Riluzole in Huntington's Disease

Primary objective: * The primary objective of the study is to establish that riluzole slows down (1) the decrease in total functional capacity (TFC), (2) the increase of the motor score of the Unified Huntington\'s Disease Rating Scale (UHDRS) as well as (3) the increase of a combined score of these. Secondary objectives: Secondary objectives are to assess * changes in the other UHDRS subscales * the number of patients who need antichoreic treatment and the time until this treatment has to be initiated * the safety/tolerability of riluzole in Huntington patients