| Predominantly axonal pathophysiology |
Initial tests: - Serum glucose and glycohemoglobin
- Serum vitamin B12 level
- SPEP and UPEP with immunofixation
- Thyroid function tests
- Serum antinuclear antibodies
- Erythrocyte sedimentation rate and C-reactive protein
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Additional testing, if history suggestive: - HIV serology
- Urine/blood for heavy metals
- Urine/blood for porphyrins
- Rheumatoid factor
- Sjögren's disease testing (anti-Ro, anti-La antibodies)
- Paraneoplastic antibody panel (in patients with sensory neuronopathy)
- Lyme testing
- Vitamin B1 (thiamine) erythrocyte transketolase activation assay or whole blood level
- Methylmalonic acid and homocysteine levels (in patients with borderline low serum vitamin B12 levels)
- Hepatitis screen (for types B and C)
- Cryoglobulins
- Antineutrophil cytoplasmic antibodies (ANCA)
- CBC with differential (looking for eosinophilia)
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| Predominantly demyelinating pathophysiology |
Initial tests: - SPEP and UPEP with immunofixation
- Hepatitis screen (for types B and C)
- Lumbar puncture
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Additional testing, if history suggestive: - Antimyelin associated glycoprotein (MAG) antibodies (in patients with predominantly sensory symptoms)
- Nodal and paranodal antibodies (eg, anti-GM1, neurofascin 155, contactin-1, and contactin-associated protein 1 antibodies) in patients with predominantly motor symptoms
- HIV
- Genetic testing for Charcot-Marie-Tooth disease; generally, the electrophysiology is also suggestive of a hereditary condition
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