Celebrity Health

6:16 PM PT -- A rep for Rihanna tells TMZ the singer took antibiotics for three days leading up to the show, but they didn't work. Rihanna was then examined by a doctor at her rehearsal Monday, who decided to put her on vocal rest for 48 hours because the singer was at risk of damaging her vocal cords.

Rihanna has just cancelled her Grammy performance ... TMZ has learned.

The singer arrived at the Staples Center but did not walk the red carpet. She went to rehearsals and left.

Sources connected to the production tell us, Rihanna has been struggling with bronchitis and is on meds. We're told a doctor on site recommended that she pull the plug on the performance because it could permanently damage her vocal cords.

Our sources say Rihanna wanted to perform but reluctantly decided she had to listen to her doctors. She left Staples and is going home.

She was going to sing "Kiss It Better." She even rehearsed twice but in the end the show just could not go on.

No one wants to see LeBron James get the Zika virus during the Olympics ... especially Team USA managing director Jerry Colangelo who says they're doing everything they can to protect the players.

With everyone talking about the Zika scare in Latin America (and specifically in Brazil) ... people are wondering if it's worth sending our athletes to compete if there's a risk they'll get the virus.

"I sure hope no one's going to come back with the virus," Colangelo tells TMZ Sports.

"I think all the precautionary steps are being taken by the World Health Org., by the USOC and USA Basketball to limit that to hopefully nothing."

Stone Cold Steve Austin does NOT believe the WWE has a CTE problem on its hands -- saying the issues with Daniel Bryan are isolated ... and a direct result of his wrestling style.

Bryan retired from wrestling earlier this week -- citing health concerns (including post-concussion seizures) after suffering at least 10 concussions during his career.

The big question ... will Bryan's issues lead to a sweeping changes in pro wrestling to protect the entertainers?

Stone Cold doesn't think so.

Boxer Antonio Tarver says he was SET UP -- claiming he never used banned substances for his August '15 fight with Steve Cunningham ... and claims he's the victim in a diabolical frame job.

Tarver was suspended 6 months by the New Jersey State Athletic Control Board for testing positive for a synthetic testosterone.

Now, in a video statement from Tarver ... the 47-year-old is calling BS on the positive test -- saying he took several other tests that same week and passed with flying colors.

In fact, Tarver says only the test administered by a company hired by the fight promoter tested positive -- and Tarver says he was set up because he's adamant he never took a PED.

Tarver says he's asked to have his dirty sample sent to an independent lab to be tested -- but his requests have been ignored.

"I'm here to tell you today that I did nothing wrong," Tarver said ... "It's a frame job."

Rosie O'Donnell pissed off the autism community with a joke about autistic kids, which is why they're now calling Rosie a "piece of dog s***" ... and Rosie now has regrets.

O'Donnell performed at Carolines on Broadway Sunday, where she joked that parenting her teenagers was so tough she'd trade them in for autistic triplets in an instant.

A rep for the National Autism Association says her org is beyond offended. The rep didn't hold back, saying Rosie wasn't only "dog s***," she was mushy dog s*** on the bottom of their shoe.

The rep railed on, saying O'Donnell "crossed all lines of being a good human being to make a desperate, low-blow joke."

U.S. track superstar Sanya Richards-Ross says she's definitely concerned about the Zika virus scare in Brazil ... but it won't keep her from competing in the Olympic games in Rio later this year.

It's an issue athletes from all over the world are dealing with -- especially with the Zika virus spreading at a frightening rate in Latin America.

But SRS -- who's won gold before in the 400m and the 4x400 relay -- says she's not ready to cancel her travel plans.

"As of right now ... no, I would not consider not going to the Olympic games because it just means too much to me. This will probably be my last hurrah."

Sanya does however, acknowledge the Zika virus -- which can cause birth defects -- is still a real concern.

U.S. Olympic legend Amy Van Dyken just got a full-fledged apology from the U.S. Postal Service -- after a USPS truck blocked her from parking in a disabled spot at her neurologist's office.

Amy -- who uses a wheelchair after suffering a spinal cord injury back in 2014 -- took video at the Barrow Neurological Institute in Phoenix ... showing a truck parked in the disabled space despite the fact there are BUNCH of other open spaces in the parking lot.

Now, we've learned the USPS has reached out to Amy to apologize calling the situation "absolutely unacceptable."

In fact, the USPS sent a statement to Van Dyken saying ... "The action documented in your video is against Postal Service policy and is absolutely not acceptable behavior."

"We sincerely apologize for your experience, and assure you we are looking into this situation to ensure it does not happen again in the future. Thank you for bringing this to our attention."

Atlanta Falcons owner Arthur Blank has just revealed he's been diagnosed with prostate cancer -- but says he's battling like hell ... and vows to defeat it.

73-year-old Blank says he was diagnosed in December -- and has since visited with several doctors and hospitals to come up with the best battle plan.

Blank -- who co-founded The Home Depot in 1978 -- says he has chosen an "aggressive approach" which will require surgery -- and the overall prognosis is good.

Lamar Odom is doing so well, if you didn't know he was at death's door in October, you would never know he suffered 12 strokes and was unable to walk or speak.

As we reported, Lamar went hiking with Kim and Khloe over the weekend. The doctors never thought they would see the day. But even more surprising ... Lamar's cognitive functions have significantly returned ... he's able to process thoughts, speak them and carry on conversations.

Lamar had significant problems recognizing people -- even family members -- for several months after he was rushed to the hospital. But now his recall is back.

We're told Lamar's not completely back. He's still "a bit slow," and has memory lapses and sometimes has problems speaking. But the issues are subtle.

As for the hike, we're told his goal is to be able to run again. He's not there, but he's determined and believes he still has a shot at playing basketball again.

We're told Lamar's trajectory is so miraculous, he has a shot at living independently in a matter of months.

Zsa Zsa Gabor was rushed to the ER Monday ... 2 days after her 99th birthday, TMZ has learned.

Gabor was having difficulty breathing ... husband Frederic von Anhalt tells us.

Zsa Zsa's doctor came to her home and removed mucus from her throat, but it didn't cure the problem. Zsa Zsa was admitted to an L.A. hospital Monday morning.

Docs determined she has a feeding tube-related lung infection.

We're told Zsa Zsa's scheduled to undergo surgery to have her breathing tube removed.

Gabor has made frequent trips to the hospital over the last decade. Her right leg was amputated in 2011.

WWE superstar Daniel Bryan is officially DONE in the squared circle -- claiming he's retiring at 34 years old for medical reasons.

Bryan just issued a statement saying, "Due to medical reasons, effective immediately, I am announcing my retirement. Tonight on Raw, I'll have a chance to elaborate. #gratitude."

Bryan has talked about his medical issues in the past -- telling "Busted Open" he had concussion issues.

He has also praised WWE for protecting him by making him seek treatment from a barrage of specialists and preventing him from getting in the ring until he was cleared by doctors.

Now, with this announcement ... it doesn't appear he'll ever get the clearance and that might be why he's hangin' it up for good.

Story developing ...

Playboy and Instagram sensation Katie May took a nasty fall during a photo shoot last week, injuring her neck, and that is the leading candidate for what caused her fatal stroke ... TMZ has learned.

Sources with direct knowledge of Katie's situation tell us the accident happened late last week when she was shooting in Los Angeles. We're told Katie's neck pain after the fall was so bad, she went to a hospital to get checked out, and was released later that day.

But on Friday the pain remained -- she tweeted, "Pinched a nerve in my neck on a photoshoot and got adjusted this morning. It really hurts!"

Our sources say the operating theory is the 34-year-old model did not pinch a nerve, but instead tore the carotid artery in her neck. As we first reported, doctors told Katie's family the tear caused a blood clot which broke off and caused her stroke on Monday. It's called a carotid artery dissection.

Seems Michael Schumacher's health has taken another turn for the worse -- so says his former Ferrari boss who gave a cryptic update about the 7-time Formula One champ.

"I have news and unfortunately it is not good," said Luca di Montezemolo, the former president of Ferrari.

Luca didn't get into specifics when addressing reporters Thursday.

"Mob Wives" star Big Ang is in dire straits in her fight against stage 4 lung and brain cancer so her family is turning to marijuana as a last resort.

Ang didn't respond to the chemo treatments she started after the New Year, in fact her family says one of the tumors got bigger. Her sister Janine tells us Ang isn't on her deathbed, but her breathing is labored and she's in a lot of pain.

They've decided to try managing her pain with cannabis oil. Some patients believe the alternative treatment can even shrink tumors (that hasn't been scientifically proven) -- but it ain't cheap, going for as much as $60 per gram. The family is raising money via a GoFundMe page.

Ang is too tired to do anything, but Janine is hoping the cannabis oil will at least keep her pain-free.

Rob Kardashian is contacting his old party buddies and his family thinks it's a sign he's off the wagon in a big way ... and they blame it all on Blac Chyna.

Sources connected to the Kardashians tell TMZ, about 2 weeks ago -- the same day Khloe came home from a trip and found Rob and Chyna in her kitchen -- someone in the family received a call from a guy who used to party with Rob. We're told the guy is now clean and wanted them to know Rob had been calling other party friends as well, and he says Rob was trying to score drugs.

Chyna wanted to make it appear she was making Rob healthy again, cooking for him and inspiring him to exercise. Yet as we first reported, in addition to being drunk in Austin, cops say they found ecstasy pills in her sunglasses case.

The Kardashians believe it's clear ... Rob is in great danger of relapsing, and they believe it's all Chyna's doing.

What's more, the family is deeply concerned Rob's life is in danger because they think he's not taking his diabetes meds. We've learned when Kris Jenner beelined it for Chyna's house last Friday, she arrived with Rob's insulin and other Rx meds, worried he had stopped taking them.

Problem is ... Rob's not listening to anyone -- except Blac Chyna.

Leo DiCaprio may have won a SAG award, but he's lost respect from the American Lung Association for his e-cigarette display at the ceremony.

The actor was sitting at a table Saturday during the awards presentation, smoking a vape pen.

It's illegal to smoke vape pens in the city of L.A. in restaurants, bars and other public places, but interesting, the prohibition does not apply to "theatrical production sites." Presumably, the Shrine Auditorium, where the SAG awards were held, qualifies as a theatrical production site.

Nevertheless, the American Lung Association is now calling Leo out, calling his conduct "deeply troubling." The Ass'n notes vape pens expose others to secondhand dangers, including cancer.

We reached out to Leo's people ... so far, no word back.