Senator Mitch McConnell, the longtime Republican leader who had a serious head injury in a fall earlier this year, froze midsentence during an appearance at his weekly news conference in the Capitol on Wednesday and was briefly escorted away from the microphones to recover.
In what seemed to be a medical episode, Mr. McConnell, 81, appeared to lose his train of thought when beginning his remarks on a pending Pentagon policy bill and was unable to continue speaking. Colleagues and aides waited a few awkward moments before intervening, taking the senator by the arm and leading him away from the microphones.
“Are you good Mitch?” asked Senator Joni Ernst of Iowa, a member of the Republican leadership, as Mr. McConnell remained silent and gazed around, appearing disoriented.
Senator John Thune of South Dakota, the No. 2 Republican, quickly stepped in and picked up where Mr. McConnell had left off, followed by the rest of his leadership team.
Mr. McConnell then returned to take a number of questions from the news media — more than usual — and answered them clearly. Asked what had occurred, Mr. McConnell said only, “I’m fine,” and said he was able to continue with his leadership duties.
Aides later said that he had experienced some lightheadedness but noted he was able to resume speaking within minutes, and not long after, held his regular weekly meeting with Speaker Kevin McCarthy, Republican of California. They declined to elaborate on his medical status, including whether he had been examined by a physician in the aftermath of the episode.
The situation was just the latest reminder of the advanced age and frail condition of the top Republican in the Senate, raising questions about his future and that of his party.
Mr. McConnell, a Kentucky lawmaker who became the longest-serving Senate leader in history at the beginning of the year, has moved more slowly and struggled with hearing loss since he fell at a Washington hotel in March during a fund-raising event, sustaining a concussion. His allies have rejected any suggestion that his abilities have declined, saying he remains in charge in private sessions. They expressed confidence again on Wednesday.
“I was concerned when he fell and hit his head a number of months ago and was hospitalized,” said Senator John Barrasso of Wyoming, the No. 3 Republican and a medical doctor, who escorted Mr. McConnell to his office on Wednesday after the minority leader fell mute. “And he has made a remarkable recovery. He’s done a great job leading our conference, and he was able to answer every question that the press asked him today. And, you may note, he answered more questions than he normally does.”
Still, Mr. McConnell has appeared physically diminished since the fall, in which he also broke a rib, spent time in a rehabilitation center and was absent from the Senate for more than a month before returning. The Republican leader, who had polio as a child, has always tread carefully and avoided stairs but has been noticeably more careful since his recent injuries when moving around the Senate.
He has taken a step back from the dominant role he has played at the helm of his party in the Senate for decades. He kept his distance from intense negotiations between the White House and congressional Republicans earlier this year on a deal to avert a catastrophic federal debt default, ceding the issue entirely to Mr. McCarthy.
Mr. McConnell speaks less frequently at the weekly closed-door Republican luncheon in the Capitol, according to attendees.
And in recent days, he has sometimes been less active in the Senate’s legislative work. It was Mr. Thune, who is widely regarded as a potential successor, who led negotiations for Republicans on the structure of the debate on the annual Pentagon bill, a role usually relished by Mr. McConnell, who is keenly interested in military policy.
Wednesday’s episode was clearly alarming to colleagues accompanying him at what is known as the weekly stakeout following the closed party lunch. It took a few moments for both members of the news media and the Senate to recognize that Mr. McConnell was struggling, since he often picks his words carefully at media events and has a penchant for remaining silent when he does not wish to respond to a question. On a few recent occasions, Mr. McConnell, who uses hearing aids, also seemed to have difficulty hearing questions directed to him.
But on Wednesday, it was obvious that something else was the matter.
“Is there anything else you want to say, or should we just go back to your office?” Mr. Barrasso asked Mr. McConnell during the episode, taking him by the arm. “Do you want to say anything else to the press?”
There are several possible explanations for the episode, two neurologists said, although they stressed that they did not examine Mr. McConnell and only saw video of the incident.
Dr. Lee Schwamm, a neurologist and stroke expert at Yale, and Dr. Jeffrey Saver, a neurologist at the U.C.L.A. School of Medicine, said that the two most likely reasons for the episode were a transient ischemic attack — a sort of mini stroke — or a partial seizure.
“If I were his doctor or was in that audience, I would have recommended he go to the emergency room immediately,” Dr. Schwamm said.
Transient ischemic attacks occur when blood flow to part of the brain is temporarily blocked. They usually last for five to 10 minutes, Dr. Schwamm said.
A seizure, perhaps resulting from a head injury, was also possible, Dr. Saver said. The neurologists said a migraine was another less likely possible cause of the episode.
Mr. McConnell was re-elected to a seventh term in 2020, and he would be on the ballot again in 2026 if he chose to run. He was re-elected as party leader in November after holding off a challenge from Senator Rick Scott of Florida, who decided to oppose Mr. McConnell after overseeing a Senate campaign operation that was unable to regain the majority. Mr. McConnell had the support of an overwhelming majority of Republicans, but the challenge itself was noteworthy because Mr. McConnell had typically been named leader without a contest.
His fall and the subsequent health issues were another display of the challenges faced in an institution with an aging membership. Senator Dianne Feinstein, Democrat of California, who recently turned 90, was away from the Senate for months earlier this year with a variety of health issues, and her absence temporarily slowed Democrats from confirming some contentious judicial nominees in the narrowly divided Senate.
After returning to speak to reporters on Wednesday, Mr. McConnell coherently answered questions on the prospects for the House impeaching President Biden, the criminal case of Hunter Biden and the state of the appropriations process.
One question he chose not to answer and laughed off before walking away was a query about who he would favor to replace him as leader if he stepped aside.
Gina Kolata, Kayla Guo and Luke Broadwater contributed reporting.