Congenital Myasthenic Syndrome: Diagnostic Approach and Treatment

Clinical Features and Diagnostic Testing

The American Academy of Neurology recommends neuromuscular junction testing with repetitive stimulation and/or jitter studies to diagnose Congenital Myasthenic Syndrome (CMS) 1
The European Neurological Society suggests that antibody testing, including AChR and anti-striated muscle antibodies, should be performed to evaluate for concurrent myositis 1, 2
Muscle enzyme markers, such as CPK and aldolase, should be evaluated to assess for concurrent myositis 1, 2
Inflammatory markers, including ESR and CRP, should be assessed to evaluate for inflammation 1, 2
Pulmonary function tests, including negative inspiratory force (NIF) and vital capacity (VC), should be performed to assess respiratory muscle strength 1, 2

The American Academy of Neurology recommends pyridostigmine as the first-line treatment for most CMS subtypes, starting at 30 mg orally three times daily and gradually titrating to maximum 120 mg four times daily based on symptoms 1, 2
The European Neurological Society suggests that corticosteroids, such as prednisone 0.5 mg/kg orally daily, may be added if symptoms persist despite maximum pyridostigmine dosing 1, 2
IVIG (2 g/kg IV over 5 days) or plasmapheresis can be considered as steroid-sparing alternatives 1, 2

The American Academy of Neurology recommends avoiding beta-blockers, IV magnesium, fluoroquinolones, aminoglycosides, and macrolide antibiotics in CMS patients, as they can worsen myasthenic symptoms 1, 2, 3