What is the classic CSF finding in Guillain-Barré syndrome?

• A. Albuminocytologic dissociation—high CSF protein with a normal cell count.
• B. Elevated CSF white blood cell count.
• C. Elevated opening pressure with normal protein.
• D. Oligoclonal bands in CSF.

Answer: (D)

In Guillain-Barré syndrome the classic CSF finding is albuminocytologic dissociation: elevated protein with a normal white blood cell count. This happens because peripheral nerve demyelination and inflammation disrupt the blood-nerve barrier, allowing plasma proteins to leak into the CSF, while there isn’t a concurrent CNS inflammatory cell influx. The protein rise often becomes evident after the first week of symptoms.

Elevated CSF white blood cells would suggest infection or CNS inflammation rather than a peripheral demyelinating process. Elevated opening pressure with normal protein isn’t typical for Guillain-Barré. Oligoclonal bands in CSF are more characteristic of CNS demyelinating diseases like multiple sclerosis. So the hallmark CSF pattern in Guillain-Barré is high protein with a normal cell count.