Myasthenia Gravis Management

Introduction

• Myasthenia gravis is a chronic autoimmune disorder that requires comprehensive management, including diagnostic tests such as the ice pack test, edrophonium (Tensilon) test, repetitive nerve stimulation, and single-fiber electromyography (SFEMG) 1, 2

Diagnosis

• Electrodiagnostic studies, including repetitive nerve stimulation and single-fiber EMG, should be performed to confirm the diagnosis, with single-fiber EMG considered the gold standard for diagnosis with >90% sensitivity for ocular MG 3, 1, 2
• A comprehensive workup for myasthenia gravis is recommended, including neurology consultation, antibody testing, electrodiagnostic studies, and chest imaging to evaluate for thymoma, with additional tests based on clinical presentation, as suggested by the American Academy of Neurology 3

Treatment Approach

• The American College of Neurology recommends starting treatment with pyridostigmine and adding corticosteroids, such as prednisone 1-1.5 mg/kg PO daily, for patients with more than mild disease, with a positive response rate of 66-85% to corticosteroids 3
• Pyridostigmine is recommended as the first-line medication for patients with myasthenia gravis, with a starting dose of 30 mg orally three times daily, which can be gradually increased to a maximum of 120 mg orally four times daily as tolerated based on symptoms, as recommended by the American College of Neurology 3, 1
• The maximum daily dose of pyridostigmine can be up to 600 mg daily for myasthenic symptoms, with 30 mg oral pyridostigmine corresponding to 1 mg IV or 0.75 mg neostigmine IM, according to the American College of Neurology 4
• For patients with inadequate response to pyridostigmine alone, corticosteroids, such as prednisone 0.5-1.5 mg/kg orally daily, may be added, with 66-85% of patients showing a positive response to corticosteroids 3, 1, 5
• Steroid-sparing agents, such as methotrexate, azathioprine, or mycophenolate mofetil, should be initiated concurrently with corticosteroids to minimize steroid exposure, with recommended dosing as follows:

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Crisis Management

• For myasthenic crisis, hospital admission and ICU monitoring are recommended, with treatment options including IVIG 2 g/kg over 5 days or plasmapheresis for 5 days, as suggested by the American College of Neurology 3

Medication Considerations

• The American College of Neurology advises avoiding medications that can worsen myasthenia, including β-blockers, IV magnesium, fluoroquinolones, aminoglycosides, and macrolides, due to their potential to exacerbate the disease 3
• Propofol, Sevoflurane, isoflurane, Fentanyl, remifentanil, Lidocaine, and bupivacaine are considered safe anesthetic agents for patients with myasthenia gravis, as recommended by the National Comprehensive Cancer Network 7
• Atracurium, mivacurium, and succinylcholine should be avoided in patients with myasthenia gravis, according to the National Comprehensive Cancer Network 7
• Rocuronium is preferred as it can be antagonized with sugammadex, as recommended by the National Comprehensive Cancer Network 7

Monitoring and Assessment

• Regular neurological assessments and pulmonary function tests, including negative inspiratory force (NIF) and vital capacity (VC), are essential for monitoring disease progression and response to treatment, with close monitoring and potential intervention recommended for patients with NIF -20 to -60 cm H₂O 3
• The following table summarizes the interpretation of NIF values:

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• Negative Inspiratory Force (NIF) measurements are essential for monitoring respiratory function in myasthenia gravis patients and should be routinely used to detect early respiratory compromise and guide treatment decisions during exacerbations, according to the American Thoracic Society and the American College of Chest Physicians 8

Thymoma and Thymectomy

• Patients with thymoma require special consideration, and approximately 30-50% of patients with thymomas have myasthenia gravis, as noted by the National Comprehensive Cancer Network 9
• Thymectomy is indicated for thymoma and may reduce symptoms in specific age-based and immune-based characteristics, with remission rates of approximately 11.6% reported after thymectomy in patients with thymoma or AChR antibody-positive generalized MG up to age 65 3, 1

Multidisciplinary Care

• A multidisciplinary team involving surgical, anesthesia, and perioperative medical teams should be involved in the care of patients with myasthenia gravis, as recommended by the National Comprehensive Cancer Network 7
• Regular follow-up with a neuromuscular specialist is necessary, along with genetic counseling for family planning, monitoring for disease progression, and adjustment of medications based on clinical response, as recommended by the American Academy of Neurology, with a strength of evidence based on clinical guidelines 10