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.