There are three common reasons for the sudden forehead depression: first, that is, the higher incidence is the forehead area is traumatized, subject to strong, violent external force resulting in skin, soft tissue and even bone damage, when the forehead will have obvious depression. Second, there may be fatty tissue atrophy or soft tissues produce certain inflammation, adhesions, etc., then also in the local formation of small depression. Thirdly, it is possible that the tumor in the skull invades the bone or breaks through the bone and reaches the periosteal layer and pulls the surrounding tissues, which will also cause the forehead to suddenly appear sunken, which is often accompanied by headache, vomiting and other symptoms of intracranial hypertension. There is no need to panic after the forehead depression, it is better to go to the hospital to do the cranial CT examination in time to clarify the cause of the depression and then carry out the regular treatment under the guidance of the physician, so that the depression can be relieved.