Physical and mental fatigue in myasthenia gravis and its correlation with other symptoms

Introduction: Muscle weakness and easy fatigability are the clinical hallmarks of myasthenia gravis (MG). However, fatigue perception, which can be seen quite often in myasthenic patients, and its effect on the quality of life, irrespective of motor deficit, has not been elucidated yet. The aim is to evaluate the frequency of fatigue in myasthenic patients with nearly full muscle strength and the effect of fatigue on quality of life by assessing its correlation with other symptoms.

Methods: Fifty-three patients with ocular or mild generalized MG in remission or minimal manifestations completed the questionnaires measuring the severity of MG and quality of life (MG Composite Scale and MG-Activities of Daily Living Profile). Both patient group and control group (53 healthy volunteers)completed the scales assessing fatigue [Fatigue Assessment Scale (FAS) and Fatigue Impact Scale (FIS)], depression [Beck Depression Inventory (BDI)] and sleep (Epworth Sleepiness Scale). Disease severity was assessed using MG Foundation of America (MGFA) and MGFA Post-Intervention Status classifications.

Results: FAS, FIS physical and BDI scores were significantly higher in patients compared to the control group (p = 0.003, p = 0.001, and p = 0.003, respectively) and fatigue was associated with depression and daytime sleepiness. Inpatient group, depressive symptoms and daytime sleepiness were higher in females (p = 0.019 and p = 0.013). The mean values of FIS total and cognitive scores were higher in patients with generalized MG (p = 0.033 and p = 0.045). Fatigue scores correlated with motor signs.

Discussion: Fatigue can be seen in MG independently from muscle weakness and is an important symptom worsening the quality of life.