Certified Neuroscience Registered Nurse (CNRN) Practice Exam

What is the most common route for malignant tumors to spread to the CNS?

1. Via lymphatic circulation

2. Via blood circulation

3. Direct invasion

4. Ventilation route

The correct answer is: Via blood circulation

The most common route for malignant tumors to spread to the central nervous system (CNS) is through blood circulation. This hematogenous spread occurs when cancer cells enter the bloodstream and can subsequently travel to various organs, including the brain and spinal cord. When malignant tumors metastasize, they often release tumor cells into the bloodstream, where these circulating tumor cells can lodge in the microvasculature of the CNS. The blood-brain barrier (BBB) plays a critical role in this process, as it can both limit and facilitate the entry of certain tumor cells depending on their characteristics. Once in the CNS, these cells can form secondary tumors, contributing to the overall complexity and severity of the disease. In contrast, while lymphatic circulation and direct invasion can also contribute to the spread of cancer, neither is as prevalent for CNS metastasis compared to the hematogenous route. The ventilation route is not a recognized pathway for tumor spread in this context. Understanding these routes is crucial for recognizing how malignancies impact neural tissues and for planning therapeutic interventions.