Lesions on the brain are anatomical abnormalities of any part of the brain. A brain lesion may be due to trauma or any disease that can cause inflammation, malfunction, or destruction of a brain cells or brain tissue.
Examples of brain lesions include head injuries, tumors, vascular malformations, damage due to stroke, and damage due to inflammation resulting from infections or chronic diseases.
The brain is a soft and delicate organ. A hard blow to the head can injure the brain or spinal cord even when there are no visible signs of trauma to the scalp or face. That’s why all head injuries are considered serious and should be assessed by your doctor or the nearest hospital emergency department.
Head injuries can be classified as:
Open – with bleeding wounds to the face or head
Closed – no visible signs of injury to the face or head.
A brain tumor is a mass of unnecessary cells growing in the brain or central spine canal.
There are two basic kinds of brain tumors – primary brain tumors and metastatic brain tumors. Primary brain tumors start and tend to stay, in the brain. Metastatic brain tumors begin as cancer elsewhere in the body and spread to the brain.
Tumors are diagnosed, and then named, based on a classification system. Most medical centers now use the World Health Organization (WHO) classification system for this purpose.
Normally, arteries carry blood containing oxygen from the heart to the brain, and veins carry blood with less oxygen away from the brain and back to the heart. When an arteriovenous malformation (AVM) occurs, a tangle of blood vessels in the brain or on its surface bypasses normal brain tissue and directly diverts blood from the arteries to the veins.
Brain AVMs occur in less than one percent of the general population. It is estimated that about one in 200–500 people may have an AVM. AVMs are more common in males than females.
Brain AVMs can occur anywhere within the br ain or on the covering of the brain. This includes the four major lobes of the front part of the brain (frontal, parietal, temporal, occipital), the back part of the brain (cerebellum), the brainstem, or the ventricles (deepspaces within the brain that produce the cerebrospinal fluid).
Source and More Info: University of Chicago