The comparison of external anal sphincter electromyography between patients of diabetic polyneuropathy and multiple system atrophy

Abstract

Objective To investigate the impact of peripheral neuropathy on the external anal sphincter electromyography (EAS-EMG). Methods EAS-EMG was performed in 36 patients with diabetic polyneuropathy (DPN), 58 patients with multiple systemic atrophy (MSA) and 19 healthy controls.The routine nerve conduction study was done and standard EMG was recorded from external anal sphincter, common digital muscle and anterior tibial muscle.Parameters studied included spontaneous activity (fibrillation potentials and positive sharp waves), duration, amplitude, percentage of polyphasic wave of motor unit action potential (MUAP), satellite potential and average phases. Results The EAS-EMG of DPN showed significant difference from the health controls: amplitude ((716.7±127.7) μV vs (586.4±85.4) μV, t=3.176, P=0.006), duration ((12.4±2.1) ms vs (9.2±0.5) ms, t=5.037, P=0.000), percentage of polyphasic (56.4%±22.4% vs 37.5%±21.8%, t=3.517, P=0.002), average phases (5.5±1.4 vs 4.4±1.1, t=3.567, P=0.002), respectively and also significant difference from those values in MSA patients: amplitude ((829.2±167.6) μV, t=3.663, P=0.001) and duration ((15.9±2.6) ms, t=7.471, P=0.000).Besides, percentage of MUAP that duration more than 10 ms and percentage of satellite potential were significant higher than those of the controls and lower than MSA patients. Conclusions EASEMG discovers neurogenic changes in patients with DPN, however, their duration, amplitude and percentage of satellite potentials are significantly lower than those in patients with MSA.EAS-EMG diagnosis should be combined with clinical evidence. Key words: Diabetic neuropathies; Multiple system atrophy; Anal canal; Electromyography