Certified Neuroscience Registered Nurse (CNRN) Practice Exam

What is the most common source of infection leading to brain abscesses?

1. Direct contact with infected tissue

2. Hematogenous spread from distant infected sites

3. Contaminated surgical instruments

4. Inhalation of bacteria from the environment

The correct answer is: Hematogenous spread from distant infected sites

The most common source of infection leading to brain abscesses is hematogenous spread from distant infected sites. This process occurs when bacteria from an infection elsewhere in the body enter the bloodstream and travel to the brain, where they can cause localized areas of infection, resulting in abscess formation. Conditions that can lead to such infections include endocarditis, lung infections, or infections in other areas like the teeth, which can lead to bacteria entering the systemic circulation. Hematogenous spread is particularly significant because once bacteria reach the cerebral tissue, they can multiply and elicit a strong inflammatory response, contributing to the development of a brain abscess. In contrast, direct contact with infected tissue typically does not contribute significantly to the formation of brain abscesses, as the brain is well protected by barriers. Contaminated surgical instruments can lead to infection, but brain abscesses from surgical procedures are less common. Inhalation of bacteria from the environment may be a factor in respiratory infections or pneumonia but is not a primary mechanism for brain abscess development.