Bill Pennington / New York Times News Service

BOSTON — The drumbeat of alarming stories linking concussions among football players and other athletes to brain disease has led to a new and mushrooming American phenomenon: the specialized youth sports concussion clinic, which one day may be as common as a mall at the edge of town.

In the last three years, dozens of youth concussion clinics have opened in nearly 35 states — outpatient centers often connected to large hospitals that are now filled with young athletes complaining of headaches, amnesia, dizziness or problems concentrating. The proliferation of clinics, however, comes at a time when there is still no agreed-upon, established formula for treating the injuries.

“It is inexact, a science in its infancy,” said Dr. Michael O'Brien of the sports concussion clinic at Boston Children's Hospital. “We know much more than we once did, but there are lots of layers we still need to figure out.”

Deep concern among parents about the effects of concussions is colliding with the imprecise understanding of the injury.

To families whose anxiety has been stoked by reports of former NFL players with degenerative brain disease, the new facilities are seen as the most expert care available.

That has parents parading to the clinic waiting rooms.

The trend is playing out vividly in Boston, where the phone hardly stops ringing at the youth sports concussion clinic at Massachusetts General Hospital.

“Parents call saying, 'I saw a scary report about concussions on Oprah or on the 'Doctors' show or Katie Couric's show,'” Dr. Barbara Semakula said, describing a typical day at the clinic. “Their child just hurt his head, and they've already leapt to the worst possible scenarios. It's a little bit of a frenzy out there.”

About three miles away, at Boston Children's Hospital, patient visits per month to its sports concussion clinic have increased more than fifteenfold in the last five years, to 400 from 25. The clinic, which once consisted of two consultation rooms, now employs nine doctors at four locations and operates six days a week.

“It used to be a completely different scene, with a child's father walking in reluctantly to tell us, 'He's fine; this concussion stuff is nonsense,'” said Dr. William Meehan, a clinic co-founder. “It's totally the opposite now. A kid has one concussion, and the parents are very worried about how he'll be functioning at 50 years old.”

Doctors nationwide say the new focus on the dangers of concussions is long overdue. Concerned parents are properly seeking better care, which has saved and improved lives. But a confluence of outside forces has also spawned a mania of sorts that has turned the once-ignored concussion into the paramount medical fear of young athletes across the country.

Most prominent have been news media reports about scores of relatively young former professional athletes reporting serious cognitive problems and other later-life illnesses. Several ex-NFL players who have committed suicide, most notably Junior Seau, a former San Diego Chargers and New England Patriots star, have been found posthumously to have had a degenerative brain disease linked to repeated head trauma.

State legislatures have commanded the attention of families as well, with 43 states passing laws requiring school-age athletes who have suffered a concussion to have written authorization from a medical professional, often one trained in concussion management, before they can return to their sport.

The two Boston clinics, one started in 2007 and the other in 2011, are typical examples of the concussion clinic phenomenon, busy centers of a new branch of American health care and windows into the crux of a mounting youth sports fixation.

“We are really in the trenches of a new medical experience,” said Richard Ginsburg, the director of psychological services at Massachusetts General Hospital's youth sports concussion clinic. “First of all, there's some hysteria, so a big part of our job is to educate people that 90 percent of concussions are resolved in a month, if not sooner. As for the other 10 percent of patients, they need somewhere to go.

“So we see them. We see it all.” Paul McDonough, of Quincy, Mass., whose daughter, Erin, is a high school hockey player and cheerleader who has had three concussions, said: “When you're reading autopsy results of NFL players with head trauma, as a parent, it doesn't make you very patient or put you at ease. That's why we're all going to specialists.”

Erin McDonough saw Dr. Cynthia Stein at the Boston Children's clinic. Among the things Stein routinely explains to patients is that pro football players like Seau may have taken thousands of hits to the head in youth leagues, high school and college — in addition to 10 or more years in the NFL

“Who knows how many concussions someone like Junior Seau really had?” Stein said. “And we don't know why he died. It's not an appropriate comparison. Our patients, if their concussions are managed properly, are going to heal on their own. The body knows how to take care of itself.”

The nationwide proliferation of youth sports clinics is a reaction to a health care demand. But are the clinics also profit centers?

Interviews with directors of youth concussion clinics nationwide produced a consensus that the clinics were not significant moneymakers because they were not procedure driven, meaning that they do not typically lead to expensive imaging tests or operations. Instead, they tie up doctors in lengthy, multifaceted patient consultations.

But Michael Bergeron, the executive director of the National Youth Sports Health and Safety Institute, offered an additional perspective. Bergeron agreed that the clinics do not usually lead to costly procedures, but he said the volume of patients they attracted to an institution or an individual practice could have residual benefits that boosted the bottom line.

“Concussion clinics might be seen as a loss leader for the halo effect they bring the institution,” Bergeron said. “People recognize you as an authority offering a timely service that is very much in the news. It might make them consider you for other treatments, too. It's another dimension to promote on your website. It's an opportunity to lift your profile.”

Most clinic patients go to the clinics because they are referred by their pediatricians, their primary care physicians or the doctors attending to them during an emergency room visit. Emergency room visits by children and adolescents with brain injuries have increased by more than 60 percent in the past eight years, according to the federal Centers for Disease Control and Prevention.

“Parents are better informed and they want these injuries better managed, which is the right reaction,” said Kevin Guskiewicz, the founding director of the Matthew Gfeller Sport-Related Traumatic Brain Injury Research Center at the University of North Carolina. “So I'm not surprised there are all these concussion clinics sprouting up to treat their kids. Time will tell if it is a novelty. What happens when the heightened awareness and fear subsides?”