Objectives:

1. SFEMG is the most sensitive but not specifi c diagnostic test for myasthenia gravis;
2. The presence of jitter on SFEMG is a nonspecifi c fi nding and can represent multiple etiologies including myasthenia gravis and CPEO; and
3. Muscle biopsy is indicated for possible diagnosis of CPEO in patients diagnosed with myasthenia gravis but not responding to pyridostigmine.