Johnny Sexton has hit back at comments from a French neurologist who speculated over the Ireland captain's history of concussion.

Sexton described Dr Chermann's comments as "inaccurate and highly inappropriate".

The Ireland captain is going through return-to-play protocols having been taken off following a clash of heads in the second half of Ireland's defeat by Wales on Sunday, after which he received a head injury assessment.

Should he pass the next stage of the process, he will be allowed to take part in non-contact training with the team on Thursday, before returning to full-contact training if he receives approval on Friday.

What was said?

Dr Chermann recommended Sexton's three-month break in 2014 after the fly-half sustained a series of head injuries in a short space of time.

Sexton played for Paris-based side Racing from 2013 to 2015.

"The doctor's part, fundamental to this story, is... if there are symptoms, if his tests are disturbed, the doctor must stop him from playing on Sunday," Dr Chermann said on Tuesday.

"Conversely, if there are no symptoms, if the tests are perfect, the fact that he has had many concussions before is a problem. But I think we do not have enough obvious elements to prevent him from continuing his rugby career."

Speaking to the media on Wednesday, Sexton said he was "shocked and saddened" by Dr Chermann's comments.

"I just think it's totally inappropriate that a doctor who I last saw many years ago now felt it was appropriate to come out and talk to whoever it was and say those things," Sexton said.

"I'm pretty disappointed but I'm so used to it that it's sort of like water off a duck's back - but for my wife and mum, it's very upsetting but that's the world we live in.

"I thought there was patient-doctor confidentiality; I'm pretty sure that exists in the world.

"I just can't get over the fact that someone thought it was appropriate to just come out of nowhere and start saying things that weren't even accurate, that's the most hurtful thing.

"We've been here before and could sit here talking about it for 20 minutes, but I'm never going to win out of it.

"Last time I did it, this has happened twice before, I tried to give facts and defend myself and I'm in the papers for being selfish and not looking after younger players going through the system."

'Sometimes it can wear you down'

Having endured a generally disappointing spell in France, Sexton often becomes the focal point of the build-up to Ireland and France's annual Six Nations meeting.

Should Sexton fail the return-to-play protocols, head coach Andy Farrell will call upon either Billy Burns or Ross Byrne to fill in for the captain.

"It seems to be always the French game coming up where something happens, either before or after," Sexton said.

"You get used to dealing with these type of things when you're captain of your country.

"It's a privileged position to be in. Sometimes it can wear down on you and you need to be reminded that there's a lot of people that would swap in for your job, so try to enjoy it."

Having lost to Wales, Ireland's hopes of winning the tournament realistically require them to win their four remaining games.

France dismantled Italy in their opening Six Nations game and come to Dublin as favourites to win this year's competition.