Evaluation of muscle oxygenation by functional near-infrared spectroscopy in patients with myasthenia gravis during rest and exercise

Introduction: Myasthenia gravis (MG) is an autoimmune disease that is caused by autoantibodies targeting the neuromuscular junction. A few studies in the literature show that MG may negatively affect muscle metabolism. However, no current study investigates MG pathophysiology’s effect on muscle oxygenation. In this study, we aimed to investigate the difference in muscle oxygenation in MG disease and to evaluate its clinical Pathophysiological implications. Methods: 19 MG patients and 19 age, gender and body mass index (BMI) matched healthy controls participated in the study. Functional near-infrared spectroscopy (fNIRS) recordings were recorded from six channels over the biceps brachii muscles during the rhythmic elbow flexion-extension task. Results: It was observed that oxygenated-hemoglobin (HbO) (p = 0.008) and total hemoglobin (HbT) (p = 0.017) values during exercise were significantly lower in MG patients in the motor point of the biceps brachii muscle. In addition, at rest, deoxygenated-hemoglobin (HbR) levels were significantly lower in patients (p<0.05) in the motor point and the lateral region of the biceps brachii muscles. Additionally, a difference is observed in fNIRS values between the moderate-severe MG group and healthy controls. Also, a negative correlation was observed between exercise-state HbO and rest-state HbR values and disease severity (p<0.05). Conclusion: MG patients show deterioration in muscle oxygenation values during exercise and rest. Oxygenation values show significant differences in disease severity and negatively correlate with disease severity. Based on these findings, MG disease may affect muscle oxygenation and can be monitored by fNIRS.