12-phase flow (12)

1. 1FRAME
   Frame this as a TYPICAL-vs-ATYPICAL optic-neuritis pivot, not a single disease. Typical = young, unilateral, painful, partial, normal/mildly swollen disc, demyelinating/MS-associated, ONTT-governed. Atypical (severe/NLP, bilateral simultaneous, painless, severe disc swelling/haemorrhage, no recovery, age extremes, recurrent) mandates AQP4/MOG serology + NMOSD/MOGAD/infectious/granulomatous/paraneoplastic workup. The hard guardrail set up here: IVMP speeds recovery but oral prednisone ALONE is contraindicated (ONTT — Beck NEJM 1992 PMID 1734247). Chronic disease ownership is routed OUT by engine_id.
   advance: typical/atypical framing set; ONTT oral-prednisone-alone guardrail foregrounded
2. 2ENTRY
   Recognise the entry pattern: subacute monocular loss + pain-on-eye-movement + dyschromatopsia (typical triad), OR a severe/bilateral/painless/non-recovering optic neuropathy (atypical), OR a known-demyelinating relapse, OR an age-extreme presentation. Capture pain-on-movement and laterality/simultaneity up front (the first pivot binaries) (Beck ONTT NEJM 1992 PMID 1734247; Petzold Lancet Neurol 2022 PMID 36179757).
   inputs: pain_on_eye_movement, laterality_and_simultaneity
   actions: workup.acute_vision_loss
   advance: entry pattern present; pain-on-movement + laterality/simultaneity recorded
3. 3CONTEXT
   Build the pretest priors: age (15-50 typical; pediatric MOGAD/ADEM; ≥50 atypical → exclude arteritic AION/GCA + compressive), visual-acuity nadir (profound loss is atypical and raises the AQP4-NMOSD prior), demyelinating/autoimmune history (NMOSD/MOGAD relapse reframes therapy), and infectious/granulomatous/paraneoplastic exposures. This phase assigns the typical-demyelinating vs NMOSD vs MOGAD vs AION vs compressive priors.
   inputs: visual_acuity_severity_nadir, age, demyelinating_or_autoimmune_history, infectious_granulomatous_paraneoplastic_exposure
   actions: workup.ms_flare
   advance: typical-vs-atypical priors assigned by age × pain × laterality × severity × history
4. 4RED_FLAGS
   Can-not-miss screen: (1) age ≥50 + GCA cluster (headache/jaw claudication/scalp tenderness/PMR) → arteritic AION mimics ON; empiric high-dose steroid then route to rheum.giant-cell-arteritis.core.v1, do NOT delay for ESR/biopsy; (2) bilateral severe simultaneous or rapidly sequential loss → NMOSD/MOGAD emergency aggressive IVMP ± early PLEX; (3) progressive painless loss with proptosis/optociliary shunt/headache → compressive or infiltrative — urgent neuro-imaging not steroid; (4) recent vaccination/infection in a child → MOGAD/ADEM. Recognised and started here; chronic ownership routed OUT.
   inputs: gca_symptom_cluster_if_age_over_50
   actions: workup.gca_temporal_arteritis, calc.news2
   advance: GCA, bilateral-severe NMOSD/MOGAD, compressive, and pediatric-MOGAD red flags screened and time-critical action initiated
5. 5INITIAL_WORKUP
   Bedside afferent exam: visual acuity each eye, RAPD (the key localiser; absent in functional/symmetric-bilateral), colour vision/red desaturation, confrontation + formal fields (central/cecocentral scotoma typical; altitudinal favours AION; bitemporal favours chiasmal/compressive), dilated fundus (normal retrobulbar ~2/3 vs mild papillitis vs SEVERE swelling/peripapillary haemorrhage = atypical). STAT ESR/CRP if ≥50 (GCA — never delays empiric steroid). CBC + inflammatory + metabolic baseline.
   inputs: rapd_relative_afferent_pupillary_defect, dyschromatopsia_red_desaturation, disc_appearance, esr_crp_if_age_over_50
   actions: workup.acute_red_eye, panel.cbc, panel.inflammation, panel.cmp, calc.nihss
   advance: afferent exam + fields + fundus done; GCA inflammatory labs sent if ≥50
6. 6BRANCHING_WORKUP
   Gadolinium MRI brain + orbits is the pivotal test: optic-nerve enhancement length/location (long/posterior/chiasmal → NMOSD; long anterior + perineural/optic-sheath → MOGAD; short/anterior + ≥1 periventricular Dawson-finger white-matter lesion → typical MS-risk demyelinating) and the ONTT 15-year MS-risk stratification (0 lesions ~25% vs ≥1 lesion ~72% MS at 15 y — Beck Arch Neurol 2008 PMID 18541792). If ANY atypical feature: send serum AQP4-IgG + MOG-IgG (cell-based assay), CSF (cells/protein/OCB/infectious panel), and a targeted infectious/granulomatous/paraneoplastic panel (RPR-TPPA, ACE/CXR for sarcoid, Bartonella/TB/Lyme/HIV, paraneoplastic CRMP-5/anti-CV2 if indicated). Temporal-artery biopsy if GCA suspected (never gates steroid).
   inputs: mri_brain_orbits_with_contrast, aqp4_igg_serum, mog_igg_serum, csf_analysis
   actions: workup.ms_flare, workup.acute_headache, panel.csf
   advance: MRI pattern + MS-risk band assigned; AQP4/MOG/CSF/infectious panel sent if atypical
7. 7DIFFERENTIAL
   Terminal differential with named pivot findings: TYPICAL demyelinating ON (young + unilateral + pain-on-movement + dyschromatopsia + RAPD + normal/mild disc + good recovery pivot) vs AQP4-NMOSD ON (severe/NLP + bilateral/recurrent + long posterior/chiasmal enhancement + AQP4-IgG+ + poor recovery pivot) vs MOGAD ON (severe but recovers + bilateral + SEVERE disc swelling/perineural enhancement + MOG-IgG+ + steroid-responsive/steroid-dependent + pediatric pivot) vs arteritic AION/GCA (≥50 + pallid disc edema + jaw claudication + ↑ESR/CRP/platelets pivot — route to rheum.giant-cell-arteritis.core.v1) vs non-arteritic AION (sudden painless + altitudinal field + small crowded "disc at risk" + vasculopath + normal ESR pivot) vs papilloedema (BILATERAL disc swelling + preserved acuity early + headache/pulsatile tinnitus + raised ICP pivot) vs CRAO/CRVO (retinal not optic-nerve fundus signs pivot — route to ophtho.acute-vision-loss.core.v1) vs compressive optic neuropathy (slowly progressive painless + optociliary shunt/proptosis + mass on MRI pivot) vs toxic/nutritional (bilateral painless symmetric + cecocentral + B12/folate/ethambutol/methanol pivot) vs LHON (young male + bilateral sequential painless + telangiectatic disc + mtDNA pivot) vs functional (normal RAPD/fundus/OCT/VEP + non-physiologic fields pivot — diagnosis of exclusion).
   advance: single best diagnosis selected; typical-vs-atypical pivot explicitly resolved; arteritic-AION pivot explicitly excluded if ≥50
8. 8RISK_STRATIFICATION
   Stratify by (a) MS-conversion risk — ONTT MRI-lesion count drives the 15-year MS probability and the DMT discussion (0 lesions ~25% vs ≥1 ~72% — Beck Arch Neurol 2008 PMID 18541792); (b) attack severity — profound loss / bilateral / AQP4-positive NMOSD → aggressive IVMP + early-PLEX threshold (Weinshenker Ann Neurol 1999 PMID 10589540); (c) relapse risk — MOGAD/NMOSD seropositivity predicts a relapsing course needing chronic immunotherapy (Jarius J Neuroinflammation 2016 PMID 27793206). Systemic-instability overlay (NEWS2) for an unwell atypical/infectious presentation.
   inputs: mri_brain_orbits_with_contrast, visual_acuity_severity_nadir
   actions: calc.news2
   advance: MS-risk band + attack-severity tier + relapse-risk tier assigned
9. 9TREATMENT
   ONTT-governed, typical/atypical-stratified, route-OUT-after-acute: (1) Typical demyelinating ON → IV methylprednisolone 1 g/day × 3-5 d SPEEDS recovery but does NOT change final acuity; oral prednisone ALONE is CONTRAINDICATED (↑recurrence vs placebo — Beck ONTT NEJM 1992 PMID 1734247); steroid is optional (recovery occurs without it). (2) Post-IVMP oral prednisone TAPER is acceptable only as a taper, never as standalone therapy. (3) Severe / bilateral / AQP4-NMOSD / steroid-refractory attack → plasma exchange (Weinshenker Ann Neurol 1999 PMID 10589540; ~76-83% objective response in refractory NMOSD — Zhang Ann Palliat Med 2021 PMID 33752428). (4) MOGAD → steroid-responsive but steroid-dependent — slow taper, do NOT stop abruptly (Jarius J Neuroinflammation 2016 PMID 27793206). (5) Chronic immunotherapy / DMT initiation is NON-PHARM ROUTED — MS DMT via neuro.multiple-sclerosis.core.v1, AQP4/MOG chronic therapy via neuro.nmosd-mogad.core.v1 (do NOT start MS DMTs in AQP4-NMOSD — can worsen). Symptomatic: analgesia for movement pain. Pregnancy/renal gating applied.
   inputs: pregnancy_or_postpartum, creatinine, visual_acuity_severity_nadir
   advance: acute therapy decided per typical/atypical (oral-prednisone-alone guardrail enforced); PLEX considered if severe/NMOSD; chronic ownership routed by engine_id
10. 10DISPOSITION
    Typical mild ON → outpatient with rapid neuro-ophthalmology + MRI; observation/IVMP infusion as needed. Severe / bilateral / NMOSD / steroid-refractory → admit for IVMP ± PLEX + urgent neurology/neuro-immunology. Atypical infectious/granulomatous/paraneoplastic → admit for targeted workup. ≥50 with GCA suspicion → admit, empiric steroid, route to rheum.giant-cell-arteritis.core.v1. Compressive lesion on MRI → urgent neurosurgery/ophthalmology. Functional vision loss → reassurance + outpatient neuro-ophthalmology after organic exclusion.
    inputs: visual_acuity_severity_nadir
    advance: disposition + routed engine_id documented
11. 11MONITORING
    Typical ON: serial acuity/colour/fields — most recover useful acuity by months even WITHOUT steroid (ONTT — Beck Arch Ophthalmol 1993 PMID 8512477); IVMP only changes the speed. NMOSD/MOGAD: visual recovery is often worse and incomplete — vigilance for the next attack and the fellow eye (Jarius J Neuroinflammation 2016 PMID 27793206). Failure to recover at the expected window is itself an ATYPICAL flag → re-open the AQP4/MOG/infectious/compressive workup. Steroid-pulse monitoring (glucose, BP, mood, infection). ESR/CRP trend if GCA on steroid.
    inputs: visual_acuity_severity_nadir
    actions: panel.inflammation
    advance: recovery trajectory tracked; non-recovery re-triggers atypical workup; steroid-pulse safety monitored
12. 12FOLLOWUP
    The long-tail deliverable is RISK-STRATIFIED DISEASE-MODIFYING ROUTING: (1) Typical ON + ≥1 MRI lesion → high 15-year MS risk → MS DMT discussion via neuro.multiple-sclerosis.core.v1 (Beck Arch Neurol 2008 PMID 18541792). (2) AQP4-NMOSD → lifelong chronic immunotherapy (rituximab/eculizumab/inebilizumab/satralizumab class — routed) and explicit MS-DMT avoidance via neuro.nmosd-mogad.core.v1 (Wingerchuk Neurology 2015 PMID 26092914). (3) MOGAD relapsing/steroid-dependent → chronic immunotherapy + slow steroid taper via neuro.nmosd-mogad.core.v1 (Banwell Lancet Neurol 2023 PMID 36706773). (4) Reciprocal handoff with ophtho.acute-vision-loss.core.v1 (the upstream triage engine). Low-vision rehabilitation for incomplete recovery; relapse-warning education.
    inputs: demyelinating_or_autoimmune_history, mri_brain_orbits_with_contrast
    advance: MS-risk-stratified DMT / NMOSD-MOGAD chronic-immunotherapy ownership handed to the routed engine_id; reciprocal acute-vision-loss handoff documented