Anatomy & Organs

Skull Base – Structure, Function & Diseases

Skull base

The lower part of the skull is called the skull base . The brain lies on its inside . A total of twelve cranial nerves and blood vessels enter the neck and facial skeleton through openings in the base of the skull.

What is the base of the skull?

The base of the skull represents a cranial fossa on which the brain rests. It is also referred to as the basis cranii. In English it is called scull base. Through the base of the skull, the brain is connected to the neck and facial skeleton via a number of nerves and blood vessels. The inner skull base (basis cranii interna) is divided into the anterior, middle and posterior cranial fossa. It is the side facing the brain.

The outer base of the skull (basis cranii externa) is the side facing away from the brain. Strictly speaking, it represents the facial skull. According to a strict definition, only the base cranii interna is called the base of the skull. It is made up of five bones , namely the frontal bone (Os frontale), the ethmoid bone (Os ethmoidale), the sphenoid bone (Os sphenoidale), the occipital bone (Os occipitale) and the temporal bone (Os temporale).

Anatomy & Structure

The internal skull base consists of the anterior cranial fossa (fossa cranii anterior), middle cranial fossa (fossa cranii media) and posterior cranial fossa (fossa cranii posterior). The anterior cranial fossa is made up of the ethmoid bone and the laterally attached temporal and frontal bones. The anterior cranial fossa is separated from the middle cranial fossa (fossa cranii media) by the small wing of the sphenoid bone.

The median cranial fossa houses part of the brainstem, the middle part of the brain, and the temporal lobe of the cerebrum. The middle cranial fossa is divided into two halves by the so-called Turk’s saddle. In the middle of the Turk’s saddle (Sella turcica) there is a depression for the pituitary gland (Fossa hypophysialis). The posterior cranial fossa (Fossa cranii posterior) consists of the three cranial bones: the occipital bone (Os occipitale), the sphenoid bone (Os sphenoidale) and the temporal bone (Os temporale). The occipital foramen (foramen magnum) is located in the middle of the posterior cranial fossa. The medulla oblongata leaves the interior of the skull through the foramen magnum and passes into the spinal cord . In the posterior cranial fossa there are other passages for cranial nerves andarteries .

Function & Tasks

The base of the skull has the task of protecting the brain from external influences. At the same time, it has many passages for cranial nerves and blood vessels that keep the brain connected to the rest of the body. Without a skull base, however, the brain would very easily suffer concussions and lose its ability to function. A total of twelve passages through the base of the skull are necessary for nerves and blood vessels to make contact with the other organs of the body.

The optic canal is a passage in the anterior sphenoid of the middle cranial fossa. Both the optic nerve and the ophthalmic artery pass through this opening. Both are responsible for the care of the eyes . The hypoglossal nerve, which is responsible for the motor function of the tongue , passes through the hypoglossal canal. The internal jugular vein (vena jugularis interna) enters the neck through the foramen jugulare (the choke hole). The Arteria carotis interna (internal carotid artery) passes through the carotid canal. A bony canal in the petrous bone, the canalis musculotubarius, serves as an opening for the Eustachian tube. The purely sensory maxillary nerve leaves the cranial cavity through the foramen rotundum.

Other passages in the skull base are the foramen ovale, the foramen spinosum and the foramen lacerum for important nerve cords as well as the porus acusticus internus for the auditory canal and the foramen alar caudale for the arteria maxillaris.

Diseases

A fracture of the base of the skull is a serious disease of the base of the skull . This results in fractures in the anterior, middle, or posterior cranial fossa. The frontobasal ( nose and base of skull) and laterobasal ( ear and base of skull) fractures are the most common.

Cerebral fluid and blood typically leak from the nose and ear. Due to the actual trauma or bleeding into the brain, clouding of consciousness and neurological deficits occasionally occur. Since many nerves pass through small openings in the base of the skull, they can become trapped. This can result in paralysis and sensory loss. A skull base fracture is a highly life-threatening condition whose outcome is unpredictable. However, there are also diseases at the base of the skull that are characterized by space-occupying growth processes in this area. Most are benign skull base tumors.

Despite their benign nature, these tumors can cause significant symptoms. They are able to destroy the bony structures at the base of the skull and grow around the cranial nerves or blood vessels. When cranial nerves are affected, symptoms such as visual disturbances , disturbances in smell and taste , paralysis of facial muscles , facial pain or numbness in parts of the face, and hearing loss may occur. Furthermore, it can also lead to tinnitus , dizziness , swallowing disordersor weakness of the muscles of the face, head and shoulders. Tumors at the base of the skull are not always responsible for these symptoms. Inflammation and injuries in this area are also possible causes.

The examination is carried out using imaging methods such as MRI or CT . In the event of injuries, immediate action must be taken. The benign tumors should only be treated surgically if the quality of life is severely restricted. Sometimes anti-growth drugs can stop the tumor from growing.

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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.