Senate Minority Leader Mitch McConnell, R-Ky., is being treated for a concussion after falling Wednesday evening and is expected to remain hospitalized "for a few days," a spokesperson announced Thursday afternoon.

"The Leader is grateful to the medical professionals for their care and to his colleagues for their warm wishes," spokesman David Popp said. McConnell is expected to remain in the hospital for observation and treatment, he added.

The 81-year-old senator was attending a private dinner at a Washington hotel when he tripped.

That dinner followed a reception at the Waldorf Astoria for the Senate Leadership Fund, a super PAC that raises unlimited donations to support GOP candidates, where McConnell had spoken earlier in the evening.

Senators received an update on McConnell's condition on Thursday afternoon at a private lunch, where they were told he would remain in the hospital for several more days, several senators said. Sen. John Barrasso, R-Wyo., a member of McConnell's leadership team, said after the briefing that he had not spoken to McConnell since his fall but that he was under the impression that he was "awake and talking."

"I expect him to make a full recovery," Barrasso said.

Sen. Mitt Romney, R-Utah, said they were told McConnell was "up most of the night" in the hospital but was in "fine spirits." Senators were told McConnell is following a concussion protocol that means he has been kept awake for hours.

As of early Thursday afternoon, many of McConnell's top deputies, including Sen. John Thune of South Dakota, the No. 2 Republican in the Senate, said they had not spoken to him personally yet.

Several senators said they were not told when McConnell was expected to be back, but projected confidence about his condition. "He's just tough as a boot," said Sen. John Neely Kennedy. R-La..

President Joe Biden, who served in the Senate for years with McConnell, tweeted, "Jill and I are wishing Senator McConnell a speedy recovery. We look forward to seeing him back on the Senate floor."

McConnell, who was first elected to the Senate in 1985 and is serving his seventh six-year term, became GOP leader in 2007. He has held that post longer than anyone else and for years has been among the most powerful elected officials in Washington.

He underwent surgery in August 2019 after he fractured his shoulder tripping outside his Louisville home. The recovery kept him out of the public eye for weeks as he spent the congressional break recuperating at home and undergoing physical therapy.

The senator, who overcame polio as a child, also has a history of heart issues and had triple bypass surgery in 2003, just after being promoted to the Senate's No. 2 Republican post.

When pictures emerged in 2020 showing his hands bruised and bandaged, McConnell downplayed interest in his health as media hype.

In November, McConnell was reelected Senate minority leader, overcoming the first challenge to his leadership following a disappointing performance for Republicans in the midterm elections. McConnell easily defeated Sen. Rick Scott, R-Fla., on a 37-10 vote. The GOP infighting underscored that while McConnell has overwhelming support in his conference, he has lost key allies to retirement. As of December, the average age in the Senate was 64.

Republican hopes of capturing the Senate majority in a difficult year for Biden and Democrats were dashed by ineffective and problematic candidates who had the backing of Donald Trump. McConnell blamed the former president, saying he "proved to be decisive" in the midterms' outcome, highlighting the rift between the two men.

Trump is a frequent critic of McConnell, who accused the then president of provoking the Jan. 6, 2021, attack on the U.S. Capitol. Trump has repeatedly mocked McConnell's wife, former transportation secretary Elaine Chao, and has made racist remarks about her.

"I disagree with almost everything he does, but I certainly would like him to get well," Trump told reporters on a call Thursday. "I want him to be well, and then get back and be strong."

This week, McConnell denounced the leadership of Fox News for airing Tucker Carlson's vision of the assault on the Capitol, holding up a letter from U.S. Capitol Police Chief Tom Manger that said Carlson's show was "filled with offensive and misleading conclusions."

"It was a mistake, in my view, for Fox News to depict this in a way that's completely at variance with what our chief law enforcement official here in the Capitol thinks," McConnell told reporters Tuesday.

Less than three months into the session, the Senate has already dealt with the absence of other lawmakers. Sen. Dianne Feinstein, D-Calif., the oldest senator at 89, was recently hospitalized for shingles and is recovering at home. Sen. John Fetterman, D-Pa., checked himself into Walter Reed National Military Medical Center for clinical depression nearly three weeks ago; an aide recently said he "will be back soon." Other Democratic lawmakers missed votes in the past few weeks for medical procedures or visits to ill family members.

The absences could make it challenging for Democrats, who hold a narrow majority, to confirm some of Biden's nominees or get them through committees. Last week, Vice President Harris had to serve as a tiebreaking vote to approve two U.S. district judge nominations.

"This is my world I live in," Sen. Richard J. Durbin of Illinois, the Senate's No. 2 Democrat, said earlier this week of the challenges of navigating around the absences. "These things are going to happen and they happen on both sides of the aisle."

On the Senate floor Thursday morning, Majority Leader Charles E. Schumer, D-N.Y., said he had called McConnell and spoken "briefly with his staff to extend my prayers and well wishes." He said he was praying for "strength and healing for the leader and his family."

Robert Cantu, a professor of neurosurgery and neurology at Boston University's School of Medicine, said a concussion patient is not typically admitted for several days of observation. Most are checked for other head injuries via an MRI or CT scan and sent home to recuperate.

But given McConnell's age and the possibility that he has other conditions, or is taking medications such as blood thinners, doctors are probably being very cautious with him, Cantu said. He stressed that he had no first-hand knowledge of McConnell's condition or care.

Steven Broglio, director of the University of Michigan's Concussion Center, said physicians watch closely for signs of more significant injuries after a fall, including bleeding from the brain.

While everyone becomes more fragile as they age, that protocol applies about equally to younger and older people, Broglio said.

The list of symptoms of concussion is 22 items long and includes headache, fatigue, difficult sleeping, difficulty concentrating and brain fog, he said.

The incidence of concussion is highest in people between their mid-teens and mid-20s, declines a bit as people engage in fewer risky activities with age, and then rises somewhat in later years, Broglio said.

- - -

The Washington Post's Leigh Ann Caldwell, Michael Scherer and Missy Khamvongsa contributed to this report.