Study Population: Adult, untreated patients with PP-MS with disability ranging from none to moderately severe will be included in the trial. The upper age limit in this study has been set at 65; setting an age limit should permit us to focus on the potential neuroprotective effect of idebenone in PP-MS and limit the confounding factor of the natural aging process and its known negative influence on neuro-regeneration. Published data indicate that higher doses (10-50 mg/kg) of idebenone per day are required for beneficial effects on neurological disability in comparison to the lower doses (5-10mg/kg) that are sufficient for beneficial effects on cardiac/systemic functions in Friedreich s ataxia (FRDA) patients. Therefore, in order to target the CNS compartment, we will use a daily dose of 2250mg (750mg 3 times per day), which will provide target values of 10-50mg/kg for virtually all adult patients.