CSF Findings in CIDP
Typical CSF Profile
The hallmark CSF finding in CIDP is elevated protein (typically >450 mg/L) with minimal or no pleocytosis (leukocytes <10 cells/µL), a pattern termed "albuminocytologic dissociation." 1, 2
Protein Elevation
- Mean CSF protein levels in CIDP patients reach approximately 1150 mg/L 2
- Elevated protein occurs in 94% of CIDP cases 2
- This elevation reflects blood-nerve barrier disruption and is highly supportive of the diagnosis 1
Cell Count Considerations
- Mild to moderate pleocytosis (≥10 cells/µL) occurs in approximately 6% of CIDP patients and does not exclude the diagnosis 3
- When pleocytosis is present, it is typically mild and most commonly seen in patients with subacute onset or antecedent infection 3
- CSF leukocyte counts may spontaneously decrease before treatment initiation 3
- Normal cell counts are the expected finding and should not delay antibody testing or diagnosis 4
Additional CSF Markers
- Oligoclonal IgG bands may be detected in some CIDP patients, potentially suggesting associated CNS inflammation 2
- The CSF/serum albumin quotient (albumin index) may be elevated, reflecting blood-nerve barrier dysfunction 2
Clinical Interpretation Pitfalls
When CSF shows pleocytosis (≥10 cells/µL) in a patient with demyelinating neuropathy, CIDP remains possible—particularly with subacute onset—but alternative diagnoses must be systematically excluded 3, 5:
- Infectious causes (bacterial, viral, fungal meningitis/radiculitis)
- Inflammatory CNS disorders (multiple sclerosis, neurosarcoidosis)
- Malignant infiltration (lymphomatous/carcinomatous meningitis)
- Other immune-mediated neuropathies with CNS involvement
Repeat lumbar puncture may be valuable when initial CSF shows unexpected pleocytosis, as cell counts often normalize spontaneously 3
Treatment Implications
First-Line Therapies
The three established first-line treatments for CIDP show comparable efficacy 5, 6:
- Intravenous immunoglobulin (IVIG): 0.4 g/kg/day for 5 days, then maintenance dosing
- Corticosteroids: Prednisone or methylprednisolone with gradual taper
- Plasma exchange (PLEX): Typically 5 exchanges over 2 weeks
Treatment Response Monitoring
- CSF protein levels do not reliably correlate with clinical response 2
- Complement activation products (C3a, C5a, sTCC) remain unchanged with IVIG therapy, indicating IVIG efficacy operates through mechanisms other than complement inhibition 7
- Objective outcome measures (strength testing, functional scales, nerve conduction studies) should guide treatment decisions rather than CSF parameters 5
Treatment-Refractory Cases
When patients fail to respond to first-line therapy 5, 6:
- Verify the diagnosis by reviewing electrodiagnostic criteria and excluding CIDP mimickers
- Consider atypical CIDP variants that may require different approaches
- Trial alternative first-line agents before escalating to second-line immunosuppressants
- Monitor for treatment complications (e.g., thrombotic events with PLEX) 6