Is FND a rare disease? Yes

Is FND a rare disease? In sort yes!

Under( N.O.R.D ) National Organisation's for Rare Diseases , FND is still considered a rare disorder.

What is FND you might ask?

Functional neurological disorder (FND) is a medical condition in which there is a problem with the functioning of the nervous system and how the brain and body sends and/or receives signals, rather than a structural disease process such as multiple sclerosis or stroke. FND can encompass a wide variety of neurological symptoms, such as limb weakness or seizures.

FND is a condition at the interface between the specialties of neurology and psychiatry. Conventional tests such as MRI brain scans and EEGs are usually normal in patients with FND. This had led, historically, to the condition being relatively neglected by both clinicians and researchers. However, it is now established that FND is a common cause of disability and distress, which may overlap with other problems such as chronic pain and fatigue. Encouraging studies support the potential reversibility of FND with specifically tailored treatments. New scientific findings are influencing how patients are diagnosed and treated which is creating an overall change in attitude towards people with FND.

Older ideas that FND is “all psychological” and that the diagnosis is made only when someone has normal tests have changed since the mid-2000s. The new understanding, including modern neuroscientific studies, has shown that FND is not a diagnosis of exclusion. It has specific clinical features of its own and is a disorder of the nervous system functioning in which many perspectives are necessary. These vary a lot from person to person. In some people, psychological factors are important, in others they are not.

But what Causes FND you might ask?

The exact cause of FND is unknown, although ongoing research is starting to provide suggestions as to how and why it develops. Many different predisposing factors can make patients more susceptible to FND such as having another neurological condition, experiencing chronic pain, fatigue or stress. However, some people with FND have none of these risk factors.

At the time FND begins, studies have shown that there may be triggering factors like a physical injury, infectious illness, panic attack or migraine which can give someone the first experience of the symptoms. These symptoms normally settle down on their own. However, in FND the symptoms become ‘stuck’ in a ‘pattern’ in the nervous system. That ‘pattern’ is reflected in altered brain functioning. The result is a genuine and disabling problem, which the patient cannot control. The aim of treatment is to ‘retrain the brain’, for example by unlearning abnormal and dysfunctional movement patterns that have developed and relearning normal movement.

One way of thinking about FND is looking at it as a bit like a ‘software’ problem on a computer. The ‘hardware’ is not damaged but there is a problem with the ‘software’ and so the computer doesn’t work doesn’t work properly. Conventional structural MRI brain scans are usually normal in FND unless the person has another neurological condition. Functional’ brain scans (fMRI) are starting to provide early evidence for how the brain goes wrong in FND. fMRI scans show changes in patients with FND which look different from healthy patients without these symptoms as well as healthy people ‘pretending’ to have these symptoms. Functional imaging is still a research tool and is not developed enough to be used in the diagnosis of FND. Scans support what patients and researchers already know – these are genuine disorders in which there is a change in brain functioning, which is out with the control of the person with FND.

Historically, FND has traditionally been viewed as an entirely psychological disorder in which repressed psychological stress or trauma gets ‘converted’ into a physical symptom. This is where the term ‘conversion disorder’ comes from. Psychological disorders and stressful life events, both recent and in childhood, may be risk factors for developing the condition in some patients, but they rarely provide a full explanation for the cause of the condition and are absent in many patients. Patients do not have to be depressed, anxious or the survivor of adverse childhood experience to develop FND.

Modern theories propose that FND has many causes, which vary from patient to patient. One comparison is to think about heart disease. There are lots of causes of heart disease – smoking, genetic factors, diet and even stress-related / psychological factors such as depression. Smoking may be a factor in heart disease in many people, but it is not in everyone. The same analogy can be made for FND. In some psychological factors such as past trauma or stress at the time of symptom onset in FND are important in understanding how the brain has gone wrong. In others the presence of a problem like migraine or a physical injury may be the most important thing.

The exact prevalence of FND is unknown. However, research suggests FND is the second most common reason for a neurological outpatient visit after headache/migraine; accounting for one sixth of diagnoses. This means FND is as common as multiple sclerosis or Parkinson’s disease.

FND can affect anyone, at any time, although it is uncommon in children under 10. FND is more likely to affect women than men for most symptoms, although when patients present over the age of 50 then it occurs equally in both groups.

( resources : fnd NORD, fnd hope , fnd site 1 , my own experience. )