Washington ? Democratic Sen. Tim Johnson, whose emergency brain surgery earlier this week raised the prospect of a shift in power in the Senate, showed signs of recovery on Friday, his office reported.

Considering the seriousness of the medical problem found in his brain, “his progress is encouraging,” Dr. Anthony Caputy said in a statement released by the lawmaker’s staff.

Caputy was a member of the team that operated on the 59-year-old South Dakotan Wednesday night.

Johnson was experiencing post-surgery swelling in his brain, but that was considered routine. “Much like a bruise, it takes time to heal,” Caputy said.

With Democrats having captured a one-seat majority in the Senate that convenes in January, Johnson’s affliction has interested Washington’s political community.

Should he die or decide to resign from office, South Dakota’s GOP governor has the authority to replace him with a Republican, knotting the Senate at 50-50. Vice President Dick Cheney, the Senate’s presiding officer, would break the tie, returning the chamber to Republican control. But news of Johnson’s improvement and increasing alertness quelled such speculation substantially.

After becoming disoriented Wednesday, Johnson was rushed to George Washington University Hospital, where doctors performed emergency surgery to relieve bleeding in his head stemming from a congenital condition known arteriovenous malformation. AVM, as the condition is called, can lead to speech problems, paralysis or, in rare cases, death.

A CT scan performed on Johnson Friday morning showed “that the pressure has been relieved from his brain and there is no further bleeding,” Dr. Vivek Deshmukh, the lead surgeon, said in the statement from the senator’s office.

“Currently, his brain pressures are normal,” Deshmukh said.

Johnson’s office has not disclosed the precise location of the tangle of arteries and veins that caused the bleeding in his head, a critical factor in determining what kind of long-term effects he may suffer.

Johnson was complaining of weakness on his right side when he arrived at the hospital and the doctors said they anticipate physical therapy will be part of his recovery process.