A longitudinal study of cognition in primary progressive multiple sclerosis

Camp, Sj; Stevenson, Vl; Thompson, Aj; Ingle, Gt; Miller, Dh; Borras, C; Brochet, B; Dousset, V; Falautano, M; Filippi, Massimo; Kalkers, Nf; Montalban, X; Polman, Ch; Langdon, Dw