Certified Neuroscience Registered Nurse (CNRN) Practice Exam

What is the most common route by which infective agents enter the central nervous system (CNS)?

1. Direct inoculation

2. Hematogenous spread

3. Via cerebrospinal fluid

4. Through peripheral nerves

The correct answer is: Hematogenous spread

The hematogenous spread is identified as the most common route by which infective agents enter the central nervous system (CNS). This process occurs when pathogens spread through the bloodstream, allowing them to cross the blood-brain barrier and infect CNS tissues. Several types of pathogens, including bacteria, viruses, and fungi, utilize this route, particularly during systemic infections where they gain access to the vascular system and subsequently migrate to the CNS. Hematogenous spread is significant because it can lead to conditions such as meningitis, encephalitis, and abscess formation, highlighting the critical nature of recognizing the potential for systemic infections to impact the CNS. Additionally, the blood-brain barrier's selective permeability plays a vital role in restricting or facilitating this spread, which factors into the susceptibility of the CNS to various pathogens. The other routes of entry, like direct inoculation, involve specific trauma such as surgery or penetrating injuries, which are not as common as hematogenous spread. Infection via cerebrospinal fluid could occur post-procedure or in certain pathological conditions, but again, this is typically less frequent. Likewise, entry through peripheral nerves is notably less common, as it usually pertains to specific neurotropic viruses and is contingent upon the context of the infection. Overall,