The 26-year old, who joined the Bees in 2010 following a loan spell at the club, has played 17 games for the League One table-toppers this season.
"Toumani is a very important member of our squad," Brentford manager Mark Warburton told the club's website. "We are approaching a very busy period of games in March and April.
"It is vitally important all the players are fit and ready to contribute during that period. Toumani will be able to get valuable pitch time and be ready when required to play his part in what we hope will be an important conclusion to the season."
The France-born midfielder came through Watford's academy before opting to join Hereford United after making only six appearances for the first team.