A brain tumour caused a 40-year-old man to become obsessed with sex and to molest children, doctors have reported.

The married schoolteacher from the United States, who had no previous history of sex offences, had an egg-sized tumour in the right lobe of the orbifrontal cortex, according to a report from newscientist.com.

This is the part of the brain responsible for judgement, impulse control and social behaviour.



The difference in this case was that the patient had a normal history before he acquired the problem

Dr Jeffrey Burns, University of Virginia

Doctors said that the location of the tumour played a key role in this case.

They said there was no evidence to suggest that other types of brain tumours could have a similar effect.

The man first began secretly visiting child pornography websites and soliciting prostitutes at massage parlours.

His wife evicted him from the family home after discovering he had made subtle sexual advances to young children.

Guilty verdict

He was then found guilty by the courts of molesting children and entered a treatment programme for convicted paedophiles.

A judge ordered him to sign up to a Sexaholics Anonymous rehabilitation programme or face going to prison.

However, the man was expelled from the programme after continuously asking women there for sex.

The evening before he was due to go to prison, he went to hospital complaining of a headache and saying he was afraid he would rape his landlady.

After he was remanded to psychiatric care, he complained of balance problems. A MRI scan revealed he had an egg-sized brain tumour.

Further tests found he was also unable to write or copy drawings and was unconcerned when he urinated on himself.

The tumour was removed and within seven months the man had completed the Sexaholics Anonymous treatment programme and was once again living at home.

In October 2001, he complained of headaches and started to secretly collect pornography again.

A MRI scan revealed that the tumour had regrown. It was removed and his behaviour disappeared.

Medical reasons

Russell Swerdlow and Jeffrey Burns of the University of Virginia who treated the patient said it suggested that doctors should consider brain tumours as the reason why some people became sex offenders.

But they warned that this only applied to people who suddenly become obsessed with sex and who have no previous history.

"If someone argues that every paedophile needs a MRI, the difference in this case was that the patient had a normal history before he acquired the problem," Dr Burns said.

"Most paedophiles develop problems early on in life."

But Dr David Rosenfield, a behavioural neurologist at the Baylor College of Medicine in Houston, said further research is needed.

"They have an interesting patient. I would wonder whether the tumour caused hormonal changes," he told newscientist.com.

The case study was presented at the annual meeting of the American Neurological Association in New York.