You are in: eMedicine Specialties > Radiology > BRAIN/SPINE Epidural HematomaArticle Last Updated: Feb 3, 2006AUTHOR AND EDITOR INFORMATIONSection 1 of 10
  Author: Douglas K McDonald, MD, Clinical Fellow, Vascular and Interventional Radiology, Harvard Medical School; Fellow, Vascular and Interventional Radiology, Department of Radiology, Massachusetts General Hospital Douglas K McDonald is a member of the following medical societies: Alpha Omega Alpha, American College of Radiology, American Medical Association, New Mexico Medical Society, Radiological Society of North America, and Texas Medical Association Coauthor(s): L Gill Naul, MD, Professor and Head, Department of Radiology, Texas A&M University College of Medicine; Chair, Department of Radiology, Chief, Section of Magnetic Resonance Imaging, Scott and White Memorial Hospital and Clinic Editors: Lucien M Levy, MD, PhD, Director of Neuroradiology, Professor of Radiology, Department of Radiology, George Washington University Medical Center; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; James G Smirniotopoulos, MD, Professor of Radiology, Neurology, and Biomedical Informatics, Chairman, Department of Radiology and Radiological Sciences, Uniformed Services University of the Health Sciences Author and Editor Disclosure Synonyms and related keywords: EDH, extradural hematoma, subdural hematoma INTRODUCTIONSection 2 of 10
  BackgroundEpidural hematoma (EDH) is defined as hemorrhage into the potential space between the dura, which is inseparable from cranial periosteum, and the adjacent bone. EDH can occur intracranially or intraspinally, and it can result in clinically significant morbidity and/or mortality if it is not diagnosed and treated promptly. PathophysiologyAlmost always associated with preceding head trauma, most intracranial EDHs result from skull fractures and the associated disruption or laceration of the arteries that lie along the inner table of the calvaria between the skull and the dura. The most common site of EDH is the temporoparietal region, where the anterior or posterior division of the middle meningeal artery or its trunk is lacerated. Blood then accumulates at the site of arterial injury, seldom crossing the cranial suture lines because of the tightly adherent periosteum at the suture margins. Another cause of EDH is disruption of the dural venous sinuses in the dura adjacent to a skull fracture. As many as 30% of EDHs are venous. When due to laceration of a dural venous sinus, EDHs usually occur in the frontal, parieto-occipital, or occipital region because of disruption of the superior sagittal sinus, torcular herophili, or lateral sinuses. The injured dural sinus is commonly stripped away from the adjacent calvaria by the expanding hematoma and occasionally occluded by an intimal tear resulting from the fracture. Because of the generally slow growth of a venous EDH, it may be found incidentally. Presenting symptoms, such as hydrocephalus resulting from mass effect on the cerebellum with a posterior fossa hematoma, may be delayed. In young children, open sutures and compliant bones result in increased calvarial flexibility, which may permit outward bending of the calvaria without fracture. This bending may lead to separation of the periosteum from the inner table of the skull and disruption of perforating arteries or veins, causing an EDH. Many factors contribute to the risk of skull fracture and the resultant EDH, including the thickness of the extracranial soft tissues at the site of injury, the thickness and density of the calvaria, the position of head at the time of injury, and the nature of the force producing the injury. The rate of EDH enlargement is also multifactorial and depends on whether the hematoma is of venous or arterial origin, whether it is contained to form a pseudoaneurysm, whether it drains into a meningeal vein through a fistulous communication, or whether it decompresses into the subgaleal space through the skull fracture. The transected vessel may also undergo spasm, resulting in the cessation of bleeding. Staging of intracranial EDH is based on the age of the hematoma. Zimmerman types 1, 2, and 3 refer to acute, subacute, and chronic stages, respectively. As a result of early detection after the inciting injury, acute hematoma is seen in 58% of patients at the time of diagnosis. EDH is discovered in 31% of patients in the subacute stage and in 11% in the chronic stage. Spinal EDH is also almost always associated with trauma related to lumbar puncture, anticoagulants, vasculitis, vascular malformations, and bleeding diathesis (those seen in alcoholism and leukemia are also implicated). Spinal EDH is most often located dorsally in the thoracic spine, where it closely approximates the bony margins of the spinal canal. When seen in the lumbar spine, EDH may be associated with small disk herniations and annular tears. Spinal EDH is difficult to distinguish from subdural hematoma, and it may coexist with this condition. FrequencyUnited StatesEDH occurs in approximately 1-2% of patients presenting with head trauma and in about 10-20% of patients presenting with traumatic coma. Spontaneous spinal hematoma is rare, with an annual incidence of approximately 1 person per 1 million population. InternationalLittle information is available about the international frequency of EDH. It is likely similar to that in the United States. Mortality/Morbidity
RaceNo known race predilection is known. SexBecause of their increased incidence of head trauma, male individuals are affected 4 times as often as female individuals. AgeEDH is most common in middle age and less frequently seen in children younger than 2 years and individuals older than 60 years. It is less common after 40 years of age than before because increased adherence of the periosteal layer of the dura to the adjacent bone resists mechanical dissection. AnatomyThe meninges are the protective layers of the brain that are responsible for the distribution of cerebrospinal fluid and for venous drainage of the brain. They consist of 3 layers of tissue: the dura mater, the arachnoid layer, and the pia mater. The dura mater is the thickest, outermost layer, and it is composed of dense fibrous connective tissue and collagen. The dura is dual layered, containing an outer periosteal layer and an inner meningeal layer. The outer periosteal layer is inseparable from the periosteum of the inner table of the calvaria. The inner meningeal layer forms multiple partitions of the brain, including the falx cerebri, the tentorium cerebelli, and the falx cerebelli. A potential space known as the subdural space separates the dura mater from the arachnoid, the middle avascular membranous layer. The pia mater constitutes the final layer. It is closely applied to the brain and spinal cord, carrying blood vessels that supply both. Clinical DetailsLess than 20% of patients have the classic clinical presentation of an initial injury with or without a temporary loss of consciousness followed by a lucent phase when they remain conscious as the hematoma enlarges. A fistulous connection between venous channels or extension through the fracture into the subgaleal space with resultant pseudoaneurysm formation may act to decompress the hematoma and halt expansion; however, EDH is considered a neurosurgical emergency in which somnolence, coma, and even herniation can result if it is untreated. Differential considerations for spinal EDH include extradural lipomatosis and spinal angiolipomas, which are usually epidural and located in the midthoracic region. Both of these entities can be differentiated from EDH. On MRIs, lipomatosis demonstrates signal intensity similar to that of fat, and angiolipomas often result in bone erosion and pathologic fracture in addition to cord compression. Preferred ExaminationCT is the examination of choice in the evaluation of suspected intracranial EDH. MRI should be performed when spinal EDH is considered possible. Limitations of TechniquesBecause of volume averaging with adjacent bone, small EDHs can be difficult to detect with CT. Although MRI is sensitive for EDH, it is seldom the preferred examination because of its limited availability outside of urban institutions and because of problems with MRI-incompatible equipment that is often needed in treating a patient with trauma or one in an unstable condition. DIFFERENTIALSSection 3 of 10
Meningioma, Brain Subdural Hematoma
| ||||||||||||||||||||||||||||||||||||||||||
| Media file 1: An epidural hematoma demonstrates the classic lenticular configuration that overlies the lateral aspect of the left temporal lobe. Areas of diminished attenuation in the hematoma suggest ongoing hemorrhage. | |
 | View Full Size Image | Media type: CT |
| Media file 2: The epidural hematoma shown in Image 1 extends superiorly to overlie the lateral aspect of the left frontal lobe with associated sulcal effacement, as well as a rightward midline shift of 5-6 mm. | |
 | View Full Size Image | Media type: CT |
| Media file 3: A nondisplaced linear fracture is present in the left temporoparietal region. | |
 | View Full Size Image | Media type: CT |
| Media file 4: An epidural hematoma overlies the right frontal lobe with right-to-left subfalcine herniation of approximately 7 mm. Areas of low attenuation in the hematoma are again seen. These indicate continued hemorrhage at the time of the examination. Overlying soft-tissue swelling is present in the right frontal aspect of the scalp. | |
 | View Full Size Image | Media type: CT |
| Media file 5: Image depicts a fracture of the right frontal bone anterior to the coronal suture. | |
 | View Full Size Image | Media type: CT |
Article Last Updated: Feb 3, 2006
