BOSTON (CBS) – Retired New England Patriots tight end Rob Gronkowski is taking issue with what an expert on concussions said about CTE.

Gronkowski revealed in a recent CBS News interview that he’s probably suffered 20 concussions in his football career, including “five blackout ones.” He went on to say he’s now “fixed.”

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Dr. Chris Nowinski is the CEO of the Concussion Legacy Foundation and co-founded Boston University’s CTE Center. The former Harvard University football player has a Ph.D. in behavioral neuroscience and is considered an expert on Chronic Traumatic Encephalopathy, or CTE.

“I appreciate and respect that you have the guts to talk honestly about concussions and CTE,” Nowinski tweeted Thursday in response to Gronkowski’s interview. “But right now CTE cannot be fixed – I invite your help in changing that.”

Gronkowski replied the next day.

“It is fixable. I fixed mine,” he tweeted. “There are plenty of methods in this world that allow the brain to recover from severe damage. That is also why I would allow my kid to play football.”

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Nowinski responded he’s glad the 30-year-old is doing well, “but neurodegenerative diseases (CTE, Alzheimer’s, etc.) cannot be ‘fixed’ or cured today. They eventually win.” He also invited Gronk to come to BU’s brain bank, where thousands of people, including NFL players, have pledged to donate their brains for CTE research.

CTE is a degenerative brain disorder associated with repetitive hits to the head, and has been seen in many professional football players. According to the BU CTE center, “there is no cure for CTE” at this time.

Nowinski told WBZ-TV, “The one message I want to leave people with is Gronk was referring to the effects of concussions, and we can fix the effects of concussions so if you have problems, go see a doctor and they can help you. However, it’s important to appreciate we cannot yet fix CTE and that’s something you should think about when you choose whether or not and when to enroll your child in tackle football.”

Since his retirement, Gronkowski has been promoting CBD products that he said have made him pain-free for the first time in a decade.

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He later tweeted again and said he is “not saying I cured it” but he found “unconventional methods to improve my conditions.”