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neuro.gbs-aman.v1

Guillain-Barré Syndrome — AMAN (acute motor axonal)

neurologyacuteadultpediatricacuteinpatient
Start encounter →Print handoutPRODUCTION

Phase C shard-3 neuro wave-12 recovery (2026-05-15): authored at SCAFFOLDED — no AMAN-specific workup in clinical-tools-registry.ts (only workup.gbs registered for the shared GBS-spectrum pathway). AMAN = ~15-20% Western GBS, much higher in Asia/Central/South America; pure motor axonal variant with preserved sensation; strong post-Campylobacter association via molecular mimicry (anti-GM1/GD1a vs LOS). 5 setting playbooks: home (EMS recognition + preserved sensation pivot from AIDP) → ed (Brighton + EGRIS + LP + axonal NCS + anti-GM1/GD1a + stool Campylobacter) → icu (20-30-40 rule + autonomic + early IRF planning) → inpatient (extended rehab) → outpatient (longer trajectory + CIDP surveillance). 7 severity_triggers: pure_motor_axonal_NCS, post_campylobacter, anti-GM1_GD1a_positive, pediatric_aman_high, rapidly_progressive_quadriparesis, slower_recovery_axonal, preserved_sensation_pivot. 6 PMID evidence anchor: Hughes Cochrane IVIG (25238327), Raphael Cochrane PLEX (22786475), van Doorn 2011 (25023340), Fokke Brighton criteria validation Brain 2013 (24163275), EGRIS Walgaard Ann Neurol 2010 (20517939), Yuki NEJM 2012 GBS review (Campylobacter mimicry) (22694000). All marked NEEDS_SOURCE_REVIEW. IVIG vs PLEX equivalent per Hughes Cochrane 2014 — same dose as AIDP. Steroids NOT effective. Avoid succinylcholine. Key clinical pivot: PRESERVED SENSATION distinguishes AMAN from AIDP at bedside; document explicitly in exam. Schema-blocked: calc.egris, calc.megos, calc.brighton, calc.mrc_sum_score, calc.gbs_disability_scale, workup.aman_ncs_pattern, workup.anti_GM1_GD1a_panel, workup.stool_campylobacter_culture — surfaced in depth bundle. Siblings: neuro.gbs-aidp.v1 (same-commit), neuro.gbs-miller-fisher.v1 (same-commit), neuro.gbs.core.v1 (parent PRODUCTION), neuro.mg-crisis.core.v1 (real engine), neuro.transverse-myelitis.v1 (real engine).

Entry points (6)

  • symptom
    Pure motor ascending symmetric weakness with PRESERVED sensation; areflexia (van Doorn 2011 PMID 25023340)
    pure_motor_ascending_weakness
  • history
    Preceding Campylobacter jejuni gastroenteritis (diarrhea) 1-3 wk prior — strong AMAN association (Yuki 2007 PMID 22694000)
    post_campylobacter_diarrhea
  • imaging
    NCS pure motor axonal pattern: reduced CMAP amplitudes WITHOUT slowing; preserved sensory NCS (van Doorn 2011 PMID 25023340)
    ncs_axonal_pattern_pure_motor
  • lab_abnormality
    Anti-GM1 / anti-GD1a antibodies positive (~60-80% in AMAN) (Yuki 2007 PMID 22694000)
    anti_GM1_GD1a_positive
  • symptom
    Rapidly progressive quadriparesis within 24-48 h (AMAN often more rapid than AIDP) (IGOS Doets 2018)
    rapidly_progressive_quadriparesis
  • symptom
    Pediatric AMAN — high prevalence in Asian children (post-Campylobacter outbreaks) (van Doorn 2011)
    pediatric_aman_endemic

Required inputs (13)

  • agerequired
    demographic • used at CONTEXT
    Age + geographic/ethnic context informs AMAN likelihood (van Doorn 2011 PMID 25023340)
  • preceding_diarrhea_1_3wkrequired
    history • used at CONTEXT
    Campylobacter gastroenteritis 1-3 wk prior strong AMAN risk factor (Yuki 2007 PMID 22694000)
  • pure_motor_pattern_preserved_sensationrequired
    symptom • used at FRAME
    Pure motor pattern (preserved sensation) pivots AMAN from AIDP (van Doorn 2011)
  • mrc_sum_scorerequired
    symptom • used at RISK_STRATIFICATION
    MRC sum 0-60 quantifies severity + tracks progression (AAN 2012)
  • fvc_nifrequired
    vital • used at RED_FLAGS
    20-30-40 rule — FVC <20 mL/kg or NIF magnitude <30 cmH2O triggers elective intubation (AAN 2012)
  • hrrequired
    vital • used at RED_FLAGS
    Autonomic — paroxysmal tachy/brady (IGOS Doets 2018)
  • sbprequired
    vital • used at RED_FLAGS
    Autonomic BP swings (IGOS Doets 2018)
  • csf_protein_cell_countrequired
    lab • used at INITIAL_WORKUP
    Albumino-cytologic dissociation — present in ~50% wk 1, 75% wk 2 (AAN 2012)
  • anti_GM1_GD1a_panelrequired
    lab • used at BRANCHING_WORKUP
    Anti-GM1 / GD1a in ~60-80% AMAN; supports diagnosis (Yuki 2007 PMID 22694000)
  • stool_campylobacter_culture
    lab • used at BRANCHING_WORKUP
    Stool Campylobacter culture / PCR — confirms preceding infection (Yuki 2007)
  • iga_levelrequired
    lab • used at INITIAL_WORKUP
    IgA deficiency screen before IVIG (anaphylaxis risk) (EAN/PNS 2023)
  • mri_spine_with_contrastrequired
    imaging • used at INITIAL_WORKUP
    Exclude transverse myelitis / cord compression (NICE 2024)
  • ncs_emg_axonal_pure_motorrequired
    imaging • used at BRANCHING_WORKUP
    Reduced CMAP without slowing + preserved sensory NCS confirms AMAN (van Doorn 2011 PMID 25023340)

12-phase flow (12)

  1. 1FRAME
    Confirm AMAN — pure motor ascending areflexic weakness + preceding Campylobacter + axonal NCS pattern (Brighton 2011 PMID 24163275; van Doorn 2011 PMID 25023340)
    inputs: pure_motor_pattern_preserved_sensation
    advance: AMAN-compatible pattern; cord compression excluded
  2. 2ENTRY
    Pure motor ascending areflexic weakness + post-Campylobacter (Yuki 2007 PMID 22694000)
    inputs: age, preceding_diarrhea_1_3wk
    advance: AMAN entry features captured
  3. 3CONTEXT
    Vitals (FVC/NIF, HR, BP), bulbar exam, autonomic screen, geographic/ethnic context (EAN/PNS 2023)
    inputs: fvc_nif, hr, sbp, mrc_sum_score
    advance: Neuromuscular + autonomic baseline complete
  4. 4RED_FLAGS
    Respiratory failure (FVC <20, NIF magnitude <30), bulbar airway, autonomic instability → ICU + intubation (AAN 2012)
    inputs: fvc_nif, hr, sbp
    actions: workup.gbs
    advance: Airway secured/stable + ICU allocated
  5. 5INITIAL_WORKUP
    CSF, MRI spine with gad, CBC/CMP/LFT, IgA, pregnancy test, HIV (EAN/PNS 2023)
    inputs: csf_protein_cell_count, mri_spine_with_contrast, iga_level
    actions: panel.cbc, panel.renal, panel.lft, panel.coag
    advance: CSF + MRI back; IgA documented pre-IVIG
  6. 6BRANCHING_WORKUP
    NCS/EMG axonal pure motor pattern + anti-GM1/GD1a panel + stool Campylobacter (Yuki 2007 PMID 22694000)
    inputs: ncs_emg_axonal_pure_motor, anti_GM1_GD1a_panel
    advance: AMAN electrodiagnostic + serology confirmed
  7. 7DIFFERENTIAL
    AMAN (this engine) vs AIDP (route gbs-aidp; demyelinating + sensory) vs MFS (route gbs-miller-fisher) vs AMSAN (encoded in parent severity) vs botulism vs tick paralysis (van Doorn 2011)
    advance: AMAN phenotype confirmed
  8. 8RISK_STRATIFICATION
    EGRIS ventilation risk; mEGOS outcome (axonal pattern → slower recovery prognostic); MRC sum + GBS disability scale (Walgaard 2009 PMID 20517939; Walgaard 2011 PMID 21403108)
    inputs: mrc_sum_score
    actions: calc.nihss
    advance: EGRIS + disability + axonal-loss prognosis documented
  9. 9TREATMENT
    IVIG 0.4 g/kg/d × 5 d OR PLEX 5 sessions q48h (equivalent dose to AIDP per Hughes Cochrane 2014 PMID 25238327); do NOT combine; NO steroids; DVT prophylaxis; neuropathic pain
    inputs: iga_level
    advance: Immunomodulation started + supportive bundle
  10. 10DISPOSITION
    ICU if EGRIS ≥5 / FVC <20 / rapidly progressive; neuro ward otherwise; serial FVC q4-6h (NICE 2024)
    inputs: fvc_nif
    advance: Level-of-care decision made
  11. 11MONITORING
    q4-6h FVC/NIF, continuous ECG, MRC + disability score; AMAN has slower recovery — extended rehab planning (Walgaard 2011 PMID 21403108)
    inputs: fvc_nif, mrc_sum_score
    actions: panel.cbc
    advance: Monitoring plan + extended rehab anticipation documented
  12. 12FOLLOWUP
    Neuro rehab (often longer than AIDP due to axonal loss), CIDP surveillance, psychology (NICE 2024)
    advance: Extended rehab + neurology follow-up scheduled