What is a functional neurological disorder?
Functional neurological disorder (FND) is a medicinal condition in which there is a problem with the operative of the nervous system and how the brain and body send and/or receive signals, rather than a structural disease process such as multiple sclerosis or a stroke. The functional neurological disorder can encompass a wide variety of neurological symptoms, such as limb weakness or seizures.
A functional neurological disorder is a condition at the interface between the specialties of neurology and psychiatry. Conventional tests, such as brain MRIs and EEGs, are usually normal in patients with functional neurological disorders. This has historically led to both doctors and researchers neglecting the disease.
However, it has now been established that functional neurological disorder is a common cause of disability and distress, which can overlap with other problems such as chronic pain and fatigue. Encouraging studies support the possible reversibility of functional neurological disorder with specifically designed treatments. New scientific findings are influencing the way patients are diagnosed and treated, which is creating a general shift in attitudes towards people with functional neurological disorders.
Older ideas that functional neurological disorder is “totally psychological” and that diagnosis is made only when someone has normal tests have changed since the mid-2000s. New understanding, including modern neuroscientific studies, has shown that FND it is not a diagnosis of exclusion. It has specific clinical features of its own and is a disorder of nervous system functioning in which many perspectives are needed. These vary greatly from person to person. In some people, psychological factors are important, in others they are not.
Signs and symptoms of functional neurological disorder
Patients with a functional neurological disorder can experience a wide range and combination of physical, sensory, and/or cognitive symptoms. The most common include:
- Functional weakness/paralysis of the limbs
- Functional movement disorders; including tremors, spasms (dystonia), jerky movements (myoclonus), and trouble walking (gait disorder)
- Functional speech symptoms; including whispering (dysphonia), slurred speech, or stuttering
- Functional sensory disturbance includes altered sensation; eg numbness, tingling, or pain in the face, torso, or extremities. This often occurs on one side of the body
- functional visual symptoms; including vision loss or double vision
Episodes of altered consciousness
- Dissociative (non-epileptic) seizures, fainting spells, and fainting spells: These symptoms may overlap and may look like epileptic seizures or blackouts (syncope)
Symptoms often fluctuate and can vary from day to day or be present all the time. Some patients with a functional neurological disorder may experience a substantial or even complete remission followed by sudden relapses of symptoms.
Patients with the functional neurological disorder often experience other physical and psychological symptoms, but they may not be present. These include chronic pain, fatigue, trouble sleeping, memory symptoms, bowel and bladder symptoms, anxiety, and depression.
Causes functional neurological disorder
The exact cause of the functional neurological disorder is unknown, although ongoing research is beginning to provide suggestions on how and why it develops. Many different predisposing factors can make patients more susceptible to FND, such as having another neurological condition, experiencing chronic pain, fatigue, or stress. However, some people with functional neurological disorders do not have any of these risk factors.
By the time FND begins, studies have shown that there can be triggers such as a physical injury, infectious disease, panic attack, or migraine that can give someone the first experience of symptoms. These symptoms usually go away on their own.
However, in FND the symptoms “get stuck” in a “pattern” in the nervous system. This “pattern” is reflected in altered brain function. The result is a genuine and disabling problem, which the patient cannot control. The goal of treatment is to “retrain the brain,” for example, by unlearning abnormal and dysfunctional movement patterns that have developed and re-learning normal movement.
One way to think about FND is to think of it as a “software” problem on a computer. The “hardware” is not damaged, but there is a problem with the “software”, so the computer does not work, it does not work properly. Conventional structural magnetic resonance imaging of the brain is usually normal in FND unless the person has another neurological condition.
Functional brain scans (fMRI) are beginning to provide early evidence of how the brain fails in FND. Functional magnetic resonance imaging shows changes in FND patients who look different from healthy patients without these symptoms, as well as from healthy people who “pretend” to have these symptoms.
Functional imaging is still a research tool and is not sufficiently developed to be used in the diagnosis of FND. The scans support what patients and researchers already know: These are genuine disorders in which there is a change in how the brain works, which is beyond the control of the person with FND.
Diagnosis of functional neurological disorder
The diagnosis of a functional neurologic disorder depends on the positive features of the history and examination.
Positive features of functional softness on examination include the Hoover sign, when there is the weakness of hip extension that regularizes with contralateral hip flexion, and the abductor thigh sign, thigh abduction weakness which is normalized with the abduction of the contralateral thigh. Signs of functional tremors include entrainment and distraction.
The trembling patient should be asked to copy the rhythmic movements with one hand or one foot. If the tremor on the other hand follows the same rhythm, stops, or if the patient has trouble copying a simple movement, this may indicate a functional tremor.
Functional dystonia usually presents with an inverted ankle stance or with a clenched fist. Positive features of dissociative or nonepileptic seizures include prolonged immobile unresponsiveness, long-lasting episodes (> 2 minutes), and dissociative symptoms before the seizure. These signs can be usefully discussed with patients when making the diagnosis.
Patients with functional movement disorders and limb faintness may experience the onset of symptoms triggered by an episode of acute pain, bodily injury, or physical trauma. They may also experience symptoms when faced with a psychological stressor, but this is not the case for most patients. Patients with functional neurological disorders are more likely to have a history of another disease, such as irritable bowel syndrome, chronic pelvic pain, or fibromyalgia, but this cannot be used to make a diagnosis.
FND does not show up on blood tests or structural brain images, such as MRI or CT. However, this is also the case for many other neurological conditions, so negative investigations should not be used alone to make the diagnosis. However, FND can occur along with other neurological diseases, and tests can show nonspecific abnormalities that confuse clinicians and patients.
Treatment for a functional neurological disorder
There is no best treatment for a conversion disorder. A physician is likely to provide support and reassurance and tailor treatment goals to the specific situation.
Most doctors will explain the limits of what the physical exam and tests could show about symptoms. They try to avoid confronting the individual with the idea that the symptoms are “false”, because the symptoms are often distressing and are not under the control of the person. It is helpful to avoid overly intrusive and uncomfortable medical tests, while still monitoring symptoms.
Symptoms occasionally go away on their own after the stress has been reduced, the conflict has been resolved, or the family or public has responded with concern and support.
If symptoms do not recover relatively quickly, more vigorous rehabilitation may be required. Physical or occupational therapy can be helpful.
Psychotherapy can deliver relief, although there is no evidence that one type of therapy is more effective than another. Many therapists will focus on encouragement and motivational interviewing, with the goal of improving functioning.
If the source of the conflict or stress can be determined, it can be helpful to know what triggered the symptoms. For instance, the person may be in conflict about leaving home, starting a new job, or having a first child.
In psychotherapy, the person can learn to cope with conflict or withdraw from the source of distress. In either case, the physical symptoms can go away. Performance remains a higher priority than knowledge.
As with psychotherapy, there is no single drug that is best for this disorder. Medication can be helpful in treating an underlying problem with anxiety or depression.