Scientists are preparing to do a microscopic study of the Las Vegas gunman's brain, but whatever they find, if anything, likely won't be what led him to kill 58 people in the worst mass shooting in modern US history, experts said.

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, Las Vegas authorities said.

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

The brain will arrive in California soon, and Stanford has been instructed to spare no expense for the work, The New York Times reported.

It will be further dissected to determine if Paddock suffered from health problems such as strokes, blood vessel diseases, tumors, some types of epilepsy, multiple sclerosis, degenerative disorders, physical trauma and infections.