Epidural hematoma results from skull fractures that cause bleeding between the dura and skull. It presents as a lenticular or biconvex mass that cannot cross suture lines. Subdural hematoma occurs between the dura and arachnoid membranes from cortical vein tears. It appears as a crescent-shaped mass that can cross sutures. Both require urgent CT imaging and surgical evacuation via burr holes.

1. Neuroradiology Traumatic Hemorrhage By: Luke Aldo, MSIV LECOM Erie, Pennsylvania

2. Layers of the Meninges

3. Epidural Hematoma Accumulation of blood in the potential space between dura mater and bone EDH is considered to be the most serious complication of head injury, requiring immediate diagnosis and surgical intervention (mortality rate associated with epidural hematoma has been estimated to be 5-50%)

4. Pathophysiology Usually results from a brief linear contact force to the calvaria that causes separation of the periosteal dura from bone and disruption of interposed vessels due to shearing stress Skull fractures occur in 85-95% of adult cases Extension of the hematoma usually is limited by suture lines owing to the tight attachment of the dura at these locations. The temporoparietal region and the middle meningeal artery are involved most commonly (66%)

5. Frequency Epidural hematoma complicates 2% of cases of head trauma (approximately 40,000 cases per year) Alcohol and other forms of intoxication have been associated with a higher incidence of epidural hematoma Sex more frequent in men, with a male-to-female ratio of 4:1 Age rare in individuals younger than 2 years rare in individuals older than 60 years because the dura is tightly adherent to the calvaria

6. History Head trauma Lucid interval between the initial loss of consciousness at the time of impact and a delayed decline in mental status (10-33% of cases) Headache Nausea/vomiting Seizures Focal neurological deficits (eg, visual field cuts, aphasia, weakness, numbness)

7. Diagnostic Imaging Noncontrast CT scanning of the head (imaging study of choice for intracranial EDH) not only visualizes skull fractures, but also directly images an epidural hematoma It appears as a hyperdense biconvex or lenticular-shaped mass situated between the brain and the skull, though regions of hypodensity may be seen with serum or fresh blood MRI also demonstrates the evolution of an epidural hematoma, though this imaging modality may not be appropriate for patients in unstable condition

12. Subdural Hematoma Rapidly clotting blood collection below the inner layer of the dura but external to the brain and arachnoid membrane Typically, low-pressure venous bleeding of bridging veins (between the cortex and venous sinuses) dissects the arachnoid away from the dura and layers out along the cerebral convexity It conforms to the shape of the brain and the cranial vault, exhibiting concave inner margins and convex outer margins (crescent shape) Frequency is related directly to the incidence of blunt head trauma It’s the most common type of intracranial mass lesion, occurring in about a third of those with severe head injuries

13. Mortality/Age Mortality Simple SDH (no parenchymal injury) is associated with a mortality rate of about 20% Complicated SDH (parenchymal injury) is associated with a mortality rate of about 50% Age It’s associated with age factors related to the risk of blunt head trauma More common in people older than 60 years (bridging veins are more easily damaged/falls are more common) Bilateral SDHs are more common in infants since adhesions existing in the subdural space are absent at birth Interhemispheric SDHs are often associate with child abuse

14. History Usually involves moderately severe to severe blunt head trauma Acute deceleration injury from a fall or motor vehicle accident, but rarely associated with skull fracture Generally loss of consciousness Any degree or type of coagulopathy should heighten suspicion of SDH Commonly seen in alcoholics because they’re prone to thrombocytopenia, prolonged bleeding times, and blunt head trauma Patients on anticoagulants can develop SDH with minimal trauma and warrant a lowered threshold for obtaining a head CT scan

15. Diagnostic Imaging MRI is superior for demonstrating the size of an acute SDH and its effect on the brain, however noncontrast head CT is the primary means of making a diagnosis and suffice for immediate management purposes Noncontrast head CT scan (imaging study of choice for acute SDH) The SDH appears as a hyperdense (white) crescentic mass along the inner table of the skull, most commonly over the cerebral convexity in the parietal region. The second most common area is above the tentorium cerebelli Contrast-enhanced CT or MRI is widely recommended for imaging 48-72 hours after head injury because the lesion becomes isodense in the subacute phase In the chronic phase, the lesion becomes hypodense and is easy to appreciate on a noncontrast head CT scan

20. Summary Epidural Hematoma Potential space between the dura in the inner table of the skull Can’t cross sutures Skull fractures in temporoparietal region Middle meningeal artery Lenticular or biconvex shape Lucid interval Common in alcoholics Medical emergency CT without contrast Evacuate via burr holes Subdural Hematoma Between the dura mater and the arachnoid mater Can cross sutures Cortical bridging veins Crescent shape Loss of consciousness Common in elderly Common in alcoholics Medical emergency CT without contrast Evacuate via burr holes

21. Bibliography Abramson, Nina, MD. Subdural Hematoma. Brigham Radiology: 1994 Nov. Azmoun, Leyla, MD. Epidural Hematoma. Brigham Radiology: 1995 Nov. Liebeskine, David, MD. Epidural Hematoma. Emedicine.com: 2006 Apr; 1-10. Scaletta, Tom, MD. Subdural Hematoma. Emedicine.com: 2006 May; 1-10.