Extracranial hemorrhages
Soft tissue injuries often occur before bone fractures.
- Subgaleal hematoma (Subgaleal haematoma). Blood accumulates beneath the epicranial aponeurosis (occipitofrontalis muscle), superficial to the periosteum. A crucial feature is that it is not limited by cranial sutures.
- Cephalhematoma (Cephalohaematoma). Occurs between the bone and the periosteum. Frequently associated with instrumental delivery during childbirth.
Cranial vault fractures
These injuries (Calvarial fractures) are divided into two major groups.
- Simple fractures (Simple fractures). These include linear fractures of the outer and inner tables, as well as diastatic (gaping) fractures running along cranial sutures or synchondroses. Diastatic fractures are particularly characteristic of children (the spheno-occipital, petro-occipital, and occipitomastoid sutures are frequently involved).
- Comminuted fractures (Comminuted fractures). More than two bone fragments are formed. In penetrating injuries (by a sharp object), fragments may be elevated (elevation). A severe direct impact results in depression (depressed) of the fragments. Depressed fractures carry a high risk of brain tissue injury.
If the intracranial space communicates with the external environment, it is referred to as an open fracture of the cranial vault (open TBI), which carries a significant risk of infection and CSF leakage.
Specific conditions: pneumocephalus and growing skull fracture
When evaluating CT scans, it is important to look for pneumocephalus — the presence of air within the cranial cavity (best visualized in the lung window). This indicates that the fracture has involved the paranasal sinuses or temporal bones, or that the injury is open.
In young children, a growing skull fracture (leptomeningeal cyst) may occur. It develops if the dura mater is torn during the fracture. The arachnoid/pia mater or brain herniates through the tear. The pulsation of cerebrospinal fluid gradually widens the bone defect, erodes the fracture margins, and prevents bone healing.
Skull base fractures
The skull base (Skull Base Fracture) is formed by five bones: the occipital, temporal, sphenoid, orbital part of the frontal, and the cribriform plate of the ethmoid bone. Injuries here are dangerous due to cranial nerve palsies, vascular damage, and CSF leakage.
- Anterior skull base: fractures are frequently combined with facial injuries. If the nasofrontoethmoidal complex is involved, there is a high risk of meningitis, CSF leakage, and anosmia (loss of smell).
- Central skull base: the fracture line usually runs sagittally or obliquely, involving the sphenoid sinus and sella turcica. Trauma in this zone may damage the optic nerves, carotid arteries, and nerves within the cavernous sinus (cranial nerves III, IV, V1, V2, VI).
- Lateral region (temporal bone): fractures are divided into otic capsule-sparing and otic capsule-violating. The latter are much more likely to result in facial nerve palsy, deafness, and otorrhea (CSF leakage from the ear).
- Posterior skull base: typically injured by a direct blow to the occiput, affecting the occipital bone and the petrous part of the temporal bone.
Briefly: answers to topical questions
What indirect CT signs indicate a skull base fracture?
Indirect CT signs of skull base injury may include air accumulations:
- Pneumocephalus (pneumocephalus) — the presence of air inside the skull; detected when evaluating head CT in the lung window. Air may indicate a fracture involving the paranasal sinuses or temporal bones.
- Pneumolabyrinth (pneumolabyrinth) — the presence of air within the cochlea, which may accompany a transverse fracture of the temporal bone pyramid.
What types are temporal bone fractures divided into based on the longitudinal axis of the pyramid?
Relative to the longitudinal axis of the pyramid, temporal bone fractures are divided into two main types.
- Transverse (Transverse) — account for 20% of cases, typically result from occipital or frontal trauma, and originate at sites of bone weakness.
- Longitudinal (Longitudinal) — account for 80% of cases, occur as a result of temporoparietal trauma, frequently involve the external auditory canal, and extend into the middle ear cleft.
The modern approach emphasizes that the fracture line often has an oblique orientation.
Class and exam questions
What is the main difference between a subgaleal hematoma and a cephalhematoma?
A subgaleal hematoma is located superficial to the periosteum and is not limited by cranial sutures. A cephalhematoma lies subperiosteally and is restricted to the boundaries of a single bone.
What is a diastatic fracture?
This is a gaping fracture whose line runs along cranial sutures or synchondroses. It is particularly common in pediatric practice.
Why do growing skull fractures occur in children?
Due to a tear in the dura mater. The meninges or brain parenchyma herniate into the defect, and CSF pulsations continuously widen the fracture margins, preventing bone healing.
Why is a temporal bone fracture involving the otic capsule dangerous?
It is accompanied by a very high risk of facial nerve palsy, sensorineural hearing loss, and cerebrospinal fluid leakage (CSF otorrhea).
What else to study on this topic
- Anatomic boundaries of the skull base compartments
- CT appearance of pneumocephalus and window selection for visualization
- Mechanisms of vascular injury in central skull base fractures
- Diagnosis of complex nasofrontoethmoidal fractures
- Traumatic meningoceles associated with destruction of the tegmen tympani
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