Myasthenia Gravis Diagnosis and Treatment

Clinical Presentation

Myasthenia gravis is characterized by fatigable or fluctuating muscle weakness that typically affects proximal more than distal muscles, with ocular and bulbar involvement being common presenting features that can progress to potentially life-threatening respiratory compromise 1
Proximal muscle weakness is more pronounced than distal weakness in patients with myasthenia gravis 1
Bilateral presentation is common in myasthenia gravis, although weakness can be asymmetrical 1
Ptosis (drooping eyelids) and diplopia (double vision) from extraocular muscle weakness are common ocular manifestations of myasthenia gravis 1
Dysarthria (slurred speech), dysphagia (difficulty swallowing), facial weakness, and neck weakness are common bulbar manifestations of myasthenia gravis 1
Respiratory muscle weakness can lead to respiratory insufficiency or failure in patients with myasthenia gravis 1

The Myasthenia Gravis Foundation of America (MGFA) classifies myasthenia gravis into five classes: Class I (ocular MG only), Class II (mild generalized weakness), Class III (moderate generalized weakness), Class IV (severe generalized weakness), and Class V (myasthenic crisis requiring intubation) 1

Acetylcholine receptor (AChR) and antistriated muscle antibodies in blood are used to diagnose myasthenia gravis 2, 3, 4
If AChR antibodies are negative, consider muscle-specific kinase and lipoprotein-related 4 antibodies to diagnose myasthenia gravis 3, 4
Pulmonary function assessment with negative inspiratory force (NIF) and vital capacity (VC) is used to evaluate respiratory involvement in myasthenia gravis 2, 3, 4
Electrodiagnostic studies, including neuromuscular junction testing with repetitive stimulation and/or jitter studies, are used to diagnose myasthenia gravis 2, 3, 4
Ice pack test for ocular symptoms is highly specific for myasthenia gravis 5

Pyridostigmine (acetylcholinesterase inhibitor) is a first-line treatment for myasthenia gravis, starting at 30 mg orally three times daily and gradually increasing to a maximum of 120 mg orally four times daily as tolerated 2, 3, 4
Corticosteroids are used as a second-line treatment for moderate to severe myasthenia gravis symptoms 2, 3, 4
Intravenous immunoglobulin (IVIG) 2 g/kg IV over 5 days or plasmapheresis for 5 days are used to treat severe myasthenia gravis (Grade 3-4) 2, 3, 4

β-blockers, IV magnesium, fluoroquinolones, aminoglycosides, and macrolides should be avoided in patients with myasthenia gravis due to potential exacerbation of symptoms 2, 3, 4
Frequent pulmonary function assessment and daily neurologic review are necessary for patients with generalized myasthenia gravis 2, 3, 4
50-80% of patients who initially present with ocular symptoms may progress to generalized myasthenia gravis 1
ICPi-associated myasthenia gravis may be monophasic and may not require additional corticosteroid-sparing agents 2, 3, 4

Electrodiagnostic studies, including single-fiber electromyography, are essential for diagnosing Myasthenia Gravis, with a positivity rate of over 90% in patients with ocular MG, according to the American Academy of Ophthalmology 6, 7
Repetitive nerve stimulation testing is less sensitive, with a positivity rate of only one-third of patients with ocular MG, as reported by the American Academy of Ophthalmology 6, 7

About half of patients with strabismus-associated myasthenia show minimal response to pyridostigmine, as noted by the American Academy of Ophthalmology 6
Corticosteroids are used as second-line treatment for moderate to severe symptoms, with 66-85% of patients showing a positive response, according to the American Academy of Ophthalmology 6
Immunosuppressive therapy with azathioprine is effective as a steroid-sparing agent, as reported by the American Academy of Ophthalmology 6
Efgartigimod alfa-fcab has recently been FDA approved for patients who test positive for anti-acetylcholine receptor antibodies, as noted by the American Academy of Ophthalmology 6
Thymectomy is indicated in all cases with thymoma and may substantially reduce symptoms in certain subpopulations, according to the American Academy of Ophthalmology 6, 8

Reduction of diplopia and strabismus is a key goal of management, as reported by the American Academy of Ophthalmology 8
Restoration of normal ocular alignment, appearance, and improved self-image are important objectives, according to the American Academy of Ophthalmology 8
Restoration of binocular function is a crucial aspect of management, as noted by the American Academy of Ophthalmology 8
Reduction of compensatory head position (if present) is an essential goal, according to the American Academy of Ophthalmology 8
Prevention of morbidity and mortality from generalized MG is a primary objective, as reported by the American Academy of Ophthalmology 8

Remission or stabilization of the disease is often possible after 2-3 years of treatment, as noted by the American Academy of Ophthalmology 6, 7
Surgical intervention for strabismus may be considered after disease stabilization if prism use is insufficient, according to the American Academy of Ophthalmology 6
Recurrence risk is relatively low (2-5%), as reported by the European Academy of Neurology 9

Diagnosis and management require collaboration between an experienced ophthalmologist and neurologist, particularly for patients with ocular involvement, as recommended by the American Academy of Ophthalmology 6
Rehabilitation programs with physical and occupational therapy are crucial for recovery, according to the European Academy of Neurology 9
Psychological support may be beneficial as rapid loss of physical function can cause anxiety and/or depression, as noted by the European Academy of Neurology 9