Which diagnostic marker in CSF is indicative of multiple sclerosis?

The presence of oligoclonal bands in cerebrospinal fluid (CSF) is a key diagnostic marker for multiple sclerosis. In patients with multiple sclerosis, oligoclonal bands are detected in the CSF but not in the serum, indicating a local increase in immunoglobulin production due to inflammatory processes affecting the central nervous system. This finding is significant because it reflects the immune-mediated nature of the disease and supports the diagnosis of multiple sclerosis, especially in the context of other clinical and radiological findings.

Oligoclonal bands result from the activation of B cells and the subsequent production of antibodies specifically in the central nervous system, which is characteristic of multiple sclerosis. The presence of these bands serves as a useful diagnostic criterion, especially in cases where the clinical presentation is suggestive of the disease but other imaging or clinical evidence may not be conclusive.