Brain abscesses occur due to canton of bacteria or fungi within lung parenchyma, a place that is normally sterile. Infectious contamination will cause an immediate defensive reaction from the brain, which tries to preserve its integrity and functions and is trying to fight this aggression. As a result, local it will appear an inflammatory reaction, whose intensity varies with the reactivity of the immune system.
The more it is relevant,the more infection will be located and neutralized quickly. The inflammation will cause swelling of brain parenchyma and meningeal irritation, which will clinically yield by characteristic symptoms. In an attempt to control the infection, this area will be delimited by the remaining intact parenchyma , with a capsule (or membrane) fibrous of inflammatory nature, of which presence is defining for abscess.
Despite the fact that inflammation is aimed to limit the attack, most times she comes to do more harm than good. All this perpetual inflammation will result in cerebral edema.For the brain, an organ located in a very narrow space, which is not expansible, if for some reason intracerebral pressure becomes increased , edema is a real tragedy. Bone walls of the skull cavity do not allow any change adaptation, so that very high pressure will even get to compress parenchyma.
In addition, there is real danger that intracerebral vessels to be blocked by infectious embolism, which will further aggravate cerebral edema.There have been identified three major ways by which pathogens, regardless of their type, can reach the brain parenchyma and may lead to abscess development.
1. Direct extension of suppuration of an outbreak nearby: represents 45-50% of all cases. Such extension occurs in necrosis areas of frontal sinuses, sphenoid or ethmoid and is frequently associated with chronic otitis and mastoiditis and less with sinusitis. Dental infections can spread also in intracranial space either directly or by marrow. In general, infections that extend direct can cause other local complications, such as cavernous sinus thrombosis, retrograde meningitis and even the formation of abscesses, especially epidural, subdural.
2. Marrow enlargement from an outbreak in remote locations: is incriminated in 25% of cases.Abscesses are usually released by endocarditis complications, lung infections, skin infections, abdominal infections and / or pelvic, HIV infection or intravenous drug use.
3. Trauma: are responsible for 10% of infections which are underlying brain abscess formation. Injuries are dangerous because they create a solution of continuity between the skin (and the external environment) and brain parenchyma. So is permitted direct passage of bacteria from outside, inside the brain.