Ratings of subjective mental fatigue relate to cognitive performance in patients with myasthenia gravis.

We examined ratings of fatigue and cognitive performance in myasthenia gravis (MG) patients and healthy subjects. All participants were administered self-report measures of mental and physical fatigue before and after completing a demanding cognitive work battery. Change in fatigue indices was recorded and examined in relation to cognitive function. Results of the study revealed that baseline ratings of fatigue did not relate to cognitive performances for either group. By contrast, increased mental fatigue from the baseline to the post-test assessment correlated with cognitive measures for patients but not control subjects. MG patients reported that physical fatigue also increased following the work battery, but only ratings of mental fatigue correlated with cognitive performances. The results indicate that cognitive impairments may be associated with perceived fatigue in MG. Copyright 2002 Elsevier Science Ltd. All rights reserved.