What is a Brain Abscess?
An abscess is a limited purulent-inflammatory process in the brain tissue. A combination of the symptoms of a brain mass and inflammatory process is clinically noted. Rarely, epidural and subdural abscesses occur.
Frequency 1 per 100,000 population.
Causes of Brain Abscess
Risk factors are pulmonary pathology, “blue” heart defects, bacterial endocarditis, open and penetrating traumatic brain injury, and immunodeficiency states. The most frequent pathogens are: streptococci, staphylococci, pneumococci, meningococci, E. coli, anaerobic bacteria, toxoplasma, fungi. 25% of the abscess is sterile. The spread of infection to the brain is hematogenous (metastatic) or contact.
Pathogenesis during brain abscess
The most common in the clinic are contact abscesses caused by mastoiditis, otitis media, purulent processes in the bones of the skull, nasal cavities, eye socket, and meninges. About half of all brain abscesses are of otogenic origin. Chronic purulent otitis is more often complicated by an abscess than acute inflammatory processes in the ear. Infection with otitis penetrates the temporal bone through the roof of the tympanic cavity and cavernous sinuses per continuitatem into the middle cranial fossa, causing an abscess of the temporal lobe of the brain. Otogenic infection can also spread to the posterior cranial fossa through the labyrinth and sigmoid sinus, leading to abscess of the cerebellum. Rhinogenic abscesses are localized in the frontal lobes of the brain. Initially, local pachymeningitis develops, then adherent limited meningitis, and finally, the inflammatory process spreads to the substance of the brain with the formation of limited suppurative encephalitis. In more rare cases, oto-and rhinogenic abscesses may occur by hematogenous due to venous thrombosis, sinuses, septic arteritis. At the same time, abscesses are located in the deep parts of the brain, far from the primary focus.
Metastatic brain abscesses are most often associated with pulmonary diseases – pneumonia, bronchiectasis, abscess, pleural empyema. Metastatic abscesses can also complicate septic ulcerative endocarditis, osteomyelitis, and abscesses of the internal organs. The mechanism of infection in the brain is septic embolism. In 25-30% of cases, metastatic abscesses are multiple and usually localized in the deep parts of the white matter of the brain.
Traumatic abscesses usually develop with open trauma to the skull. If the dura mater is damaged, the infection penetrates the perivascular crevices into the brain tissue. In cases of penetration into the brain of a foreign body, the infection enters with it. An abscess is formed along the wound channel or directly in the area of a foreign body. Traumatic abscesses in peacetime make up 15% of all brain abscesses; their percentage increases sharply during the war and in the post-war period.
Pathomorphology
Stages of abscess formation: Stage 1 – early brain inflammation in the first 1-3 days, there is no demarcation from the surrounding healthy brain substance, there are perivascular infiltrates, toxic changes in neurons. Stage 2 — late; central necrosis appears on the 4–9th day of the disease; 3rd stage – early encapsulation, on the 10-13th day of the disease, pronounced necrosis of the central part is detected, a connective tissue capsule is formed along the periphery; Stage 4 – the stage of late encapsulation, occurs after the 14th day of illness, there is a clear collagen capsule with a necrotic center, a zone of gliosis around the capsule.
Brain Abscess Symptoms
Brain abscess is manifested by general infectious, cerebral and local (focal) symptoms. The latter characterize the localization of the abscess.
Generally infectious symptoms: fever (sometimes intermittently), chills, blood leukocytosis, increased ESR, signs of a chronic infection process (pallor, weakness, weight loss).
Cerebral symptoms appear due to an increase in intracranial pressure caused by an abscess. The most constant symptom is headache, often with vomiting. In the fundus stagnant discs or optic neuritis. Bradycardia is periodically determined up to 40-50 contractions per minute, mental disorders. Attention is drawn to the lethargy and apathy of the patient, the slowness of his thinking. Gradually, sleepiness develops; in severe cases without treatment – coma. As a consequence of intracranial hypertension, general epileptic seizures may occur.
Focal symptoms depend on the localization of the abscess in the frontal, temporal lobes, cerebellum. Abscesses located in the depth of the hemispheres outside the motor area, can proceed without conductive symptoms. Otogenic abscesses sometimes form not on the side of otitis, but on the opposite, giving the appropriate clinic. Along with focal symptoms, symptoms associated with edema and compression and dislocation of brain tissue can be observed. When an abscess is close to the sheaths and an abscess of the cerebellum, meningeal symptoms are detected.
In the cerebrospinal fluid revealed pleocytosis (25-300 cells), consisting of lymphocytes and polynuclears, increased protein levels (0.75-3 g / l) and increased pressure. However, liquor is often normal.
Flow
The onset of the disease is usually acute, with a rapid manifestation of hypertensive and focal symptoms with a rise in temperature. In other cases, the onset of the disease is less defined, and then the clinical picture resembles the course of a common infection or meningitis. Rarely, the initial stage of an abscess occurs latently with minimal symptoms and low temperature. After the initial manifestations, after 5-30 days, the disease passes into a latent stage, corresponding to the abscess’s accumulation. This stage is asymptomatic or manifests itself with moderately pronounced symptoms of intracranial hypertension – frequent headache, vomiting, mental retardation. The latent stage can last from several days to several years. Subsequently, under the influence of someone of an external factor (infection), and more often without obvious reasons, cerebral and focal symptoms begin to progress rapidly. An extremely serious complication of an abscess, possible at any stage, is its breakthrough into the ventricular system or subarachnoid space, which usually ends in death.
Diagnosis of Brain Abscess
Recognition of brain abscess is based on anamnesis (chronic otitis media, bronchiectasis, other foci of infection, trauma), the presence of focal, cerebral symptoms, a sign of increased intracranial pressure, the onset of the disease with elevated temperature and its characteristic progressive course. For the diagnosis, repeated echoencephaloscopy is important, which reveals the displacement of the median brain structures during abscesses in the hemisphere of the brain. On craniograms, signs of increased intracranial pressure, as well as inflammatory lesions of the paranasal sinuses and temporal bones are determined. In the fundus – stagnant discs or a picture of optic neuritis.
Lumbar puncture in the presence of hypertensive syndrome should be performed carefully, and at a grave condition of the patient – to refrain from it, since the rise of intracranial hypertension extraction CSF promotes dislocation and infringement cerebellar tonsils in the foramen magnum (in abscess cerebellum) or temporal lobes in the gap cerebellar tent (with abscess of the temporal lobe) with compression of the trunk, which can be fatal.
Differential diagnosis depends on the stage of the abscess. In the initial acute period of the disease, an abscess must be distinguished from purulent meningitis, the cause of which may be the same as an abscess. It is necessary to take into account the greater severity of rigidity of the neck muscles and Kernig’s symptom in purulent meningitis, the constancy of high temperature (with abscess, the temperature is often hectic), large neutrophilic pleocytosis in the cerebrospinal fluid, and the absence of focal symptoms.
The course and symptoms of a brain abscess have a lot in common with a brain tumor.
Differential diagnosis is difficult in this case, since a malignant tumor may cause leukocytosis in the blood and an increase in temperature. Of particular importance in these cases are the data of anamnesis, i.e. the presence of factors contributing to the development of an abscess. It should be borne in mind that by the time the abscess is formed, the primary purulent focus can already be cured. Important information is obtained with CT and MRI of the brain.
Brain Abscess Treatment
The treatment is carried out in a neurosurgical hospital: medication (antibiotics, nootropic drugs, vitamins), neurosurgical (osteoplastic craniotomy with removal of an abscess, preferably with a capsule, or repeated puncture with suction of pus). The choice of specific antibacterial therapy is possible after analyzing the microflora isolated from the abscess. When staphylococcal flora shows adequate doses of new antibiotics. Symptomatic treatment is also needed.
The prognosis for life is favorable. Mortality does not exceed 10%. Residual neurological symptoms, most often focal convulsive seizures, persist in 30% of recovered ones.