Intracranial aneurysm is not a brain tumor? Then what is it? With the word “aneurysm”, it does not look like a good thing, at most it is not a malignant tumor, it is benign, why is it not a tumor? Intracranial aneurysm is indeed not a tumor, it is an abnormal protrusion (usually round or lobulated) on the wall of intracranial artery. Because its shape is somewhat similar to that of a typical brain tumor, it was historically thought to be a tumor of arterial origin, so it was called an aneurysm at that time. Later studies found that it occurs by a completely different mechanism than a normal brain tumor, which is damage to the arterial wall and local expansion. However, because people are used to it, they still call it an artery “aneurysm”. In fact, people care whether aneurysm is brain tumor or not, what they worry about are those annoying characteristics of brain tumor, so let’s compare them. 1. Morbidity form: Brain tumor is generally occupying effect (squeezing normal brain tissue and brain structures), causing headache, epilepsy, limb hemiparesis, sensory loss, and of course, some special manifestations. Aneurysm mainly causes rupture and bleeding, 85% of ruptured aneurysm causes subarachnoid hemorrhage, others can be manifested as subdural hemorrhage, intracerebral hematoma, etc. The patient’s sensation is mainly headache (unbearable severe headache like being hit by a hammer), and some people are in coma as soon as they bleed. 2. Treatment: Most of the brain tumors need to be removed by craniotomy, while a small number of brain tumors can be removed by other surgical methods without craniotomy (such as transsphenoidal resection of pituitary tumor). There are also a small number of brain tumors that can be treated by radiotherapy such as r-knife (without craniotomy). The classical treatment of aneurysm is craniotomy. In recent years, with the development of interventional technology, most of the aneurysms can be cured by interventional embolization (without craniotomy). 3.Follow up plan: Brain tumor is divided into benign and malignant, malignant brain tumor has high recurrence rate and threatens the life of patients; benign tumor has relatively lower lethality, but also has recurrence chance.