Mysterious condition dogs many

It’s been described as one of the greatest medical mysteries of all time. All of a sudden, a patient is struck down by blindness. Others are paralysed. Some endure violent fits.

But when doctors do all the usual tests, they struggle to find anything physically wrong with them. There is nothing wrong with their eyes. They don’t have epilepsy. When they sleep, their paralysis disappears.

It is a condition thought to affect up to 30 per cent of people referred to neurology clinics, and others not yet diagnosed.

‘‘There are thousands of people out there right now that probably have this disorder and don’t know it,’’ says Professor Richard Kanaan, from the The Florey Institute of Neuroscience and Mental Health.

The condition is named conversion disorder or a type of functional neurological disorder.

Some also believe that conversion disorder explains cases of shell shock in traumatised World War I soldiers – the men pulled from the trenches, trembling and struggling to see, who were sometimes tried and punished for their ‘‘cowardice’’.

In modern times there has been an enduring theory that conversion disorder’s physical symptoms are often prompted by stress or trauma. But the condition has long been stigmatised and doubted, even by some in the medical profession.

Psychiatrists who work with conversion disorder patients have no doubt the symptoms are real, although research into the mechanism of the disorder could be misunderstood.

Kanaan said research he’s been involved in found many patients fall sick when the sickness can provide escape from stress – what’s described as a ‘‘secondary benefit’’. One patient was a woman who collapsed, had a fit and was left on the ground unable to move when her partner of 12 years broke up with her.

Dr Andrew Court, a psychiatrist and paediatrician at Australia’s Royal Children’s Hospital, said he also sees child patients overwhelmed with stress who experience seizures, blindness and lose the ability to walk. He stressed the disorder is ‘‘unconscious and not put on’’.

Brisbane neurologist Dr Alex Lehn of the Mater Centre for Neurosciences sees about 100 patients each year and believes it is generally multiple factors (biological, physical, psychological and social) that ‘‘push people over the line’’.

Lehn said while not everyone had a functional neurological disorder, everyone has probably experienced symptoms at some time – like a child who, during a school play, freezes and can’t get a word out.

‘‘Functional symptoms are super, super common – and they live in all of us,’’ he said.