Symptoms. There are three types of altitude sickness. Acute mountain sickness is the most mild and common form. The symptoms are similar to when someone is intoxicated. High-altitude cerebral edema can happen if someone has acute mountain sickness and does not get treatment. The symptoms can include confusion, extreme drowsiness, difficulty walking and irritability. This type can be fatal without treatment. The third type is high-altitude pulmonary edema. This can occur on its own or stem from high-altitude cerebral edema. The symptoms can include severe coughing, shortness of breath and weakness. This type can also be fatal without treatment.