Treatment of GBS AMSAN
Treat AMSAN with intravenous immunoglobulin (IVIg) at 0.4 g/kg/day for 5 consecutive days (total dose 2 g/kg), which is equally effective as plasma exchange but preferred due to easier administration and wider availability. 1, 2
First-Line Treatment Options
Current guidelines do not differentiate treatment recommendations between AMSAN and other GBS subtypes—both IVIg and plasma exchange remain equally effective first-line options for all variants 2. However, IVIg is generally preferred because it:
- Has significantly higher completion rates compared to plasma exchange 1, 2
- Is easier to administer and more widely available 1, 2
- Requires fewer monitoring considerations 1
Plasma exchange (200-250 ml/kg over 5 sessions) remains an equally effective alternative, particularly in resource-limited settings where cost is a major factor 3, 2.
Critical Timing and Patient Selection
- Initiate treatment immediately in patients unable to walk unaided (GBS disability score ≥3) with moderate to severe weakness, especially with rapid progression 1, 2
- Treatment should begin within 2 weeks of symptom onset for maximum effectiveness 1, 2
- AMSAN patients often present later and more severely than AIDP patients, making early recognition crucial 3
Essential Monitoring Requirements
Admit all patients to a monitored unit with rapid ICU transfer capability, as approximately 25% of GBS patients develop respiratory failure 2:
- Use the "20/30/40 rule" to assess respiratory failure risk: patient at risk if vital capacity <20 ml/kg, maximum inspiratory pressure <30 cmH₂O, or maximum expiratory pressure <40 cmH₂O 1, 2
- Calculate EGRIS (Erasmus GBS Respiratory Insufficiency Score) to predict probability of requiring mechanical ventilation within 1 week 1, 2
- Monitor for autonomic dysfunction, cardiac complications, and neuropathic pain 1
Critical Pitfalls to Avoid
Never use corticosteroids alone—they are ineffective and may worsen outcomes 1, 2:
- Avoid medications that worsen neuromuscular function: β-blockers, IV magnesium, fluoroquinolones, aminoglycosides, and macrolides 1, 2
- Do not routinely give a second course of IVIg to patients with poor prognosis, as this increases serious adverse events without proven benefit (except in treatment-related fluctuations occurring within 2 months) 2
Managing Treatment Response
Approximately 40% of patients do not improve in the first 4 weeks following treatment—this does not necessarily indicate treatment failure 1, 2:
- Treatment-related fluctuations (TRFs) occur in 6-10% of patients within 2 months of initial improvement 1, 2
- For TRFs, repeating the full course of IVIg or plasma exchange is appropriate 1, 2
- Pharmacokinetic variability exists: patients with low serum IgG increase 2 weeks post-treatment may have worse outcomes, though routine second dosing is not recommended outside of TRFs 4
Supportive Care Essentials
- Manage neuropathic pain with gabapentin, pregabalin, or duloxetine—avoid opioids 1, 2
- Provide DVT prophylaxis and pressure ulcer prevention 1
- Address constipation/ileus, which is common in GBS patients 1
- Evaluate for dysphagia and provide nutritional support if necessary 1
Expected Outcomes for AMSAN
AMSAN is a severe variant with prolonged recovery compared to AIDP 5, 6:
- About 80% of GBS patients overall regain walking ability at 6 months 1, 2
- Mortality remains 3-10%, primarily from cardiovascular and respiratory complications 1, 2
- AMSAN patients may require prolonged mechanical ventilation with tracheostomy and have persistent neurological sequelae requiring long-term care 6
- Rehabilitation is crucial for optimal recovery 5
Special Considerations in Resource-Limited Settings
In low- and middle-income countries where AMSAN is more prevalent 3: