Recommended IVIG Dosing for Acute Motor-Sensory Axonal Neuropathy (AMSAN)
The recommended dose of Intravenous Immunoglobulin (IVIG) for AMSAN is 2 g/kg of ideal body weight, typically divided over 5 days (0.4 g/kg/day) as a total treatment course. 1
Dosing Protocol and Administration
AMSAN is a rare axonal variant of Guillain-Barré syndrome (GBS) that requires prompt immunomodulatory treatment. The dosing protocol follows established guidelines for similar acute inflammatory neuropathies:
- Standard dosing: 2 g/kg total dose 1
- Administration schedule: Typically divided over 5 days (0.4 g/kg/day) 1
- Alternative administration: For doses exceeding 80g, consider administering over 3-5 days at 0.4 g/kg/day 2
- Duration: Single course initially, with consideration for repeat treatment if clinical deterioration occurs after initial improvement 1
Pre-Treatment Assessment
Before administering IVIG, the following assessments should be performed:
- Serum IgA level: Must be checked before administration as IgA deficiency may lead to severe reactions including fever, infusion reactions, and anaphylaxis 2
- If IgA deficient: Use IVIG preparation with reduced IgA levels 2
- Cardiac function and fluid status: Assess before administration to minimize risks 1
Monitoring During Treatment
- Neurological assessments: Perform frequent evaluations to monitor treatment response 1
- Pulmonary function: Monitor closely as respiratory compromise can occur rapidly in AMSAN 1
- Autonomic function: Watch for dysautonomia which can complicate the clinical course 1
Treatment Considerations
- Hospitalization: Patients should be admitted to a facility with capability for rapid transfer to ICU-level monitoring 1
- Alternative treatment: If IVIG is unavailable or contraindicated, plasma exchange (200-250 ml plasma/kg in five sessions) is an acceptable alternative 1
- Supportive care: Address complications such as neuropathic pain (with pregabalin, gabapentin, or duloxetine) and constipation/ileus if present 1
Potential Adverse Effects
IVIG therapy carries several risks that require monitoring:
- Common: Headache (most frequent during loading dose), infusion reactions 3
- Serious: Thromboembolic events, renal dysfunction, aseptic meningitis, hemolysis 1
- Long-term safety: Studies in other neurological conditions suggest decreasing adverse event rates with continued treatment 3
Clinical Pearls
- AMSAN has a worse prognosis than demyelinating forms of GBS, making prompt treatment crucial
- The diagnosis should be confirmed with EMG and nerve conduction studies before initiating treatment 4
- Unlike AMAN (which is often associated with Campylobacter jejuni), AMSAN has less clear triggering factors, though associations with EBV and autoimmune conditions like SLE have been reported 4, 5, 6
- Early treatment initiation is associated with better outcomes
IVIG remains the first-line therapy for AMSAN due to its efficacy and relatively favorable side effect profile compared to alternatives, with treatment protocols following established guidelines for GBS variants.