Lightning... can cause fits and injury to the brain

Professor Andrew Lees, neurologist

However researchers from the Lightning Data Center of St Anthony Hospital in Denver, USA, say they found four lightning-strike patients who developed similar symptoms.

Professor Andrew Lees from the National Hospital for Neurology in London, said: "Lightning can injure the nervous system in many different ways.

"It can cause fits and injury to the brain."

However, the US research was unable to identify whether IMD symptoms were directly linked to lightning strikes or may have been incidental to the strikes.

They say further research needs to be carried out to establish the true picture and identify treatment options.

Electric shock therapy

Professor Lees identified several cases where people had been electrocuted and later developed IMDs.

He said: "It could be the electric shock was the straw that broke the camel's back in someone where IMDs were brewing."

IMDs are very difficult to treat and are usually irreversible, said Professor Lees.

However, he stressed that lightning strikes are uncommon and IMDs will not always follow.

He said: "Lightning is a very rare event.

"If you looked at 1,000 people who had been struck by lightning you may find one case of movement disorders."

He went on to point out that electric shock treatment is sometimes used as therapy for cases of severe depression which do not respond to medication, without undue side effects.

He said: "It is used less widely now, but has proved to be beneficial in clinical trials and psychiatrists still use it with the patient's consent."