Neurosurgery Service, Alicante University General Hospital, Alicante Institute for Health and Biomedical Research (ISABIAL – FISABIO Foundation), Alicante, Spain.
A brain abscess is a focal area of necrosis starting in an area of cerebritis surrounded by a membrane.
Brain abscesses are suppurative infections of the brain parenchyma surrounded by a vascularized capsule.
see also Intracranial abscess.
It is a potentially life-threatening condition requiring prompt radiological identification and rapid treatment.
The most frequent intracranial locations (in descending order of frequency) are: frontal-temporal, frontal-parietal, parietal, cerebellar, and occipital lobes.
In a article, Chen review the literature to find out how the epidemiology of this disease has changed through the years and re-visit the basic pathological process of abscess evolution and highlight the new research in the biochemical pathways that initiate and regulate this process 1).
The epidemiology of brain abscess has changed with the increasing incidence of this infection in immunocompromised patients, particularly solid organ and bone marrow transplant recipients, and the decreasing incidence of brain abscess related to sinusitis and otitis 2).
There have been several trends in the epidemiology of brain abscess over recent decades. One trend is that there appears to be a trend toward a decreasing incidence of brain abscess. In a population-based study of residents of Olmstead County, Minnesota, the incidence rate was 1.3 per 100,000 patient-years from 1935 to 1944 compared with 0.9 per 100,000 patient-years from 1965 to 1981 3).
Clinical presentation is non-specific, with many cases having no convincing inflammatory or septic symptoms.
Abscess formation should be considered in case of clinical deterioration, headache, and any neurological deficit after febrile episodes.
Similar to any other mass lesion but tend to progress rapidly.
Symptoms of raised intracranial pressure, seizures and focal neurological deficits are the most common forms of presentation
Eventually, many abscesses rupture into the ventricular system, which results in a sudden and dramatic worsening of the clinical presentation and often heralds a poor outcome.
Cerebral abscesses result from pathogens growing within the brain parenchyma. Initial parenchymal infection is known as cerebritis, which may progress into a cerebral abscess.
Cerebral infection is commonly divided into four stages with distinct imaging and histopathologic features:
early cerebritis (a focal infection without a capsule or pus formation,can resolve or develop into frank abscess) late cerebritis
early abscess/encapsulation – may occur 10 days after infection
late abscess/encapsulation – may occur >14 days after infection
Significant advances in the diagnosis and management of bacterial brain abscess over the past several decades have improved the expected outcome of a disease once regarded as invariably fatal. Despite this, intraparenchymal abscess continues to present a serious and potentially life-threatening condition 4).
There has been a gradual improvement in the outcome of patients with brain abscess over the past 50 years, which might be driven by improved brain imaging techniques, minimally invasive neurosurgical procedures, and protocoled antibiotic treatment. Multicenter prospective studies and randomized clinical trials are needed to further advance treatment and prognosis in brain abscess patients.
Our understanding of brain abscesses has increased by meta-analysis on clinical characteristics, ancillary investigations, and treatment modalities. Prognosis has improved over time, likely due to improved brain imaging techniques, minimally invasive neurosurgical procedures, and protocoled antibiotic treatment 5).
Current evidences suggest that for encapsulated brain abscess in superficial non-eloquent area, abscess resection compared to abscess aspiration had lower post-operative residual abscess rate; lower re-operation rate; higher rate of improvement in neurological status within 1 month after surgery, shorter duration of post-operative antibiotics and average length of hospital stay. There was no statistically significant difference in the rate of improvement in neurological status at 3 months post-operative and the mortality 6).
Intraventricular rupture of brain abscess (IVROBA)
Strongly influences poor outcome in patients with cyanotic heart disease. The key to decreasing poor outcomes may be the prevention and management of IVROBA. To reduce operative and anesthetic risk in these patients, abscesses should be managed by less invasive aspiration methods guided by computed tomography. Abscesses larger than 2 cm in diameter, in deep-located or parieto-occipital regions, should be aspirated immediately and repeatedly, mainly using computed tomography-guided methods to decrease intracranial pressure and avoid IVROBA. IVROBA should be aggressively treated by aspiration methods for the abscess coupled with the appropriate intravenous and intrathecal administration of antibiotics while evaluating intracranial pressure pathophysiology 7).
Brain abscess case reports from the General University Hospital Alicante
Known space-occupying lesion, centered in the right frontal anterior white matter, with estimated diameters of 3.5 x 3 x 3.5 cm. It shows well-defined contours and a practically spherical shape. A predominantly hypointense signal on T1 and homogeneously hyperintense on T2, with a wall with hypointense behavior on T2-weighted sequences. After contrast administration, only enhancement of its wall was observed, in a fine and linear way, without identifying solid poles. The lesion shows diffusion sequence restriction and low values of rVSC in perfusion. Marked surrounding vasogenic edema, which causes a mass effect on the neighboring sulci, as well as mild subfalcian herniation, with a deviation from the midline of approximately 6 mm (significant improvement compared to previous CT control). The discrete mass effect is also on the knee of the corpus callosum and the frontal horn of the right ventricle. The findings are compatible with a brain abscess. A small solution of continuity is observed in its anterior wall, in contact with the meninge, which is thickened in a laminar manner in relation to inflammatory involvement, without clearly identifying empyema. Extensive occupation of the frontal sinus bilaterally, with an enhancement of its wall. Retrospectively, the CT study showed slight permeation on the posterior wall of one of the loculations of the frontal sinus close to the abscess. Small hyperintense foci in subcortical and periventricular white matter with a chronic ischemic profile of a small vessel, to a mild degree. Diagnostic impression: Findings compatible with a right frontal parenchymal abscess, 3.5 cm in diameter, with inflammatory changes and thickening of the adjacent pachymeninge, although without clear associated empyema.
see Brain abscess books.