Pennsylvania Sen. John Fetterman, who had a stroke during his campaign last year, remained hospitalized and undergoing tests after feeling lightheaded, with tests so far negative for another stroke or seizure, his office said Thursday evening.

An MRI at George Washington University Hospital, along with other tests run by doctors, rule out a new stroke, Fetterman’s communications director Joe Calvello said in a statement Thursday evening.

Fetterman was being monitored with an electroencephalogram (EEG) — an instrument that measures brainwaves — for signs of a seizure, Calvello said.

“So far there are no signs of seizure, but he is still being monitored,” Calvello said.

Calvello gave no indication about when Fetterman might leave the hospital, but had said late Wednesday that Fetterman was “in good spirits and talking with his staff and family.”

Fetterman felt lightheaded Wednesday while attending a Democratic retreat in Washington and went to the hospital, staying overnight for testing.

In November, Fetterman, 53, won the seat held by now-retired Republican Pat Toomey after a hard-fought contest against GOP nominee Mehmet Oz.

Fetterman, who was the lieutenant governor, defeated the celebrity heart surgeon by 5 percentage points, flipping a seat that was key to Democrats holding the Senate majority. More than $300 million was spent during the campaign, making it the most expensive Senate race in 2022.

His campaign was derailed on May 13 when he had what he later called a near-fatal stroke just days before the Democratic primary.

He underwent surgery to implant a pacemaker with a defibrillator to manage two heart conditions, atrial fibrillation and cardiomyopathy, and spent much of the summer recovering and off the campaign trail.

He refused to release his medical records or allow his doctors to answer reporters’ questions, as Oz made an issue of whether his opponent was honest about the effects of the stroke and whether Fetterman was fit to serve. The Democrat insisted his doctors said he could have a full recovery.

As a result of the stroke, Fetterman has struggled with auditory processing disorder, a common aftereffect that can can leave a person unable to speak fluidly and quickly process spoken conversation into meaning.

The effects of the stroke were apparent in Fetterman’s uneven performance during the fall campaign’s only debate when he struggled to complete sentences and jumbled words.

On election night, he told cheering supporters he ran for “anyone that ever got knocked down that got back up.”

Fetterman, a presence at 6-foot-8 with a clean-shaven head and a goatee and known for wearing hoodies and shorts, was lieutenant governor from 2019-2023. He served as mayor of Braddock, Pennsylvania, from 2006-2019.

(AP)