Functional Neurologic Disorder

Etiology

Psychological, social, and biological factors can all contribute to, precipitate, or perpetuate functional neurologic disorder. Often, there is a trauma, adverse life event, or acute/chronic stressor preceding symptoms of functional neurologic disorder. Many patients with functional neurologic disorder are found to have a history of childhood abuse, both emotional and sexual. Other psychological factors contributing to functional neurologic disorder include poor coping skills and internal psychological conflicts. Patients with functional neurologic disorder are more likely to have certain psychiatric disorders (depression, anxiety, and personality disorders) than patients with known neurologic conditions. They are also more likely to have a history of multiple somatic complaints, including symptoms like generalized fatigue, weakness, or pain, without a known cause.[3] Physical injury or actual neurologic illness (such as a stroke or migraine) may “trigger” the symptoms of functional neurologic disorder. Less educated people, those of lower socioeconomic status, and patients living in developing or rural areas are more likely to develop functional neurologic disorder. There are two major models or hypotheses for functional neurologic disorder.

• Psychodynamic models. These models suggest that somatic symptoms of functional neurologic disorder are a product of emotional conflict. This emotional conflict becomes repressed into the unconscious mind and converted into a symptom. The postulation is that this scenario is a type of defense mechanism against negative feelings that the emotional conflict would induce. Other psychodynamic models focus on the development of inadequate coping mechanisms and negative interpersonal relationships that develop earlier in a patient’s life. Later in life, these coping mechanisms or behaviors may recur if the patient encounters another traumatic event.

• Cognitive-behavioral models. One well-studied model suggests that exposure to information related to a specific symptom can lead to the creation of representation in memory. Functional neurologic disorder then occurs when this representation is “activated” by an individual worrying excessively about or looking for signs of the symptom. This activation passes a specific threshold in the mind, where it overrides sensory input and becomes an actual symptom. An example would be an individual seeing someone have a seizure in a movie and creating a memory or a representation of this event in their mind. Later, they encounter anxiety, light-headedness, or dizziness and fear that they may be experiencing symptoms preceding a seizure. They worry about having a seizure, which activates the representation or memory of a previously created seizure. This activated pathway causes them to have a psychogenic non-epileptic seizure. Cognitive-behavioral models hypothesize that behavioral and perceptual processing occurs automatically and outside of an individual’s awareness. They state that symptoms of functional neurologic disorder may result from psychological influences at lower levels of processing.

The hypotheses formulated to explain the etiology and the pathogenetic mechanisms of FND are manifold. For example, the role of microglia and neuroimmunity and, in turn, the altered control of synaptic plasticity have theoretical explanations. These processes could explain the FND-associated motor dysfunctions.[4]  

Epidemiology

The incidence of functional neurologic disorder depends largely on the populations studied. Akagi and House found that the average incidence of functional neurologic disorder across varying geographic settings was approximately 4 to 12 per 100000 per year.[2] Population-based case registries would place the rate of functional neurologic disorder higher, at 50 per 100000 per year. The Scottish Neurologic Symptoms Study was a cohort study looking at 3781 individuals in an outpatient neurology setting; of these individuals, an estimated 5.6% had functional neurologic disorder. Another analysis that was conducted by Perkin included 7836 individuals seen in the outpatient neurology setting. This research was a retrospective study, and it concluded that approximately 4% of patients had symptoms consistent with functional neurologic disorder. However, this study took place in 1989.[5]

Research has revealed that adult women diagnosed with functional neurologic disorder outnumber adult men in a ratio ranging from 2 to 1 to 10 to 1. Patients of lower socioeconomic class and with less education have higher incidences of functional neurologic disorder. Race does not appear to be a factor. Studies have shown that functional neurologic disorder in children is rare under age 5 and occurs most commonly during puberty and adolescence.[6] The incidence of functional neurologic disorder in children is also largely population-based; one study conducted in Germany found the rate of functional neurologic disorder in the pediatric population was 0.2%. In another study conducted in Australia, the rate of functional neurologic disorder in the pediatric population was 2.3 to 4.2 per 100000 per year. Over ten years of age, girls demonstrated a three times more likely chance to develop functional neurologic disorder than boys.[7]

Pathophysiology

Neurobiological models suggest that functional neurologic disorder results from changes in higher-order cortical processing. The general, broad hypothesis is that frontal and subcortical areas of the brain may be activated by emotional stress, which then leads to input to inhibitory basal ganglia-thalamocortical circuits, which then reduce conscious sensory or motor processing. There is not currently an abundance of studies looking at the neural mechanisms of functional neurologic disorder with large sample sizes. Functional neuroimaging has helped shed some light on these mechanisms and will be a crucial tool in future studies. One study conducted by Spence et al. compared three patients with weakness secondary to functional neurologic disorder with both normal controls and controls that researchers asked to feign weakness.[8] The patients were asked to move a joystick while undergoing PET comparison. The patients with functional neurologic disorder demonstrated decreased left dorsolateral prefrontal cortical activity when they attempted to move the affected limb. This study suggests that patients with functional neurologic disorder are distinct from those who are feigning symptoms. The left dorsolateral prefrontal cortex has a role in volition and willed action. Another study by Voon et al. examined the relationship between emotion and symptom production in patients with functional neurologic disorder. Researchers asked the patients to perform an emotional task, and functional MRI showed an abnormal correlation between activation of the amygdala and the supplementary motor area.[9]

History and Physical

Obtaining an appropriate history is a crucial factor in functional neurologic disorder. Making the patient feel comfortable and encouraging them to share their symptoms and stories is crucial. One method to consider is creating a list of the patient’s symptoms at the initial visit; allow the patient to list all symptoms they have been experiencing recently. This initial step is essential so that one can document any subtle changes in symptoms throughout the illness and see if the patient lists multiple somatic symptoms. It is essential to ask the patient for a list of symptoms for which they have received treatment previously or suspected neurologic diagnoses. The clinician should focus on gathering details, such as the time frame of symptoms and context. Without revealing the suspected diagnosis, it is important to ask about recent events or stressors in the patient’s life and complete a psychiatric history. Family history should also include psychiatric components. The clinician may wait until the end of the interview to ask for psychiatric history. If the patient has experienced similar symptoms in the past, what was their diagnosis, and how were they treated? Patients with a history of functional neurologic disorder are more likely to have repeat episodes, even without a past diagnosis. These questions can also help shed light on the patient’s view of other providers and to show which specialists they have seen and what work-up they have had. Involving the patient is crucial to building rapport; ask them what they feel is happening. Instead of focusing on what the patient cannot do at the time of the interview, ask them to describe the last time they remember being symptom-free and ask them to describe what a typical day looks like for them.

Functional neurologic disorder cannot truly be considered a diagnosis of exclusion, but diagnosis relies on the clinician to exclude major neurologic diseases and to look for inconsistencies on an exam, as well as clinical signs and symptoms that are not characteristic of organic disorders. Inconsistent symptoms, negative labs/imaging, and/or a significant psychiatric disorder are reliable indicators of functional neurologic disorder. However, the clinician should still exclude all other organic disorders with a thorough exam. Also, patients with functional neurologic disorder may have comorbid neurologic disorders, potentially making the diagnosis more difficult.

The Diagnostic and Statistical Manual of Mental Disorders, 5TR edition (DSM-5TR) categorizes functional neurologic disorder as part of the “somatic symptom and related disorders.” In previous editions of the DSM, clear psychologic comorbidities were a required part of the diagnosis and the ability to show that the symptoms were not intentionally produced.[10] The DSM-5 has also removed “la belle indifférence” (a patient’s apparent indifference to their condition) as a diagnostic criterion. These are now considered features that support the diagnosis of functional neurologic disorder. Other supporting features include associated dissociative symptoms and recent psychological or physical trauma.

The diagnostic criteria for functional neurologic disorder, according to the DSM-5TR, are as follows:

1. One or more symptoms of altered voluntary motor or sensory function.
2. Clinical findings can provide evidence of incompatibility between the symptom and recognized neurological or medical conditions.
3. Another medical or mental disorder does not better explain the symptom or deficit.
4. The symptom or deficit results in clinically significant distress or impairment in social, occupational, or other vital areas of functioning or warrants medical evaluation.

The presence of symptoms defines an acute episode of functional neurologic disorder for less than six months, and persistent functional neurologic disorder includes the presence of symptoms for greater than six months. Functional neurologic disorder can also have the specifier of with or without the psychological stressor. The DSM-5TR recognizes several subtypes of functional neurologic disorder, as listed below. There are many ways to differentiate between organic disorders and these subtypes of functional neurologic disorder.

• Psychogenic nonepileptic seizures – This is the most common subtype of functional neurologic disorder. Psychogenic nonepileptic seizures characteristically demonstrate features such as generalized limb shaking, hip thrusting, and lack of postictal confusion. They may be longer in duration than an actual seizure, with a waxing and waning course, and these patients typically do not lose control of bowel or bladder function or endure injury (such as tongue-biting). They will have no paroxysmal activity on an electroencephalogram. They often do not respond to antiepileptic medications or exhibit worsening of seizure-like activity with attempted treatment. One feature that may present on physical exam is forced eye closure; an examiner will encounter resistance when trying to open the patient’s eyes, which is not characteristic of an epileptic seizure.

• Paralysis or weakness – Weakness is a common presenting symptom with functional neurologic disorder. When paralysis occurs, it is usually confined to one-half of the patient’s body or a single limb. It does not follow any specific anatomical pattern. When paraplegia occurs, normal deep tendon reflexes will still be present, and the Babinski sign will be absent. The most apparent sign of psychogenic weakness is inconsistency. The examiner must observe the patient carefully during both examinations and when they engage in other actions, such as entering or leaving the room. Common tests/signs used to identify psychogenic weakness are as follows:

• Hoover’s sign – This simple test has its basis on the fact that patients extend their hip when our contralateral hip flexes against resistance. This test is useful for patients with functional weakness in the lower extremities; the examiner has the patient lay supine, place one hand under the affected heel, and ask the patient to lift their unaffected leg against resistance. Patients with functional weakness will have downward pressure on the affected heel.

• Co-contraction sign—Co-contraction is the contraction of an antagonist muscle (such as the triceps) when the agonist muscle (such as the biceps) contracts. This test is possible in any agonist/antagonist muscle group to detect the absence of true weakness.

• Arm-drop test – In this test, the examiner holds the patient’s outstretched arm in front of them and then releases it. Jerky or slow descent of the arm onto the patient’s lap is typical of functional weakness.

• Sternocleidomastoid test – Patients with functional neurologic disorder will often exhibit weakness when asked to rotate their head towards the affected side, whereas patients with the organic disease will not.

• Collapsing weakness – This phenomenon can be elicited by asking a patient to hold one of their limbs in a specific position; the examiner then applies light force to the limb, and it appears to “collapse” suddenly.

• Abnormal movement – Several psychogenic movement disorders are common in functional neurologic disorder, as listed below. Features typical of all psychogenic movement disorders include rapid onset, improvement with distracting tasks (such as counting or performing physical tasks simultaneously), and variability (in frequency, amplitude, or affected region of the body). As with paralysis and weakness, it is essential to carefully observe the patient in several settings to pick up these indicators.

• Tremor – Functional tremors are often present at rest and with action. They usually fluctuate in frequency. Organic tremors are present either with rest or action and have a rhythmic consistency. Functional tremors tend to be abrupt in onset (whereas organic tremors are more gradual), often triggered by an emotional or traumatic experience. Upon onset, functional tremors are typical of maximum severity and may start unilaterally. If weights are applied to the affected limb, patients with a functional tremor will generally exhibit an increase in tremor amplitude; patients with organic tremors will show a decrease in tremor amplitude. An examiner can also ask a patient to make a rhythmic movement with their unaffected limb. The unaffected limb tends to take on the frequency/rhythm of the affected limb, or the patient is unable to keep a steady rhythm; this is called entrainment.

• Gait disorder – Functional gait disorder is characterized by a gait that does not adhere to typical patterns seen in neurologic/organic disorders. Patients with unilateral weakness of one leg tend to drag their leg behind them and maintain their hip in internal or external rotation, which causes the affected foot to point outwards or inwards. Several other features are commonly seen in functional gait disorder. The first is sudden knee-buckling, with prevention from an actual fall. Another feature is a “walking on ice” pattern, where the patient acts as if they are walking on a slippery surface, with stiff knees and ankles, broad and slow gait, and arms sometimes abducted. Patients with functional gait disorder may also exhibit excessively slow gait initiation and the appearance of their feet sticking to the ground. They may also engage in pseudoataxia, with a very unsteady gait, crossed legs, and/or sudden side-stepping. Examination of these patients will likely reveal uneconomic postures that displace the natural center of gravity.

• Dystonia – Features seen in functional dystonia include severe pain of the affected limb, adult-onset, fixed posture (present even during sleep), a clenched fist, or an inverted foot. There are often inconsistent movements and multiple somatic complaints associated. Patients with functional dystonia will often have complete remission of symptoms after the placebo, suggestion, or administration of general anesthesia.

• Myoclonus – Organic myoclonus is characterized by jerking or spastic movements caused by sudden muscle contractions or decreased muscle tone. Functional myoclonus will be inconsistent in frequency or amplitude. It may also resolve with placebo treatment or suggestion. Patients with functional myoclonus can be very stimuli sensitive, though, unlike a typical response to an abrupt stimulus, they will exhibit a long and variable latency.

• Anesthesia or sensory loss – Functional sensory loss is a less specific manifestation of functional neurologic disorder. Often, the sensory loss does not follow typical dermatomal patterns or patterns indicative of neurologic disorders. Patients may report a sharp demarcation of their sensory loss, which is often a joint or at the end of their extremity, shoulder, or groin. Other patients may exhibit a “hemisensory syndrome,” with sensory loss of an entire side of their body; this can be accompanied by a sensation of feeling “cut in half” or ipsilateral hearing/vision issues. One test that is possible with midline splitting involves placing a tuning fork over the left and right side of the sternum or the frontal bone. Patients should feel the vibrations equally despite their supposed sensory loss, as these bones should vibrate as a single unit. However, patients with functional sensory loss often do not feel the vibration on the affected side.

• Special sensory symptom – This category includes visual (blindness, tunnel vision, double vision), hearing, and olfactory disturbances. 

Visual disturbances – In general, visual disturbances are very common in functional neurologic disorder. If a patient exhibits complete blindness, they are more likely to have factitious symptoms. In functional neurologic disorder, the patient’s pupillary reflex is present. We would expect a recent diagnosis of true blindness to result in the patient having some difficulty maneuvering and perhaps an increased incidence of injury, with superficial bruising/wounds; this is not present in functional neurologic disorder. The following tests can aid in proper diagnosis:

• Mirror test – This test involves holding a mirror in front of the patient with their eyes open. The examiner moves the mirror from side to side, and the test is positive if the patient tracks themselves in the mirror, indicating that they are not truly blind.

• Fingertip test – In this test, the patient is asked to bring the tips of their index fingers together. Patients with functional neurologic disorder usually exhibit difficulty with this task, whereas truly blind patients use proprioception to complete the test appropriately.

• Signature test – This simple test involves asking the patient to write their signature on a piece of paper. Patients with functional neurologic disorder will often be unable to complete this test, but truly blind patients can write their signatures without difficulty.

• Optokinetic test - This test involves placing a large rotating drum, which has black and white vertical stripes on it, in front of the patient’s eyes. If one observes optokinetic nystagmus, this indicates that the patient’s brain can detect the stripes.

• Menace reflex – The menace reflex is tested by presenting a threat to the patient’s vision. An example would be quickly bringing the examiner’s hand close to the patient’s face as if they were to strike the patient. Patients with functional neurologic disorder will typically blink or flinch, whereas blind patients will not.

• Tearing reflex – The tearing reflex is tested by placing a strong light in front of the patient’s eyes. If their vision is intact, as is the case with functional neurologic disorder, the patient will start to tear up. 

Olfactory or hearing disturbances are less common than visual disturbances. Patients with functional neurologic disorder typically report anosmia or deafness. Patients with anosmia can take a taste test, in which they will usually indicate a normal sense of taste. In true cases of anosmia, patients have a decreased sense of taste or exhibit some signs of nutritional deficiency/malnourishment. In patients with symptoms of deafness, the examiner can attempt to confront the patient with a loud sound, which will usually elicit a blink or some form of startle response.

• Swallowing symptoms – Patients with swallowing symptoms typically describe the sensation of a lump or tightness in their throats, which is referred to as globus sensation or globus pharyngeus. This functional esophageal disorder has no apparent physiologic cause, including no underlying structural abnormality, gastroesophageal reflux disease, or motility disorder. It is also seen in patients without functional neurologic disorder, though they often have a comorbid psychiatric condition. Other features of globus pharyngeus include occurrence in between meals and the absence of odynophagia or dysphagia.

• Speech symptom – Several symptoms of impaired speech can occur with functional neurologic disorder. The most common symptom is functional dysphonia (hoarseness or whispering), but other symptoms include slurred speech, articulatory issues, stuttering, foreign accent syndrome, and mutism. The examiner can ask patients with symptoms of functional dysphonia to cough or sing during lung exam; often, they will be able to perform these functions, whereas patients with true dysphonia have difficulty doing so. The inspection of the vocal cords will be normal.

Evaluation

The primary tools used to diagnose functional neurologic disorder are the history and physical exam; however, laboratory studies or imaging may be required to rule out underlying medical conditions. The studies ordered are highly dependent on the nature of the patient’s symptoms and their initial presentation. For example, patients who present with psychogenic nonepileptic seizures may undergo an electroencephalogram to show a lack of true seizure activity, or they may have laboratory studies such as prolactin or creatine phosphokinase drawn to help differentiate their condition from an epileptic seizure. A vast majority of patients presenting with weakness as a primary symptom will undergo electromyography or magnetic resonance imaging tests. Studies may also be ordered for patients with possible comorbid diagnoses.

Treatment / Management

The first step in the treatment of functional neurologic disorder involves an effective presentation of the diagnosis to the patient. General recommendations are that the clinician does not reveal the diagnosis during the first encounter. Instead, it is essential to build a strong therapeutic alliance with the patient. The clinician should ask the patient what they feel is wrong with them and encourage discussion of their feelings regarding their symptoms. During subsequent encounters, several important points merit focus:

• Focus on the fact that the patient’s symptoms are real and that you understand the effects of these symptoms on the patient.
• Do not tell the patient that there is nothing wrong with them or that this is “just” a psychologically-based illness.
• Give the patient examples of organic diseases that can be induced or worsened by stress, such as irritable bowel syndrome or peptic ulcer disease. Also, provide examples of other common physical manifestations of underlying stress/psychological illness, such as sweating, shaking, or palpitations during an episode of acute anxiety.
• Explain how the diagnosis was made, and point out the differences in physical exam and history that helped you differentiate between organic/neurologic disease and functional neurologic disorder.
• Explain that their symptoms are potentially reversible because although they are not functioning properly, there is no underlying structural damage.
• Emphasize the fact that understanding and accepting the diagnosis of functional neurologic disorder is essential for proper treatment, as it allows the patient to fully engage in treatment instead of focusing on figuring out what is wrong.
• Reach out to any other providers the patient has to ensure a cohesive approach to the presentation and treatment of the disorder.

Psychotherapy is the first-line treatment in most cases of functional neurologic disorder. Different types of therapy can be useful, but the most effective throughout the literature seems to be cognitive-behavioral therapy (CBT).[11] CBT works by looking at how someone thinks and feels about a situation and how that influences their behavior. Predisposing factors can be analyzed, and patients should focus on improving their communication and ability to express emotions properly. Goldstein and his colleagues conducted one study highlighting the efficacy of CBT in treating functional neurologic disorder; although it used a small sample size, the study showed that CBT successfully reduced dissociative seizure frequency by at least 50%.[12] Other types of therapy that may prove helpful include psychodynamic psychotherapy (individualized and best for patients who have already accepted that their symptoms may be secondary to past trauma), group therapy (this may help patients learn from and support each other), and family therapy (this may help improve communication). Furthermore, hypnotherapy can ameliorate functioning and physical symptoms of functional neurologic disorder, even in particularly severe cases. These approaches seem to be effective, especially in the case of comorbidities, such as chronic pain conditions.[13][14] However, hypnosis is considered a second-line treatment that may be helpful for patients with speech symptoms or sensory loss.

Another first-line treatment that clinicians should offer in conjunction with CBT is physical therapy. This approach is more useful for functional motor symptoms and helps patients feel as though their clinical team takes their symptoms seriously. The therapist can usually decrease functional motor symptoms by encouraging normal movements and slowly working on more complex tasks at each session. Physical therapy can also prevent secondary weakness or true deficit caused by the patient’s functional motor symptoms. Hypnosis is a second-line treatment that may be helpful for patients with speech symptoms or sensory loss.

Pharmacotherapy is most effective when there is a comorbid mental illness, such as anxiety or depression. Medications such as antidepressants, anxiolytics, or mood stabilizers would be chosen based on the underlying illness. Some studies have suggested that antidepressants, specifically those that target pain (such as serotonin and norepinephrine reuptake inhibitors), may be helpful for certain symptoms of functional neurologic disorder, even if the underlying mental illness is not clear. Among the pharmacological approaches, several investigations have taken place to evaluate the effects of antipsychotics. Recent studies suggest that quetiapine and haloperidol have a comparable effect in relieving patients from functional neurologic disorder symptoms; however, the occurrence of extrapyramidal symptoms seems to be significantly lower with the atypical antipsychotic quetiapine.[15](A1)

Transmagnetic stimulation (TMS) may be beneficial for patients with functional neurologic disorder, though no published control studies have been published. There are hypotheses that TMS may have neuromodulating effects that can change beliefs or expectations about symptoms. There have been mixed reviews on paradoxical intention treatment, which involves asking patients to intentionally engage in unwanted behavior that elicits functional neurologic disorder symptoms. Some critics feel that this is harmful to the patient-clinician relationship, and others believe that it may help the patient realize that specific thoughts or situations trigger their symptoms. One of the most critical aspects of treatment in functional neurologic disorder is frequent follow-up appointments with all involved clinicians. Frequent follow-up prevents the patient from visiting other facilities, such as urgent care or the emergency department.

Differential Diagnosis

Several psychiatric disorders are included in the differential diagnosis of functional neurologic disorder.

• Factitious disorder – In factitious disorder, patients exhibit signs and symptoms consistent with specific medical or psychiatric disorders, as occurs with functional neurologic disorder. However, patients with factitious disorder deliberately deceive physicians by exaggerating, faking, or lying about symptoms, hurting themselves to create symptoms, or altering their test results. The definition of this disorder is the patient having the desire to appear ill to obtain medical care but not to achieve personal or financial gain. There is also factitious disorder by proxy, in which a person acts as if someone under their care is sick. Patients with functional neurologic disorder do not intentionally create their symptoms to obtain care.

• Somatic symptom disorder – When the DSM-5 was released, the disorders previously referred to as somatoform disorders (including hypochondriasis and somatization separately) are now referred to as “somatic symptom disorder” collectively. The diagnostic criteria for somatic symptom disorder include one or more somatic symptoms that cause distress or lead to significant disruption of daily life, excessive thoughts, feelings, or behaviors related to these symptoms (which can present as mild, moderate, or severe in intensity), and persistence of symptoms (typically for greater than six months). There may be some overlap between somatic symptom disorder and functional neurologic disorder, as patients with functional neurologic disorder often display somatic symptoms that cause distress or disrupt daily life. However, patients with functional neurologic disorder typically do not have as exaggerated a response to their symptoms, and their symptoms tend to be inconsistent with true medical diagnoses.

• Illness anxiety disorder – Illness anxiety disorder was previously referred to as “hypochondriasis” in the DSM-4. Patients will illness anxiety disorder have very few somatic symptoms, if any. They present as having a preoccupation with having or acquiring a serious illness. These patients exhibit excessive health-related behaviors (e.g., repeatedly checking themselves for signs of disease) or exhibit maladaptive avoidance (eg, avoiding appointments with doctors or hospital visits). Patients with functional neurologic disorder do not typically display the level of preoccupation that patients with illness anxiety disorder do.

• Malingering is not a psychiatric disorder but a behavior that patients may display. Malingering is a patient feigning or exaggerating symptoms of physical or psychiatric disorders for personal or financial gain. Specific examples include patients faking symptoms of illness to avoid a criminal conviction, avoiding obligations such as work, school, or their jobs, or obtaining addictive medications when they are not warranted. Unlike patients with factitious disorder, these patients are often not compliant with complete physical exams or treatment plans.

There are many general medical conditions or neurologic disorders that may share features with those of functional neurologic disorder; this largely depends on the specific presenting symptom that the patient displays.[16][17][18][19] Some common medical conditions included in the differential are as follows:

• Multiple sclerosis – Multiple sclerosis is a demyelinating disease of the central nervous system. Patients will present with signs of central nervous system dysfunction, such as spinal cord syndrome, brainstem syndrome, or optic neuritis. Their symptoms typically follow a relapsing and remitting course. They will generally have corresponding neurologic deficits on the exam relative to their presenting symptoms. MRI showing characteristic lesions in the brain and spinal cord is diagnostic.

• Epilepsy – Some of the most common differences between psychogenic nonepileptic seizures and seizures characteristic of epilepsy were discussed above. Another helpful diagnostic tool is serum prolactin, which is often elevated after an epileptic seizure and not in psychogenic seizures. During video-EEG monitoring, clinicians may also use the placebo effect to induce a psychogenic seizure. One example would be photic stimulation, where the patient is exposed to bright, flashing lights and instructed that this may induce a seizure.

• Myasthenia gravis – Myasthenia gravis is a disorder of neuromuscular transmission characterized by weakness in the bulbar, ocular, respiratory, and extremity muscles. Aside from history and physical exam, serologic testing will often reveal positive antibodies against the acetylcholine receptor (AChR-Ab) and/or positive antibodies against muscle-specific tyrosine kinase (MuSK-Ab). Electrodiagnostic tests, such as repetitive nerve stimulation and single-fiber electromyography, can also help diagnose myasthenia gravis.

• Stroke – Strokes will have characteristics and anatomical patterns of the motor, sensory, or generalized neurologic changes.

• Spinal disorders – There are many disorders of the spinal cord that cause motor and sensory disturbances, which patients may mimic in functional neurologic disorder. Some of these conditions include cervical myelopathy, spinal stenosis, etc.

• Movement disorders – Many of the common differences between functional movement disorders and movement disorders secondary to the underlying neurologic conditions appeared in the sections above.

In strokes, spinal disorders, and movement disorders, the essential exam findings in functional neurologic disorder are inconsistencies with anatomical or neurologic patterns. 

Prognosis

The general prognosis for functional neurologic disorder is generally poor; however, this is dependent on multiple factors. Factors that promote a good prognosis include sudden onset, early diagnosis, short duration of symptoms, lack of comorbid psychiatric disorders (especially personality disorders), identifiable stressors, and a positive patient-clinician relationship. Patients with a greater number of physical symptoms of poor physical functioning before diagnosis have an increased chance of a poor outcome.

Complications

The complications of functional neurologic disorder include permanent disability and impaired quality of life. Some patients become lost to follow-up, and other patients do not complete treatment as advised. One study found that disability rates and impairment of quality of life were similar in patients with functional movement symptoms when compared to Parkinson disease. Another study found that patients with symptoms of paralysis had rates of disability similar to patients with multiple sclerosis. Overall, patients with psychogenic symptoms have comparable rates of physical disability and higher rates of psychological disability than patients with actual neurologic disorders.