Functional Neurological Disorder: Symptoms, Causes and Treatment

Does the concept of functional neurological disorder sound familiar to you? It the conversion disorder (or hysterical neurosis), in which the patient manifests neurological symptoms without an injury or organic disease to justify them.
Functional Neurological Disorder: Symptoms, Causes and Treatment
Laura Ruiz Mitjana

Written and verified by la psicóloga Laura Ruiz Mitjana.

Last update: 28 May, 2021

Functional neurological disorder is, in reality, a group of disorders or alterations of the nervous system, which can’t be explained or justified by a medical or organic cause.

That’s to say that the patient experiences a series of affectations (for example, weakness, dystonia, tremors…) but no medical cause is found that can explain them.

It’s a new term, because previously these types of disorders were called conversion disorders (and for many years they were also called “hysterical neurosis”). If you want to know what they consist of, as well as their symptoms, causes, and treatments, then keep reading!

Functional neurological disorder: what is it?

Functional neurological disorder is common.
These patients often suffer from motor disorders without an underlying organic cause.

Functional neurological disorder (FND) is a medical condition in which patients experience a number of neurological symptoms, such as sensory disturbances, fainting, dizziness, weakness, or movement disorders.

However, there’s no medical disease or organic disorder that can explain these symptoms (hence the nomenclature of “functional”).

At the incidence level, according to a review study by Restrepo et al. (2019), carried out at the CES University of Medellín (Colombia), it’s a type of disorder that affects 2.5 people out of every 100,000. On the other hand, they usually appear between 20 and 40 years of age.

The above conversion disorders

We currently speak of “functional neurological disorders” in the plural, because the concept encompasses a series of disorders or alterations that can be heterogeneous.

The concept was also popularly called “hysterical neurosis” and, in fact, they have long been called conversion disorders as well.

Said conversion disorder was defined in a similar way – as a series of symptoms or neurological deficits that develop unconsciously and involuntarily and that affect a motor or sensory function.

Term of new appearance

In short: FND is quite a recent term. People who suffer from a functional neurological disorder suffer symptoms linked to the nervous system that, as we said before, can’t be explained by any type of neurological disease (or any other type of disease).

The symptoms that the patient feels are real, and they create significant anguish, as well as interference in their daily life.


The symptoms that each patient with a functional neurological disorder experiences can be very diverse. Thus, these can vary in degree, severity, and type (even though they’re neurological symptoms).

In addition to this, the signs and symptoms may have specific patterns. In a generic way, we can speak of alterations in the motor area (movements) or the sensory area (senses). This includes an impairment in a person’s ability to see, hear, swallow, walk…

Symptoms can be short or long-lasting, but they all share one characteristic: they either interfere with the patient’s life (and it’s a clinically significant interference) and/or cause distress. They can’t be produced intentionally, and much less controlled. But what symptoms are we talking about?

Symptoms affecting movement

Among the symptoms that affect the functioning of the body and movement, we find the following:

  • Difficulty swallowing (or feeling like you have a “lump” in your throat).
  • Periods where you feel a lack of reaction or response.
  • Weakness or paralysis in any part (s) of the body.
  • Loss of balance or dizziness.
  • Abnormal movement (for example, tremors, difficulties walking…).
  • Seizures or episodes of tremors.
  • An apparent loss of consciousness (non-epileptic seizures).

Symptoms that affect the senses

Other symptoms of functional neurological disorder are those related to the senses. Among these, we find:

  • Speech disturbances or problems (for example, the inability to speak or babbling)
  • Vision problems (for example, blindness or double vision)
  • Hearing disturbances (for example, deafness)
  • Numbness or loss of sensitivity to touch

Causes of FND

The exact causes of functional neurological disorders aren’t known. There are several theories about what happens in the brain when these types of symptoms appear. These are complex theories, which encompass various mechanisms that cause this type of disorder.

We know that there are certain areas of the brain responsible for controlling the muscles and the senses, which would be altered, and which could be an etiological factor in this disorder. However, there’s no prior illness or underlying medical abnormality that can justify these symptoms.

On the other hand, there are certain triggers for this disorder, such as:

  • Stressful episodes
  • Physical or emotional trauma)
  • Traumatic events
  • Brain alterations or changes (at a structural, cellular or metabolic level)

Despite the knowledge of the existence of these possible triggering factors, it isn’t always easy to identify them as causing a functional neurological disorder.

Risk factors

Beyond the possible causes of functional neurological disorders, there are a number of risk factors that could increase their likelihood. Among them we find:

  • Family history (having a relative with the same disorder)
  • Have a mental disorder (for example, dissociative disorder, anxiety disorder, depression…)
  • A physical trauma
  • An emotional trauma
  • Recent significant stress
  • Having a previous neurological disease (such as epilepsy, a movement disorder, migraines…)
  • A history of childhood sexual (or physical) neglect or abuse


Functional neurological disorder is reversible. This means that the symptoms that appear very often disappear on their own with time.

The most common treatments for this type of disorder are neuropsychological rehabilitation and physical therapy, without forgetting psychological therapy (to treat the emotional symptoms derived from the disorder).

Let’s not forget that it’s a disorder (or group of disorders) where there’s neither an injury nor an organic alteration. That’s why there’s no drug capable of reversing it, but it is a disorder that disappears over time. The therapeutic options that we’ve mentioned can accelerate the patient’s recovery process.

Neuropsychological rehabilitation

Functional neurological disorder requires treatment.
Mental therapy is very important in these cases.

But what exactly is this intervention? According to Maater (2006), it would be a type of intervention that groups together “all those activities aimed at improving general cognitive performance or any of its processes and/or components in patients with some type of injury to the central nervous system”.

Thus, it’s a type of intervention that encompasses all the methods, techniques, and instruments necessary to reduce the underlying disability of the patient, which allows him to reach his most optimal level in terms of autonomy and social integration.

In the case of functional neurological disorder, even if there’s no “real” damage, this type of intervention can also be beneficial.

What should we take into account in rehabilitation?

There are a number of factors that must be taken into account when designing a treatment for this type of patient. These factors or variables can influence the results of therapy, but also its development. We’re talking here about:

  • Evolution time (how long does it take for the patient to start to improve)
  • Personal factors (for example, the age of the patient, cognitive reserve, motivation for change…)
  • Contextual factors (environment, family…)
  • Rehabilitation (attitude, skills, experience…)


As we have seen, movement disorders are frequent symptoms in this type of disorder. Physiotherapy will be focused on facilitating the usual movements of the patient, through various exercises. The important thing, in these cases, will be to focus on abnormal and/or dysfunctional movement patterns in order to correct or modify them.

Psychological therapy

Psychological therapy, for its part, will be aimed at promoting the emotional well-being of the patient, and treating all the psychological and emotional symptoms derived from the functional disorder itself.

We’re talking about possible anxiety, depressive symptoms, and also emotional suffering in general, derived from the limitations or interference generated by FND.

The importance of good follow-up

As we have seen, functional neurological disorder encompasses a series of alterations in the body, related to movement and the senses.

What we mean here is that the symptoms that appear in it are neurological, but the difference with other non-functional neurological disorders or diseases (for example, multiple sclerosis, amyotrophic lateral sclerosis [ALS]…) is that there’s no organic or medical cause that can justify these symptoms.

That’s why the disorder is called “functional”. Its symptoms, very often, resolve spontaneously with time, although good follow-up of the patient (in addition to good treatment) can help the symptoms disappear sooner.

In addition, we mustn’t forget the emotional changes that can come from this condition, which will also be very important to address with psychotherapy.

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