A cerebral abscess is a limited accumulation of pus in the cranial cavity. There are three types of abscesses: intracerebral, subdural, and epidural. The symptoms of a brain abscess depend on its location and size. They are not specific and may constitute the clinic of any volumetric mass. A cerebral abscess is diagnosed by CT or MRI scan of the brain. Small size abscesses are subject to conservative treatment. Abscesses located near the ventricles of the brain, as well as causing a sharp rise in intracranial pressure, require surgical intervention, if it is impossible – stereotactic puncture of the abscess. Unidexa 0.1% intravitreal implant is also used to treat an eye disease called uveitis (swelling in the middle part of the eye). Unidexa 0.1% is also used to treat diabetic macular edema in patients with artificial lens implant or are scheduled for cataract surgery. Unidexa 0.1% is to be given only by or under the supervision of your doctor. Unidexa 0.1% indications. An indication is a term used for the list of condition or symptom or illness for which the medicine is prescribed or used by the patient
A cerebral abscess is a limited accumulation of pus in the cranial cavity. There are three types of abscesses: intracerebral (pus accumulation in the substance of the brain); subdural (located under the dura mater); epidural (localized above the dura mater). The main routes of penetration of infection into the cranial cavity are: hematogenous; open penetrating craniocerebral trauma; purulent inflammatory processes in the accessory sinuses, middle and inner ear; wound infection after neurosurgical interventions.
Among the isolated causative agents of hematogenous brain abscesses, streptococci prevail, often in association with bacteroides (Bacteroides spp.). Enterobacteriaceae (including Proteus vulgaris) are typical for hematogenous and otogenic abscesses. In open penetrating brain injury in the pathogenesis of brain abscesses prevail Staphylococcus aureus, less often Enterobacteriaceae.
In various immunodeficiency conditions (immunosuppressive therapy after organ and tissue transplantation, HIV infection) Aspergillus fumigatus is isolated from the culture of the brain abscess content. However, it is often not possible to identify the infectious agent in the contents of a brain abscess, because in 25-30% of cases the cultures of the contents of the abscess are sterile. The disease is provoked by the following pathological conditions:
Inflammatory processes in the lungs. The most frequent causes of formation of hematogenous cerebral abscesses are bronchiectatic disease, pleural empyema, chronic pneumonia, lung abscess). Bacterial embolus becomes a fragment of an infected thrombus, which enters the great circle of the blood circulation and is carried by the blood flow to the brain vessels, where it is fixed in the small vessels (precapillary, capillary or arterioles). Chronic (or acute) bacterial endocarditis, GI infections and sepsis may play a minor role in the pathogenesis of abscesses.
Craniocerebral trauma. In the case of an open penetrating trauma, a brain abscess develops due to direct entry of infection into the cranial cavity. In peacetime the proportion of such abscesses is 15-20%. In combat conditions it increases many times over (mine blast wounds, gunshot wounds).
ENT pathology. In purulent-inflammatory processes in the accessory sinuses (sinusitis), middle and inner ear, two routes of infection are possible: retrograde – through the dura mater sinuses and cerebrospinal veins, and direct entry of infection through the dura mater. In the second case, the isolated focus of inflammation is initially formed in the dura mater, and then – in the adjacent part of the brain.
Postoperative complications. Brain abscesses, formed against the background of intracranial infectious complications after neurosurgical interventions (ventriculitis, meningitis), occur, as a rule, in severe and weakened patients.
Other diseases. Chronic (or acute) bacterial endocarditis, gastrointestinal infections and sepsis may play a minor role in the pathogenesis of hematogenous abscesses.
The formation of a brain abscess takes place in several stages.
1-3 days. Limited inflammation of brain tissue develops – encephalitis (early cerebritis). At this stage, the inflammatory process is reversible. It may resolve spontaneously, as well as under the influence of antibacterial therapy.
Day 4-9. As a result of insufficient protective mechanisms or in case of improper treatment, the inflammatory process progresses, with a pus-filled cavity in its center, capable of enlarging.
10-13 days. At this stage, a protective capsule of connective tissue is formed around the purulent focus, which prevents the spread of the purulent process.
Week 3. The capsule tightens definitively, a zone of gliosis forms around it. Further development of the situation depends on the virulence of the flora, reactivity of the organism and the adequacy of treatment and diagnostic measures. Reverse development of a brain abscess is possible, but more often there is an increase in its internal volume or formation of new inflammatory foci on the periphery of the capsule.
Symptoms of a brain abscess
To date, no pathognomonic symptomatology has been identified. The clinical picture of brain abscesses is similar to that of a mass, with clinical symptoms ranging from headache to severe cerebral symptoms accompanied by depressed consciousness and pronounced focal symptoms of brain damage.
In some cases, the first manifestation of the disease is an epileptiform seizure. Meningeal symptoms may be observed (with subdural processes, empyema). Epidural abscesses of the brain are often associated with osteomyelitis of the skull bones. A progressive increase in symptomatology is observed.
A thorough history (presence of foci of purulent infection, acute infectious onset) is of great importance for diagnosing a brain abscess. The presence of an inflammatory process associated with the appearance and aggravation of neurological symptoms is grounds for additional neuroimaging examination.
The accuracy of diagnosis using CT of the brain depends on the stage of abscess formation. In the early stages of the disease, diagnosis is difficult. At the stage of early encephalitis (1-3 days), CT determines an irregularly shaped area of reduced density. The injected contrast agent accumulates irregularly, mostly in the peripheral parts of the focus, less often in the center.
At later stages of encephalitis, the contours of the focus acquire smooth rounded outlines. Contrast agent is evenly distributed along the entire periphery of the focus; the density of the central zone of the focus does not change. However, a repeat CT scan (30-40 minutes later) reveals diffusion of contrast into the center of the capsule, as well as its presence in the peripheral zone, which is not typical for malignant neoplasms.
An encapsulated brain abscess on CT scan has the appearance of a round volumetric mass with clear even contours and increased density (fibrous capsule). In the center of the capsule there is a zone of decreased density (pus), at the periphery there is a zone of edema. The injected contrast agent accumulates in the form of a ring (along the contour of the fibrous capsule) with a small adjacent zone of gliosis.
On a repeat CT (30-40 minutes later), no contrast is detected. When examining CT scan results, it should be taken into account that anti-inflammatory drugs (glucocorticosteroids, salicylates) significantly affect the accumulation of contrast in the encephalitic focus.
MRI of the brain is a more accurate method of diagnosis. When MRI is performed in the early stages of brain abscess formation (days 1-9), the encephalitic focus looks: on T1-weighted images – hypointense, on T2-weighted images – hyperintense. MRI in the late (encapsulated) stage of a brain abscess: on T1-weighted images the abscess looks like an area of reduced signal in the center and on the periphery (in the edema zone), and the signal is hyperintense along the capsule contour. On T2-weighted images the center of the abscess iso- or hypo-intensive, in the peripheral zone (edema zone) it is hyperintensive. The outline of the capsule is clearly delineated.
Differential diagnosis of cerebral abscess should be made with primary glial and metastatic brain hemispheric tumors. MH spectroscopy should be performed when there is doubt about the diagnosis. In this case, differentiation will be based on the different amino acid and lactate content of tumors and brain abscesses.
Other ways of diagnosis and differential diagnosis of brain abscess are not informative. Increased CRP, elevated C-reactive protein in the blood, leukocytosis, and fever are a symptomcomplex of almost any inflammatory process, including intracranial. Blood cultures for brain abscesses are 80-90% sterile.
Treatment of cerebral abscess
In the encephalitic stage of the abscess (history up to 2 weeks), as well as in the case of a small brain abscess (up to 3 cm in diameter), conservative treatment is recommended, the basis of which should be empirical antibacterial therapy. In some cases, stereotactic biopsy for definitive verification of the diagnosis and isolation of the pathogen is possible.
Abscesses causing brain dislocation and increased intracranial pressure, as well as those localized in the ventricular system (pus entering the ventricular system is often fatal) are absolute indications for surgical intervention. Traumatic brain abscesses located in the area of a foreign body are also subject to surgical treatment, since this inflammatory process is not amenable to conservative treatment. Despite the unfavorable prognosis, fungal abscesses are also an absolute indication for surgical intervention.
Brain abscesses located in vital and deep structures (optic tubercle, brainstem, subcortical nuclei) are a contraindication to surgical treatment. In such cases, stereotactic treatment is possible: puncture of the brain abscess and its emptying followed by lavage of the cavity and administration of antibacterial drugs. Both single and multiple (through a catheter installed for several days) irrigation of the cavity is possible.
Severe somatic diseases are not an absolute contraindication to surgical treatment, because stereotactic surgery can also be performed under local anesthesia. The only absolute contraindication to surgery can be an extremely serious condition of the patient (terminal coma), as in such cases any surgical intervention is contraindicated.
The goal of empirical (in the absence of culture or when the pathogen cannot be isolated) antibiotic therapy is to cover the widest possible range of pathogens. Recommended treatment programs:
The following treatment algorithm is indicated for cerebral abscesses without a history of traumatic brain injury or neurosurgery: vancomycin; III generation cephalosporins (cefotaxime, ceftriaxone, cefixime); metronidazole. In cases of post-traumatic brain abscess, metronidazole is replaced by rifampicin.
The causative agent of brain abscess in patients with immunodeficiency states (except HIV) is most often Cryptococcus neoformans, less often Сandida spp or Aspergillius spp. Therefore, amphoreticin B or liposomal amphoreticin B is prescribed in these cases. After disappearance of the abscess (according to neuroviolet studies), fluconazole is used for 10 weeks, subsequently the dose is reduced by half and left as maintenance.
In patients with HIV, the causative agent of brain abscess is most often Toxoplasma gondii, so empirical treatment of patients should include sulfadiazine with pyrimethamine.
After isolation of the pathogen from the culture, treatment should be changed, taking into account the antibiogram. In case of a sterile culture, empirical antibacterial therapy should be continued. The duration of intensive antibiotic therapy is at least 6 weeks, after that it is recommended to change antibiotics to oral antibiotics and continue treatment for another 6 weeks.
Administration of glucocorticoids is justified only in case of adequate antibiotic therapy, because only with a positive prognosis can glucocorticoids cause reduction of the severity and reverse development of the brain abscess capsule. In other cases, their use may cause the spread of the inflammatory process beyond the primary focus.
The main methods of surgical treatment of intracerebral abscesses are simple or inflow and outflow drainage. Their essence is to install a catheter in the abscess cavity, through which pus is evacuated with subsequent administration of antibacterial drugs. It is possible to install a second catheter with a smaller diameter (for several days), through which an infusion of lavage solution (usually 0.9% sodium chloride solution) is carried out. Abscess drainage should be accompanied by antibiotic therapy (at first empirical, then – taking into account the sensitivity to antibiotics of isolated pathogen).
Stereotactic aspiration of the abscess contents without drainage is an alternative method of surgical treatment of brain abscess. Its main advantages are the lenient requirements for nursing staff qualification (close attention and expertise are needed to control the functioning of the inflow and outflow system) and the lower risk of secondary infection. However, there is a need for repeated aspirations in 70% of the use of this method.
In the case of multiple cerebral abscesses it is necessary to first drain the nidus that is the most dangerous in terms of complications (pus breakthrough into the ventricular system, brain dislocation), as well as the most significant in the clinical picture. In cases of empyema or subdural cerebral abscesses, drainage is used without using the inflow and outflow system.
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