Part 5. Reading Comprehension

Decoding a Disorder at the Interface of Mind and Brain

It all began with a cough. Three years ago Tracey McNiven, a Scottish woman in her mid-30s, caught a bad chest infection that left her with a persistent cough that refused to subside, even after medication. A few months later strange symptoms started to appear. McNiven noticed numbness spreading through her legs and began to feel that their movement was out of her control. When she walked, she felt like a marionette, with someone else pulling the strings. Over the course of two weeks the odd loss of sensation progressively worsened. Then, one evening at home, McNiven's legs collapsed beneath her. "I was lying there, and I felt like I couldn't breathe," she recalls. "I couldn't feel below my waist." McNiven's mother rushed her to the hospital where she remained for more than half a year.

During her first few weeks in the hospital, McNiven endured a barrage of tests as doctors tried to uncover the cause of her symptoms. It could be a progressive neurodegenerative condition such as motor neuron disease, they thought. Or maybe it was multiple sclerosis, a disease in which the body's own immune cells attack the nervous system. Bafflingly, however, the brain scans, blood tests, spinal taps and everything else came back normal.

McNiven's predicament is not uncommon. According to one of the most comprehensive assessments of neurology clinics to date, roughly a third of patients have neurological symptoms that are deemed to be either partially or entirely unexplained. These may include tremor, seizures, blindness, deafness, pain, paralysis and coma and can parallel those of almost any neurological disease. In some patients, such complications can persist for years or even decades; some people require wheelchairs or cannot get out of bed. Although women are more often diagnosed than men, such seemingly inexplicable illness can be found in anyone and across the life span.

Generations of scientists have tried to understand these bizarre conditions, which have historically been given diverse names, such as hysteria, conversion disorder or psychosomatic illness. These labels have, however, long imposed particular explanations for what many researchers now regard as a complex illness at the interface of psychiatry and neurology. Some are still in use today, but the newest name for these conditions, functional neurological disorder (FND), is deliberately neutral, simply denoting a problem in the functioning of the nervous system.

Patients with FND have long struggled to obtain adequate care. They have been accused of feigning or imagining symptoms, painfully but often fruitlessly probed for childhood trauma and dismissed by doctors who did not know how to treat someone who, based on all the usual tests, appeared to be healthy. "For many, many years physicians have underestimated the prevalence of these disorders and the human toll it takes," says Kathrin LaFaver, a neurologist who specializes in movement disorders at Northwestern University's Feinberg School of Medicine. "These people have really fallen [in the gap] between the fields of neurology and psychiatry."

Over the past decade or so, however, using techniques such as functional magnetic resonance imaging (fMRI), researchers have begun to understand what happens in the brains of patients with this enigmatic illness. And by applying new models of how the brain works, they are gaining a better understanding of how the condition arises and how it may be treated.

Enigmatic Illnesses

More than 3,000 years ago Mursili II, king of the Hittites, was caught in a terrifying thunderstorm. The experience left him with a temporary speech impediment that went away – only to return several years later, after the monarch woke from a nightmare about the incident. His subjects attributed their king's curious ailment to the wrath of the Storm God, one of the most important deities of the ancient civilization. When modern-day scholars revisited the documents detailing the event, they interpreted it as functional aphonia (the inability to speak).

Like the Hittites, people throughout history have turned to the supernatural – gods, witchcraft and demonic possession – to explain illnesses that today would likely be diagnosed as FND. According to some historical interpretations, the first scientific attempt to account for them emerged around 400 B.C.E., when Greek physicians, including Hippocrates, coined the term "hysteria" to describe a wide collection of ailments, among them paralysis, headaches, dizziness and pain, in the belief that they were caused by the uterus (hystera, in Greek) wandering about the body.

Hysteria had its heyday in the 19th century, when it moved from the womb to the brain. Among several physicians who studied it was Jean-Martin Charcot, regarded by many as the "father of neurology." At the Salpêtrière Hospital in Paris, he painstakingly detailed the symptoms of patients with hysteria and, after they died, conducted autopsies on their brains. Although Charcot was unable to identify any structural aberrations in those subjects, he was convinced that the impairments he saw were associated with unobservable, fluctuating changes in the brain, which he called "dynamic or functional lesions."

Charcot also discovered that, contrary to common belief, male hysteria was not rare; instead it often went undetected. He highlighted, for example, cases of hysteria among workers at a national railway company that had seemingly emerged after minor physical injuries. His work popularized the study of hysteria, inspiring several researchers, including Joseph Babinski, Pierre Janet and Sigmund Freud, to investigate it as well.

Unlike Charcot, however, these men viewed the condition as a disorder of the mind rather than the brain. Freud proposed that it arose when repressed trauma from childhood abuse or other disturbing events was transformed into physical symptoms; accordingly, he called it conversion disorder. That view and label cemented the displacement of the disorder from the realm of neurology to that of psychiatry and became the dogma for much of the 20th century.

A century later a new generation of investigators has turned its attention to this condition. Careful observation of patients indicates that despite the drop in diagnoses in the latter half of the 1900s, these disorders have not disappeared. And new research reveals that the condition encompasses both neurology and psychiatry. In 2013 some physicians, concerned that the term "conversion disorder" was not widely accepted by patients and perhaps incorrectly pointed to psychology as an exclusive driver for the condition, lobbied for a change – causing FND to be included as an alternative name for the ailment in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5).

Predictions Gone Awry

A year after landing in the hospital because of her FND, McNiven was referred to a psychologist. At first, she did not think she needed to be there – her symptoms had been improving with physiotherapy. After several sessions of psychotherapy, however, McNiven made a shocking discovery: she had blocked the memory of certain key events in her childhood. Among those forgotten experiences were years of physical abuse at the hands of a family friend.

Although she had initially been reluctant to consider the role of psychological factors in her illness, McNiven now says that she thinks they do contribute. "I don't think it's just purely down to that," she tells me. "But it certainly does have a big impact." Many of those who study FND today would agree – with caveats. Unlike Freud, who focused on the role of repressed trauma, researchers now recognize that myriad factors are associated with this condition. These include predisposing factors, such as adverse experiences during childhood, a previous physical injury or mood and anxiety disorders; triggers such as physical injury or a stressful life event; and maintaining factors, such as a lack of access to proper treatment or a patient's responses to and beliefs about the condition. The leading framework for thinking about FND, the so-called biopsychosocial model, takes all these factors into account.

An abridged version of an article from Scientific American, 1 November 2020