The California senator recovered at home for some three months.
California Sen. Dianne Feinstein suffered complications from shingles that included Ramsay Hunt syndrome and encephalitis, or inflammation of the brain, her office confirmed on Thursday.
Feinstein, a Democrat, was diagnosed with shingles in February and was away from the Senate while recovering at home for some three months.
The New York Times first reported earlier Thursday that Feinstein suffered from encephalitis and Ramsay Hunt syndrome -- which affects facial nerves and can cause paralysis -- as a result of her shingles.
"Not everybody has complications with shingles but if you do they can be chronic and debilitating," said UCSF's Dr. Peter Chin-Hong, who is not associated with Dianne Feinstein, but an expert in the field.
A spokesperson for Feinstein subsequently said in a statement that "the senator previously disclosed that she had several complications related to her shingles diagnosis. As discussed in the New York Times article, those complications included Ramsay Hunt syndrome and encephalitis."
"While the encephalitis resolved itself shortly after she was released from the hospital in March, she continues to have complications from Ramsey Hunt syndrome," the spokesperson said.
Congressman Ro Khanna, a Democrat who represents part of the South Bay says, "I have a lot of respect for Senator Feinstein and I am wishing her the best in her return and recovery. That being said, I stand by my call for her to resign."
But that may be the opinion of just of a few. Political science professor and dean Melissa Michelson of Menlo College says Democrats are in a better position with her not resigning.
"At this point as long as she can show up and vote, it's better for the Democratic Party that she stays because even if she were to resign and Gavin Newsom appointed a new senator, the entire Senate would have to agree to give that new senator committee assignments," said Michelson.
Former lawmaker and current ABC7 political contributor Jackie Speier fired back at anyone calling for her resignation.
"The calls for her to resign really are three people out of 535. Right now, she's the senator, she's the senator, and she is back working at the capitol so I think those that have been asking for her to resign should just zip it!" said Speier.
Senator Feinstein has already been questioned over her contradicting responses to retirement questions and to where she was the last three months. Dr. Chin-Hong spoke about the risks after having brain complications with shingles.
"Puts you at risk for dementia, about twice the rate of dementia in older individuals," said Dr. Chin-Hong.
"There's no question that she has memory loss problems, there's no question about that, just take a look at the tapes take a look at the video. Does that keep her from doing her job? That's the question. Right now as far as Washington is concerned, her job is to hold up her hand and vote, after that they'll talk later," said ABC 7 News political insider Phil Matier.
At 89, Feinstein is the oldest member of the Senate. She has said she will retire at the end of her current term, in January 2025.
This is a developing story. Please check back for updates.
ABC7 News reporter J.R. Stone contributed to this report.