Mr. Big drummer Pat Torpey has been forced to sit out the group's upcoming world tour as he battles Parkinson's disease.

The rocker tells he has been fighting symptoms for the past two years, but his diagnosis was only confirmed recently.

He says, "I intend to fight the disease with same intensity and tenacity that I drum and live my life by and will continue recording and performing, as always, to the best of my ability."

Torpey is still expected to join his bandmates during acoustic sets, but a replacement drummer will take his place on the band's upcoming tour.

The drummer reunited with his Mr. Big co-founders Eric Martin, Paul Gilbert and Billy Sheehan in 2009. The group formed in 1988 and enjoyed a string of chart hits, including To Be With You and Just Take My Heart.