Quantificazione obbiettiva del sintomo fatica in pazienti con sclerosi multipla

Fatigue is a pervasive and disabling symptom in MS: up to now no specific tests give objective evidence for this symptom. We performed a muscular fatigue test and Motor Evoked Potentials in 21 Definite-MS patients with slight or absent pyramidal functional system involvement and no evidence of spasticity, severe disability, cognitive impairment or affective disorders. 14 patients complained of fatigue (F) whereas 7 did not (NF). Fatigue test was performed on an isokinetic device (LidoActive): maximal knee extension on movements 180°/sec, 0-90 degrees, were required at the imposed cadence of 1 every 2 second for one minute. Strength versus joint position was recorded at t0 and after 15, 30 and 60 seconds (t1, t2, t3). We compared patients data with records obtained from 14 matched controls (two-way ANOVA force vs group and time). Patients' force was lower than in controls (by 28.6 and 20.2% in F and NF group respectively). Patients force at t0 was lower than controls by 24%. At t3 force decreased was not related to initial force values. In 8 out of 14 F patients CMCT was increased with respect to normal values. The relative decrease of force at t3 was not higher than in other 6 F subjects. Results suggest that organic muscle weakness underlies subjective fatigue in MS. A central basis for this symptom is strongly suspected.