This test is a fluid analysis of cerebral spinal fluid (CSF). CSF is the fluid that bathes, cushions, and protects the brain and spinal cord. It flows through the skull and spine in the subarachnoid space, which is the area immediately surrounding the brain. CSF chemistry refers to the analysis of the fluid to look for things, such as protein and glucose content, as well as other components, which can often help in diagnosing disease.