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  • Amara Ahmed and Kevin M. Rice, MD

Subtle Subdural Hematoma

Updated: May 7, 2021

29F with trauma and headache • Xray of the Week

CT of Subtle Subdural Hematoma

Figure 1. What is the important finding on this CT scan.

CT of Subtle Subdural Hematoma

Figure 2.

A. Coronal CT brain with standard window width of 70. It is very difficult to visualize the left superior parietal acute subdural hematoma.

B. Coronal CT brain with wider window width of 150. Note the small superior parietal acute subdural hematoma (red arrow).

CT of Subtle Subdural Hematoma

Figure 3. Coronal and axial CT brain with standard window width of 70. It is very difficult to visualize the left superior parietal acute subdural hematoma. SDH is not well seen on the axial image, even on a wide window, due to the hematoma being in the same plane.

Sagittal CT of patient with bridging cortical veins

Figure 4. Sagittal CT of a different patient with atrophy which demonstrates several bridging cortical veins (white arrows) as they cross the subdural space and drain into the superior sagittal sinus. Subdural hemorrhages are due to tearing of these veins when there is a rapid acceleration or deceleration of the head.


Acute subdural hematoma (SDH) occurs when blood accumulates in the subdural space, between the arachnoid and dura layers of the brain (1,4). They can result from traumatic accidents that cause tears in the bridging veins that cross the subdural space. Acute SDH's are common in the elderly because brain atrophy during aging causes the bridging veins to stretch, making them more susceptible to tears (2) (Fig. 4). Other etiologies of acute SDH include coagulopathy or medical coagulation, non-traumatic hemorrhage, surgery, and intracranial hypotension (3).

Acute SDH's are typically unilateral and can be visualized as crescent-shaped and hyperdense regions on CT (1,4). The acute SDH in this case is seen only with wide windowing. Small SDH's such as the one in this case may be difficult to detect with standard brain windows compared to the subdural window so it is important to window the CT scan appropriately for smaller hematomas (1). In addition, this SDH was not well seen on the axial images due to the hematoma being in the same plane (Fig.3).

SDH's can usually be distinguished from epidural hematomas since epidural hematomas have a biconcave-lens appearance on CT and show pooling of blood between the skull and the dura mater and they cannot expand past the sutures of the skull (1,4). Purulent accumulation of cerebrospinal fluid in the subarachnoid space can also have a similar appearance to SDH's, especially when there is decreased brain mass (4). Patients with subarachnoid hemorrhage due to ruptured aneurysms may also present with hyperdense subdural effusions which appear similar to acute SDH's but they may resolve on follow-up examination (5). Acute SDH can be distinguished from subacute and chronic SDH on CT. Subacute SDH will appear isodense to grey matter on CT (6). Chronic SDH will appear isodense to CSF on CT often with a biconvex shape rather than a crescentic shape, and it can also appear as a calcified mass (7). Treatment for acute SDH is usually surgical particularly when there is neurologic deficit. Moreover, surgery is indicated if the clot thickness is more than 1 cm or midline shift is more than 0.5 cm, even without significant neurologic deficit (8). Conservative management may be used in asymptomatic patients with small or chronic SDH (8). In this particular case, the SDH resolved without surgery.


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1. Heit JJ, Iv M, Wintermark M. Imaging of Intracranial Hemorrhage. J Stroke. 2017;19(1):11-27. doi:10.5853/jos.2016.00563 2. Miller JD, Nader R. Acute subdural hematoma from bridging vein rupture: a potential mechanism for growth. J Neurosurg. 2014;120(6):1378-1384. doi:10.3171/2013.10.JNS13272 3. Vega RA, Valadka AB. Natural History of Acute Subdural Hematoma. Neurosurg Clin N Am. 2017;28(2):247-255. doi:10.1016/ 4. Pierre L, Kondamudi NP. Subdural Hematoma. [Updated 2019 Dec 30]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: 5. Zamora CA, Lin DD. Enhancing subdural effusions mimicking acute subdural hematomas following angiography and endovascular procedures: report of 2 cases. J Neurosurg. 2015;123(5):1184-1187. doi:10.3171/2014.10.JNS142172

6. Yadav YR, Parihar V, Namdev H, Bajaj J. Chronic subdural hematoma. Asian J Neurosurg. 2016;11(4):330-342. doi:10.4103/1793-5482.145102 7. Kpelao E, Beketi KA, Moumouni AK, et al. Clinical profile of subdural hematomas: dangerousness of subdural subacute hematoma. Neurosurg Rev. 2016;39(2):237-240. doi:10.1007/s10143-015-0669-4

8. Gerard C, Busl KM. Treatment of Acute Subdural Hematoma. Curr Treat Options Neurol. 2014 Jan;16(1):275. doi: 10.1007/s11940-013-0275-0

Amara Ahmed

Amara Ahmed is a medical student at the Florida State University College of Medicine. She serves on the executive board of the American Medical Women’s Association and Humanities and Medicine. She is also an editor of HEAL: Humanism Evolving through Arts and Literature, a creative arts journal at the medical school. Prior to attending medical school, she graduated summa cum laude from the Honors Medical Scholars program at Florida State University where she completed her undergraduate studies in exercise physiology, biology, and chemistry. In her free time, she enjoys reading, writing, and spending time with family and friends.

Follow Amara Ahmed on Twitter @Amara_S98

Kevin M. Rice, MD

Kevin M. Rice, MD is the president of Global Radiology CME

Dr. Rice is a radiologist with Renaissance Imaging Medical Associates and is currently the Vice Chief of Staff at Valley Presbyterian Hospital in Los Angeles, California. Dr. Rice has made several media appearances as part of his ongoing commitment to public education. Dr. Rice's passion for state of the art radiology and teaching includes acting as a guest lecturer at UCLA. In 2015, Dr. Rice and Natalie Rice founded Global Radiology CME to provide innovative radiology education at exciting international destinations, with the world's foremost authorities in their field. In 2016, Dr. Rice was nominated and became a semifinalist for a "Minnie" Award for the Most Effective Radiology Educator.

Follow Dr. Rice on Twitter @KevinRiceMD

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