The duration of coma following brainstem hemorrhage is uncertain. It mainly depends on two factors:

The first factor is the amount of bleeding. For brainstem hemorrhages of less than three milliliters, the level of coma is relatively shallow, and some patients may not experience any coma at all, with a high chance of successful resuscitation. For hemorrhages greater than three milliliters, as the amount of bleeding increases, the depth of the patient's coma also deepens, potentially leading to death shortly after the onset of the condition, or the patient might remain comatose for a prolonged period before eventually succumbing.

The second factor is whether timely and effective treatment was administered after the brainstem hemorrhage, including medication, necessary surgical interventions, active prevention of complications, and the stabilization of the condition, as well as treatments aimed at promoting awakening, among others.