Comparison of Amplitude to Area of Compound Muscle Action Potentials after Peripheral Nerve Injury

ABSTRACT

The evaluation of peripheral nerve disorders has traditionally relied on clinical history, physical examination, and electrodiagnostic studies. The electrodiagnostic study is currently most popular procedure. The purpose of this study is to assess the significance of the changes of amplitude and area of compound muscle action potentials(CMAPs) in peripheral nerve injury. After compression of sciatic nerve in 65 Korean house rabbits, the amplitude and the area of CMAPs were compared to each other before and after compression injury. The correlation coefficients between the changes of the parameters, amplitude and area, were obtained at a scheduled interval, and the parameters were also assessed when the evidence of denervation and regeneration was seen. In addition, the relationship between the degree of abonormal spontaneous activities and each parameter was assessed. At preinjury state, there was a significantly high correlationship between two parameters. The correlation coefficients were 0.764 and 0.756 with distal and proximal stimulations respectively in abductor hallucis recordings, and 0.649 in gastrocnemius recording. At postinjury, there was more significant high correlationship between two parameters. The correlation coefficients were 0.955 and 0.962 with distal and proximal stimulations respectively in abductor hallucis recordings, and 0.930 in gastrocnemius recording. Nineteen cases showed denervation activities at postinjury 4th day. Of those cases, the amplitude was decreased earlier in 2 cases and the area in 3 cases at the same day. Of 10 cases regenerated, the amplitude was normalized earlier than the area in 2 cases. There was a significant decrement tendency in both amplitude and area with the degree of abnormal spontaneous activities. Therefore, both the amplitude and the area of CMAPs are good quantitative indices of peripheral neuropathy and useful parameters in long-term follow up study.