Neuro-Ophthalmology
Neuro-Ophthalmology
What You'll Learn
- Pupil-involving CN III palsy: PComm aneurysm until proven otherwise — pupil fibers travel superficially on CN III, compressed by aneurysm before microvascular ischemia reaches them
- RAPD: localizes to optic nerve (or massive retinal disease) — NEVER caused by cataracts, refractive error, or media opacity
- INO: MLF lesion → ipsilateral adduction deficit + contralateral abducting nystagmus; young bilateral = MS, old unilateral = stroke
- GCA: start glucocorticoids BEFORE temporal artery biopsy. Use IV pulse methylprednisolone for threatened vision loss / cranial ischemia; high-dose oral prednisone is standard for active GCA without cranial ischemia (per 2021 ACR/VF). Jaw claudication is the most specific symptom.
- ONTT: low-dose oral prednisone alone increases optic neuritis recurrence — do not use. High-dose oral corticosteroids bioequivalent to IV methylprednisolone have similar short-term outcomes in typical ON (modern data).
- Horner syndrome + ipsilateral pain: carotid dissection until proven otherwise (3rd-order neuron)
- Visual field defects: more congruous = more posterior; macular sparing = occipital lobe (best explained by bilateral cortical representation + large cortical magnification of the macula; the classical "dual PCA/MCA blood supply" teaching is not well supported by anatomic data)
HighYield Pearls
- Pupil-involving CN III palsy: PComm aneurysm → urgent CTA/angiography; SAH risk — never call it microvascular until imaging is clean
- Painful Horner + neck pain: carotid dissection until proven otherwise → urgent CTA neck/MRA; apraclonidine reverses anisocoria to confirm Horner
- Suspected GCA: start glucocorticoids immediately BEFORE temporal artery biopsy — IV pulse methylprednisolone for threatened vision/cranial ischemia, high-dose oral prednisone for active GCA without cranial ischemia (2021 ACR/VF). Tocilizumab is steroid-sparing; fellow eye blinds within days if untreated
- Optic neuritis (ONTT): IV methylprednisolone speeds recovery and delays MS conversion at 2 yr; low-dose oral prednisone alone (as used in ONTT) INCREASES recurrence — do not use. High-dose oral corticosteroids bioequivalent to IV MP have similar short-term outcomes.
- Atypical ON (bilateral, severe, painless, recurrent, NLP) → send AQP4-IgG and MOG-IgG; treat as NMOSD until proven otherwise (plasma exchange if steroid-refractory)
- Bilateral INO in a young patient: MS until proven otherwise; unilateral INO in older vasculopath → brainstem stroke
- Vertical supranuclear gaze palsy + preserved VOR (doll’s eyes): PSP — downgaze affected first; pair with axial rigidity and early falls
- Spasmus nutans (child: head bobbing + nystagmus + torticollis) → MRI to rule out chiasm/hypothalamic glioma — do NOT call it benign without imaging
- IIH with vision threat: escalate beyond acetazolamide — ONSF, CSF shunt, or venous sinus stenting; transient visual obscurations & enlarging blind spot are red flags
- Foster Kennedy syndrome (unilateral optic atrophy + contralateral papilledema) → frontal mass (olfactory groove meningioma) until imaged
- Ocular myasthenia: fatigable ptosis + variable diplopia, normal pupils; ice pack test improves ptosis; check anti-AChR and screen for thymoma
🔍 Quick ReferenceClinical · Visual field / pupils / gaze · Workup / treatment
Clinical phenotype
- Painful monocular vision loss + red desaturation in a young woman → optic neuritis (MS)
- Jaw claudication + scalp tenderness + new headache age >50 + chalky-white swollen disc → arteritic AION (GCA)
- Vasculopath wakes with altitudinal field defect + crowded "disc at risk" → NAION
- Young male, bilateral subacute painless central vision loss + telangiectatic peripapillary microangiopathy + maternal inheritance → LHON (m.11778G>A)
- Down-and-out eye with dilated pupil after sudden headache → PComm aneurysm CN III palsy
- Vertical diplopia worse going downstairs + compensatory head tilt → CN IV (trochlear) palsy
- Proptosis + lid lag + EOM enlargement sparing tendon insertions → thyroid (Graves) ophthalmopathy
- Fatigable ptosis + Cogan twitch + ice-pack improvement → ocular myasthenia gravis
- Obese young woman + headache + pulsatile tinnitus + transient visual obscurations → idiopathic intracranial hypertension
Pupil / VF / gaze findings
- RAPD (Marcus-Gunn pupil) + central scotoma → optic nerve lesion (ON/AION)
- Mild ptosis + miosis + anhidrosis → Horner syndrome (painful + neck → carotid dissection)
- Dilated pupil + sluggish to light + brisk to near + slow redilation + tendon areflexia → Adie tonic pupil (Holmes-Adie)
- Small irregular pupils that accommodate but do not react ("prostitute pupil") → Argyll Robertson (neurosyphilis / DM)
- Ipsilateral adduction failure + contralateral abducting nystagmus + preserved convergence → INO (MLF lesion)
- Ipsilateral conjugate gaze palsy + ipsilateral INO → one-and-a-half syndrome (paramedian pontine + MLF)
- Vertical supranuclear gaze palsy with intact VOR/doll’s eyes → PSP
- Homonymous hemianopia with macular sparing → occipital cortex (PCA) stroke
- "Pie in the sky" superior quadrantanopia → temporal lobe (Meyer loop); "pie on the floor" → parietal optic radiations
- Bitemporal hemianopia → chiasm (pituitary adenoma / craniopharyngioma); junctional scotoma → anterior chiasm / distal optic nerve
- Downbeat nystagmus → cervicomedullary junction (Chiari, MS, lithium/AED toxicity); upbeat → brainstem
- Pendular nystagmus + palatal tremor → oculopalatal myoclonus (hypertrophic olivary degeneration / Mollaret triangle)
- See-saw nystagmus → parasellar / chiasmal lesion; periodic alternating nystagmus → cerebellar (nodulus/uvula)
- Unilateral optic atrophy + contralateral papilledema → Foster Kennedy syndrome (frontal mass)
- Cortical blindness + denial/confabulation → Anton syndrome (bilateral occipital); simultanagnosia + optic ataxia + ocular apraxia → Balint (bilateral parieto-occipital watershed)
Workup / treatment
- ESR ≥50, CRP elevated, platelets ≥400K in patient >50 with new visual loss → start glucocorticoids immediately (IV pulse methylprednisolone if vision threatened / cranial ischemia; otherwise high-dose oral prednisone), then temporal artery biopsy
- Apraclonidine reverses anisocoria (dilates the miotic pupil) → confirms Horner syndrome
- Low-dose pilocarpine (0.125%) constricts a dilated tonic pupil → denervation supersensitivity — Adie pupil
- AQP4-IgG serum (cell-based assay) → NMOSD; MOG-IgG serum → MOGAD; oligoclonal bands → MS
- MRI orbits with fat suppression + gadolinium → optic neuritis (short-segment enhancement = MS; long-segment/perineural = MOGAD; chiasmal = NMOSD)
- LP opening pressure >25 cm H₂O with normal CSF in obese young woman → IIH → acetazolamide + topiramate + weight loss; ONSF / CSF shunt / venous stenting for vision threat
- Empty sella, posterior globe flattening, distended optic nerve sheath, transverse sinus stenosis on MRV → IIH imaging signature
- Pupil-involving CN III palsy → urgent CTA / catheter angiogram for PComm aneurysm
- Anti-AChR / anti-MuSK + chest CT for thymoma; ice pack + edrophonium (historical) → ocular myasthenia workup; treat with pyridostigmine ± steroids
- RPR/VDRL + FTA-ABS + CSF VDRL → Argyll Robertson / neurosyphilis
- Mitochondrial DNA testing (m.11778G>A, m.14484T>C, m.3460G>A) → LHON; idebenone trialed
Optic Neuritis
Typical vs Atypical Optic Neuritis
| Feature | Typical ON (MS-associated) | Atypical ON |
|---|---|---|
| Age | 20–45 years | Any age (children, >50) |
| Pain | Periorbital, worse with eye movement (92%) | May be painless or severe |
| Vision loss | Mild–moderate; central scotoma | Severe (NLP possible in NMOSD) |
| Laterality | Unilateral | Bilateral (NMOSD, MOGAD, sarcoid) |
| Disc appearance | 66% retrobulbar (normal disc); 33% disc edema | Disc edema more common (MOGAD, NMOSD) |
| Recovery | Good (>90% recover to 20/40 by 1 year) | Poor recovery (NMOSD); good in MOGAD |
| MRI orbits | Short-segment enhancement (<50% nerve length) | Long-segment or perineural enhancement |
| Key associations | MS (50% develop MS within 15 yr) | NMOSD, MOGAD, sarcoid, syphilis, lupus |
MS vs NMOSD vs MOGAD Optic Neuritis
| Feature | MS | NMOSD (AQP4+) | MOGAD |
|---|---|---|---|
| Severity | Mild–moderate | Severe (often ≤20/200) | Moderate–severe |
| Bilateral | Rare (unilateral) | Simultaneous or sequential bilateral | Often bilateral (especially children) |
| Disc edema | Uncommon (retrobulbar) | Common | Very common (prominent edema) |
| Enhancement pattern | Short segment, no perineural | Posterior/chiasmal involvement | Anterior, long segment, perineural sheath |
| Recovery | Excellent | Poor without treatment | Excellent (often complete) |
| Recurrence | Common | Very common (attack-driven damage) | Common; relapsing form exists |
| OCT (RNFL) | Mild thinning | Severe thinning | Variable |
| Antibody | Oligoclonal bands (CSF) | AQP4-IgG (serum) | MOG-IgG (serum) |
Treatment — ONTT Key Findings
- IV methylprednisolone (3 days) → oral taper: faster recovery; no difference in final visual outcome at 1 year
- Low-dose oral prednisone alone (as used in ONTT): INCREASED recurrence rate — should not be used. High-dose oral corticosteroids bioequivalent to IV methylprednisolone have similar short-term outcomes in typical optic neuritis.
- Observation: acceptable for mild cases; equivalent long-term visual outcome to IV steroids
- MS risk: ≥1 brain MRI lesion at presentation → 72% MS risk at 15 yr; 0 lesions → 25%
💎 Board Pearl
- ONTT: low-dose oral prednisone alone increases recurrence — the #1 tested fact from this trial. High-dose oral corticosteroids bioequivalent to IV MP are acceptable (similar short-term outcomes).
- RAPD is the hallmark of optic neuritis — if absent, reconsider the diagnosis
- Uhthoff phenomenon: transient visual worsening with heat/exercise (demyelinated nerve conducts worse when warm)
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