Educational Pearls Subdural hematomas can happen in the elderly because of brain atrophy, and can manifest with neurological deficit. Subdural hematomas are caused by rupture of the bridging veins of the brain. This can be caused by trauma, brain atrophy, or possibly by anticoagulant use. They are crescent-shaped on head CT.   Epidural hematomas, in contrast, are caused by rupture of meningeal arteries secondary to trauma. They are usually lens-shaped on head CT. Subdurals are difficult to pick up on head CT because they may be isodense to brain tissue. References: Management of Recurrent Subdural Hematomas Desai, Virendra R. et al. Neurosurgery Clinics , Volume 28 , Issue 2 , 279 - 286