Sen. Johnson returning after December surgery

WASHINGTON (Reuters) - Sen. Tim Johnson, a Democrat who has been recovering from brain surgery since December, plans to return to his Senate office on September 5, his office said on Wednesday.

Johnson will be in his home state of South Dakota for the next few days before returning to Washington and he "plans to be in his Senate office and on the Senate floor on Wednesday, September 5th," according to his office.

The two-term Democrat underwent emergency surgery on December 13 to stop bleeding from a malformation of blood vessels in his brain. He remained in the hospital and then in a rehabilitation center for several months after the operation.

Johnson's speech and ability to walk are still impaired.

With Democrats controlling the Senate with a narrow 51-49 margin, Johnson's sudden illness that left him in critical condition in December raised questions about what would happen if he could no longer serve, giving South Dakota's Republican governor the chance to appoint a fellow Republican to fill out Johnson's term.

That could have tipped Senate control to the Republicans.

Johnson's second six-year term ends next year and the 60-year-old senator has not formally declared whether he will seek another term.