D6 Analysis of cerebrospinal fluid (CSF, lumbar puncture)

Topic

Cerebrospinal fluid, obtained via lumbar puncture, provides direct information on three distinct aspects of the central nervous system: intracranial pressure, immune status, and the integrity of the blood-brain barrier. Each of these three aspects is reflected in a specific characteristic of the cerebrospinal fluid that is measured separately.

Cerebrospinal fluid opening pressure, measured at the time of the lumbar puncture, is directly related to intracranial pressure—the same intracranial pressure described in cases of traumatic brain injury and brain tumors: the higher the intracranial pressure, the higher the opening pressure recorded upon accessing the cerebrospinal fluid.

The volume of cerebrospinal fluid, meanwhile, results from a dynamic balance between the amount of fluid produced and the amount reabsorbed: when production exceeds reabsorption, the volume increases, and when the reverse occurs, the volume decreases.

The cerebrospinal fluid cell count—referred to as pleocytosis when elevated—reflects the degree of inflammation or infection within the central nervous system: the greater the inflammation or infection, the higher the cell count. Specifically in bacterial infections, the ratio of cerebrospinal fluid glucose to plasma glucose characteristically decreases, as the bacteria present consume the glucose in the cerebrospinal fluid. Total protein concentration in cerebrospinal fluid increases when the blood-brain barrier is damaged—the same barrier whose integrity can be compromised in other conditions included in this catalog; the greater the damage to the blood-brain barrier, the more total protein leaks into the cerebrospinal fluid, resulting in a higher concentration.

The cerebrospinal fluid oligoclonal band index quantifies intrathecal immunoglobulin synthesis—that is, the amount of immunoglobulin produced within the central nervous system itself rather than derived from the blood—and serves as a key marker in the diagnosis of multiple sclerosis. In addition to these specific measurements, cerebrospinal fluid acts as the reference biological matrix for other biomarkers described elsewhere in this catalog. Ultimately, it is this fluid—obtained via lumbar puncture—that allows for the assessment of intracranial pressure, immune status, and the integrity of the central nervous system's blood-brain barrier within a single sample.

ID:4302