Definition
A brain abscess is an encapsulated inflammation in the brain. The capsule consists of newly formed tissue (granulation tissue), which is naturally formed during the defence against pathogens and the healing process. In the capsule, the existing cells are destroyed and pus is formed.
Due to the inflammatory process, fluid is stored in the surrounding tissue, which leads to a so-called brain edema. This cerebral edema can increase the cerebral pressure (see: Increased Cerebral Pressure) – a potentially dangerous process for the patient. A brain abscess can have various causes. The possibilities range from an infection with various pathogens, to inflammation caused by injury or surgery, to delayed infections of the respiratory tract or heart.
Causes
The causes of a brain abscess are varied, but can mainly be divided into three groups. An abscess can form in the front or side lobes of the brain due to the conduction of an inflammation of the paranasal sinuses (sinusitis), the middle ear (otitis media) or certain structures of the skull close to the ear (mastoiditis). The most common pathogens are streptococci and staphylococci and are spherical bacterial species.
Bacteria of the genus Bacteroides, which also occur in our natural intestinal flora and are important for humans, can also be responsible for a brain abscess in the wrong place – in the brain. People with damaged immune systems are also susceptible to otherwise rare pathogens. In them the brain abscess can be caused by a fungal infection or toxoplasmosis.
More rarely, another disease such as pneumonia or endocarditis can be blamed for a brain abscess. Besides the pathogen-induced brain abscesses, traumatic abscesses caused by injuries or interventions such as surgery also play a role. In some patients (10 – 20%) no cause for the brain abscess can be found even after intensive diagnostics. The doctor calls this a cryptogenic brain abscess.
Symptoms
The symptoms of an existing brain abscess are very impressive and get progressively worse over time. Since the abscess is usually only located on one side of the brain, a so-called hemiparesis develops. In this process, certain muscles or entire extremities (arms and legs) of one half of the body are partially or completely paralyzed and thus unable to move.
In addition, the examining doctor can observe a congestion papilla by looking into the patient’s eyes. This is a bulging of the optic nerve in the back of the eye, which can be seen by means of an ophthalmoscopy (funduscopy). It is caused by brain edema.
Another noticeable symptom is the clouding or complete loss of consciousness. In this stage, quick action should be taken to prevent consequential damage. The examining doctor should also look out for infections that could be the cause of a brain abscess, such as known inflammation of the respiratory tract and inflammation or injury to the face or head. In rare cases a so-called meningismus occurs, a strong pain when the head is actively bent in a flat position of the patient. The meningismus is actually a symptom of meningitis, but can also be an indication of a brain abscess if the abscess is located at the edge of the brain in addition to severe headaches.