Stone's husband was recently bitten by a lizard

Strokes, seizures and the loss of mobility, speech, vision and memory are among the complications that could occur within that time, Dr Teitelbaum - who is not treating the actress - told People magazine.

Stone will have a second scan on Friday to find out whether she has an aneurysm, a weak spot on a blood vessel.

"You can't take something like this lightly," Dr Teitelbaum said.

The star was rushed to hospital on Saturday by her husband, San Francisco Chronicle executive editor Phil Bronstein.

A brain scan revealed the 43-year-old actress had a subarachnoid haemorrhage, or bleeding into the space between the brain and the middle membrane covering the brain.

She starred with Michael Douglas in Basic Instinct

She is now on medication.

Research suggests about 20% of stroke cases are caused by ruptured blood vessels leaking blood into the brain - called haemorrhagic strokes.

"If they didn't find an aneurysm, this bleeding could have come from some other source," Dr Ashok Anant, chief of neurosurgery at Maimonedes Medical Center in New York, said earlier.

"If they had found an aneurysm, she probably already would have had surgery."

Stone and her husband were also in hospital recently after Mr Bronstein was attacked by a reptile during a visit to the zoo in June.

The five-foot Komodo dragon bit him on the foot as he and his wife were given a private tour of Los Angeles zoo.

The lizard got hold of Mr Bronstein's foot after a zookeeper asked him to remove his white tennis shoes when he entered the cage, to keep the reptile from mistaking them for the white rats it is fed.