Open AccessElectrophysiological study in neuromuscular junction disorders
Author(s) -
Ajith Cherian,
Neeraj N Baheti,
Thomas Iype
Publication year - 2013
Publication title -
annals of indian academy of neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.427
H-Index - 31
eISSN - 1998-3549
pISSN - 0972-2327
DOI - 10.4103/0972-2327.107690
Subject(s) - repetitive nerve stimulation , medicine , neuromuscular junction , neuromuscular transmission , electrophysiology , myasthenia gravis , stimulation , electromyography , anesthesia , neuroscience , physical medicine and rehabilitation , psychology
This review is on ultrastructure and subcellular physiology at normal and abnormal neuromuscular junctions. The clinical and electrophysiological findings in myasthenia gravis, Lambert-Eaton myasthenic syndrome (LEMS), congenital myasthenic syndromes, and botulinum intoxication are discussed. Single fiber electromyography (SFEMG) helps to explain the basis of testing neuromuscular junction function by repetitive nerve stimulation (RNS). SFEMG requires skill and patience and its availability is limited to a few centers. For RNS supramaximal stimulation is essential and so is display of the whole waveform of each muscle response at maximum amplitude. The amplitudes of the negative phase of the first and fourth responses are measured from baseline to negative peak, and the percent change of the fourth response compared with the first represents the decrement or increment. A decrement greater than 10% is accepted as abnormal and smooth progression of response amplitude train and reproducibility form the crux. In suspected LEMS the effect of fast rates of stimulation should be determined after RNS response to slow rates of stimulation. Caution is required to avoid misinterpretation of potentiation and pseudofacilitation.