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Skull Fracture

Practice Essentials

The brain is surrounded by cerebrospinal fluid (CSF), enclosed in meningeal covering, and protected inside the skull. Furthermore, the fascia and muscles of the scalp provide additional cushioning to the brain. Test results have shown that 10 times more force is required to fracture a cadaveric skull with overlaying scalp than the one without.
Although these layers play a protective role, meningeal attachments to the interior of the skull may limit the movement of the brain, transmitting shearing forces on the brain.

Fractures of the skull can be classified as linear or depressed. Linear fractures are either vault fractures or skull base fractures.Vault fractures and depressed fractures can be either closed or open (clean or dirty/contaminated).

A transverse temporal bone fracture is shown in the image below.

Transverse temporal bone fracture (courtesy of Ada

Transverse temporal bone fracture (courtesy of Adam Flanders, MD, Thomas Jefferson University, Philadelphia, Pennsylvania)

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CSF plays a major role in coup and countercoup injuries to the brain. A blow to a stationary but moveable head causes acceleration, and the brain floating in CSF lags behind, sustaining an injury directly underneath the point of impact (coup injury). When a moving head hits the floor, sudden deceleration results in an injury to the brain on the opposite side (countercoup injury).

CT scan is the criterion standard modality for aiding in the diagnosis of skull fractures.
Thinly sliced bone windows of up to 1-1.5 mm thick, with sagittal reconstruction, are useful in assessing injuries. Helical CT scan is helpful in occipital condylar fractures, but 3-dimensional reconstruction usually is not necessary.

The American Colllege of Radiology Appropriateness Criteria for head trauma includes the following

Skull radiography has been supplanted by CT in characterizing skull fractures in the setting of acute traumatic brain injury, though it may be useful in limited circumstances, such as radiopaque foreign bodies.

Contrast-enhanced MRI or CT may be helpful if posttraumatic infection is clinically suspected in patients with risk factors such as skull base fractures.

Traumatic dural sinus thrombosis is most commonly seen in patients with skull fractures that extend to a dural venous sinus or the jugular foramen.

Cerebrospinal fluid leak occurs in 10-30% of skull base fractures and most often presents with rhinorrhea (80% of cases) in the setting of frontobasal fracture.

In children, radiographs of the skull are known to have a low predictive value in determining intracranial injury. However, in contrast to accidental head trauma, where radiographs have largely been replaced by CT, skull radiographs are still often performed as part of the skeletal survey in evaluation of suspected nonaccidental trauma. It has been generally accepted that skull radiographs and head CT are complementary examinations, since fractures in the plane of the transaxial CT image may not be apparent on the head CT examination.

Adults with simple linear fractures who are neurologically intact do not require any intervention and may even be discharged home safely and asked to return if symptomatic. Infants with simple linear fractures should be admitted for overnight observation regardless of neurological status.

The role of surgery is limited in the management of skull fractures. Infants and children with open depressed fractures require surgical intervention. Most surgeons prefer to elevate depressed skull fractures if the depressed segment is more than 5 mm below the inner table of adjacent bone. Indications for immediate elevation are gross contamination, dural tear with pneumocephalus, and an underlying hematoma.

A study of 66 skull fractures in children (mean age, 5.9 yr) supported previous evidence that routine skull radiographs are of little benefit in cases of minor head trauma and that additional CT scans are not indicated in symptomatic children with linear fractures. The authors noted that CT scans should be used only in cases in which neurologic symptoms are present.

Anatomy of fracture

The causative forces and fracture pattern, type, extent, and position are important in assessing the sustained injury. The skull is thickened at the glabella, external occipital protuberance, mastoid processes, and external angular process and is joined by 3 arches on either side. The skull vault is composed of cancellous bone (diploë) sandwiched between 2 tablets, the lamina externa (1.5 mm), and the lamina interna (0.5 mm). The diploë does not form where the skull is covered with muscles, leaving the vault thin and prone to fracture.

The skull is prone to fracture at certain anatomic sites that include the thin squamous temporal and parietal bones over the temples and the sphenoid sinus, the foramen magnum, the petrous temporal ridge, and the inner parts of the sphenoid wings at the skull base. The middle cranial fossa is the weakest, with thin bones and multiple foramina. Other places prone to fracture include the cribriform plate and the roof of orbits in the anterior cranial fossa and the areas between the mastoid and dural sinuses in the posterior cranial fossa.

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