pathological consequences may result, for example neurological and neurocognitive impairments in case of lesion of the frontal lobe: motor disorders, limitations of olfactory perception and many more. In addition, injuries affecting only small areas of the frontal lobe can also impair working memory. Not only external injuries, but also neurodegenerative diseases can be considered as a cause of damage to the frontal lobe. Lesions to the blood vessels that pass through the openings of the anterior cranial fossa can damage the adjacent neural pathways and tissue structures, leading to corresponding deficits. People suffering from schizophrenia tend to show peculiarities in the frontal lobe. Schizophrenia is a mental disorder belonging to the group of psychoses. The multifaceted clinical picture includes symptoms such as hallucinations, delusional thoughts and ego disorders. Persons with ego disorders find it difficult to distinguish between ego and environment: When thoughts spread, for example, those affected have the impression that their own (unexpressed) thoughts “infect” other people. In addition, negative symptoms such as affective flattening, depressed mood, apathy, or anhedonia often occur.