High-Altitude Cerebral Edema (HACE) is a serious condition that can occur when individuals ascend to high altitudes, typically above 8,000 feet (2,400 meters). It results from the swelling of the brain due to a lack of oxygen, which can lead to symptoms such as headache, confusion, and difficulty walking. HACE is often associated with Acute Mountain Sickness (AMS) and can develop rapidly. If not treated promptly, it can be life-threatening. The best prevention is gradual ascent and acclimatization, while treatment may involve descending to lower altitudes and administering oxygen or medications.