An acute subdural hematoma occurs in most cases after trauma1 and, depending on the extent of the hemorrhage, is considered a neurosurgical emergency requiring immediate treatment. In this condition, bleeding occurs between the brain and the dura mater.
Causes
In the vast majority of cases, an acute subdural hematoma results from direct traumatic impact to the skull and the resulting injury to the bridging veins2, leading to venous bleeding beneath the dura mater. As the bleeding increases, compression and displacement of the brain tissue toward the opposite side occur, resulting in a life-threatening situation.
In significantly rarer cases, an acute subdural hematoma can also develop atraumatically as a result of excessively rapid lumbar drainage of cerebrospinal fluid, such as with a lumbar drain3 or a surgically induced CSF leak[^3]. This can result in intracranial hypotension, which may cause injury to the bridging veins and thus lead to bleeding.
Diagnosis
The gold standard for diagnosing an acute subdural hematoma is CT imaging. However, the diagnosis can also be readily established with MRI.
Clinically, an acute subdural hematoma can manifest differently depending on its extent. When the hemorrhage has a significant mass effect, a decreased level of consciousness occurs in most cases, with considerable variation in severity. A hemisyndrome contralateral to the side of the hemorrhage is also typical. If the hematoma is very thin, it may also first become symptomatic in many cases through epileptic seizures.
Location
In theory, an acute subdural hematoma can occur anywhere in the subdural space. Traumatic subdural hematomas are most commonly found over the convexity, interhemispherically, and in the tentorial region.
Conservative treatment
In patients with very thin acute subdural hematomas without midline shift and without neurological deficits who are asymptomatic, conservative treatment without surgery may also be appropriate45. If conservative treatment is chosen, follow-up imaging is recommended to rule out further enlargement of the hematoma as well as chronicization.
Surgical treatment
Surgical evacuation of the hematoma is indicated in clinically symptomatic patients and in cases of extensive acute subdural hematomas with midline shift. This involves performing a craniotomy over the hematoma, opening the dura, and subsequently removing the hematoma. Normally, the removed bone flap is replaced. In situations in which markedly increased intracranial pressure is observed intraoperatively, the bone flap may also not be replaced, in the form of a decompressive hemicraniectomy6. The procedure is performed under general anesthesia.
Prognostic outcome factors
Acute subdural hematoma is one of the most serious traumatic neurosurgical conditions. Patient outcomes depend on many factors. A significantly negative impact on outcome has been demonstrated for the following factors: motorcycle accident as the mechanism of injury, patient age over 65, a GCS of 3 to 4 on arrival at the trauma center, and a postoperative ICP of > 45 mmHg7.
In patients with a GCS from 3 to 7, mortality was 66 % and functional recovery was 19 % among those who required surgery because of an acute subdural hematoma8.
In the study by Wilberger et al. from 19919, outcomes were stratified according to initial GCS and age in 101 patients as follows.
Outcome stratification by GCS
| GCS | Outcome mortality10 | Functional recovery11 |
|---|---|---|
| 3 | 90 % | 5 % |
| 4 | 76 % | 10 % |
| 5 | 62 % | 18 % |
| 6-7 | 51 % | 44 % |
Outcome stratification by age
Stratification of outcomes by age in patients with an initial GCS of 3 to 712.
| Age | Outcome mortality | Functional recovery |
|---|---|---|
| 34 | 54,3 % | 31,4 % |
| 35-50 | 61,9 % | 23,8 % |
| 51-65 | 70,6 % | 11,8 % |
| >65 | 82,1 % | 3,6 % |
Time to surgery also plays an important prognostic role. In 1981, it was shown that patients with an acute subdural hematoma who underwent surgery within 4 hours after trauma had a mortality of 30 %, whereas patients who required more than 4 hours to reach surgery had a mortality of 90 %13.
References
Gennarelli T, Thibault L. Biomechanics of acute subdural hematoma. J Trauma. 1982;22(8):680-686.. ↩ ↩ ↩ ↩
Dardik A, Perler B, Roseborough G, Williams G. Subdural hematoma after thoracoabdominal aortic aneurysm repair: an underreported complication of spinal fluid drainage? J Vasc Surg. 2002;36(1):47-50..
[^3 ]: Sciubba D, Kretzer R, Wang P. Acute intracranial subdural hematoma following a lumbar CSF leak caused by spine surgery. Spine (Phila Pa 1976). 2005;30(24):E730-2. ↩ ↩Croce M, Dent D, Menke P, et al. Acute subdural hematoma: nonsurgical management of selected patients. J Trauma. 1994;36(6):820-826; discussion 826-7. ↩ ↩
Bender MB, Christoff N. Nonsurgical Treatment of Subdural Hematomas. Archives of Neurology. August 1974:73-79. ↩ ↩
Ransohoff J, Benjamin MV, Gage EL, Epstein F. Hemicraniectomy in the management of acute subdural hematoma. Journal of Neurosurgery. January 1971:70-76. ↩ ↩
Wilberger, Jack E., Mark Harris, and Danial L. Diamond. "Acute subdural hematoma: morbidity, mortality, and operative timing." Journal of neurosurgery 74.2 (1991): 212-218. ↩ ↩ ↩ ↩ ↩ ↩ ↩ ↩ ↩ ↩ ↩ ↩
Seelig, John M., et al. "Traumatic acute subdural hematoma: major mortality reduction in comatose patients treated within four hours." New England Journal of Medicine 304.25 (1981): 1511-1518. ↩ ↩