Editing Myasthenia gravis (section)

===Electrodiagnostics===
[[File:Tumor Thymoma1.JPG|thumb|A chest CT-scan showing a thymoma (red circle)]]
[[File:Myasthenia gravis ptosis reversal.jpg|thumb|Photograph of a person showing right partial ptosis (left picture), the left lid shows compensatory pseudo lid retraction because of equal innervation of the m. levator palpabrae superioris ([[Hering's law of equal innervation]]): Right picture: after an edrophonium test, note the improvement in ptosis.]]

Muscle fibers of people with MG are easily fatigued, which the [[repetitive nerve stimulation]] test can help diagnose. In single-fiber [[electromyography]], which is considered to be the most sensitive (although not the most specific) test for MG,<ref name="Scherer2005" /> a thin needle electrode is inserted into different areas of a particular muscle to record the action potentials from several samplings of different individual muscle fibers. Two muscle fibers belonging to the same motor unit are identified, and the temporal variability in their firing patterns is measured. Frequency and proportion of particular abnormal action potential patterns, called "jitter" and "blocking", are diagnostic. Jitter refers to the abnormal variation in the time interval between action potentials of adjacent muscle fibers in the same motor unit. Blocking refers to the failure of nerve impulses to elicit action potentials in adjacent muscle fibers of the same motor unit.<ref name="Selvan">{{Cite journal |vauthors=Selvan VA |date=January 2011 |title=Single-fiber EMG: A review |journal=Annals of Indian Academy of Neurology |volume=14 |issue=1 |pages=64–67 |doi=10.4103/0972-2327.78058 |pmc=3108086 |pmid=21654930 |doi-access=free}}</ref>