| PART 1: The Study of Mean Duration in Anal Sphincter Electromyography: Overview of 335 Cases of Multiple System Atrophy and Related Neurological DiseasesBackground and Objectives Anal sphincter electromyography (ASEMG) is an important diagnostic tool in multiple system atrophy (MSA). The mean duration of motor unit action potential (MUAP) exceeding 10ms has been widely accepted as the main criteria for "neurogenic impairment". However, longer duration of MUAP than 10ms could also present in other diseases, such as Parkinson's disease (PD), Parkinson's syndrome and cauda equine lesion, etc. The value of ASEMG, therefore, is challenged for its low specificity. It has been reported that the mean duration longer than 13 ms could be more specific in differentiating MSA from PD while satellite potentials (SP) seem special in MSA patients, but the related studies with a large sample size is lacking.Methods We established an ASEMG data bank prospectively since the end of 2003. 335 cases with intact data were selected from the data bank, including 131 patients with MSA, 44 with PD, 76 with PDS, 36 with cauda equine lesion (CEL), 10 with cerebella ataxia (CA), 20 with orthostatic hypotension (OH) and 18 patients as normal control. The results of the ASEMG were reviewed retrospectively. Sensitivity and specificity of mean duration and SP rate or their combined use in differentiating MSA-probable from PD and other related diseases were evaluated by ROC curves.Results The mean duration was significantly longer in MSA-probable (15.69±2.66ms) than in PD (12.40±1.44), PDS (12.60±1.79), CA(12.46±2.25), OH (12.91±1.79), CEL (13.24±2.49) and normal control (11.56±1.59 )(P<0.001). No statistical difference was found among the patients groups. The SP rate of MSA-probable (24.00%±11.89%) was higher than PD (10.18%±7.78%), PDS (11.29%±8.78%), CA (10.40%±6.43%), OH (12.98%±8.41%), CEL (13.33%±10.35%) and normal control (6.83%±6.98%) (P<0.001) . When the cut-off level of 10ms in MD was employed, the sensitivity of MD in differentiating MSA from other diseases was high (98.8%-100%), while the specificity was lower than 10%. The specificity of MD in differentiating MSA-probable from PD,PDS, and CA could be improved (81.8,78.4,and 80, respectively) with the sensitivity of 73.8%, if 13.7 ms was accepted as the cut-off level. When a cut-off level of 20.87% was adopted, the sensitivity of SP rate in differentiating MSA-probable from other diseases was 58.7% while the specificity was 91.9% in differentiating MSA-probable from PD and more than 80% from other disease. If MD and SP rate were combined, the sensitivity and specificity could be 80 % and 81%(MD>10ms ,SP rate >20%), or 80% and 66.7%( MD>13.7ms,SP rate>l 0%).Conclusion ASEMG is valuable in differentiating MSA-probable from PD and other neurological diseases. 13.7ms is more specific as a cut-off value of MD than 10ms. SP rate was helpful in differentiating MSA from other related diseases. The combined use of MD and SP rate had a higher sensitivity and specificity in differentiating MSA from PD than their use separately. PART 2: The Value of Satellite Potential in Anal Sphincter Electromyography in the differentiation between Multiple System Atrophy and Parkinson's DiseaseBackground and Objectives It's difficult to differentiate multiple system atrophy (MSA) from Parkinson's disease (PD) in their early stage. Anal sphincter electromyography (ASEMG) was reported to be helpful for the differentiated diagnosis within the first five years after onset. However, it's still controversial. In our previous studies, Satelite Potential (SP) was found to be of diagnostic value in MSA. In this study, we aimed to further elaborate the features of SP in MSA and PD. We also investigated the value of SP in the differentiation between MSA and PD.Methods Fifty-four patients with probable MSA and twenty patients with PD presented in PUMC hospital during the period of 2004 and 2006 were enrolled in this study. The SP was defined as the spikes appearing preceding or following the main component of a MUAP and separated from it by an almost constant, isoelectrical interval of 1 ms or 5 ms. We analyzed the features of SP, which included the SP number, SP rate, the mean duration of MUAP with SP, the SP latency, the interval between the main spike and SP, the mean spike duration of MUAP with SP, in the two patient groups. The mean duration of MUAP with SP and the SP rate with ideal sensitivity and specificity in differentiating MSA from PD were determined according to the ROC curve. The uniformed MSA rating scale-IV (UMSA-IV) was used for the evaluation of the patient prognosis. The correlation between SP rate and prognosis rating score was determined by COX regression analysis.Results All the parameters were significantly different between MSA and PD whether the isoelectrical interval was accepted as 1ms or 5ms. The SP rate in MSA and PD was 30.41%±12.54% (9.50-55.00%) versus 9.61%±7.94%(0-25%)(P<0.001), when 1ms was accepted as the isoelectrical interval. If 5ms was accepted, the SP rate was 15.87%±11.92%(0-45%) versus 4.17±5.09%(0-15%) correspondingly (P<0.001). With the 1ms criterion being used, the SP rate, ideal sensitivity and specificity in differentiating MSA from PD were 15%,83.3% and 85% or 21%,70.4%,and 90%. When the 5ms criterion was adopted, they are 9.76%, 70.4%, and 80%. The significant difference of SP rate in MSA and PD was independent on the disease duration and the isoelectrical interval criterion. The SP rate and prognosis rating scale was not correlated statistically.Conclusion Both 1ms and 5ms could be accepted as the isoelectrical interval of SP in ASEMG. The SP rate is the most important parameter with an ideal sensitivity and specificity in differentiating MSA from PD, even within the first 3 years after onset. The prognosis of MSA couldn't be predicted by the SP alone.
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