McConnell công bố thư xác nhận “Hoàn toàn khỏe” để tiếp tục làm việc sau sự cố.

Senator Mitch McConnell, the minority leader, on Thursday released a letter from the attending physician of Congress pronouncing him “medically clear” to continue his schedule as planned, a day after the Kentucky Republican froze up suddenly at a news conference in what appeared to be a medical episode similar to one he had on camera last month.

“I have consulted with Leader McConnell and conferred with his neurology team,” Dr. Brian P. Monahan said in a brief statement on his letterhead that was made public by Mr. McConnell’s office on Thursday afternoon. “After evaluating yesterday’s incident, I have informed Leader McConnell that he is medically clear to continue with his schedule as planned.”

Dr. Monahan said that “occasional lightheadedness is not uncommon in concussion recovery and can also be expected as a result of dehydration.” Mr. McConnell sustained a concussion this year after falling at a Washington hotel.

Dr. Monahan did not say that he had examined Mr. McConnell, 81, whose increasingly frail appearance and recent string of medical incidents have alarmed his colleagues and raised questions about his ability to continue in his post.

In a piece published on Thursday shortly after Mr. McConnell released Dr. Monahan’s assessment, the editors of the conservative National Review wrote that it was obvious that the episodes had affected Mr. McConnell’s ability to represent Senate Republicans. “The time has come for the Kentucky senator, after his long, impressive run, to make the decision to step aside from leadership,” they wrote.

Neurologists said that concussions could lead to a range of more prolonged symptoms, especially in combination with other medical conditions in older patients, and that it was difficult to assess Mr. McConnell without examining him.

But they said that abrupt cessations in speech followed by relatively quick recoveries were not the most common patterns of symptoms in patients suffering from nothing more than lightheadedness or dehydration.

They said that Mr. McConnell’s symptoms appeared to be more indicative of seizures, electrical surges in the brain that can leave patients awake and aware enough to answer very simple questions even as they abruptly lose the ability to speak or process more complicated questions.

Another possible explanation was ministrokes, formally known as transient ischemic attacks, resulting from a clot that reduces blood flow to the brain, though some experts said those attacks were less likely to look so similar on two separate occasions.

“Someone with these types of events needs to see a neurologist,” said Dr. Joshua Willey, an associate professor of neurology at the Columbia University Vagelos College of Physicians and Surgeons. “If someone experiences a spell like this, please don’t say, ‘It’s just dehydration.’”

Dr. Monahan’s short statement was the only medical information to be released by the famously tight-lipped Mr. McConnell in months, since his March fall. That incident left him absent from the Senate for weeks as his office shared little about his health status. Since then, he has had at least two more falls, which his office did not disclose.

Last month, after Mr. McConnell froze midsentence during an appearance at his weekly news conference in the Capitol and was briefly escorted away from the microphones to recover, his office did not even say whether he had been evaluated by a doctor. Instead, it emphasized that he had continued with business as usual for the rest of his day, even attending a reception hosted by Major League Baseball that same evening.

After Wednesday’s spell, a spokesman said Mr. McConnell planned to be examined by a doctor before continuing on to his next event, but no update was provided about a diagnosis.

Unlike the president, who is required to make public the detailed results of his annual physical, members of Congress are not required to release any information about their health. But the second public episode, which took place in Covington, Ky., increased the pressure on Mr. McConnell to offer some explanation of what was going on.

With his fellow senators scattered on congressional trips and family vacations during Congress’s long summer recess, Mr. McConnell was taking steps to reassure worried colleagues — mostly left in the dark about his condition — that he was in good health and able to continue serving as minority leader. His office circulated the brief statement from Dr. Monahan to senators, and he was also making personal calls to underscore the message that nothing was amiss.

Senator Susan Collins, Republican of Maine, said Mr. McConnell reached out to her Thursday and sounded fine during their conversation. He blamed dehydration for the episode, she added, and said that it was only the second time such a thing had occurred.

Mr. McConnell, who spoke with members of his leadership team on Wednesday after the incident, also connected by phone with President Biden on Thursday.

“He was his old self on the telephone,” Mr. Biden, who has been the target of vicious Republican attacks about his age and mental acuity, told reporters on Thursday after his conversation with Mr. McConnell. Mr. Biden attributed the freezing episodes to a normal process of recovery from a severe concussion and said he was “confident he’s going to be back to his old self.”

Carl Hulse contributed reporting from Washington.