General characteristics and development
The skull forms a sturdy support for the initial segments of the respiratory and digestive tracts, and also protects critical structures of the nervous system. In total, there are 23 skull bones (ossa cranii), which are traditionally divided into paired and unpaired, and are also classified according to whether they belong to the neurocranium or viscerocranium.
The complexity of the skull architecture is due to the early formation and development of the brain and sense organs—it is their anatomy that dictates the final shape of the bony relief. Interestingly, a perfect mirror image in the structure of the left and right halves does not exist: humans are always characterized by natural individual asymmetry.
Skull bones are of particular importance in obstetrics. During labor, their configuration (displacement) occurs. In cases of a clinically narrow pelvis at the end of the first or in the second stage of labor, the physician may observe either excessive configuration or its complete absence, which is an important diagnostic sign.
Craniocerebral topography
For successful planning of trepanation, as well as precise localization of tumors and intracranial hematomas, a physician must know the projection of the cerebral lobes and sulci onto the bony structures. Directly beneath the dura mater lie the frontal, parietal, and temporal lobes.
Key landmarks of craniocerebral topography:
- Central sulcus (sulcus centralis), or Rolando's fissure. It serves as the border between the frontal and parietal lobes. Anterior to it lies the precentral (motor) gyrus, and posterior to it lies the postcentral (sensory) gyrus.
- Lateral sulcus (sulcus lateralis), or Sylvian fissure. Separates the temporal lobe from the frontal and parietal lobes.
- Parieto-occipital sulcus (sulcus parietooccipitalis). Located on the medial surface of the hemisphere and serves as the boundary between the parietal and occipital lobes.
Trauma to the skull and maxillofacial region
Injuries to the bony structures and soft tissues of the head are classified according to the scope and nature of the lesion. When two or more injuries occur within a single anatomical region, it is termed multiple trauma.
Main types of head injuries:
- Craniocerebral trauma (TBI) — damage to the skull itself, brain tissue, blood vessels, meninges, or cranial nerves. It is accompanied by clinical symptoms and morphological changes. The main diagnostic criterion is the presence of a clear traumatic history.
- Craniomaxillofacial trauma — combined lesion of the neurocranium (or brain) and the bones of the facial skeleton.
- Depressed fracture — a condition in which bone fragments are displaced inward by a distance exceeding the thickness of the adjacent bone.
Features of the facial skeleton The facial region includes 6 paired bones (maxilla, inferior nasal concha, lacrimal, nasal, zygomatic, palatine) and 3 unpaired bones (mandible, hyoid bone, vomer). Injuries to the maxillofacial region are dangerous due to pronounced morphofunctional disorders, a high risk of deformations, and, in the long term, delayed growth and development of facial tissues.
Skull base fractures
Skull base fractures are singled out into a separate category because they cause a specific severe symptom complex due to the disruption of the anatomical integrity of structures. This group includes fractures of:
- the orbital surface of the frontal bone;
- the cribriform plate;
- the sphenoid bone;
- the pyramid of the temporal bone;
- the squamous part or articular process of the occipital bone (extending to the foramen magnum).
Clinically, such injuries manifest as bleeding and leakage of cerebrospinal fluid (CSF rhinorrhea or otorrhea) from the mouth, nose, or external auditory meatus. Characteristically, bruising appears around the orbits ("raccoon eyes" sign), along with signs of damage to the facial (VII pair) and vestibulocochlear (VIII pair) cranial nerves.
To memorize the sulci on the outer surface of the brain, use the association: "Roland in the center, Sylvia on the side." The central sulcus (sulcus centralis) is central, and the lateral sulcus (sulcus lateralis) is lateral.
Class and exam questions
What is the main criterion for diagnosing craniocerebral trauma?
The key diagnostic criterion for TBI is the presence of a clear traumatic history accompanied by relevant clinical symptoms and morphological changes.
What symptoms indicate a skull base fracture?
Specific signs include the "raccoon eyes" sign (bruising in the orbital region), CSF leakage and bleeding from the nose, mouth, or ears, as well as symptoms of damage to the VII and VIII pairs of cranial nerves.
How does a depressed skull fracture differ from other types of fractures?
In a depressed fracture, the displacement of bone fragments into the cranial cavity occurs by an amount that exceeds the thickness of the injured bone itself.
Why does a surgeon need to know the projection of cerebral sulci onto the skull?
Knowledge of craniocerebral topography is critically important for the precise localization of intracranial hematomas, tumors, and proper planning of trepanation.
What else to study on this topic
- Anatomy and functions of paired and unpaired bones of the facial skeleton
- Features of skull bone configuration during childbirth
- Mechanisms of development of post-traumatic maxillofacial deformities
- Topography of the nuclei of the VII and VIII pairs of cranial nerves
- Changes in the circulatory system after birth
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