CIDP Initial Workup
The initial workup for suspected CIDP requires neurology consultation with electrodiagnostic studies (nerve conduction studies and EMG) as the cornerstone diagnostic test, combined with MRI spine with contrast, lumbar puncture for CSF analysis, and comprehensive serum testing to exclude mimickers. 1
Clinical Evaluation
Key clinical features to identify:
- Progressive or relapsing-remitting weakness and sensory loss affecting proximal and distal muscles symmetrically 2
- Symptoms evolving over at least 8 weeks (distinguishes from Guillain-Barré syndrome) 1
- Impaired ambulation, imbalance, and reduced reflexes 3, 2
- Pain occurs in 42% of cases—more common than historically recognized 4
- Variant presentations include pure motor (10%), sensory ataxic (12%), mononeuritis multiplex (9%), paraparetic (4%), and relapsing acute patterns (16%) 4
Electrodiagnostic Testing (Essential)
Nerve conduction studies and EMG are mandatory for diagnosis: 1
- Conduction block is the most common finding (73% of patients) 4
- Look for demyelinating features: prolonged distal latencies, slowed conduction velocities, temporal dispersion, conduction block 2
- Critical pitfall: Only 31% have pure demyelinating patterns—most show mixed demyelinating and axonal features 4
- Multiple A waves and low median-to-sural amplitude ratio suggest CIDP even when standard criteria aren't met 5
- Some patients with biopsy-proven CIDP don't meet strict AAN or INCAT electrodiagnostic criteria 5
MRI Spine with Contrast
Obtain MRI spine with and without contrast: 1
- Evaluates for nerve root enhancement and thickening (characteristic of CIDP) 1
- Rules out compressive lesions, structural abnormalities, and neoplastic causes 1
- Essential for excluding CIDP mimickers
Lumbar Puncture
CSF analysis should include: 1
- Cell count with differential
- Protein (typically elevated in CIDP, often >45 mg/dL) 1
- Glucose
- Cytology to exclude malignant cells and leptomeningeal disease 1
- Gram stain and bacterial/viral cultures 1
- Note: Elevated protein with normal or mildly elevated WBC is typical; elevated WBC doesn't exclude CIDP 1
Comprehensive Serum Testing
Screen for reversible causes and CIDP mimickers: 1
- HbA1c (diabetes) 1
- Vitamin B12, B6, folate, thiamine 1
- TSH (thyroid dysfunction) 1
- Serum protein electrophoresis with immunofixation (paraproteinemia/MGUS) 1, 4
- CPK (myopathy) 1
- ANA, ESR, CRP, ANCA (autoimmune/vasculitis) 1, 6
- Anti-smooth muscle, SSA/SSB, RNP, anti-dsDNA if SLE suspected 1, 6
- Antiganglioside antibodies 1
- HIV, hepatitis B/C, Lyme serology 1
Additional Testing When Indicated
Consider based on clinical phenotype: 1
- Paraneoplastic antibody panel (ANNA-1/anti-Hu, anti-MAG) if atypical features 1
- Flow cytometry in hematologic malignancy patients 1
- Genetic testing if hereditary neuropathy suspected 5
Nerve Biopsy
Reserve for diagnostically uncertain cases: 1, 5
- Useful when electrodiagnostic findings are atypical but clinical suspicion remains high 5
- Can confirm demyelination with onion bulb formation, inflammatory infiltrates 5
- Not routinely required if clinical, electrodiagnostic, and CSF findings are consistent 1
Autonomic Testing
May be considered but not essential for initial diagnosis: 1
- Useful if autonomic symptoms present (orthostatic hypotension, sweating abnormalities, constipation) 1
- Battery of validated tests recommended if performed 1
Critical Diagnostic Pitfalls
Avoid these common errors:
- Don't dismiss CIDP if electrodiagnostic studies show mixed demyelinating-axonal features—this occurs in the majority 4
- Don't exclude CIDP based solely on strict AAN/INCAT criteria—atypical presentations are common 4, 5
- Recognize that CIDP-MGUS patients present differently (more imbalance, ataxia, vibration loss) but respond similarly to treatment 4
- Distinguish from acute-onset CIDP (≥3 treatment-related fluctuations or deterioration ≥8 weeks after onset) 1
- CSF pleocytosis doesn't exclude CIDP—can occur with elevated protein 1
Distinguishing from Guillain-Barré Syndrome
Key differentiators: 1