Electromyography of the external anal sphincter in patients with Parkinson's disease and multiple system atrophy: Frequency of abnormal spontaneous activity and polyphasic motor unit potentials

Sphincter EMG for Diagnosing Multiple System Atrophy and Related Disorders

“…33,37 The first reports on neurogenic changes of EAS-EMG in MSA are attributed to Sakuta et al (1978). 62 Since then, EAS-EMG results for over 500 MSA patients have been reported, with abnormality rates of more than 70% in many studies 5,30,36,38,47,53,62,64,71 . EAS-EMG is better tolerated and yields identical results to those from EUS investigation 5 .…”

The value of external anal sphincter electromyography for the diagnosis of multiple system atrophy

“…21 Conversely, several recent studies raised suspicions on the specificity of the procedure, 18,19,23 particularly for the differential diagnosis between PD 18,23 or PSP. 19 As far as we are aware from our practice, many neurologists hesitate to refer their patients suspected of having MSA for ASEMG, not only because of the aforementioned unsolved questions regarding the specificity of the procedure, 18,19,23 but also because of its embarrassing and uncomfortable reputation, its accessibility, and its interpretation difficulties caused by poor standardization of the technique, 17 variations in quantitative motor unit analysis, 18 and confounding factors such as age, gender, and parity. 16 We report herein our results of ASEMG performed as part of a diagnostic work-up for atypical parkinsonism in 52 patients with clinical features obviously suggestive of the diagnosis of MSA 6 or with other forms of parkinsonism, in whom MSA was suspected among other diagnoses at some stage of their disease.…”

“…The mean duration of MUPs is, in our study as in others, 15 the most reliable variable, because the dispersion and overlap of individual values is less than for polyphasicity. As opposed to another study, 18 we did not find that abnormal spontaneous activity (i.e., fibrillation and complex repetitive discharges) was a common finding (38.5%), although these activities seemed quite specific for MSA in our series. Although the excellent sensitivity of the procedure is confirmed, [13][14][15][20][21][22] some values overlap with patients we classified as no MSA.…”

“…This is the result of the local anatomy, the tonic motor activity normally present in the external anal sphincter, and the influence on the results of age, gender, parity, and the quantitative analysis method used. [16][17][18] The bulk of the data on the value of ASEMG for the diagnosis of MSA comes from a pioneer center 10,11,[13][14][15] ; other experience has been reported in more limited series, 12,18-21 except for a recent abstract report on 121 cases. 22 Although the procedure seems fairly sensitive for the diagnosis of MSA, the value of ASEMG for distinguishing MSA from PD or other causes of parkinsonism, such as progressive supranuclear palsy, has been questioned.…”

“…22 Although the procedure seems fairly sensitive for the diagnosis of MSA, the value of ASEMG for distinguishing MSA from PD or other causes of parkinsonism, such as progressive supranuclear palsy, has been questioned. 18,19,23 To further assess the usefulness of ASEMG for the diagnosis of MSA among various causes of parkinsonism, we report our own results in a series of 52 patients, including the study of the sensitivity, specificity, predictive values, and possible confounding factors.…”