How long does it take for chronic subderal hematomo to show up? how rare in young adults are they? had mild concussion 1 month and 16 days ago no ct

Very rare: After head injury in a young person like you that is normal neurologically, the chances that you have subdural hematoma is very rare. Even if you did get it, it would most likely get absorbed because you should have a very full brain and the subdural hematoma will not have the space to turn into a chronic subdural hematoma which takes weeks if not months to develop.

Comments: Whole range of subdural presentations, but typically begin at time of head injury. Very rare that mild concussion is also associated with subdural bleeding. Unless you have increasing headaches, nausea and vomiting, dizziness, blurred or double vision, or unilateral weakness, no reason to worry. The absolute vast majority of closed head injuries have no critical sequelae.