Running head: TRAUMATIC BRAIN INJURY 1. Diagnosing and Managing Traumatic Brain Injuries. November 15 th, 2011

Transcription

1 Running head: TRAUMATIC BRAIN INJURY 1 Diagnosing and Managing Traumatic Brain Injuries November 15 th, 2011

2 TRAUMATIC BRAIN INJURY 2 Abstract Traumatic brain injuries are a serious and common occurrence in the United States. They are one of the leading causes of death and can cause numerous long term effects on patients. Imaging is one of the best ways to diagnose and manage a brain injury. There are five different types of traumatic brain injuries and they are diagnosed using magnetic resonance imaging and computed tomography. It is important for patients to receive quick and accurate images in order to have the best possible outcome.

3 TRAUMATIC BRAIN INJURY 3 Diagnosing and Managing Traumatic Brain Injuries Traumatic brain injury (TBI) is one of the leading causes of mortality and morbidity in the world. It is estimated that 10 million people sustain TBI each year worldwide, and the Centers for Disease Control and Prevention in the USA estimates that 1.7 million people suffer TBI annually (Kim & Gean, 2011, p.39). The use of imaging is critical in the diagnosis and management of these injuries. Computed tomography (CT) and magnetic resonance imaging (MRI) are the most common imaging modalities used to diagnose and manage TBI. Categories of Brain Injuries The two different categories of injury when discussing TBI are primary and secondary. The primary injuries, such as epidural hematoma, subdural hematoma, subarachnoid hemorrhage, cortical contusion and traumatic axonal injury, are caused by the direct result of the impact. The secondary injuries, such as cerebral swelling, herniation, and ischemia, can develop minutes to days after the primary injury. This classification highlights that TBI is not a onetime event but rather a continuous and progressive injury that necessitates optimal medical and surgical management to maximize patient recovery and prevent successive injury (Kim & Gean, 2011, p.39). Primary Injuries Epidural Hematoma An epidural hematoma (EDH) commonly occurs at the coup site, which is the site of impact, and is usually accompanied with an overlying skull fracture. EDH is caused by an "Injury to a meningeal artery/vein, diploic vein, or dural venous sinus result(ing) in a classically lentiform-shaped collection of blood that strips the dura away from the inner table of the skull" (Kim & Gean, 2011, p.40). The most common occurrence of EDHs are found in the temporal or

4 TRAUMATIC BRAIN INJURY 4 temporoparietal regions and are usually due to an injury of the middle meningeal artery, the transverse/sigmoid sinus, or the sphenoparietal sinus. In rare occasions EDHs can occur in the frontal region of the brain, opposite of the trauma site. These are called contrecoup EDHs and only nine cases have been reported in literature. EDHs are more common in males than females, with the ratio being 4:1. The peak incidence is within a mean age of years, and is rare in patients older than 50 years. It is very uncommon for a delayed EDH to occur, with a reported incidence of approximately 3% (Takeuchi, Takasato, Masaoka, & Otani, 2010, p.152). Imaging epidural hematomas When imaging EDHs, the preferred modality is CT. The hematoma in the images typically appear to be lentiform or biconvex in shape. (See Fig. 1) EDHs do not cross cranial sutures, but are able to cross the midline. This is one way to distinguish an EDH from the various other hematomas (Kim & Gean, 2011). Fig. 1 A. Epidural hematoma beneath a skull fracture. B. Arrow pointing to the skull fracture. Note. Kim, J.J. & Gean, A.D. (2011). Imaging for the diagnosis and management of traumatic brain injury. Neurotherapeutics, 8(1), Retrieved on November 4, 2011, from doi: /s Subdural Hematoma A subdural hematoma (SDH) usually occurs at the contrecoup site, even though it can occur at the coup site. SDH s are caused by an "Injury to superficial bridging veins results in

5 TRAUMATIC BRAIN INJURY 5 bleeding between the meningeal layer of the dura and arachnoid, and blood may continue to accumulate in this space" (Kim & Gean, 2011, p.41). Some of the common places for SDHs to occur are over the cerebral convexities, along the tentorium cerebelli, and along the flax cerebri. According to Cantu and Gean (2010) "an acute SDH is the most common cause of death due to head injury in sports" (p.1561). SDHs are believed to be caused by the acceleration/deceleration forces that accompany these injuries. Imaging subdural hematomas A SDH will appear crescent in shape and can be extremely subtle, so window settings and adjustments are crucial in diagnosing. SDH's are able to cross cranial suture lines, but do not cross the midline, which is the opposite of an EDH. It is common for an SDH to cause a shift in the midline. (See Fig. 2) "The volume of the extra-axial collection is proportional to the extent of mass effect and midline shift" (Cantu & Gean, 2010, p.1562). Subarachnoid Hemorrhage Fig.2 A CT image of a SDH on the left side. The image shows a midline shift that is common in a SDH. Cantu, R.C. & Gean, A.D. (2010). Second-impact syndrome and a small subdural hematoma: an uncommon catastrophic result of repetitive head injury with a characteristic imaging appearance. Journal of Neurotrauma, 27(9), Retrieved November 4, 2011, from doi: /neu A Subarachnoid hemorrhage (SAH) occurs in nearly half of patients that suffer a large head injury and can commonly be associated with other types of hemorrhages. "SAH may result from direct laceration of the small cortical vessels traversing the subarachnoid space, redistribution of intraventricular hemorrhage exiting the fourth ventricular outflow foramen, or direct extension from cortical contusion/hematoma" (Kim & Gean, 2011, p.43). The blood that

6 TRAUMATIC BRAIN INJURY 6 fills the subarachnoid space causes a rise in intracranial pressure and displaces the cerebrospinal fluid. According to Sehba, Pluta, and Zhang (2010), this moment of increased pressure is usually described by patients as "the worst headache of my life" (p.28). Imaging subarachnoid hemorrahages An SAH is observed on CT images as linear areas of high attenuation. (See Fig. 3) They can be found in the cerebral sulci, Sylvian fissures, or basilar cisterns. Some patients with TBIs may only have a small SAH as the only abnormal finding on a CT scan, so it is crucial to identify them accurately. Patients that have an accompanying SAH with other TBI's have a Fig. 3 A CT image of a SAH. The arrow head shows the linear areas. Note. Kim, J.J. & Gean, A.D. (2011). Imaging for the diagnosis and management of traumatic brain injury. Neurotherapeutics, 8(1), Retrieved on November 4, 2011, from doi: /s significantly worse outcome and are less likely to achieve a good recovery in comparison with the TBI's that are not accompanied with SAH (Kim & Gean, 2011). Cerebral Contusion A cerebral contusion (CC) can be caused by either direct trauma or acceleration/deceleration injury. CCs usually occur at the contrecoup site and are caused when a moving head collides with a stationary object. Although CC's can occur at the coup site beneath a skull fracture, they are more common and severe in contrecoup injuries. CC's are commonly referred to as a bruise in the brain that are caused by the rough and irregular surfaces of the skull. These impacts with the skull cause hemorrhagic contusions (Kim & Gean, 2011).

7 TRAUMATIC BRAIN INJURY 7 Imaging cortical contusions A CC can be imaged using CT or MRI, but MRI is more sensitive in detecting small hemorrhagic contusions. CC's appear as "small, focal areas of pepechial hemorrhage peripherally located in the brain" (Kim & Gean, 2011, p.43). They can be very subtle on the initial CT scan, but about half of Fig. 4 A. The initial CT scan of a patient, the short arrow is pointing to a small CC. B. A CT scan of the same patient 6 hours later, the short arrows pointing to a much larger CC. contusions will evolve and grow larger over time. (See Fig. 4) Due to the evolving of CC's it is crucial that serial CT imaging and close monitoring of patients is done. Traumatic Axonal Injury Note. Kim, J.J. & Gean, A.D. (2011). Imaging for the diagnosis and management of traumatic brain injury. Neurotherapeutics, 8(1), Retrieved on November 4, 2011, from doi: /s A Traumatic axonal injury (TAI) is typically caused by extreme acceleration/deceleration or by child abuse, such as shaking baby syndrome. TAI involves the loss of neural function in the areas of the brain where white and grey matter meet, which is usually away from the area of direct trauma with the skull. The white matter in the brain is denser than the gray matter, "due to the different inertial characteristics based on these densities, as the brain rotates during acceleration-deceleration events, lower density tissues move more rapidly than those of greater density. This velocity difference causes sheering of neuronal

8 TRAUMATIC BRAIN INJURY 8 axons" (Shipley, 2011, para. 4). This process is usually bilateral, covers a large area and is near the cerebral cortex, corpus callosum, or brain stem (Kim & Gean, 2011). Imaging traumatic axonal injuries Fig. 5 An MRI of a patient with a TAI, the arrows are pointing to the abnormal signal in the white matter. Note. Kim, J.J. & Gean, A.D. (2011). Imaging for the diagnosis and management of traumatic brain injury. Neurotherapeutics, 8(1), Retrieved on November 4, 2011, from doi: /s Cerebral Swelling The most diagnostic imaging modality for TAI is MRI, due to CT being insensitive to white matter lesions. Most CT scans show up normal with TAI injuries because they are nonhemorrhagic (Marquez de la Plata et al., 2011). TAI usually shows up on the MRI as multifocal areas of abnormal signal in the white matter. (See Fig. 5) Many studies have indicated that MRI can predict the length of coma in TAI patients. "The volume of white-matter lesions has been correlated to the degree of injury, as measured by MRI" (Wasserman, 2011, para. 5). Secondary Injuries The cause of cerebral swelling can be either cerebral edema or cerebral hyperemia. Cerebral hyperemia is due to "Dysautoregulation with vascular engorgement and increased cerebral blood volume" (Kim & Gean, 2011, p.46). This was believed to be the main mechanism that caused cerebral swelling. Some of the recent studies have suggested that the main causes of cerebral swelling are due to edema, which is "due to the failure of cell membrane pumps, resulting in intracellular water leakage" (Kim & Gean, 2011, p.46). Images of cerebral swelling

9 TRAUMATIC BRAIN INJURY 9 due to hyperemia appear as the loss of sulci, with gray and white matter differentiation intact. (See Fig. 6) Images of cerebral edema with appear as the loss of gray and white matter. Cerebral Herniation Cerebral herniation is due to part of the brain being compressed by a hematoma. This causes part of the brain to move from one compartment of the cranium to another. Subfalcial herniation, uncal herniation, and cerebellar tonsillar herniation are the three major types of herniation that can occur separately or in Fig. 6 A and B are CT images of a patient with cerebral swelling. Both images show differentiation in gray and white matter, with loss of sulci. Note. Kim, J.J. & Gean, A.D. (2011). Imaging for the diagnosis and management of traumatic brain injury. Neurotherapeutics, 8(1), Retrieved on November 4, 2011, from doi: /s combination (Agamanolis, n.d.). Patients that suffer from herniation "typically undergo decompressive craniectomy with mass lesion evacuation" (Kim & Gean, 2011, p.47). Cerebral Ischemia and Infarction Cerebral ischemia and infarction are not very common in TBI patients, but occasionally they are present on CT scans. Ischemia is usually due to a blood vessel being compressed by a cerebral herniation. (See Fig. 7) Infarctions are common in the anterior or posterior cerebral artery following a subfalcine or uncal Fig. 7 A CT image that has bilateral multifocal ischemic lesions. Cantu, R.C. & Gean, A.D. (2010). Second-impact syndrome and a small subdural hematoma: an uncommon catastrophic result of repetitive head injury with a characteristic imaging appearance. Journal of Neurotrauma, 27(9), Retrieved November 4, 2011, from doi: /neu

10 TRAUMATIC BRAIN INJURY 10 herniation (Kim & Gean, 2011). MRI and CT are able to provide a vast amount of information and assessment of the size, location, and severity of cerebral ischemia and infarctions (Leiva- Salinas, Wintermark, & Kidwell, 2011). Imaging traumatic brain injuries Imaging plays an important role in diagnosing and managing TBI s. It is critical that the right images are taken and the best modality is used to properly diagnose an injury. According to Kim and Gean (2011): For diagnosis of TBI in the acute setting, noncontrast CT is the modality of choice as it quickly and accurately identifies intracranial hemorrhage that warrants neurosurgical evacuation. CT readily identifies both extra-axial hemorrhage (epidural, subdural, and subarachnoid/intraventricular hemorrhage) and intra axial hemorrhage (cortical contusion, intraparenchymal hematoma, and TAI or shear injury). While CT is the mainstay of TBI imaging in the acute setting, magnetic resonance imaging (MRI) has better diagnostic sensitivity for certain types of injuries that are not necessarily hemorrhagic (p.40). Both CT and MRI are used in the prognosis and management of TBI and advancements are continually made to increase the quality of the images. Conclusion In conclusion, CT and MRI are crucial in diagnosing and managing TBI. The images that CT and MRI provide are important in identifying the acute primary injuries when making a diagnosis and identifying secondary injuries to guide the management process. Due to the large number of individuals that suffer from TBI, it is imperative that high quality images are produced to provide the best possible treatment for patients.

11 TRAUMATIC BRAIN INJURY 11 References Agamanolis, D.P., (n.d.) Traumatic brain injury and increased intracranial pressure. Neuropathology Web site. Retrieved from chapter4cherniations.html#herniations Cantu, R.C. & Gean, A.D. (2010). Second-impact syndrome and a small subdural hematoma: An uncommon catastrophic result of repetitive head injury with a characteristic imaging appearance. Journal of Neurotrauma, 27(9), doi: /neu Kim, J.J. & Gean, A.D. (2011). Imaging for the diagnosis and management of traumatic brain injury. Neurotherapeutics, 8(1), doi: /s Leiva-Salinas, C., Wintermark, M., & Kidwell, C.S. (2011). Neuroimaging of cerebral ischemia and infarction. Neurotheraputics, 8(1), Retrieved from Marquez de la Plata, C.D., Garces, J., Kojori, E.S., Grinnan, J., Krishnan, K., Pidikiti, R., Diaz-Arrastia, R. (2011). Deficits in functional connectivity of hippocampal and frontal lobe circuits after traumatic axonal injury. Archives of Neurology, 68(1), doi: /archneurol Sehba, F.A., Pluta, R.M., & Zhang, J.H. (2011). Metamorphosis of subarachnoid hemorrhage research: from delayed vasospasm to early brain injury. Mol Neruobiol, 43(1), doi: /s z Shipley, C. (2010). Traumatic brain injury and diffuse axonal injury. Trial Image Inc. Web site. Retrieved from Takeuchi, S., Takasato, Y., Masaoka, H., & Otani, N. (2010). Contrecoup epidural hematoma. Neurology India, 58(1), doi: / Wasserman, J.R. (2011). Diffuse axonal injury imaging. Retrieved from

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