Most acute SDH are due to trauma from laceration of bridging veins in the subdural space. Nontraumatic cases are rare (incidence rate 3-5%) and predominantly affects adulst in 5th to 7th decade.
Predispoding factors to spontaneous SDH:
- vascular abnormalities – cerebral aneurysm, AVM, dural AVF
- hematological disorders
- anticoagulant therapy
Mechanisms of nontraumatic SDH:
- previous minor hemorrhages fixes an aneursym to local arachnoid adhesions –> results in bleeding directly into subdural space when arachnoid tear occurs after aneurysm rupture
- hemorrhage under high pressure leading to pia arachnoid rupture and extravasation into subdural space
- sudden increase in intravenous pressure (Valsalva) – rupture of bridging dural veins
- intracranial hypotension – systemic vascular hypotension after exercise
- Modality of choice: CT; cerebral angio to exclude vascular abnormalities
- Other investigations: coagulation tests
Wang, Hui Sun, Seok Won Kim, and Sung Hoon Kim. “Spontaneous Chronic Subdural Hematoma In An Adolescent Girl”. J Korean Neurosurg Soc 53.3 (2013): 201. Web.