Objective: To investigate the clinical feature and quantitative electromyographic (QEMG) findings in the patients with post-polio syndrome (PPS).

Method: Eleven patients who had clinical evidences of antecedent poliomyelitis were evaluated with standardized clinical history, physical examination and QEMG study. If a patient had fulfilled provisional criteria for PPS, he was regarded as PPS and six patients had fulfilled the criteria. Other patients were treated as control group with stable poliomyelitis. Manual muscle testing and needle EMG study including quantitative motor unit analysis was performed at the tibialis anterior and vastus medialis muscles. The existence of abnormal spontaneous activity and parameters of quantitative motor unit analysis, mean duration and amplitude of motor unit action potentials (MUAPs), were compared between PPS and control groups. The correlation between the muscle strength and parameters of QEMG was investigated.

Results: Abnormal spontaneous activities were noted in 4 out of 11 patients (36.4%) and three of these 4 patients were PPS. Mean duration and amplitude of MUAPs of tibialis anterior and vastus medialis muscles were not different significantly between the PPS and stable poliomyelitis group (p＞0.05). The parameters of MUAPs were poorly correlated with muscle strength.

Conclusion: Distribution of abnormal spontaneous activities and parameters of QEMG study were not different in PPS and stable poliomyelitis patients. QEMG study may not have additional benefit in differentiating PPS from stable poliomyelitis.

The reference values of motor unit action potentials(MUAP) of first dorsal interosseous and tibialis anterior muscles were measured in 50 healthy subjects. The MUAPs were recorded with a concentric needle electrode and extracted with a decomposition method. Sixty six patients with neuropathy were also studied in the same way with a count of outliers and measurement of mean values.

The mean values of amplitude, area, duration and thickness were 667.74±204.34 ՌV, 992.26±253.18 ՌVms, 9.75±1.95 ms and 1.49±0.26 ms, respectively in the first dorsal interosseous muscles, and 612.88±140.13 ՌV, 1172.84±199.21 ՌVms, 11.41±2.48 ms and 1.93±0.34 ms respectively in the tibialis anterior muscles. There was no significant difference in age and gender of normal subjects. The amplitude was the most sensitive parameter to detect abnormality in a count of outliers and measurement of mean values. The outliers count in duration showed a higher sensitivity than the measurement of mean values(p＜0.05), but not in amplitude, area or thickness.

Based on the results of this study, the count of outliers was more sensitive than the measurement of mean values in the diagnosis of patients with neuropathy. Further more, less numbers of MUAPs were needed for the evaluation of the outliers count. Through this method we could save the evaluation time and the patients felt more comfortable.