Functional (psychogenic) movement disorders: Phenomenology, diagnosis, and treatment

Introduction

The terminology for functional movement disorders (FMDs) has changed over the years. Originally called hysteria, Freud called them conversion disorders based on his view of the cause. In recent years, the term psychogenic movement disorder (PMD) was most common, based on the idea that they are caused by psychological factors rather than by an organic cause. Psychogenic was the preferred term in the second edition of this book. Another term used was medically unexplained symptoms (MUS), which was a diagnosis made (rather unfortunately) when no known neurologic disorder could be identified. Most recently, there has been a shift to the use of functional movement disorder ( ). This is based on the idea that the disorder arises from a dysfunction of the brain that is structurally normal, and that the cause is multifactorial and might not necessarily be psychological. Additionally, patients seem more receptive to functional rather than psychogenic, and it is critical to get them to accept the diagnosis for therapy to be successful.

Commonly, FMD is contrasted with “organic disorders,” which was already done in the first paragraph. This would make FMD “nonorganic.” Because, as will be discussed later, there are some anatomic and physiologic changes in the patients, this is not really a fully appropriate distinction. However, no alternative terminology is available. Although perhaps better to just say FMD versus “other” neurologic disorders, we will continue to use organic as shorthand in order to be easily understood.

FMD is the movement disorder variety of functional neurologic disorder (FND) ( ; ; ; ). Functional disorders are common in all fields of neurology, and, for that matter, in all fields of medicine. FMD can be defined as “a movement disorder caused by a brain network dysfunction that does not exclude the possibility of normal function, sometimes due in part to a psychological cause, and not explained by other neurologic pathology that may or may not be present.” Most neurologic disorders lead to network dysfunction; thus, it is only with FMD that function can be normal without medication or other medical intervention.

In the current psychiatric classification Diagnostic and Statistical Manual of Mental Disorders (DSM) V, FMD falls into the category of “somatic symptom and related disorders” and is listed as “Conversion disorder (functional neurologic symptom disorder).” This is characterized as follows:

• A.

  Symptoms or deficits are present that affect voluntary motor or sensory function

• B.

  Evidence of internal inconsistency or incongruity with recognized neurologic or medical disease.

• C.

  The symptom or deficit is not better explained by another recognized medical or DSM disorder.

• D.

  The symptom or deficit is associated with clinically significant distress or impairment in social, occupational, or other important areas of function or warrants medical evaluation.

There have been two books on FMDs ( , ) and one book on FNDs ( ). After many years of neglect ( ), the field is now growing rapidly, with an increasing number of publications ( ). There is now also a society focusing on FND, the Functional Neurological Disorder Society.

Differential psychiatric diagnosis

“Somatic symptom and related disorders” also includes factitious disorder; this is defined as when the physical symptoms are intentionally produced (hence are under voluntary control) owing to psychological need. This group includes Munchausen syndrome. Factitious disorders are due to a mental disorder. They are generally associated with severe dependent, masochistic, or antisocial personality disorders.

Malingering is in the differential diagnosis but is not considered to be a mental disorder. It refers to voluntarily produced physical symptoms in pursuit of a goal such as financial compensation, avoidance of school or work, evasion of criminal prosecution, or acquisition of drugs. It is similar to factitious disorder in that it is voluntary rather than involuntary, but the person has no mental disorder.

When a physician is faced with a patient who has an apparent FMD, it is often not possible to distinguish with certainty among functional (conversion), factitious, and malingering disorders ( ). A patient’s volitional intent is often impossible to determine with certainty. Normal function when the patient does not think he or she is being observed will make a diagnosis of factitious disorder or malingering. Doctors sometimes make this observation by chance; lawyers might be employed in some situations for secret surveillance ( ).

Frequency

Movement disorder specialists appear to be seeing increasing numbers of patients with FMD, although this may be just a matter of recognition. Bradykinetic disorders, given the large number of patients with parkinsonism, are less likely than hyperkinetic ones to be functional unless one were to consider the phenomenon of deliberate slowness to be a bradykinetic disorder. Although deliberate slowness is common in FMD, it is not usually the dominant feature, but when it is pure and without accompanying abnormal movements, it is considered in the category of functional parkinsonism. Fixed postures, characteristic of functional dystonia, are also common.

Functional disorders in neurology are estimated to be approximately 6% of neurology outpatient visits with a putative community incidence rate of 4 to 12 per 100,000 per year ( ). In a large study of 3781 new patients referred to neurology clinics in Scotland, 16% had functional or psychological symptoms and 5.5% had FND ( ).

Functional disorders are present at virtually all ages and can affect persons of all socioeconomic classes and amount of education. For likely many reasons, women are affected three time more than men ( ). One factor is that women are more likely to have sexual abuse than men, and there is an association between sexual abuse and functional movement disorders in women (odds ratio, 4.821), but not men ( ).

Like other subspecialties in neurology, functional patients are not uncommon. In one large movement disorder clinic, such patients account for 10% of all nonparkinsonian new patient visits ( ). Typically, patients are diagnosed by the predominant movement feature (e.g., functional tremor, functional dystonia, functional myoclonus, etc.). When evaluated this way, tremor was the most common functional phenomenology, followed by dystonia. In a review of 321 successive patients in a movement disorder clinic in Korea, 31 (10%) had an FMD ( ). There were 27 females and 4 males, and tremor was the most common phenotype.

Neurologists usually and appropriately recognize patients with FMD, but the patients often do not accept this diagnosis and seek other opinions, going from physician to physician, seeking a diagnosis that is more to their liking. Therefore, a strategy is necessary for the best way to inform the patients of the diagnosis. This issue is discussed later in this chapter. Another common situation is that many neurologists do not offer the time-consuming care that is necessary to restore such patients to normality, preferring instead merely to diagnose the condition and have the referring physician or a psychiatrist deal with treatment.

Importance of an accurate diagnosis

The diagnosis of an FMD requires making a positive diagnosis that the movements are functional and not the result of an organic illness ( ). The identification of a psychiatric disorder or the psychodynamics that could explain the cause of the abnormal movements is not necessary but can be helpful. It is critical to recognize that patients with organic illness may also have psychiatric disorders, so overemphasis of psychiatric features can be misleading. Deciding between abnormal movements with a functional cause and an organic one can be difficult. Never having seen strange movements before and pronouncing them to be functional therefore is not a satisfactory method because not even senior movement disorder specialists have seen the whole gamut of organic abnormal movements. An organic cause of the movements needs to be excluded. But this alone is insufficient; making a diagnosis of a functional disorder depends on finding positive criteria and not simply failing to find an organic cause (for historical review, see ).

An accurate diagnosis of an FMD is often one of the most difficult tasks there is in the movement disorder specialty. It is important to be correct in the diagnosis because only then can the appropriate therapy be initiated. The results of an incorrect diagnosis are detrimental. If a patient has a functional disorder that is misdiagnosed, the patient will be given inappropriate and potentially harmful medication and is also denied the proper treatment to overcome the disabling symptoms. By postponing the appropriate treatment, the cycle of disability is perpetuated. Untreated patients with FMD are at risk for becoming career invalids with chronic disability.

If the obverse occurs—that is, if a patient is given a diagnosis of FMD when, in fact, he or she suffers from an organic one—again the wrong treatment is given. In this situation, patients might be directed to inappropriate psychiatric treatments. Moreover, a diagnosis of a functional disorder can create emotional trauma for the patient and his or her family. It is important to point out that no matter how much experience a clinician has had, encountering a new type of movement disorder for the first time does not automatically make this an FMD. For example, task-specific jaw tremor ( ) is rare, and even when it is encountered for the first time, a wise clinician should consider it to be organic ( Video 27.1 ) and not functional ( Video 27.2 ).

Video 27.1 Task-specific jaw tremor.

Video 27.2 Head shaking.

Neurologic symptoms and signs are a common result in functional disorders, and neurologists have long been fascinated by the brain’s ability to be able to produce such clinical expressions on the basis of psychological (or other) disturbances. Many great neurologists, such as Charcot and Freud, intensively studied conversion reactions, using hypnosis as a tool in their investigations and treatment ( ). In their training, neurologists are taught to differentiate the clinical findings of functional cause from those of organic. However, textbooks in the past often considered some dyskinesias, recognized today as organic, such as tics, writer’s cramp and other occupational cramps, and some other forms of dystonia, to be examples of functional disorders. As medicine advances, we hope we can make more accurate diagnoses.

Although in the great majority of patients with an FMD all their clinical features result from the same cause, some may have the FMD on top of an organic movement disorder. Early reports of this, for example, are Patient 5 in the series of functional dystonias reported by and the cases of . Perhaps 10% to 15% of patients with an FMD have an underlying organic movement disorder as well. This overlap is also seen in patients with functional seizures; 10% to 37% of patients have organic seizures as well ( ; ).

Perhaps the movement disorders with the highest prevalence rate of a functional origin are the nonfamilial, “idiopathic,” paroxysmal nonkinesigenic dyskinesias, as surveyed by . They found that of 18 patients with paroxysmal nonkinesigenic dystonias and with no known symptomatic cause or positive family history for a paroxysmal dyskinesia, the dystonias were due to functional causes in 11 patients, representing 61% of patients. The age at onset in these patients ranged from 11 to 49 years; 8 of the 11 patients were female. Thus, unless accompanied by a clear-cut family history, these paroxysmal dystonias are commonly functional, and their diagnosis is extremely difficult to make for reasons that are explained later in the chapter.

conducted a study of paroxysmal events in children. Over a 6-year period, 883 patients were monitored in their pediatric epilepsy monitoring unit; 134 patients (15.2%) were documented to have paroxysmal nonepileptic events. Children in the preschool group (age: 2 months to 5 years) ( n = 26) were eventually diagnosed with stereotypies, hypnic jerks, parasomnias, and Sandifer syndrome. The school-age group (age: 5–12 years) ( n = 61) had diagnoses of functional seizures, inattention or daydreaming, stereotypies, hypnic jerks, and paroxysmal dyskinesias. The adolescent group (age: 12–18 years) ( n = 48) had a diagnosis of functional seizures in 40 patients (83%). The authors concluded that in patients with paroxysmal nonepileptic events, conversion disorder was seen in children older than 5 years of age, and its frequency increased with age, becoming the most common type of paroxysmal nonepileptic events among adolescents. In adolescents, conversion disorder was more common in females, whereas males predominated in the school-age group. Concomitant epilepsy with nonepileptic events occurred in all three age groups to a varying extent.

Physiologic basis for functional neurologic disorders

Understanding FND, like any illness, requires understanding of both cause and pathophysiologic features. The cause relates to the root sources, and the pathophysiologic processes relate to the genesis of the symptoms. The etiologic factors of FMD lead to changes in the brain that lead to the dysfunctional circuitry that produces the symptoms. There is progress in understanding both cause and pathophysiologic features of FMD.

The cause of FMD seems best explained with the biopsychosocial model ( ). This model is multifactorial, including biologic factors, psychological issues, and social situation, all three of which interact with each other. For example, persons with different underlying biology from genetic differences may react to a social situation differently and only in some circumstances lead to a psychiatric disorder. A genetic polymorphism has been identified that is more frequent in patients than controls in the TPH2 gene which is relevant in the metabolism of serotonin ( ). Different persons will develop different amounts of stress and anxiety in the same situation. The biopsychosocial model should be interpreted that each person will have different relevant factors in different proportions.

What we know is that patients with FMD have more depression and anxiety than nonaffected persons ( ). Additionally, the patients report more childhood trauma—physical, sexual, and psychological—compared with normal subjects ( ). In one study of 64 patients compared with healthy volunteers and patients with a disease control, focal hand dystonia, the FMD patients had higher rates of total childhood trauma, greater fear associated with traumatic events, and a greater number of traumatic episodes ( ). Emotional abuse, physical neglect, fear with traumatic events, and the number of traumas were significant also after covarying for depression.

Early life stress, even stress of the mother when the child is in utero, can lead to problematic changes. Increased cortisol levels can lead to shrinkage of the hippocampus and epigenetic changes of specific genes that then predispose to psychiatric abnormalities ( ; ). Current stress is often thought to be a factor in the precipitation and maintenance of an FMD. Although patients often deny it, stress is often evident, although it must be noted that stress is common in today’s world. An objective measure of current stress is the 24-hour cortisol levels. In one study of 33 patients and matched controls with salivary cortisol levels at five times during the diurnal cycle, there was no difference between groups ( ). Thus, there was no objective evidence of higher amounts of stress in the patients. Stress may well play a role in some patients, but it might be the reaction to the stress rather than the “objective” amount of stress. This result also raises caution for neurologists to not insist that stress is a problem for the patient (particularly if the patient does not agree).

There is some evidence for a difficulty in dealing with stress. Heart rate monitoring for 14 to 24 hours revealed decreased root mean square of successive differences between adjacent NN intervals ( ). This is indicative of deficient vagal tone, which correlates with impaired ability of the individual to adapt appropriately to environmental demands.

Neuroimaging studies of brain structure in patients reveal subtle anatomic abnormalities ( ; ). These would not be apparent in individual patients but show up as significant group differences. For example, in one study on 48 patients with clinically definite FMDs compared with 55 age- and sex-matched healthy controls, group differences in gray matter volume using voxel-based morphometry was studied ( ). Patients with FMD exhibited increased volume of the left amygdala, left striatum, left cerebellum, left fusiform gyrus, bilateral thalamus, and decreased volume of the left sensorimotor cortex.

Another social factor is secondary gain, and this is often noted in the patients’ situations. Sometimes it certainly seems that getting better from the disorder will put the person into a worse social situation, and this would reduce the motivation for getting well.

As to the pathophysiologic process, there are two main features to explain: (1) what is the genesis of the movements (or paresis or slowness) and (2) why are the movements experienced as involuntary. It is intellectually intriguing that the brain can create neurologic deficits—such as paralysis, sensory loss, blindness, seizures, and movement disorders—from psychological factors. This mysterious ability fascinated pioneers working on hysteria, such as Charcot and Freud. These issues are now being carefully investigated with clinical neurophysiologic testing and neuroimaging.

Analyzing functional myoclonus with clinical neurophysiology, the jerk-like movements are essentially identical to quick voluntary movements ( ; ). The electromyographic (EMG) pattern is characteristic and quite different from most organic myoclonias such as posthypoxic myoclonus. Moreover, the movement is preceded in the electroencephalogram (EEG) by a slow potential called the Bereitschaftspotential, first described with voluntary movement and indicating preparatory activity in the premotor cortex and the supplementary motor area (SMA). Sensory evoked functional myoclonus behaves like voluntary reaction time movements. Functional tremor, with EMG, looks like voluntary repetitive movements, and like voluntary movements, the tremor can be affected by movements of another body part. For example, the frequency of the tremor can be entrained to the voluntary frequency. Such clinical neurophysiologic observations not only make clear the physiologic features, they also have been used diagnostically to identify or confirm that a movement is functional.

Neuroimaging studies show significant abnormalities of brain function in these patients ( ; ; ; ; ). An early observation was a study of brain activation in patients with functional tremor, comparing their involuntary tremor with a voluntary mimicking of the tremor. The most prominent abnormality was a decrease of activation of the temporoparietal junction (TPJ) during the involuntary tremor ( ). This observation seemed to explain the sense of involuntariness, because the TPJ is a relevant region generating the sense of self-agency for movement ( ). This finding has been supported by other studies. A resting state functional magnetic resonance imaging (fMRI) study of 35 patients compared with healthy volunteers showed decreased functional connectivity between the right TPJ and the right sensorimotor cortex, cerebellar vermis, bilateral SMA, and right insula ( ). Abnormal functioning of the TPJ and its related network was also shown with voluntary movements with experimenter externally varying the amount of agency ( ). Other evidence for a decrease in agency even with voluntary movements is that patients have decreased action-effect binding ( ). Specifically, the subjective times of button press and resultant tone did not move as much closer together for patients as it did for healthy volunteers.

There is also evidence for overactivity of the limbic system in these patients, with increased connection to the motor system. Two studies have shown increased amygdala response to emotional faces with increased activity or connection to the SMA ( ; ). With motor preparation, there was greater activity in the amygdala in patients than matched controls ( ). Another study of 10 patients with matched controls looked at the ability to maintain a constant grip force while viewing emotional images ( ). Normal subjects reduced force with unpleasant images, but patients preserved the force, perhaps indicating an effect of negative affect on movement. During this task, patients had greater activity in a cerebellar-limbic network than controls. The startle response was studied in 17 patients and 15 matched controls ( ). The startle response was similar in form but had increased amplitude in patients. The startle response is under control of the amygdala, and, therefore, the result is compatible with increased limbic activity. Other studies show abnormal activation of the ventromedial prefrontal cortex ( ) and the anterior and midcingulate cortex ( ) giving more evidence for limbic abnormality.

The picture is far from complete, but the evidence is accumulating for aberrant movement generation from an overactive limbic system and a failure of the network for self-agency. Because there is not much evidence for any abnormality of feedback (sensory processing) in the patients, a failure of self-agency would likely derive from an abnormal feedforward signal. If the limbic system is indeed triggering movement in an abnormal fashion, there might not be a proper feedforward signal.

Degree of certainty of the diagnosis of a functional movement disorder

categorized patients into four levels of certainty as to the likelihood of their having “psychogenic dystonia”; these categories can be applied to all FMDs. These four degrees of certainty are: (1) documented, (2) clinically established, (3) probable, and (4) possible. Here the criteria have been expanded somewhat, taking into account additional observations since the original publication.