Star neurosurgeon Dr Charlie Teo has told a medical disciplinary hearing he has more expertise in brainstem tumours than almost anyone in the world.
The Health Care Complaints Commission inquiry is investigating the circumstances surrounding two brain tumour operations performed by Dr Teo that left the patients with catastrophic brain injuries.
Appearing before the commission in Sydney on Thursday, the 65-year-old disagreed with two other neurologists, Professor Bryant Stokes and Associate Professor Andrew Morokoff, who appeared as expert witnesses the previous day.
The evidence related to whether one of the patient's tumours had spread to the left side of the brain, which both experts said it had, but Dr Teo said in his medical opinion that was not the case.
"My opinion was this was focal. Their opinion was this was diffuse," he told the inquiry.
"When I did this case I was hoping that I was right that there was a focal tumour that could be removed.
"I even said to the family, 'If I've got it wrong it could be terrible. If I've got it right it could be great'."
Dr Teo was grilled by the commission's counsel Kate Richardson about why he disagreed with the evidence of the two experts.
He said he would not expect them to know as much about brainstem tumours as he did because it wasn't their specialty.
"It's not just reading a brain scan, it's the nuances of a sub-sub-speciality," Dr Teo said.
"I have more experience with brainstem tumours and surgery thereof than almost anyone in the world."
At times the controversial surgeon became frustrated during Ms Richardson's questioning.
"I don't blame you for being confused ... but it's what I do for a living," he told her.
Ms Richardson said she would try to demonstrate a thread of Dr Teo not accepting the view of other practitioners regarding risk, which related to the potential for public harm.
Dr Teo, who is famous for performing neurosurgery on cancer patients with tumours other doctors have deemed inoperable, has been accused of charging exorbitant fees and offering some patients false hope.
In one of the cases, Dr Teo told the patient if she didn't have surgery by the following Tuesday she would be "f***ing dead by Friday", her husband told the hearing.
During the 2019 surgery, the woman received a frontal lobectomy in which a significant portion of her brain was removed - something her husband told the committee was not disclosed before the operation.
Medical consent experts Paul Komesaroff and Chris Ryan told the hearing that risk needed to be conveyed to patients to allow them to make informed consent.
On Wednesday, Assoc Prof Morokoff, Prof Stokes and another neurosurgeon, Professor Paul D'Urso, told the inquiry it was common during the course of operations to remove healthy brain tissue without first informing the patient.
"I think every brain surgeon in the country would be guilty of not declaring they take out normal brain tissue when they remove a brain tumour," Prof D'Urso said.
"You'd have nothing else to do other than have neurosurgeons in your commission if that was the line you took."
Dr Teo was restrained by the NSW Medical Council in August 2021 from operating without the approval of another doctor after an investigation by the state's health care complaints commission.
He has repeatedly denied any wrongdoing.
