This is the most difficult of the issues raised to address, because as you can imagine, FND cannot be diagnosed without physically seeing, talking to and examining a person, and sometimes also having access to specific test results. I am sorry therefore to those of you who write asking if your specific symptoms could be due to FND: this is not a question that I am in a position to answer.
What I can try to do though is to explain how the diagnosis should be made. This is a diagnosis that should, where at all possible, be made on the basis of positive features that are gathered by the doctor during history taking (i.e. talking to the patient about their symptoms and how they have developed) and during physical examination. There are some other positive features that can be revealed during certain investigations.
Let me give you some examples:
There are some other positive features that can be revealed during certain investigations.
Below are two examples:
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A person may have developed sudden onset of weakness down one side of the body. The most likely explanation for this is a stroke, but let us assume that a good quality MRI scan of the brain and spinal cord is normal. This does not automatically mean the person has a functional weakness, although it is quite likely as it is quite hard to think of neurological diseases that could cause a weakness like this without any abnormalities on the scan. The diagnosis of FND is actually made by examining the person. In the examination the person will not be able to move the weak leg, but when they are asked to make a hip flexion movement with the good leg, the doctor will be able to feel that the power in the weak leg comes back. This is a sign called “Hoover’s sign”. It shows that movement is possible in the weak leg (i.e. all the basic wiring is working), but the person’s access to it voluntarily is not normal. This is a fundamental property of functional symptoms: “wiring” that is normal and can be revealed to be working when movement happens “automatically”, but an inability to make things work when the person is consciously trying. You, I hope, see the point about how the diagnosis of FND should be made – normal tests can be helpful in ruling things out, but in the end one should be looking for positive features to make the diagnosis securely.
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[icon_box icon=”icon-bold” icon_color=”#ea7223″]A person with what look like epileptic seizures. A person with this problem might have episodes where they collapse and shake and are apparently unconscious, although they might retain some awareness of what is going on around them but be unable to respond to people. Let’s imagine that the shaking attacks can last on and off for up to 2 hours. Here, the diagnosis of a functional “non-epileptic attack” comes from the description of the attack. We know from years of study of patients with epilepsy that epileptic attacks rarely last more than a few minutes, and when they do (as in epileptic “status”) prolonged attacks often lead to brain damage and even death. In addition patients with prolonged attacks of epileptic seizures never retain awareness during an attack. The person I am describing here might go on to have a brainwave recording (EEG) hoping to record brainwaves during attacks. In functional non-epileptic seizures, these recordings will show a pattern of brainwaves that is usually seen when people are awake and functioning normally, despite what the person is experiencing. So here the combination of positive features on the history and a specific investigation (which is actually not always necessary to make this diagnosis) have worked together to make a positive diagnosis.
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There are situations where things are more complicated. For example, in people who experience pain or numbness or fatigue it can be hard to gather as much positive evidence to make a positive diagnosis of FND. Here one is often in the situation of trying to prove that the basic sensation wiring is normal (this can be done with electrical tests), making sure that other tests are normal, and thinking about whether the pattern of loss of sensation or pain could fit with what we know about the basic way in which the nervous system is wired up. In this way one can come to a decision that a functional sensory problem is most likely.
You will see that I have not made any mention of psychological factors so far in the description of how the diagnosis is made. This is because there is no good evidence that psychological difficulties MUST be present in people with FND. It is also the case that many people with neurological disease, particularly when it affects the brain, will have psychological problems (which makes sense when you realise that the mind and the brain are the same organ). For this reason, I would never make the diagnosis of FND just because a patient presents with a neurological symptom and is depressed/anxious/suffered emotional traumatic events. By saying this, I am NOT saying that psychological factors are unimportant for some people with FND, just that they are not the way in which the diagnosis should be made.
This discussion about the diagnosis shows that it requires attention to detail, expertise and skill. The good news is that, on the whole, neurologists do seem to get the diagnosis right. So, in studies which have looked at how often the diagnosis of FND is changed at long-term follow up, this happens in only 1-5% of patients. If this sounds like a lot, then it is useful to know that when experts in Parkinson’s disease make a diagnosis of Parkinson’s disease, they are wrong about 10% of the time. Of course, neurologists can get the diagnosis wrong, and in my experience this has most often happened when they have relied just on the presence of psychological problems to make the diagnosis. Along with others I am involved in trying to research more reliable ways of making the diagnosis and educating other neurologists about how to make the diagnosis more securely. I think it is always good practice to keep an open mind about the diagnosis and to re-evaluate people if their symptoms change. It is also possible for people to have a typical neurological illness and FND together. So, finding a neurologist you can trust and keeping an ongoing relationship with him/her over time is often really helpful.
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