1. Department of Social and Health Services and Research, Italian Multiple Sclerosis Society, Genoa 16128, Italy,
2. Institute of Hygiene, University of Siena, Siena 53100, Italy
3. Department of Social and Health Services and Research, Italian Multiple Sclerosis Society, Genoa 16128, Italy
4. Department of Neurological Science and Vision, University of Genoa, Genoa 16132, Italy