Coma is a state of prolonged unconsciousness that can be caused by a variety of problems — traumatic head injury, stroke, brain tumor, drug or alcohol intoxication, or even an underlying illness, such as diabetes or an infection. Coma is a medical emergency. Swift action is needed to preserve life and brain function.
https://www.mayoclinic.org/diseases-conditions/coma/symptoms-causes/syc-20371099