Dale Earnhardt Jr.'s frustrating Sprint Cup season took another rough turn Thursday when he was ruled out of Sunday's race in New Hampshire with concussion symptoms.
Earnhardt will be replaced in the No. 88 Chevrolet by Alex Bowman. There is no timetable for Earnhardt's return to NASCAR's top circuit.
He was first evaluated by doctors this week in Charlotte. He was not cleared to drive Thursday in a follow-up appointment with a neurologist.
Earnhardt, 41, has a history with concussions and has been in recent crashes during races at Michigan and Daytona.
According to Hendrick Motorsports, Earnhardt felt poorly before last weekend's race in Kentucky and initially thought he was suffering from allergies. He was given medicine for allergies and a possible sinus infection, and when those didn't provide relief from his symptoms, Earnhardt consulted with a neurologist.
"Because of my symptoms and my history with concussions, and after my recent wrecks at Michigan and Daytona, I reached out and met with a neurological specialist," Earnhardt said in a statement released by Hendrick Motorsports.
"After further evaluation, they felt it best for me to sit out."
Earnhardt, perennially voted NASCAR's most popular driver, has not won a points race this season. His best results this year are second-place finishes at Atlanta, Bristol (Tenn.), Texas and Pocono (Pa.), so he still is in good shape to qualify for the season-ending Chase.
"I'm disappointed about missing New Hampshire this weekend," Earnhardt said. "I'm looking forward to treatment with the goal of getting back into the race car when the doctors say I'm ready."
Team owner Rick Hendrick commended Earnhardt on Thursday for seeking out medical help.
"I'm proud of Dale for standing up," Hendrick said. "The No. 1 priority is his health, so we're going to give him all the time he needs.
"We completely support the decision by the doctors and will be ready to go win races when he is 100 percent. In the meantime, we have full confidence in (crew chief) Greg (Ives) and the team, and we know they'll do a great job."
Earnhardt confirmed during April that he will donate his brain for medical research into concussion effects. Upon his death, his brain will go to the Concussion Legacy Foundation, which has ties to Boston University.
"Anything I can do to help others," Earnhardt said at the time. "It seemed like a reasonable thing to do."
While discussing his decision to donate his brain, Earnhardt said the key message to athletes is "to understand that it's OK to self-diagnose and get help."
NBC Sports Network NASCAR analyst Jeff Burton said it's important to change the culture of auto racing in regard to concussions.
"It takes a lot of bravery for Dale Jr., to step up and say, 'Hey, I'm not feeling right,' " Burton said on the air Thursday evening. "This is not how it worked in the past. The understanding of the long-term ramifications of concussions has opened a lot of people's eyes."
Bowman, 23, grew up in Tucson, Ariz., and now lives in Mooresville, N.C. He drove a Sprint Cup schedule in 2014 and '15, finishing 35th in the points standings as a rookie and 33rd in his second season. His best finish in 71 Sprint Cup starts is 13th in the second race at Daytona in 2014.
Bowman drove two races for what then was the Nationwide series for Earnhardt's JR Motorsports in 2014.
