Fatigue in Multiple Sclerosis Compared to Stroke.

OBJECTIVES: Fatigue is typically associated with multiple sclerosis (MS), but recent studies suggest that it is also a problem for patients with stroke. While a direct comparison of fatigue in, e.g., Stroke and MS is desirable, it is presently not easily possible because of different definitions and assessment tools used for the two conditions. In the present study, we therefore assessed fatigue in Stroke and MS using a generic, not disease-specific instrument to allow transdiagnostic comparison. METHOD: A total of 137 patients with MS and 102 patients with chronic stroke completed the SF-36, a generic questionnaire assessing health related quality of life. Fatigue was measured through the vitality scale of the SF-36. The vitality scale consists of two positive items ("lot of energy," "full of life") and two negative ones ("worn out," "tired"). The two negative ones were scaled in reverse order. The vitality scale has been recommended as reciprocal index of fatigue. RESULTS: Normalized vitality scores in MS (35.3) and stroke (42.1) were clearly lower than published reference values from the SF-36 in age-matched healthy controls. The sum score of the vitality items was lower in MS than in stroke patients. This difference could not be explained by age, gender, or the Physical Functioning Scale of the SF-36. Both patient groups showed no positive correlation between fatigue and physical functioning. Fatigue - as determined with the vitality scale of the SF-36 - correlated with the estimated working capacity in MS patients, but not in stroke patients. CONCLUSION: These findings confirm high fatigue in MS and stroke patients with higher values in MS. Fatigue has a higher impact on working capacity in MS than in stroke. Fatigue in both patient groups is not a direct consequent of physical functioning/impairment. Vitality score of the SF-36 is a suitable transdiagnostic measure for the assessment of fatigue in stroke and MS.

Modulation of alertness by sustained cognitive demand in MS as surrogate measure of fatigue and fatigability.

OBJECTIVE: This study used reaction time (RT) as an objective marker of cognitive fatigue and fatigability in patients with multiple sclerosis (MS). METHOD: RT was measured in fifteen healthy controls and in thirty MS patients with cognitive fatigue identified with the Fatigue Scale for Motor and Cognitive Function (FSMC). Secondary fatigue was excluded through the Epworth Sleepiness Scale and the Beck Depression Inventory. RT was measured at rest (t1), following a 2.5 hour test session inducing high cognitive load (t2), and a one hour recovery period (t3). RESULTS: At rest mean RT was longer in patients than in controls (391 ms vs 205 ms). After exerting cognitive load (t2), RT in patients increased dramatically but remained unchanged in controls. After the recovery period (t3), RT returned to baseline levels in most patients. Patients further showed a significant correlation between RT and FMSC scores at t1, t2 and t3. CONCLUSION: RT performance is a suitable surrogate marker for assessing fatigue. RT is sensitive to cognitive load and the recovery from cognitive demand. It hence represents an objective index for fatigability which can inform the management and treatment of MS.