U.S. Sen. Richard Blumenthal didn't get the response he was expecting from Gary Bettman when he wrote the NHL commissioner questioning the league's repeated denial of a link between concussions and a chronic brain disease.

"I was surprised and appalled, because I thought the response would be more receptive," Blumenthal told Sports Illustrated's Alex Prewitt on Thursday.

Earlier this week, Bettman responded to a letter from Blumenthal which sought answers from the NHL about its reluctance to admit a link between the sport and chronic traumatic encephalopathy, which scientists say is caused by repeated blows to the head.

The commissioner cautioned the senator against "speculation and fear mongering," reiterating his long-held stance that the relationship between concussions and CTE remains unclear.

Blumenthal said Thursday that Bettman's response should have been more proactive.

"I would've welcomed an acknowledgement for stronger action and a commitment to determining whether the game is causing these heartrending injuries with such painful consequences, rather than dismissing the link between hockey and CTE."

The senator also expressed his disappointment with the league in a series of tweets earlier Thursday morning.

Former NHL enforcer Derek Boogaard was diagnosed with CTE after his death in 2011.

Jeffrey B. Miller, a high-ranking NFL official, acknowledged a link between CTE and playing football back in March.

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