Skull fracture
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A skull fracture is a break in one or more of the bones in the skull caused by a head injury. Isolated skull fractures are not very serious injuries, but usually the presence of a skull fracture indicates that significant enough impact occurred to cause brain trauma, which is quite serious.
Skull fractures can cause significant harm: Broken fragments of skull can lacerate or bruise the brain or damage blood vessels. If the fracture occurs over a major blood vessel, significant bleeding can occur within the skull, so head injury patients with skull fracture have many more intracranial hematomas (especially epidural hematomas) than those without fractures (Graham and Gennareli, 2000; Stock and Singer, 2004). Another complication of skull fractures is dissection of cerebral arteries, which can limit blood flow to the brain. A fracture in which the skin is also broken is called an open fracture. Penetrating head injuries are those that cause a fracture in the skull and breach the dura mater, the outermost membrane of the brain's meninges.
Fractures of the skull can be comminuted, depressed, linear or diastatic (Stock and Singer, 2004).
Linear fracture
Linear skull fractures, the most common type of skull fracture, occur in 62% of patients with severe head injury (Gilbert, 1990; Graham and Gennareli, 2000). Usually caused by widely distributed forces, linear fractures often occur when the impact causes the area of the skull that was struck to bend inward, making the area around it buckle outward (Gilbert, 1990; Graham and Gennareli, 2000).In rare cases, a linear fracture can develop and lengthen as the brain swells, in what is called a growing fracture. This can cause growth of cysts in the meninges (Orlando Regional Healthcare, 2004; Graham and Gennareli, 2000). Diastatic fractures are linear fractures that cause the bones of the skull to separate at the skull sutures in young children whose skull bones have not yet fused (BAIUSA; Orlando Regional Healthcare, 2004). They are usually caused by impact with a wide area such as a wall (Gilbert, 1990).
Comminuted fracture
Comminuted skull fractures, those in which a bone is shattered into many pieces, can result in bits of bone being driven into the brain, lacerating it (Gilbert, 1990). Depressed skull fractures, a very serious type of trauma occurring in 11% of severe head injuries, are comminuted fractures in which broken bones are displaced inward (Graham and Gennareli, 2000). This type of fracture carries a high risk of increasing pressure on the brain, crushing the delicate tissue. Complex depressed fractures are those in which the dura mater is torn.Basilar skull fracture
Basilar skull fractures, breaks in bones at the base of the skull, require more force to cause than cranial vault fractures. Thus they are rare, occurring as the only fracture in only 4% of severe head injury patients (Graham and Gennareli, 2000; Orlando Regional Healthcare, 2004). Caused by a blow to the back of the head, or by sudden decelleration of torso but not head (as in traffic accidents), resulting in separation of the suture between the occipital and temporal bones. Basilar fractures have characteristic signs: blood in the sinuses; a clear fluid called cerebrospinal fluid (CSF) leaking from the nose or ears; raccoon eyes (bruising of the orbits of the eyes that result from blood collecting there as it leaks from the fracture site); and battle sign (caused when blood collects behind the ears and causes bruising). Patients with basilar skull fractures are especially likely to get meningitis (Downie, 2001). Bones may be broken around the foramen magnum, the hole in the base of the skull through which the spinal cord enters and becomes the brain stem, creating the risk that blood vessels and nerves exiting the hole may be damaged (BAIUSA).References
- Brain Injury Association of America (BIAUSA). ["Types of Brain Injury."] Available.
- Downie A. 2001. ["Tutorial: CT in Head Trauma"] Available.
- Gilbert S. 1990. ["Investigative Significance of Coup and Contrecoup Head Injuries."] Available.
- Graham DI and Gennareli TA. Chapter 5, "Pathology of Brain Damage After Head Injury" Cooper P and Golfinos G. 2000. Head Injury, 4th Ed. Morgan Hill, New York.
- Orlando Regional Healthcare, Education and Development. 2004. ["Overview of Adult Traumatic Brain Injuries."] Available.
- Shepherd S. 2004. ["Head Trauma."] Emedicine.com. Available.
- Stock A and Singer L. 2004. ["Head Trauma."] Emedicine.com. Available.
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