A man made "sexual vocalisations", masturbated and attempted to have sex with his girlfriend while asleep because he was suffering with a rare disorder.
The 33-year-old would suffer intense bouts of "sexsomnia" several nights a week.
Although his actions were not aggressive, the constant nighttime harassment would disrupt his girlfriend's sleep.
The man had no memory of his behaviour but admitted to doctors that his ex-lover would have to fend off his sexual advances.
Further investigations into the man's strange nocturnal behaviour was triggered by rapid "head jerks" or spasms, MailOnline reports.
Sexomnia is a type of sleep disorder named parasomnia, with more common examples including bed wetting and sleepwalking.
The rare disease reportedly only accounts for seven per cent of referrals to sleep clinics
But sexomnia has caused a lot of controversy in the UK in instances of men accused of rape have claimed to suffer from it.
A number of things can trigger the disorder. including narcolepsy, sleep deprivation and apnea.
As well as this, depression, teeth grinding and excessive alcohol or drug consumption can cause the strange nocturnal behaviour.
And now "sleep related head jerks" can be added to the list, thanks to the National Institute of Mental Health.
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Dr Jitka Bušková described the case as a man who was bombarding his girlfriend with "sexually motivated nocturnal behaviour".
This behaviour included "masturbation, sexual intercourse/attempted intercourse, and sexual vocalisations".
"His current girlfriend particularly complained of incitement to sexual intercourse, and her sleep was also disturbed by the patient’s sexual talking and groping," she said.
"She did not describe his behavior as being aggressive, but rather as harassing. The patient was completely unaware of it."
The man's was studied by specialists that found his non-rapid eye movement sleep, considered the most important, was interrupted by movement of his neck muscles.
These head jerks triggered activity in part of his brain, despite the fact he would remain asleep.
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