Accessory nerve stimulation in the assessment of myasthenia gravis.
Repetitive nerve stimulation (5/second) was done at the median nerve at the wrist and at the accessory nerve just behind the sternocleidomastoid muscle before and 20 seconds to 5 minutes after tetanic nerve stimulation (1 minute). Since the degree of the neuromuscular block depends on the body temperature these investigations were done successively at skin temperatures of 32 degrees C and 36 degrees C. A comparison of the results obtained revealed the highest rate of pathologic decrement with posttetanic accessory nerve stimulation (32 degrees C = 77%, 36 degrees C = 87%), whereas with posttetanic median nerve stimulation pathological results were obtained in a significantly lower proportion (32 degrees C = 50%, 36 degrees C = 60%). The advantages of the stimulation of the accessory nerve for the detection of partial neuromuscular block are: 1. The superficially located accessory nerve allows for supramaximal stimulation with rather low stimulus intensities (6-20 mA). 2. Since the accessory nerve is mainly a motor nerve, the stimulation is less painful than the stimulation of a mixed nerve. 3. Stimulation of a proximal nerve is more sensitive for detecting a defect in neuromuscular transmission than stimulation of a distal nerve. 4. There is no risk of a pneumothorax and of a traumatic nerve lesion as there is with stimulation of the brachial plexus by needle electrodes.
D000055:Accessory Nerve / Q000503:physiopathology*; D000200:Action Potentials; D000293:Adolescent; D000328:Adult; D000368:Aged; D001831:Body Temperature; D002648:Child; D004558:Electric Stimulation; D004566:Electrodes; D005260:Female; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000503:physiopathology; D008875:Middle Aged; D009119:Muscle Contraction; D009157:Myasthenia Gravis / Q000175:diagnosis* / Q000503:physiopathology