Functional Neurological Disorder (FND) : a patient's guide
including Functional/Dissociative (non-epileptic) Seizures, Functional Movement Disorder and other functional symptoms
Is the diagnosis wrong?
This study collected together all the previous studies looking at how often doctors got the diagnosis of functional neurological symptoms wrong. Rates of misdiagnoisis have been around 5% since 1970. This is the error rate for all neurological conditions. (Stone et al BMJ. 2005; 331: 989;doi:10.1136/bmj.38628.466898.55
Click above for an article written for neurologists about the pitfalls of diagnosis of functional symptoms and disorders
Patients with functional/dissociative symptoms are often concerned that their diagnosis may be wrong. Especially since there is no 'scan' or blood test that can make the diagnosis.
There are many neurological problems. The commonest ones are
•Migraine / Headache
•Functional / Dissociative Symptoms
•Motor Neuron Disease (also called Amyotrophic Lateral Sclerosis)
•Nerve Root or Spinal Cord entrapment
•B12 deficiency and Thyroid disorders
•Many hundreds of others.....
On the other hand there are also only a limited number of neurological symptoms.
The commonest ones are:
•Memory / Cognitive symptoms
•Speech / Swallowing Symptoms
•Visual Symptoms – reduced vision, double vision
•Neck, Back and Limb pain
•Tremors, jerks, spasms and contractures
In fact there are such a limited number of neurological symptoms you can see that its quite understandable for someone with more than one neurological symptom to start to wonder if they have one of the common (or uncommon) neurological diseases.
This website does not attempt to explain how a neurologist diagnoses all of these diseases. But this list emphasises that neurologists are very familiar with the conditions that you, your family or friends may have been concerned about as well as all the symptoms that you have.
You may be surprised to see functional / dissociative symptoms so high up the list because few people have heard of them. In fact around 15% of all patients seen in UK neurology clinics as new patient have symptoms that are diagnosed as functional or dissociative. Around 5% of all new outpatients have symptoms of weakness, blackouts or numbness that are functional / dissociative.
If your neurologist has decided that you have functional or dissociative symptoms it is likely that this will be for a good reason. There should be positive signs that the problems is functional, it should not just be because the scan is normal or the tests are normal. See positive signs of functional weakness, functional sensory disturbance and dissociative seizures
In the same way that neurologists diagnose Parkinson’s disease, Migraine and Epilepsy at the bedside with a detailed history and examination (and without any tests), so too can functional and dissociative symptoms be accurately diagnosed.
Things can become tricky when a patient has an underlying neurological disease (like multiple sclerosis) and they also have clear evidence of functional symptoms (like functional weakness). In some people, having a neurological disease can actually trigger the development of functional symptoms and something that a neurologist should always think about. This is often why investigations are performed even when clinically the diagnosis seems clear. Some people can have two diagnoses – one of a neurological disease and another of superimposed functional symptoms. For example, about 10% of people with dissociative seizures also have epilepsy (but 90% still do not).
You can read an article I wrote with colleagues about pitfalls in misdiagnosis of functional symptoms and neurological disease opposite
Reassuringly however, studies that have looked at how often neurologists get the diagnosis wrong have tended to agree (at least in the last 30 years) that the proportion of patients in whom the diagnosis turns out to be incorrect later on is about 5%. The graph on the right is based on 27 studies and nearly 1500 patients followed up for an average of 5 years. It shows how the diagnosis has become more accurate over the years.
A misdiagnosis rate of 5% may seem a lot but perhaps surprisingly its less than the numbers of patients misdiagnosed with epilepsy, multiple sclerosis and similar to the proportion wrongly told they have motor neurone disease.
The evidence suggests that misdiagnosis of a neurological disease when the problem is actually functional / dissociative symptoms is just as common as the other way round.
Any doctor, usually a neurologist, that makes the diagnosis of a functional or dissociative symptom should be very familiar both with the possible neurological diagnoses that those symptoms could represent and also with the positive clinical features of functional symptoms. Even then, they will sometimes get it wrong, but no more often than for other neurological diagnoses.