What is the recommended treatment for acute ocular Myasthenia Gravis (MG)?

Treatment of Acute Ocular Myasthenia Gravis

Start pyridostigmine immediately at 30 mg orally three times daily and gradually increase to a maximum of 120 mg four times daily as tolerated, then escalate to prednisone 0.5-1 mg/kg daily if symptoms persist or interfere with activities of daily living. 1, 2

Initial Symptomatic Treatment

• Begin pyridostigmine 30 mg orally three times daily as first-line therapy for all patients with ocular MG, regardless of severity 1, 2, 3
• Gradually titrate upward based on symptom response to a maximum dose of 120 mg four times daily (total 480 mg/day) 1, 2
• Expect approximately 50% of patients with ocular myasthenia to show minimal response to pyridostigmine alone, necessitating escalation to immunosuppressive therapy 1, 2

Critical pitfall: Do not rely solely on pyridostigmine for more than 1 month if symptoms persist, as ocular symptoms are highly variable and not readily remedied with symptomatic treatment alone 1, 2

Escalation to Corticosteroids

If symptoms interfere with activities of daily living or persist despite adequate pyridostigmine dosing, add prednisone 0.5-1 mg/kg orally daily (typically 50-60 mg for most adults) 4, 1, 5

• Corticosteroids demonstrate superior efficacy with 66-85% positive response rates compared to pyridostigmine's 50% response rate 1, 2
• In the highest quality study, prednisone 50-60 mg daily resolved primary gaze diplopia in 73.5% of patients, downgaze diplopia in 75.5%, and unilateral ptosis in 85.7% at 1 month, with benefits persisting for at least 2 years 5
• Increase prednisone dose gradually over 5 days to target dose to minimize risk of precipitating myasthenic crisis 6, 5
• After achieving symptom control, gradually taper to the lowest effective dose (typically 10 mg or less) 5
• Begin steroid taper 3-4 weeks after initiation based on symptom improvement 4

Essential Diagnostic Workup (Perform Concurrently)

• Measure acetylcholine receptor (AChR) antibodies and anti-striated muscle antibodies (positive in 50% of purely ocular MG) 1, 2
• If AChR antibodies are negative, test for muscle-specific kinase (MuSK) and lipoprotein-related protein 4 (LRP4) antibodies 4, 2
• Obtain CT chest with contrast to evaluate for thymoma (occurs in 10-20% of AChR-positive patients) 2
• Perform pulmonary function testing with negative inspiratory force (NIF) and vital capacity (VC) to establish baseline respiratory function 4, 2
• Consider single-fiber electromyography (>90% sensitivity for ocular MG) or repetitive nerve stimulation if diagnosis uncertain 2

Medications to Avoid Immediately

Review and discontinue these medications that can precipitate myasthenic crisis: 4, 1, 2

• β-blockers
• IV magnesium (absolutely contraindicated)
• Fluoroquinolones
• Aminoglycosides
• Macrolide antibiotics

Steroid-Sparing Agents for Refractory Cases

• Add azathioprine if high steroid doses are required or if steroids are contraindicated 2, 7
• Consider mycophenolate as an alternative steroid-sparing agent 6
• For severe refractory cases in AChR-positive patients, efgartigimod alfa-fcab is FDA-approved 2

Monitoring and Follow-up

• Assess respiratory function regularly, as 50-80% of patients with initial ocular symptoms develop generalized myasthenia within a few years 1, 2
• Schedule follow-up evaluations at 1,3-6,12, and 24 months to monitor diplopia, ptosis, and ocular motor deviation 5
• Expect recurrences in approximately 50% of prednisone-responsive patients, requiring dose adjustments 5
• Collaboration between an experienced ophthalmologist and neurologist is necessary for optimal management 1, 2

Adjunctive Non-Pharmacologic Options

• Consider occlusive devices, prisms, or eyelid supports for symptomatic relief while awaiting medication response 6
• Reserve strabismus surgery or eyelid elevation surgery only after disease stabilization, typically requiring 2-3 years of medical treatment 1, 2