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NCS-MOTOR UNIT ACTION POTENTIAL (MUAP)

Neurology

NCS-MOTOR UNIT ACTION POTENTIAL (MUAP)

1. Motor unit action potential (MUAP): potential recorded when an individual voluntarily contracts & activates a motor unit.

2. Amplitude & duration of the MUAP are proportional to the innervation ratio of the motor unit.

3. However the amplitude is also affected by the proximity of the needle to depolarizing muscle fibers, hence duration is a more reliable indicator of motor unit territory.

4. Myopathy: short-duration, low-amplitude, polyphasic MUAP, early MUAP recruitment.

5. Neuropathy: long-duration, high-amplitude, polyphasic MUAP.

6. NMJ disease: motor unit instability (MUAP will vary in size & morphology), early MUAP recruitment.


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REFERENCES

1. Wilkinson, I. (2017). Oxford handbook of clinical medicine. Oxford: Oxford University Press.
2. Hannaman, R. A., Bullock, L., Hatchell, C. A., & Yoffe, M. (2016). Internal medicine review core curriculum, 2017-2018. CO Springs, CO: MedStudy.
3. Image: no reference available.

Ⓒ A. Manickam 2018

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