Neural and muscular dysfunction in fibromyalgia

Gadallah NA, Awad MR, von Wild KR, El-Hefnawy HE, El-Arousy NH, El-Hefnawy NG, Abdou TA, El Shafie EA, El Zohiery AK. Neural and muscular dysfunction in fibromyalgia. Jpn J Compr Rehabil Sci 2013; 4: 30-38. Objectives: Our aim was to assess peripheral neural and muscular dysfunction in patients with fibromyalgia syndrome (FMS) by interrelating different electrophysiologic and histopathologic studies, in a trial to further elucidate the pathophysiology of fatigue in FMS. Methods: Thirty FMS patients and ten controls were enrolled in the study. To test for muscle fatigue, muscle fiber conduction velocity (MFCV) and quantitative surface EMG analysis were performed before and after sustained contraction. Muscle biopsies were examined by light and electron microscopy. Results: Electrodiagnostic studies revealed pathological fatigue response in patients compared to controls. Patients showed statistically significant lower MFCV (P < 0.0001) and higher percent drop in MFCV following sustained contraction (P < 0.001). Light microscopy examination of patients’ muscle biopsies revealed a significantly higher percentage of fiber size variability, increased central nucleation, increased glycogen and higher percent increase in fiber type I. Electron microscopy revealed different abnormalities. The aggregation of bizarrely-shaped mitochondria was the most remarkable finding in all patients, but in none of the controls. Conclusion: There is definite evidence of neural and muscular interconnected dysfunction. The development of fatigue in FMS is significantly influenced by fiber type composition of the skeletal muscle and disrupted muscle mitochondria.