On rare occasions, it causes headaches, fever, severe brain swelling and even death, especially among the elderly.

An autopsy showed severe brain swelling.

The other 24 pupils, all aged between 10 and 12, were injured, including three who were hospitalised with severe brain and chest injuries.

The twins have had no major complications, like excessive bleeding or severe brain swelling, he said.

In 1948 Leslie died at home after a suffering a severe brain haemorrhage.

Over his last three days he developed severe brain swelling and fell into a deep coma.

Forty percent said there were such situations, ones of extreme impairment, like being in a vegetative state or being severe brain damaged.

But, he said, there was still severe brain swelling.

In children, however, mild to severe permanent brain damage is possible, especially in infants.

It's a 20th century technique, used before the correction of the majority of prenatal defects and with some severe brain or neural accidents.