What is the epidemiology of brain abscess (cerebral abscess)?

From the Guidelines

Brain abscesses occur in approximately 0.4-1.3 cases per 100,000 people annually, as estimated in the European population 1. The epidemiology of brain abscess varies by age and geography, with higher incidence in developing countries. Some key points about the epidemiology of brain abscess include:

• The annual incidence of brain abscess is estimated to be around 0.4-1.3 per 100,000 inhabitants, which corresponds to approximately 6700 cases per year in Europe 1.
• Brain abscesses are more common in males than females, although the exact ratio is not specified in the provided evidence.
• The most frequent causative pathogens in community-acquired brain abscess are oral cavity bacteria such as Streptococcus anginosus group, Fusobacterium spp., and Aggregatibacter spp. 1.
• Predisposing factors for brain abscess include immunocompromised states, congenital heart disease with right-to-left shunts, and pulmonary arteriovenous malformations 1.
• The frontal and temporal lobes are most commonly affected, reflecting the frequency of sinus and ear infections as sources 1.

The microbiology of brain abscess varies by source, with streptococci being most common overall, followed by anaerobes, staphylococci, and gram-negative bacteria 1. In immunocompromised patients, opportunistic pathogens like Toxoplasma, Nocardia, fungi, and mycobacteria are more prevalent 1. Multiple abscesses occur in about 20-30% of cases, particularly with hematogenous spread, although this is not directly stated in the provided evidence, it can be inferred from the information about the sources of brain abscesses 1.

Brain abscesses typically result from three main sources:

• Direct spread from contiguous infections (such as sinusitis, otitis media, or dental infections) 1.
• Hematogenous spread from distant infections like endocarditis or lung abscesses 1.
• Direct inoculation from trauma or neurosurgical procedures 1.

It is essential to note that the epidemiology and treatment of brain abscess have changed significantly over time and may vary depending on socio-economic factors and the overall health status of populations 1.

From the Research

Epidemiology of Brain Abscess

• The epidemiology of brain abscess has changed in recent decades, with an increasing incidence, especially among elderly individuals 2.
• Important predisposing conditions include dental and ear-nose-throat infections, immuno-compromise, and previous neurosurgery 2.
• The incidence of brain abscess is increasing, and molecular-based diagnostics have improved our understanding of the involved microorganisms 2.
• Oral cavity bacteria, including anaerobes, are the predominant pathogens in brain abscesses 2.

Causative Microorganisms

• Streptococcus and Staphylococcus species are the most common causative microorganisms of brain abscesses 3, 4.
• Streptococcus intermedius is a dominant pathogen in some settings, with a shift away from staphylococcal brain abscesses 3.
• The geographical distribution of causative microorganisms is similar across continents and has not substantially changed over the past 60 years 4.

Clinical Characteristics and Outcome

• Brain abscesses have a high mortality rate, with a male predominance and a mean age of 34 years 4.
• Predisposing conditions are present in most patients, with contiguous or metastatic foci of infection being the most common 4.
• The classic triad of fever, headache, and focal neurologic deficits is present in only a minority of patients 4.
• The prognosis of patients with brain abscesses has improved over the past 60 years, with a decrease in case fatality rate and an increase in the rate of patients with full recovery 4, 5.

Diagnosis and Treatment

• Diagnosis relies on a combination of magnetic resonance imaging, neurosurgical aspiration or excision, and careful microbiological examinations 2.
• Local source control by aspiration or excision of brain abscess combined with long-term antimicrobials are cornerstones of treatment 2.
• Empiric first-line therapy with ceftriaxone remains appropriate on microbiological grounds, and narrower spectrum therapy may sometimes be justified 3.
• Multicenter prospective studies and randomized clinical trials are needed to further advance treatment and prognosis in brain abscess patients 5.