Neurobrucellosis.

PURPOSE OF REVIEW: Brucellosis is one of the most common zoonosis worldwide, affecting 500 000 people, annually. Neurobrucellosis incidence is approximately 4%, and it is almost always heterogeneous. As there are no typical clinical features, its diagnosis is frequently misdiagnosing by other infections. RECENT FINDINGS: Neurobrucellosis picture includes meningitis, meningoencephalitis, encephalitis, cranial neuropathies, intracranial hypertension, sinus thrombosis, hemorrhages radiculitis, peripheral neuropathy, myelitis, and psychiatric manifestations. The diagnosis should be based on symptoms and signs suggestive of neurobrucellosis, not explained by other neurological disease, cerebrospinal fluid analysis, a positive Brucella serology or culture, and a response to specific antibiotics, with a significant improvement of cerebrospinal fluid parameters. SUMMARY: Neurobrucellosis can be insidious, and despite its global distribution, it is still unrecognized and frequently goes unreported. The understanding of the current epidemiology is necessary for eradication of the disease in humans, as well as the disease control in animals and prevention based on occupational hygiene and food hygiene.

Outbreaks of Streptococcus gallolyticus subsp. pasteurianus in Goslings Characterized by Central Nervous Symptoms.

The present report describes outbreaks of Streptococcus gallolyticus subsp. pasteurianus in young geese flocks in Austria. The flocks, comprising 160-1450 goslings of 2-3 wk of age, experienced increased mortalities The clinical signs were characterized by severe central nervous symptoms, namely leg paddling and torticollis. The postmortem investigation revealed hepatitis, splenitis, and a low amount of liquid fluid in the coelomic cavity. Livers were of fragile texture, with white necrotic areas. The latter were also found in spleens. No macroscopic lesions were seen in brains. Bacteriologic investigation followed by bacterial identification by matrix-assisted laser desorption time-of-flight mass spectrometry and phylogenetic analysis of the partial 16S rRNA region revealed the presence in heart, liver, spleen, and brain of S. gallolyticus subsp. pasteurianus. Histologic investigation revealed multifocal necrosis in liver and spleen samples together with infiltration of mononuclear cells and heterophilic granulocytes. Furthermore, in the lesions, coccoid bacteria could be identified. No histopathologic changes were observed in brain samples from goslings, except in one bird in which accumulation of coccoid bacteria in blood vessels of the brain samples was present. Antibiotic sensitivity tests revealed identical profiles for all strains, which were susceptible to penicillins, cephalosporins, chloramphenicol, imipenem, and tylosin. However, resistance was found against quinolones, aminoglycosides, tetracycline, and trimethoprim-sulfamethoxazole, which are commonly used to treat infections with gram-positive bacteria.

Reporte de caso­Brotes de Streptococcus gallolyticus subsp. pasteurianus en gansitos caracterizados por síntomas nerviosos centrales. El presente informe describe brotes de Streptococcus gallolyticus subsp. pasteurianus en parvadas de gansos jóvenes en Austria. Las bandadas, que comprendían entre 160 a 1450 gansos de 2 a 3 semanas de edad, experimentaron aumento de la mortalidad. Los signos clínicos se caracterizaron por síntomas severos del sistema nervioso central, incluyendo, movimientos de pataleo y tortícolis. La investigación post mórtem reveló hepatitis, esplenitis y la presencia de líquido en la cavidad celómica en poca cantidad. Los hígados presentaron textura frágil, con áreas necróticas blancas. Estos últimos también se encontraron en bazos. No se observaron lesiones macroscópicas en el cerebro. La investigación bacteriológica seguida de la identificación bacteriana mediante espectrometría de masas MALDI-TOF y el análisis filogenético de la región parcial de ARNr 16S revelaron la presencia en el corazón, el hígado, el bazo y en el cerebro de S. gallolyticus subsp. pasteurianus. La investigación histológica reveló necrosis multifocal en muestras de hígado y bazo junto con infiltración de células mononucleares y granulocitos heterófilos. Además, en las lesiones se pudieron identificar bacterias de morfología cocoide. No se observaron cambios histopatológicos en muestras de cerebro de los gansitos, excepto en un ave en la que se observó acumulación de bacterias cocoides en los vasos sanguíneos de las muestras de cerebro. Las pruebas de sensibilidad a los antibióticos revelaron perfiles idénticos para todas las cepas, que eran susceptibles a penicilinas, cefalosporinas, cloranfenicol, imipenem y tilosina. Sin embargo, se encontró resistencia contra quinolonas, aminoglucósidos, tetraciclina y trimetoprim-sulfametoxazol, que se usan comúnmente para tratar infecciones con bacterias grampositivas.

An Outbreak of Pullorum Disease in a Young Layer Parent Flock in Austria Presented with Central Nervous System Signs.

The present report describes an outbreak of Pullorum disease in a young layer parent stock in Austria. The flock, which comprised 14,220 Lohmann brown layer chickens, experienced high mortality from the first week of life, reaching a total of 1905 chickens in the fifth week, when the flock was depopulated. Clinical signs included uneven size of the chicks, pasty vents, apathy, and diminished water and feed intake, with some birds presenting central nervous system signs such as tremors and torticollis. The postmortem investigation of 43 birds, of ages 1 to 4 weeks, revealed retained yolk sacs filled with caseous exudate, purulent airsacculitis, hepatitis with whitish pinpoint coalescing necrotic foci, splenitis with splenomegaly, hemorrhagic-mucoid enteritis in the small intestine, fibrinous typhlitis, nephromegaly, and urate deposits in the ureters and cloaca. Inflammation and/or necrosis were identified in liver, spleen, kidney, small intestine, and heart by histopathology. However, no histopathologic lesions were observed in the brain. Salmonella enterica was isolated from heart, liver, spleen, and brain in pure culture. Group-specific serotyping determined the presence of group D, with S. enterica subspecies enterica serovar Gallinarum being confirmed based on the Kauffmann-White scheme. A duplex PCR further identified S. enterica subspecies enterica serovar Gallinarum biovar Pullorum as the responsible agent for the outbreak. Subsequently, the grandparent flocks, from which the affected flock originated, were tested and found to be negative for Salmonella Pullorum, with no other progenies from the same grandparents developing disease. Although the source of the pathogen could not be identified, such findings highlight the importance of "old" pathogens such as Salmonella Pullorum causing sudden high mortality in chicks, even in a highly controlled environment.

Reporte de caso­Brote de pulorosis en una parvada de reproductores de postura jóvenes en Austria que presentó signos del sistema nervioso central. El presente reporte describe un brote de pulorosis en un lote de reproductoras de postura jóvenes en Austria. La parvada, que comprendió 14,220 gallinas de postura Lohmann, experimentó alta mortalidad desde la primera semana de vida, alcanzando un total de 1905 gallinas en la quinta semana, cuando la parvada se despobló. Los signos clínicos incluyeron tamaño desigual de pollito, empastamiento de la cloaca, apatía y disminución del consumo de agua y alimento, y algunas aves presentaron signos del sistema nervioso central como temblores y tortícolis. La investigación post mórtem de 43 aves, de 1 a 4 semanas de edad, reveló sacos vitelinos retenidos llenos de exudado caseoso, aerosaculitis purulenta, hepatitis con focos necróticos coalescentes blanquecinos, esplenitis con esplenomegalia, enteritis hemorrágica-mucoide en el intestino delgado, tiflitis fibrinosa, nefromegalia y depósitos de uratos en los uréteres y cloaca. Se identificaron inflamación y/o necrosis en hígado, bazo, riñón, intestino delgado y corazón mediante histopatología. Sin embargo, no se observaron lesiones histopatológicas en el cerebro. Se aisló Salmonella enterica de corazón, hígado, bazo y cerebro en cultivo puro. La serotipificación específica de grupo determinó la presencia del grupo D, con S entérica subespecie enterica serovar Gallinarum que se confirmó según el esquema de Kauffmann-White. Un método dúplex de PCR identificó S. enterica subspecie enterica serovar Pullorum como el agente responsable del brote. Posteriormente, las parvadas de abuelas, de las que se originó la parvada afectada, fueron analizadas y resultaron negativas para Salmonella Pullorum, sin que ninguna otra progenie de los mismos abuelos desarrollara la enfermedad. Aunque no se pudo identificar la fuente del patógeno, tales hallazgos resaltan la importancia de patógenos "viejos" como Salmonella Pullorum que causan una alta mortalidad repentina en los pollitos, incluso en un ambiente altamente controlado.

Neuroradiology of infectious diseases.

PURPOSE OF REVIEW: Early diagnosis of central nervous system (CNS) infections is crucial given high morbidity and mortality. Neuroimaging in CNS infections is widely used to aid in the diagnosis, treatment and to assess the response to antibiotic and neurosurgical interventions. RECENT FINDINGS: The Infectious Diseases Society of America (IDSA) guidelines have clear recommendations for obtaining a computerized tomography of the head (CTH) prior to lumbar puncture (LP) in suspected meningitis. In the absence of indications for imaging or in aseptic meningitis, cranial imaging is of low utility. In contrast, cranial imaging is of utmost importance in the setting of encephalitis, bacterial meningitis, ventriculitis, bacterial brain abscess, subdural empyema, epidural abscess, neurobrucellosis, neurocysticercosis, and CNS tuberculosis that can aid clinicians with the differential diagnosis, source of infection (e.g., otitis, sinusitis), assessing complications of meningitis (e.g., hydrocephalus, venous sinus thrombosis, strokes), need for neurosurgical interventions and to monitor for the response of therapy. Novel imaging techniques such as fast imaging employing steady-state acquisition (FIESTA), susceptibility-weighted imaging (SWI), and chemical exchange saturation transfer (CEST) contrast are briefly discussed. SUMMARY: Though the radiological findings in CNS infections are vast, certain patterns along with clinical clues from history and examination often pave the way to early diagnosis. This review reiterates the importance of obtaining cranial imaging when necessary, and the various radiological presentations of commonly encountered CNS infections.

Amide Proton Transfer-Weighted (APTw) Imaging of Intracranial Infection in Children: Initial Experience and Comparison with Gadolinium-Enhanced T1-Weighted Imaging.

PURPOSE: To evaluate the performance of amide proton transfer-weighted (APTw) imaging against the reference standard of gadolinium-enhanced T1-weighted imaging (Gd-T1w) in children with intracranial infection. MATERIALS AND METHODS: Twenty-eight pediatric patients (15 males and 13 females; age range 1-163 months) with intracranial infection were recruited in this study. 2D APTw imaging and conventional MR sequences were conducted using a 3 T MRI scanner. Kappa (κ) statistics and the McNemar test were performed to determine whether the hyperintensity on APTw was related to the enhancement on Gd-T1w. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of APTw imaging to predict lesion enhancement were calculated. RESULT: In twelve patients with brain abscesses, the enhancing rim of the abscesses on the Gd-T1w images was consistently hyperintense on the APTw images. In eight patients with viral encephalitis, three showed slight spotted gadolinium enhancement, while the APTw image also showed a slight spotted high signal. Five of these patients showed no enhancement on Gd-T1w and isointensity on the APTw image. In eleven patients with meningitis, increased APTw signal intensities were clearly visible in gadolinium-enhancing meninges. Sixty infectious lesions (71%) showed enhancement on Gd-T1w images. The sensitivity and specificity of APTw were 93.3% (56/60) and 91.7% (22/24). APTw demonstrated excellent agreement (κ = 0.83) with Gd-T1w, with no significant difference (P = 0.69) in detection of infectious lesions. CONCLUSIONS: These initial data show that APTw MRI is a noninvasive technique for the detection and characterization of intracranial infectious lesions. APTw MRI enabled similar detection of infectious lesions to Gd-T1w and may provide an injection-free means of evaluation of intracranial infection.

Potential Roles and Functions of Listerial Virulence Factors during Brain Entry.

Although it rarely induces disease in humans, Listeria monocytogenes (Lm) is important due to the frequency of serious pathological conditions-such as sepsis and meningitis-it causes in those few people that do get infected. Virulence factors (VF) of Lm-especially those involved in the passage through multiple cellular barriers of the body, including internalin (Inl) family members and listeriolysin O (LLO)-have been investigated both in vitro and in vivo, but the majority of work was focused on the mechanisms utilized during penetration of the gut and fetoplacental barriers. The role of listerial VF during entry into other organs remain as only partially solved puzzles. Here, we review the current knowledge on the entry of Lm into one of its more significant destinations, the brain, with a specific focus on the role of various VF in cellular adhesion and invasion.

Molecular and Histologic Diagnosis of Central Nervous System Infections.

Infections of the central nervous system cause significant morbidity and mortality in immunocompetent and immunocompromised individuals. A wide variety of microorganisms can cause infections, including bacteria, mycobacteria, fungi, viruses, and parasites. Although less invasive testing is preferred, surgical biopsy may be necessary to collect diagnostic tissue. Histologic findings, including special stains and immunohistochemistry, can provide a morphologic diagnosis in many cases, which can be further classified by molecular testing. Correlation of molecular, culture, and other laboratory results with histologic findings is essential for an accurate diagnosis, and to minimize false positives from microbial contamination.

Cranial Melioidosis Presenting as Osteomyelitis and/or Extra-Axial Abscess: Literature Review.

BACKGROUND: Central nervous system (CNS) melioidosis is rare. Clinical presentations depend on the region of endemicity. Despite treatment, neurologic disease has relatively high mortality rates. Less than 80 cases of CNS involvement have been reported. METHODS: A literature review was performed by searching online databases for melioidosis presenting as osteomyelitis or scalp/extra-axial abscess (OSEAA). In addition, 3 similar cases managed at my institute have been presented. RESULTS: Including this report of 3 cases, 20 additional cases have been reported. Of these, 12 cases (60%) were from India. The mean age of patients was 45.5 years (range, 29-74 years), and none were in the pediatric age group. Patients in the fifth to sixth decades were most frequently affected. The male to female ratio was 5.3:1. Eleven patients had predisposing factors. Fever, headache, and scalp swelling were the most common features. Five cases had history of previous melioid infection. Seven cases had systemic disease. Debridement was performed in 11 cases. The average intensive phase treatment duration was 4.6 weeks (range, 2-8 weeks) and 5.5 months (range, 3-12 months) for the maintenance phase. Mean follow-up duration was 13.5 months (range, 2 weeks-40 months). Two deaths (10%) were reported, and 1 case of residual frontal abscess had relapse. CONCLUSIONS: Cranial melioidosis presenting as OSEAA is associated with good outcome, in contrast with other neurologic presentations. Intensive phase for at least 2-3 weeks followed by maintenance phase for 3-6 months is the standard treatment, similar to other melioid presentations. A high degree of suspicion and accurate identification of the organism is crucial. Patients need to be monitored for recurrences, both clinically and radiologically.

Multi-systemic melioidosis: a clinical, neurological, and radiological case study from Hainan Province, China.

BACKGROUND: Melioidosis is a tropical disease caused by Burkholderia pseudomallei (B. pseudomallei). It can infect any organ system and lead to multiple abscesses. A few studies reported that central nervous system (CNS) is also involved. We present a diabetic patient with multi-systemic melioidosis that affected the CNS, thorax, and spleen. The aim was to study the clinical and radiological features of melioidosis and enhance understanding of the disease. CASE PRESENTATION: A 38-year-old male presented with cough and expectoration mixed with blood for several days. Chest computed tomography (CT) showed a patchy opacity in his left lung, and multiple low-density lesions in his spleen. After 10 days of antibiotics treatment, his clinical symptoms improved and he was discharged from the hospital. But 8 months later, the patient experienced sudden onset of left limb weakness and seizure and was re-admitted to the hospital. Brain CT indicated a low-density lesion over the right frontal lobe, and magnetic resonance imaging (MRI) indicated a well-enhanced lobulated lesion with multiple diffusion restriction areas in the lesion. He had a neuronavigation-guided open surgery but no malignancy was found. B. pseudomallei was cultured from the operative samples. After 4 months of systemic and intraventricular antibiotic administration treatment, he recovered complete consciousness with left hemiparesis. CONCLUSIONS: Multi-systemic melioidosis may present atypical clinical, neurological, and radiological manifestations. It is extremely important to accurately diagnose before treatment is selected. CNS melioidosis in early stage manifests similar symptoms to malignancy or stroke. It might mislead to a false diagnose. Diffusion weighted imaging (DWI) can help in differentiate abscesses from cystic tumours.

Actinomicosis diseminada con compromiso de sistema nervioso central / Disseminated actinomycosis with central nervous system involvement

Resumen La actinomicosis diseminada es muy infrecuente, así como la afección del sistema nervioso central (SNC) asociada, con mortalidad de hasta 28%. Sus manifestaciones pueden ser similares a cuadros infecciosos de otras etiologías, por lo que el conocimiento de la entidad aumenta la sospecha clínica y permite brindar un tratamiento oportuno. Se presenta el caso clínico de un adulto con edema en una extremidad superior como manifestación de una tromboflebitis y una lesión abscedada axilar, en que se confirmó una infección por actinomicetos. Presentó una diseminación hematógena con compromiso de SNC, de evolución fatal.

Actinomycosis is very rare, as well as the central nervous system (CNS) condition associated with it, presenting a mortality up to 28%. Its manifestations could be similar to infectious conditions from other etiologies, thus, having a better understanding of the entity increases clinical suspicion and also it can provide a timely treatment. The clinical case of an adult with edema in an upper extremity is presented as a manifestation of thrombophlebitis and an abscessed axillary lesion, in which actinomycetes infection was confirmed. He presented a haematogenous spread with CNS involvement, with fatal ending.

Central nervous system melioidosis in the pediatric age group: review.

PURPOSE: Melioidosis is a potentially fatal infectious disease caused by Burkholderia pseudomallei. Neurologic involvement in pediatric age group is very rare, and only a handful of cases have been reported in literature. We sought to provide a systematic review of pediatric neurologic melioidosis. METHODS: Literature review was performed to analyze reported cases of pediatric neurologic melioidosis (≤16 years) by searching online database (PubMed/MEDLINE). RESULTS: Twenty-seven cases were analyzed. Mean age was 6.7 years (range 2 days-14 years) and around 50% were older children (>5 years). Cranial nerve palsies and fever were most common presenting features. Major manifestations were meningoencephalitis in 16 (59%) and cerebral abscesses in eight (29%) cases. Abscesses were mostly located in parietal lobe. Among older children, abscesses were common than meningeal disease, while being converse for neonates. Mean follow-up duration was 11.5 months. Ten cases showed good to excellent outcome, while eight cases had fair (incomplete recovery) outcomes. The overall mortality rate was 18.5% (5/27) and tends to decrease with age. Among the five deaths, 4 (80%) had septicemia or pneumonia. CONCLUSIONS: Pediatric neurologic melioidosis is very rare. Meningoencephalitis is the most common presentation. Mortality is the highest in neonates. Ceftazidime appears to be the drug of choice in intensive phase, although the best drug in maintenance phase cannot be commented upon, especially in very young children.

Increased Neurotropic Threat from Burkholderia pseudomallei Strains with a B. mallei-like Variation in the bimA Motility Gene, Australia.

Neurologic melioidosis is a serious, potentially fatal form of Burkholderia pseudomallei infection. Recently, we reported that a subset of clinical isolates of B. pseudomallei from Australia have heightened virulence and potential for dissemination to the central nervous system. In this study, we demonstrate that this subset has a B. mallei-like sequence variation of the actin-based motility gene, bimA. Compared with B. pseudomallei isolates having typical bimA alleles, isolates that contain the B. mallei-like variation demonstrate increased persistence in phagocytic cells and increased virulence with rapid systemic dissemination and replication within multiple tissues, including the brain and spinal cord, in an experimental model. These findings highlight the implications of bimA variation on disease progression of B. pseudomallei infection and have considerable clinical and public health implications with respect to the degree of neurotropic threat posed to human health.

[Disseminated actinomycosis with central nervous system involvement]. / Actinomicosis diseminada con compromiso de sistema nervioso central.

Actinomycosis is very rare, as well as the central nervous system (CNS) condition associated with it, presenting a mortality up to 28%. Its manifestations could be similar to infectious conditions from other etiologies, thus, having a better understanding of the entity increases clinical suspicion and also it can provide a timely treatment. The clinical case of an adult with edema in an upper extremity is presented as a manifestation of thrombophlebitis and an abscessed axillary lesion, in which actinomycetes infection was confirmed. He presented a haematogenous spread with CNS involvement, with fatal ending.

Multiple nocardial abscesses of the brainstem and spinal cord diagnosed after an open biopsy through a cervical partial central corpectomy: case report.

Nocardiosis of the central nervous system is a challenging and difficult diagnosis for the clinician. The combination of infections of the brain and spinal cord is even more rare. The authors report on a patient with multiple lesions in the brainstem and cervical spinal cord. This 81-year-old immunocompetent woman presented with symptoms of progressive walking difficulty and ataxia. The results of an extensive workup with laboratory investigation, MRI, lumbar puncture, positron emission tomography (PET), and bone marrow biopsy remained inconclusive. Only after an open biopsy of a cervical lesion by an anterior approach through a partial central corpectomy of the cervical spine, was the diagnosis of nocardiosis made, allowing for specific antibiotic treatment.

Bacterial, Fungal, and Parasitic Infections of the Central Nervous System: Radiologic-Pathologic Correlation and Historical Perspectives.

Despite remarkable progress in prevention and treatment, infectious diseases affecting the central nervous system remain an important source of morbidity and mortality, particularly in less-developed countries and in immunocompromised persons. Bacterial, fungal, and parasitic pathogens are derived from living organisms and affect the brain, spinal cord, or meninges. Infections due to these pathogens are associated with a variety of neuroimaging patterns that can be appreciated at magnetic resonance imaging in most cases. Bacterial infections, most often due to Streptococcus, Haemophilus, and Neisseria species, cause significant meningitis, whereas the less common cerebritis and subsequent abscess formation have well-documented progression, with increasingly prominent altered signal intensity and corresponding contrast enhancement. Atypical bacterial infections are characterized by the development of a granulomatous response, classically seen in tuberculosis, in which the tuberculoma is the most common parenchymal form of the disease; spirochetal and rickettsial diseases are less common. Fungal infections predominate in immunocompromised hosts and are caused by yeasts, molds, and dimorphic fungi. Cryptococcal meningitis is the most common fungal infection, whereas candidiasis is the most common nosocomial infection. Mucormycosis and aspergillosis are characterized by angioinvasiveness and are associated with high morbidity and mortality among immunocompromised patients. In terms of potential exposure in the worldwide population, parasitic infections, including neurocysticercosis, toxoplasmosis, echinococcosis, malaria, and schistosomiasis, are the greatest threat. Rare amebic infections are noteworthy for their extreme virulence and high mortality. The objective of this article is to highlight the characteristic neuroimaging manifestations of bacterial, fungal, and parasitic diseases, with emphasis on radiologic-pathologic correlation and historical perspectives.

Peptidylarginine deiminases: novel drug targets for prevention of neuronal damage following hypoxic ischemic insult (HI) in neonates.

Neonatal hypoxic ischaemic (HI) injury frequently causes neural impairment in surviving infants. Our knowledge of the underlying molecular mechanisms is still limited. Protein deimination is a post-translational modification caused by Ca(+2) -regulated peptidylarginine deiminases (PADs), a group of five isozymes that display tissue-specific expression and different preference for target proteins. Protein deimination results in altered protein conformation and function of target proteins, and is associated with neurodegenerative diseases, gene regulation and autoimmunity. In this study, we used the neonatal HI and HI/infection [lipopolysaccharide (LPS) stimulation] murine models to investigate changes in protein deimination. Brains showed increases in deiminated proteins, cell death, activated microglia and neuronal loss in affected brain areas at 48 h after hypoxic ischaemic insult. Upon treatment with the pan-PAD inhibitor Cl-amidine, a significant reduction was seen in microglial activation, cell death and infarct size compared with control saline or LPS-treated animals. Deimination of histone 3, a target protein of the PAD4 isozyme, was increased in hippocampus and cortex specifically upon LPS stimulation and markedly reduced following Cl-amidine treatment. Here, we demonstrate a novel role for PAD enzymes in neural impairment in neonatal HI Encephalopathy, highlighting their role as promising new candidates for drug-directed intervention in neurotrauma. Hypoxic Ischaemic Insult (HI) results in activation of peptidylarginine deiminases (PADs) because of calcium dysregulation. Target proteins undergo irreversible changes of protein bound arginine to citrulline, resulting in protein misfolding. Infection in synergy with HI causes up-regulation of TNFα, nuclear translocation of PAD4 and change in gene regulation as a result of histone deimination. Pharmacological PAD inhibition significantly reduced HI brain damage.

Clinical characteristics and outcome of brain abscess: systematic review and meta-analysis.

OBJECTIVE: To define clinical characteristics, causative organisms, and outcome, and evaluate trends in epidemiology and outcome of brain abscesses over the past 60 years. METHODS: We performed a systematic review and meta-analysis of studies on brain abscesses published between 1970 and March 2013. Studies were included if they reported at least 10 patients with brain abscesses, included less than 50% extra-axial CNS infections (empyema) without brain abscess, and did not solely report on brain abscesses caused by a single pathogen. RESULTS: We identified 123 studies including 9,699 patients reported between 1935 and 2012. There was a male predominance of 2.4 to 1, and the mean age of patients with brain abscesses was 34 years. The most common causative microorganisms were Streptococcus and Staphylococcus species, comprising 2,000 (34%) and 1,076 (18%) of 5,894 cultured bacteria. Geographical distribution of causative microorganisms over continents was similar and did not substantially change over the past 60 years. Predisposing conditions were present in 8,134 of 9,484 patients (86%) and mostly consisted of contiguous or metastatic foci of infection. The classic triad of fever, headache, and focal neurologic deficits was present in 131 of 668 (20%) of patients. Case fatality rate decreased from 40% to 10% over the past 5 decades, while the rate of patients with full recovery increased from 33% to 70%. CONCLUSIONS: The prognosis of patients with brain abscesses has gradually improved over the past 60 years. Important changes over time were the modality of cranial imaging, neurosurgical technique, and antimicrobial regimen.