Scientists are preparing to do a microscopic study of the Las Vegas gunman's brain, but experts say whatever they may find likely won't be what led him to kill 58 people.

Las Vegas authorities say Stephen Paddock's brain is being sent to Stanford University for a months-long examination after a visual inspection during an autopsy found no abnormalities.

Doctors will perform multiple forensic analyses, including an exam of the 64-year-old's brain tissue to find any possible neurological problems.

If a disease is found, experts say it would be false science to conclude it caused or perhaps even contributed to the worst mass shooting in modern U.S. history.

Such studies are not standard practice, but Brian Peterson, president of the National Association of Medical Examiners, said they are common in high-profile cases such as Paddock's, where so much is riding on the results that all forensic options must be exhausted.

The motive for the 1 October attack which left 58 people dead and more than 500 injured, the worse mass shooting in US history. still remains a total mystery. The shooter holed himself up on 32nd floor of the hotel in the heart of Las Vegas and opened fire on a 23,000-strong crowd attending a music concert below.