Why Can an Infection in the Brain's Ventricles Usually Be

Why can an infection in the brain's ventricles usually be detected in spinal fluid obtained from the lower back (lumbar region) ?

A) Cerebrospinal fluid (CSF) originates in the ventricles, but percolates over and around the brain and spinal cord.
B) There is a high degree of vascularity that exists, allowing easy transfer of bacteria in the cerebrospinal fluid (CSF) and the blood.
C) There is a set of lymph nodes specifically in place to drain the cerebrospinal fluid (CSF) from the ventricles. They are found in the lumbar region of the spinal column.
D) This is an incorrect statement. Since the central nervous system (CNS) is a protected site due to the blood-brain barrier, there can never BE an infection in the ventricles.
E) When ventricles are infected, the brain reacts by pumping the causative pathogens into the CFS so that they can be removed by the immune system.