Which CSF finding most supports a diagnosis of multiple sclerosis?

Which CSF finding most supports a diagnosis of multiple sclerosis?

• A. Elevated protein with neutrophilic predominance.
• B. Normal CSF.
• C. IgG index within normal range.
• D. Oligoclonal bands with elevated IgG index.

Answer: (D)

The key idea is intrathecal IgG synthesis. In multiple sclerosis, immune activity within the central nervous system leads to clonal expansion of B cells producing IgG inside the CNS. This shows up as oligoclonal bands on CSF electrophoresis and an elevated IgG index, which measures the amount of IgG produced in the CNS relative to serum IgG. The presence of oligoclonal bands together with a raised IgG index is a classic, highly supportive finding for MS because it reflects local IgG production, not just IgG that leaked from the blood. Normal CSF or a normal IgG index argues against intrathecal IgG production, and a neutrophil-predominant, protein-elevated CSF points more toward acute bacterial meningitis rather than MS.

The key idea is intrathecal IgG synthesis. In multiple sclerosis, immune activity within the central nervous system leads to clonal expansion of B cells producing IgG inside the CNS. This shows up as oligoclonal bands on CSF electrophoresis and an elevated IgG index, which measures the amount of IgG produced in the CNS relative to serum IgG. The presence of oligoclonal bands together with a raised IgG index is a classic, highly supportive finding for MS because it reflects local IgG production, not just IgG that leaked from the blood.

Normal CSF or a normal IgG index argues against intrathecal IgG production, and a neutrophil-predominant, protein-elevated CSF points more toward acute bacterial meningitis rather than MS.