Stupor is the term that is used to describe a condition when an unconcious animal can be aroused with a very strong external stimuli. Coma is the condition where animal will remain unconsious even if the same level of external stimulus is applied.
In other words, Stupor is unresponsiveness from which an animal can be aroused only by vigorous, physical stimulation. Coma is unresponsiveness from which an animal cannot be aroused. In coma, the animal's eyes remain closed.
Coma is a depressed level of consciousness. It begins with confusion, progresses through stupor, and ends up with complete loss of consciousness. A dog in a coma is insensitive to pain and cannot be awakened.
Dogs of any breed, age and gender are prone to stupor or coma.
Symptoms can be highly variable and depend on the primary disease that has led to loss of consiousness.
The major symptom is varying levels of unconsciousness, with the degree of consciousness depending on the nature and severity of the underlying disease.