Sen. Dianne Feinstein, 89, returned to Washington last week after having suffered more severe health complications from her shingles diagnosis than were previously disclosed.

Feinstein’s shingles triggered encephalitis, which is inflammation of the brain, as well as Ramsay Hunt syndrome, which causes facial paralysis, according to Feinstein spokesman Adam Russell, who added that the senator has since recovered from the encephalitis complication. The additional health issues, stemming from the case of shingles that hospitalized the six-term senator in February, were first reported by the New York Times.

Feinstein (D-Calif.) returned to the Senate last week after facing pressure to resign from a few members of Congress and California progressive groups, who complained her months-long absence was slowing judicial confirmations and imperiling the Democratic agenda.

Feinstein returned in a wheelchair and was greeted outside the Capitol by Senate Majority Leader Charles E. Schumer (D-N.Y.), who later said that he planned “to move forward on many more judges” with her vote in the coming weeks.

Although her return has resolved Democrats’ math problem on close votes, her condition has raised concerns that she might not be up for the demands of the job.

The pathbreaking senator has withstood multiple rounds of calls for her resignation even before her recent illness, as unflattering anecdotes emerged about her memory lapses and her perceived cognitive decline, as well as her visible reliance on aides in public-facing aspects of her job.

This week, that picture worsened, as she faced questions from reporters from her wheelchair as she appeared to be struggling with her vision and memory. She sounded confused in responding to one group of reporters about her weeks-long absence, saying “I’ve been here” and insisting that she hadn’t been gone from the Capitol, according to the Los Angeles Times. And on Thursday, Feinstein denied she had been diagnosed with encephalitis, characterizing it as a “really bad flu,” in a brief hallway interview with CNN.

Her office later clarified that Feinstein “misspoke” in the interview because her doctors had not used the term encephalitis with her during her treatment.

“When discussing the shingles complications with her doctors, they often spoke in broader terms when describing the complications, rather than always using medical terminology,” Russell said in a statement.

Her aides said last week she would be working a “lighter” schedule as she continued to suffer some complications from the shingles, including vision and balance trouble, and she has missed a few votes since her return.

Feinstein is not running for reelection but has said she plans to serve out the remainder of her term. Her allies and former aides say Feinstein never wavered in her desire to return to Washington and in her disinterest in resigning in recent weeks.

If she does step down, Gov. Gavin Newsom (D) has said he would appoint a Black woman to her spot, which could scramble the California Senate race to replace her, dominated by Democratic Reps. Adam B. Schiff, Barbara Lee and Katie Porter. Lee, a Black woman, would have an advantage in the primary if Newsom were to tap her as Feinstein’s replacement — a fact that has led to public sparring between allies of different candidates over Feinstein’s fate.

“It’s a sad situation,” said Rep. Ro Khanna (D-Calif.), who supports Lee and has previously called on Feinstein to resign. “I wish people just would put politics aside and talk to her about stepping down. That is the morally right thing to do and the right thing for our nation.” (Khanna added that he wanted Feinstein’s friends and family to convince her to step down.)

But Feinstein’s allies have pushed back on calls for her to resign, with Rep. Nancy Pelosi (D-Calif.), who backs Schiff in the primary, suggesting those calls are sexist.

Pelosi’s eldest daughter, Nancy Corinne Prowda, has also been accompanying Feinstein throughout her illness in San Francisco and now back at the Capitol, and has been friends with the senator for decades, according to Feinstein’s office. Prowda’s position at Feinstein’s side has led some to suggest Pelosi is supportive of Feinstein remaining in her role to boost her preferred candidate, Schiff. It’s an accusation Pelosi firmly denied Thursday.

“Speaker Emerita Pelosi and Senator Feinstein have been friends since long before their service in Congress — and their friendship is personal, not political,” Pelosi’s spokesman Aaron Bennett said in a statement. “Anyone who knows Senator Feinstein knows that her service in the Senate is entirely her own decision, and Speaker Emerita Pelosi would never suggest otherwise.”

Republicans blocked a proposal to allow Feinstein to be temporarily replaced on the Judiciary Committee during her months-long absence, putting more pressure on Feinstein to return while a few judges languished in the committee.

Democrats celebrated Feinstein’s return last week, given her vote is often crucial to push through the priorities of their narrow majority in the Senate. Sen. Richard J. Durbin (D-Ill.), chair of the Judiciary Committee who has complained that her absence hamstrung his committee at a crucial time, expressed his “relief” on May 12 that she was back. Her return also takes pressure off Schumer, who now can count on Feinstein’s vote when needed for close confirmations — even if her health troubles appear to be lingering.

“I’m back in Washington, voting and attending committee meetings while I recover from complications related to a shingles diagnosis,” the senator said in a statement. “I continue to work and get results for California.”

Feinstein has been a towering figure in California for more than five decades, entering politics in 1969 when she was elected to the San Francisco Board of Supervisors, and later becoming the first female mayor of San Francisco. Since winning her Senate seat in a special election in 1992, Feinstein has been reelected five times, tangling with the intelligence community in her determination to release information about the government’s clandestine use of torture and playing a key role in the passage of the now-expired assault weapons ban.

She’s resisted calls to step aside from some Democrats before, including when she ran for reelection at 85 years old in 2018. But she has also slowly relinquished some of her Senate roles since then. She stepped down as the top Democrat on the Senate Judiciary Committee when she was on track to become the first woman to chair the powerful panel. And last year, Sen. Patty Murray (D-Wash.) became president pro tempore of the Senate, a position third in line to the presidency given to the most senior senator of the party in power, after Feinstein declined to take the title.

When she announced earlier this year that she would retire at the end of her term, Senate colleagues regaled her legacy with high praise, calling her “a legend,” “a titan,” and, in the words of President Biden, her former Senate colleague, “one of the very best.”

Shingles is caused by the varicella-zoster virus, which causes chickenpox in childhood but can hide out in people’s nerve cells and reactivate years later. Feinstein has received the shingles vaccine, her office said previously.

A Danish study found that encephalitis related to the varicella-zoster virus occurred mainly in elderly and immunocompromised people, and risk factors for a poor outcome included advanced age.

“A full spectrum of recovery is possible, ranging from complete recovery to lingering symptoms. These almost always improve with time,” said Anne Louise Oaklander, a neurologist at Massachusetts General Hospital, who said it was impossible to know a patient’s case without examining them firsthand. She said in general, young and healthy people tend to be the most resilient.

Felicia Chow, a neuro-infectious disease specialist at the University of California at San Francisco, said that diagnosing encephalitis in shingles is tricky and that to truly understand Feinstein’s case, more information is needed on the severity of encephalitis and how quickly treatment was started. Identifying the encephalitis early usually leads to better outcomes.

She also said that a range of outcomes were possible for patients, but that age and preexisting cognitive issues could put a person at higher risk of lingering neurological impairment. “Just given her age alone, the outcomes and potential neurological issues after an infection like that are a lot higher risk for ongoing neurological impairment,” Chow said.