Cookie Consent by PrivacyPolicies.com
Skip to main content

The FND diagnosis should be made from positive signs, not negative test results.

What is FND

Understanding the diagnosis

Written by Professor Mark Edwards

There is really no more important first step then arriving at a reasonable understanding of the diagnosis that makes sense to you. This can be difficult as FND is fundamentally quite hard to understand, and is certainly easy to misunderstand. My way of understanding FND is that the symptoms it produces are real, not imagined or put on. The symptoms themselves resemble those that are seen in structural or degenerative neurological disease, but have a fundamentally different mechanism. Structural damage or degeneration causes a “wiring problem” in the brain/nerves and results in neurological symptoms this way. In FND however, the basic wiring of the nervous system is ok, and instead it is the control of the body that has gone wrong. A good example of this is Hoover’s sign for functional weakness, where a person may have significant weakness of one leg when they are consciously trying to move it, but the power in the leg returns to normal when movement is triggered in a different way, usually by asking the person to lift up their other leg. This causes a reflex pushing down of the other leg from the hip. In this way it can be positively demonstrated that the leg can move, and therefore that the basic wiring from the brain to the muscle is intact.  Functional sensory symptoms (loss of sensation/tingling/pain) can be demonstrated to have similar properties as tests of sensation “wiring” (for example electrical tests that can track sensation messages coming from the limbs into the brain) are normal. Logically this must mean that the problem in FND lies in the brain’s ability to access or control the apparently normal movement and sensation wiring. It is difficult to understand exactly how this can happen, although modern neuroscience does provide some clues. However, it does point to the theoretical possibility of improvement in symptoms, as at least on one level the nervous system is working normally and is not irreversibly damaged.

One of the commonest questions doctors are asked by people with any illness is: “why did this happen to me?”. This is a very reasonable question, but for most illnesses, particularly neurological ones, the commonest answer is “we don’t really know”. What is often more certain is that there are risk factors that make people more likely to develop a particular illness. For example we know that if you take a big group of people who have had a stroke and a big group of people who have not and compare them, then more of the people who have had a stroke will have high blood pressure, high cholesterol, will be smokers, will have a family history of stroke etc. It is important to realise that many people in the group who have had a stroke will have only one or two of these risk factors, or maybe none at all, and many of the people in the group who have not had a stroke will also have 1 or more of these risk factors too. This is because it is not true to say that, for example, stroke is an illness caused by high blood pressure. It is a strong risk factor for sure, but it is not the direct single cause.

With FND there has been historically a lot of emphasis on psychological trauma, or more broadly “stress” as a triggering factor. This is not completely unreasonable as if one does the same comparison as described above for stroke, but instead in people with FND and without FND, then more of the people with FND will have experienced traumatic/stressful life events either in the distant past or more recently to the onset of symptoms. However, this does not mean that all, even the majority of people with FND have had such experiences. It also does not necessarily mean that if such stressful life events have occurred that this is the direct cause of FND.

In my experience the commonest scenario at the onset of FND is the combination of a “typical” physical event (illness, injury) and a period prior to this of hard work a degree of fatigue caused by this and “normal” chronic life stressors that affect many people. The physical triggering event is usually something that would be expected to get better, for example a flu that would be expected to go after a few days rest, but instead symptoms continue and functional symptoms emerge. Sometimes this process can be very quick and dramatic or sometimes much slower.

Discussion of the relevance or not of psychological factors in all of this is always a difficult one for the person with FND and their doctor. Because of the way that the word “psychological” is used in normal everyday language, discussion of psychological factors can seem like being accused of the symptoms being made up, imagined, voluntary or something one should just be able to snap out of if one wanted to. In my practice I see these factors as potentially relevant to understanding why FND developed in an individual person, and because of this they should be explored in an open minded way. The reason for this is that if a person has, for example, significant depression or anxiety, previous or current stressful life experiences which they feel are relevant to the current situation, then treatment directed towards these issues can be a useful part of helping overall with FND.  There are also people who develop significant low mood/anxiety after developing FND. Of course this is quite a normal response to disabling illness of any sort. However, in some people the “normal” reactive low mood that can come with any illness develops into significant depression which is a brain condition in its own right and may need specific treatment.

After an open minded discussion of these issues, many people with FND do not have significant psychological issues that seem relevant either in triggering symptoms or as part of ongoing problems accompanying the functional neurological symptoms. This does not mean that cognitive types of treatment, if done in the right way, are irrelevant. However, generic psychological therapy for depression in a person with FND who does not experience depression is not likely to be much help: this is why ideally treatment in FND needs to be tailored to the individual person.

Fiction:

Medical tests were negative, therefore, you have FND.

Fact:

An FND diagnosis should NOT be made from negative test results.  Positive signs such as the Hoover sign for weakness and balance issues which improve with distraction are some examples.

Close
Medical Disclaimer
View Cookies Policy