A subacute subdural hematoma causes symptoms between 3 and 14 days, and a chronic subdural hematoma causes symptoms after 15 days.

亚急性硬膜下血肿在3到14天内出现症状；慢性硬膜下出血在15天后出现症状。

A chronic subdural hematoma, on the other hand, shows up as a hypodense mass, which is less white than the surrounding brain tissue.

而慢性硬脑膜下血肿，则显示为低密度区域，意味着比正常脑组织亮度更低。