Functional Neurological Disorder (FND) is the name given for symptoms in the body which appear to be caused by problems in the nervous system but which are not caused by a physical neurological disease or disorder. Health professionals sometimes call these disorders ‘medically unexplained’, psychosomatic or somatisation. We prefer the term ‘functional’ which just means that the body is not functioning quite as it should.
FND are quite common, occurring in about one quarter of the patients we see in our neurology clinics. For most people these symptoms are short-lived, but for others they persist for months or years and are very disabling. Symptoms tend to change with time, and as a result patients may often repeatedly consult their doctors for advice or investigation. Many doctors also find these conditions puzzling, and patients may find that they become frustrated by the shortage of information about why these symptoms occur and what to do about them.
The purpose of this website is to provide you with information about this common condition. The information here is based on a model we use in Sheffield. We do not claim that it is ‘the truth’, rather that the model seems to fit the illness very well and helps people understand what is going on and what to do about it. This model is based on unique experience of hundreds of patients seen in the department and works well. It is likely that ideas about FND will change in years to come, and we will keep the website updated.
Symptoms of FND can be continuous, variable or happen from time to time. There are four main types of functional symptoms:
Although often considered inexplicable or mysterious, they can actually be easily understood as interference with normal brain function by the emotional centres of the brain. This causes abnormalities of the way the brain processes sensory information coming to it from the body, and also of the link between planning a movement and carrying it out, ‘between wanting to move and actually doing it’.
The process of filtering sensations from the sensory organs of the body via the nervous system is called “gating”. Our brains are constantly bombarded by sensory information from millions of sense organs all over the body, including the skin, joints, muscles, internal organs, and other senses such as sights, sounds, smells and tastes. Most of this information is unimportant, and the brain very effectively filters it out so we are usually unaware of it.
When there is a problem with the gating or filtering system people can experience either “negative” symptoms (i.e. loss of sensation or anaesthesia like a dentist’s injection) or “positive” symptoms (extra sensations, such as pins and needles or pain) or, indeed, both.
“Negative” symptoms such as loss of sensation can come on quite suddenly. People can wake and find that they cannot feel part of their body properly, and may fear they have had a stroke. The symptoms may change with time, fluctuating sometimes minute-to-minute or hour-to-hour, and may evolve slowly with time so that a different symptom becomes the most prominent.
“Positive” sensory symptoms can be just as difficult for someone to manage as “negative” symptoms. People with FND often find they experience ‘sensory overload’ – lights feel too bright, noises too intrusive, heat and cold very uncomfortable, uncomfortable skin sensations (tingling, crawling, prickling, tenderness or pain). The difficulty with ‘gating’ may also cause problems with concentration.
A common FND sensory symptom is pain. The pain is often but not always difficult to locate and seems to come from muscles, skin or joints at various times. It gets better and worse, and is usually combined with a feeling of intense tiredness or fatigue, and difficulty concentrating. Sometimes it is worse at times of stress.
When someone is struggling to concentrate, they are not able to filter out unimportant sensory information to focus on what is important. People who are trying hard to overcome their difficulty concentrating or problems filtering sensory information often feel exhausted or fatigued a lot of the time. These symptoms are very common with FND.
A person with FND may often complain of memory problems. This is often a result of finding it difficult to concentrate. As a result you might lose things, such as keys, or find you have put the kettle in the ‘fridge’ instead of back on the worktop. You may forget appointments or things that you have done recently, and often feel that your brain is in a ‘fog’. You might also feel extremely fatigued.
The fatigue usually varies day to day, but characteristically if you overdo it one day you pay for it the next and have to take more rest to compensate. Some people complain that the fatigue is so intense, for example, that they have to spend a day in bed after they have been shopping, yet on other days they feel very bright.
Click here for more information about the South Yorkshire Chronic fatigue service
People with FND often complain of difficulty moving. They may feel slowed down, or may find that they cannot move part of their body or grip with a hand. They often complain that their limbs do not seem to do what they want them to any more. Some people may get extra involuntary movements such as twitches or tremors.
People may find that they collapse, black out or lose consciousness, with or without shaking. See our section on Functional seizures for more information.
For more information about symptoms see this dedicated website
If you have a functional neurological disorder (FND) you may have symptoms that are extremely disabling. Your symptoms also might have started quite suddenly. Often when people with FND are assessed either at a routine appointment or in an emergency, their symptoms may seem to be those of a serious physical disorder, such as a stroke, mini-stroke or multiple sclerosis. These serious neurological diseases may have been mentioned when you first told a clinician about your symptoms.
When investigations such as scans are done to check for these diseases, there are no indications that there is any neurological disease or damage in the nervous system. This indicates to the doctors that the symptoms are functional, but sometimes the doctor will not be sure and refer to a specialist.
The diagnosis of FND is not just made by ruling out physical causes. A thorough clinical assessment will usually provide other clues. The nature of the symptoms, the way they fluctuate with time and the way they evolve, can all give strong hints to the diagnosis of FND. Tests are sometimes required, partly to reassure the doctor and their patient that there is not anything else that could possibly cause the symptoms. Often these tests pick up slight abnormalities that are not relevant to the symptoms, and it is not unusual to acquire several other diagnoses along the way before the true diagnosis is clear. It often takes many years for a diagnosis of FND to be made.
