A brain abscess is a focal accumulation of inflammatory fluid (pus) in the cranial cavity. The condition is usually accompanied by headache, dizziness, nausea, and fever. A brain abscess is not an independent disease- most often, it is a complication of infections of the ear, sinuses, and/or teeth.
The classification of abscesses includes three types:
- intracerebral (with an accumulation of pus in the substance of the brain)
- subdural (localized under the dura mater)
- epidural (located above the dura mater).
The main ways of penetration of infection into the cranial cavity are:
- open penetrating head injury
- purulent-inflammatory processes in the paranasal sinuses, middle and inner ear
- wound infection after neurosurgical interventions.
The cause of the formation of hematogenous abscesses of the brain is most often inflammatory processes in the lungs (chronic pneumonia, lung abscess, bronchiectasis, pleural empyema). In this case, a bacterial embolus is a fragment of an infected thrombus that enters the systemic circulation. The blood flow transports it to the vessels of the brain, where it is deposited in small vessels (precapillary, capillary, arteriole).
In open penetrating traumatic brain injury or brain damage, pathology develops after direct infection of the infection into the cranial cavity. In peacetime, such abscesses account for 15-20% of cases. However, in conditions of hostilities, this number increases significantly (gunshot and mine-explosive wounds).
With purulent-inflammatory processes in the paranasal sinuses, middle and inner ear, the infection may spread in two ways:
- along with the sinuses of the dura mater and cerebral veins (retrograde pathway)
- direct penetration of infection through the dura mater
Brain abscess, developing against the background of intracranial infectious complications after neurosurgical interventions (ventriculitis, meningitis), occurs, as a rule, in debilitated, severe patients.
Etiology and pathogenesis
The reason for brain damage is the ingress of microorganisms into the medulla from purulent foci. The spectrum of pathogens that cause brain abscesses is vastand includes bacteria, fungi, and parasites. In 30% of cases, mixed infections (several pathogens) become the cause of cerebral abscesses. Most often, streptococci and anaerobic microorganisms are found in the abscess cavity. When monoinfected, frequent pathogens are Staphylococcus aureus, representatives of the Enterobacteriaceae family, and gram-negative microorganisms.
For an abscess to form, two conditions are necessary for the presence of a pathogenic microbe and a decrease in immunity. Microorganisms can enter the brain in various ways:
- hematogenous, lymphogenous
A brain abscess is formed in several stages.
- 1-3 days. The development of limited inflammation of the brain tissue encephalitis (early cerebritis). At this stage, the inflammatory process is reversible; its resolution is possible both spontaneously and under the influence of antibiotic therapy.
- 4-9 days. Due to insufficient protective mechanisms or improper treatment, inflammation progresses, a cavity is formed, filled with pus, and capable of enlargement.
- 10-13 days. At this stage, a protective capsule of connective tissue is formed around the purulent focus, preventing the spread of the purulent process.
- Third week. The final compaction of the capsule, the formation of a gliosis zone around it (the process of replacing dead neurons with neuroglia cells). Further, the development of the situation depends on several factors:
- body reactivity
- flora virulence
- the adequacy of diagnostic and treatment measures.
Most often, there is an increase in the internal volume of the abscess or the formation of new foci of inflammation along the periphery of the capsule.
Brain abscess symptoms. The clinical picture of brain damage is similar to the clinical picture of mass formation with varying symptoms from headache to severe cerebral symptoms associated with depression of consciousness and severe focal symptoms of brain damage.
In some cases, the first manifestation of the disease is an epileptiform seizure. Meningeal symptoms (with empyema, subdural processes) may also be observed. Then, there is a gradual increase in symptoms.
Diagnostics and treatment of brain abscess
A thorough history taking (acute infectious onset, the presence of foci of purulent infection) is of paramount importance to diagnose a brain abscess. Besides, the presence of an inflammatory process associated with the appearance and development of neurological symptoms is the basis for additional neuroimaging examination.
The accuracy of diagnosing pathology using CT of the brain depends on the stage of abscess formation in the early stages of the disease; the diagnosis is difficult.
MRI of the brain is a more accurate method for diagnosing pathology.
Other diagnostic methods for this disease are of little informative leukocytosis, increased content of C-reactive protein in the blood, and fever; this whole complex of symptoms can be attributed to almost any inflammatory process, including intracranial.
Treatment of brain damage. Treatment of brain abscesses can be both conservative and surgical; the choice of tactics depends on the stage of development of the pathology, its location, and size.
- At the encephalitic stage of an abscess (up to 2 weeks) and in the case of a small brain abscess (up to 3 cm in diameter), conservative treatment is usually carried out based on empirical antibiotic therapy.
- Abscesses that cause dislocation of the brain increase intracranial pressure, and those located in the area of
the ventricular system, have absolute indications for surgical intervention.
Traumatic brain abscesses localized in the foreign body area are also subject to surgical treatment since they do not respond to conservative treatment.
Fungal abscesses, despite a poor prognosis, are also an absolute indication for surgery.
Surgical treatment of abscesses located in vital and deep structures of the brain is contraindicated. In this case, it is advisable to use a stereotaxic treatment method, puncture the abscess, and empty it, followed by washing the cavity and introducing antibacterial drugs.
The main methods of surgical treatment of intracerebral abscesses are simple or inflow and outflow drainage. In this case, a catheter is installed into the abscess cavity, and pus is evacuated, followed by the introduction of antibacterial drugs. Drainage of the abscess is accompanied by antibiotic therapy.
- An alternative method of surgical treatment is the stereotaxic aspiration of the abscess contents without installing a drain. Its main advantage is the lower risk of secondary infection. However, in 70% of the use of this method, there is a need for repeated aspirations.
In the case of multiple brain abscesses, it is necessary to drain the focus that is most at danger from complications (dislocation of the brain, breakthrough of pus into the ventricular system), and the focus is most significant in the clinical picture.
When predicting brain abscesses, it is crucial to isolate the pathogen from inoculation and determine its sensitivity to antibiotics, as only, in this case, is it possible to carry out appropriate pathogenetic therapy. Moreover, the outcome of the disease depends on the adequacy and timeliness of therapeutic measures, the body’s reactivity, and the number of abscesses.
The percentage of deaths in brain abscesses is 10%, disability is 50%. In one-third of surviving patients, the consequence of the disease is an epileptic syndrome.Adequate and timely treatment of primary purulent processes, full-fledged primary treatment of wounds in traumatic brain injuries will significantly reduce the possibility of developing a brain abscess.