My uncle fell from a horse and is in critical condition now. the ct scans are clear but he is still unconscious. y would that be?

CT scans can pick: ...up changes in anatomy but not subtle changes in brain function. It can pick up masses (blood clots, tumors & abscesses) but not swelling unless it's severe. A neurologic exam can tell if he's in a coma. The depth of the coma, his other injuries and the health of his other vital organs all contribute to his prognosis. It's complicated! Please talk with his doctors. Best wishes.