Quantitative Analysis of Surface Electromyography for Pediatric Neuromuscular Disorders

Long-term motor activity, cardiopulmonary performance and quality of life in abdominal wall defect patients

AIM

To assess whether patients born with an abdominal wall defect (AWD) have impaired cardiorespiratory performance capacity, motor skills, core stability or quality of life in a long-term follow up.

METHODS

Patients diagnosed with AWD between 2002 and 2013 were invited to participate in the study, which included clinical examination, spirometry, cardiopulmonary exercise performance testing, assessment of motor activity, ultrasound, electromyography of the abdominal wall and assessment of the Gastrointestinal Quality of Life Index (GIQLI). The results were compared to a healthy control group matched for age, sex, BMI, and physical activity levels.

RESULTS

In total, 18 AWD patients (mean age 12.6 ± 3.5 years) were included and there were no significant differences in anthopometric data compared to the control group (n = 18). AWD patients had a significantly lower GIQLI score (AWD mean 137.2 ± 6.8 vs. control mean 141.4 ± 4.9; p = 0.038) and were affected by decreased motor abilities with significantly higher Dordel-Koch-Test values (AWD median 3.54/IQR 1 vs. control median 2.8/IQR 1; p = 0.005).

CONCLUSION

Follow-up examinations of AWD patients revealed decreased motor abilities and GIQLI scores while cardiopulmonary function was not different compared to healthy controls. The clinical impact of these findings remains to be elucidated.

IMPACT

Clinical examination, assessment of the gastrointestinal quality of life, sport medical testing, electromyography and abdominal wall ultrasound were performed in patients with congenital abdominal wall defect and compared to an age and sex matched healthy control group. Results of spirometry and spiroergometry, ultrasound or electromyography did not significantly differ between the groups. Significantly decreased locomotor function and gastrointestinal quality of life were found in patients with abdominal wall defect. However, the clinical impact of these findings remains to be elucidated.

Two-stage binary classifier for neuromuscular disorders using surface electromyography feature extraction and selection

If surface electromyography (sEMG) can be used to determine neuromuscular disorders, it can diagnose conditions more easily than needle electromyography. In this study, sEMG during maximum voluntary isometric contraction and repetitive exercise was measured, and normal, myopathy, and neuropathy were classified with high accuracy using these signals. First, a two-stage binary classifier model was constructed to classify the patient group and the normal group and categorize the cases assigned to the patient group into myopathy and neuropathy groups. To this end, features related to muscle activity and muscle fatigue were extracted using activity analysis and frequency analysis of the sEMG signal. Since the features for high performance are different for each classifier, the features with statistical differences in the data of each class were selected for each classifier. The selected features and a two-stage binary classifier were distinguished with an accuracy of 86.9%. This shows an accuracy higher than 82.3%, which was found for the two-stage binary classifier without feature selection and 73.9% of the multi-classifier. Through this, the possibility of using sEMG to diagnose neuromuscular disorders was confirmed.

Appropriate window width for the "clustering index method" in the tibialis anterior muscle

We previously reported a new quantitative analysis of single-channel surface electromyography (EMG), the "clustering index method" (CI method), in the tibialis anterior muscle, which achieved sufficiently good sensitivity to detect neurogenic or myogenic abnormalities. The window width is a fundamental parameter of the CI method, and was arbitrarily set at 15 ms in that study. In this study, we searched for the most appropriate window width using expanded patient data. The data from our previous study were reanalyzed, and new patients were enrolled. Window width in the CI method was changed from 5 to 27.5 ms with a step of 2.5 ms. For each window width, Z-score values of individual subjects were calculated and the diagnostic yield was investigated. We enrolled 67 controls, 29 subjects with neurogenic disorders, and 39 with myogenic disorders. When the window width was set at 22.5 ms, the highest sensitivity was achieved both for neurogenic (97%) and myogenic (72%) disorders, with a specificity of 97%. Seven of 10 patients with inclusion body myositis were also abnormal. Reliable results were obtained by collecting 15 epochs per subject. There are two conflicting effects that appear to be best balanced at a window width of 22.5 ms: a wider width decreases the chance that a motor unit potential (MUP) is divided into two adjacent windows, and a narrower width reduces the possibility that an MUP firing at a low-frequency is counted twice by the differential sequences. CI is promising as a non-invasive method to diagnose neuromuscular disorders.