Functional Neurologic Disorder (FND), previously known as conversion disorder, is a recognized psychiatric condition where patients present with neurological symptoms that cannot be explained by neurological disease or other medical conditions. These symptoms, affecting sensory or motor function, are genuine and significantly impair a patient’s daily life. Understanding Conversion Diagnosis is crucial for effective management and care. This article provides a comprehensive overview of FND, focusing on its diagnosis, evaluation, and management, aiming to enhance understanding for healthcare professionals and improve patient outcomes.
Understanding Functional Neurologic Disorder: Etiology and Risk Factors
Functional Neurologic Disorder is a complex condition with no single cause, but rather a combination of psychological, social, and biological factors that contribute to its development and progression. Often, a preceding traumatic event, stressful life situation, or chronic stressor is identified before the onset of FND symptoms. Many individuals diagnosed with FND report a history of childhood abuse, including emotional and sexual abuse. Other psychological elements, such as inadequate coping mechanisms and internal conflicts, also play a significant role.
Patients with FND have a higher likelihood of co-existing psychiatric disorders like depression, anxiety, and personality disorders compared to those with organic neurological conditions. They are also more prone to a history of multiple unexplained somatic complaints, such as fatigue, weakness, or pain. A physical injury or actual neurological illness, such as a stroke or migraine, can sometimes act as a trigger for FND symptoms. Socioeconomic factors also appear to be relevant, with individuals with less education, lower socioeconomic status, and those residing in developing or rural areas showing a higher predisposition to developing FND.
Two primary theoretical models attempt to explain Functional Neurologic Disorder:
Psychodynamic Models: These models propose that FND symptoms are a manifestation of unresolved emotional conflict. This conflict is repressed into the unconscious mind and then “converted” into physical symptoms. This conversion is seen as a defense mechanism against the distress that the emotional conflict would otherwise cause. Some psychodynamic perspectives also emphasize the role of early life experiences in developing maladaptive coping mechanisms and negative interpersonal patterns, which can resurface in response to later traumatic events.
Cognitive-Behavioral Models: This model suggests that exposure to symptom-related information can create a memory representation of that symptom. FND occurs when this representation is activated by excessive worry or symptom monitoring. This activation surpasses a threshold in the mind, overriding sensory input and manifesting as a real symptom. For example, witnessing a seizure in a movie might create a seizure representation in memory. Subsequent anxiety or dizziness could trigger fear of a seizure, activating this memory and leading to a psychogenic non-epileptic seizure. Cognitive-behavioral models posit that these processes operate largely outside of conscious awareness, suggesting that psychological influences can affect symptom development at lower levels of processing.
Emerging research also explores neurobiological mechanisms, such as the role of microglia and neuroimmunity in altered synaptic plasticity, which could contribute to the motor dysfunctions observed in FND.
Epidemiology of Functional Neurologic Disorder
The reported incidence of Functional Neurologic Disorder varies based on the population studied. Studies have shown a wide range, from 4 to 12 per 100,000 people per year in general populations, to higher rates of around 50 per 100,000 per year when using population-based case registries. Outpatient neurology settings show a prevalence between 4% and 5.6% of patients presenting with FND.
Adult women are diagnosed with FND more frequently than adult men, with ratios ranging from 2:1 to 10:1. As mentioned earlier, lower socioeconomic status and less education are associated with a higher incidence. Race does not appear to be a significant factor. FND is rare in children under 5 years old, with incidence increasing during puberty and adolescence. In pediatric populations, studies report rates ranging from 0.2% to 4.2 per 100,000 per year. After the age of ten, girls are approximately three times more likely to develop FND than boys.
Pathophysiology: Neural Mechanisms in Conversion Disorder
Neurobiological models of Functional Neurologic Disorder suggest that the condition arises from alterations in higher-order cortical processing. The prevailing hypothesis is that emotional stress activates frontal and subcortical brain areas, which in turn influence inhibitory basal ganglia-thalamocortical circuits. This process is thought to reduce conscious sensory or motor processing.
Research into the neural mechanisms of FND is ongoing, with functional neuroimaging playing a crucial role. A study using PET scans compared patients with FND-related weakness to both healthy controls and individuals asked to feign weakness. Patients with FND showed reduced activity in the left dorsolateral prefrontal cortex when attempting to move the affected limb. This finding distinguishes FND patients from those intentionally mimicking symptoms, as the left dorsolateral prefrontal cortex is associated with volition and intentional actions.
Another study using functional MRI investigated the relationship between emotion and symptom production in FND. It revealed an abnormal correlation between amygdala activation (the brain region associated with emotion) and the supplementary motor area during emotional tasks. These findings suggest that emotional processing and motor control are abnormally interacting in FND.
History and Physical Examination: Key to Conversion Diagnosis
A thorough history and physical examination are paramount in conversion diagnosis. Building rapport and a comfortable environment for the patient is essential to encourage them to openly discuss their symptoms and experiences. A useful approach is to begin by creating a comprehensive list of all symptoms the patient is currently experiencing. This list serves as a baseline to track any changes in symptoms over time and to identify the presence of multiple somatic complaints.
It is crucial to inquire about previous treatments or suspected neurological diagnoses the patient has received. The clinician should gather detailed information about the onset, duration, and context of the symptoms. Without suggesting a diagnosis, it is important to explore recent life events or stressors and obtain a psychiatric history, including family psychiatric history. Asking about past episodes of similar symptoms, prior diagnoses, and treatments can provide valuable insights into the patient’s experience and their interactions with healthcare providers. Understanding the patient’s perspective on their illness and what they believe is happening is also vital. Instead of focusing solely on current limitations, asking the patient to describe a symptom-free period and their typical daily routine can offer a broader understanding of their functional impairment.
While Functional Neurologic Disorder is not strictly a diagnosis of exclusion, it relies on the clinician’s ability to rule out organic neurological diseases and identify inconsistencies during the physical exam, alongside recognizing clinical signs and symptoms not typical of organic disorders. Inconsistent symptoms, negative findings on lab and imaging studies, and the presence of a significant psychiatric history are suggestive of FND. However, a comprehensive examination to exclude other organic conditions remains essential. It is also important to consider that patients with FND can have co-occurring neurological disorders, which can complicate the diagnostic process.
The Diagnostic and Statistical Manual of Mental Disorders, 5th Edition, Text Revision (DSM-5-TR), classifies Functional Neurologic Disorder under “Somatic Symptom and Related Disorders.” Previous DSM editions emphasized psychological comorbidities and the absence of intentional symptom production as diagnostic criteria. The DSM-5-TR has removed “la belle indifférence” (a patient’s apparent lack of concern about their symptoms) as a diagnostic criterion, considering it now as a supporting feature. Other supporting features include dissociative symptoms and recent psychological or physical trauma.
The DSM-5-TR diagnostic criteria for Functional Neurologic Disorder are:
- Presence of one or more symptoms of altered voluntary motor or sensory function.
- Clinical evidence demonstrates an incompatibility between the symptoms and recognized neurological or medical conditions.
- The symptom or deficit cannot be better explained by another medical or mental disorder.
- The symptom or deficit causes clinically significant distress or impairment in social, occupational, or other important areas of functioning or necessitates medical evaluation.
FND is categorized as acute if symptoms last less than six months and persistent if symptoms are present for six months or longer. It can also be specified as with or without psychological stressor. The DSM-5-TR recognizes several subtypes of FND, each with characteristic features that aid in differentiating them from organic disorders:
Psychogenic Nonepileptic Seizures (PNES): The most common FND subtype. PNES often involve generalized limb shaking, hip thrusting, and lack of postictal confusion. Seizure duration may be longer than epileptic seizures, with a waxing and waning pattern. Patients typically maintain bowel and bladder control and avoid self-injury, such as tongue biting. EEG findings are normal, without paroxysmal activity. PNES often do not respond to antiepileptic medications and may even worsen with attempted treatment. A physical exam sign, forced eye closure, where the examiner meets resistance when trying to open the patient’s eyes, is suggestive of PNES and not typical of epileptic seizures.
Paralysis or Weakness: Weakness is a frequent symptom in FND. Paralysis, when present, is usually limited to one side of the body or a single limb and does not follow anatomical patterns of neurological disease. In paraplegia, deep tendon reflexes remain normal, and the Babinski sign is absent. Inconsistency is a hallmark of psychogenic weakness. Careful observation of the patient during examination and in other activities, like entering or leaving the room, is crucial. Specific tests and signs used to identify psychogenic weakness include:
- Hoover’s Sign: This test relies on the principle that hip extension occurs when the contralateral hip flexes against resistance. For lower extremity weakness, the patient lies supine, and the examiner places a hand under the affected heel. When the patient attempts to lift the unaffected leg against resistance, downward pressure on the affected heel indicates functional weakness.
- Co-contraction Sign: This involves the simultaneous contraction of agonist and antagonist muscles (e.g., biceps and triceps). Detecting co-contraction in any muscle group suggests the absence of true weakness.
- Arm-Drop Test: The examiner holds the patient’s outstretched arm and releases it. A jerky or slow descent of the arm onto the lap is typical of functional weakness.
- Sternocleidomastoid Test: Patients with FND often show weakness when rotating their head towards the affected side, unlike those with organic weakness.
- Collapsing Weakness: When the examiner applies light force to a limb held in a specific position, the limb appears to “collapse” suddenly.
Abnormal Movement: Psychogenic movement disorders are common in FND. Typical features include rapid onset, symptom improvement with distraction (e.g., counting, performing tasks), and variability in frequency, amplitude, and body region affected. Careful observation across different settings is essential.
- Tremor: Functional tremors can occur at rest and during action, often fluctuating in frequency. Organic tremors are typically rhythmic and occur either at rest or with action. Functional tremors tend to have an abrupt onset, often triggered by emotional or traumatic events, reach maximum severity quickly, and may start unilaterally. Applying weights to the affected limb usually increases the amplitude of functional tremors, while it decreases organic tremor amplitude. Entrainment, where the unaffected limb mirrors the rhythm of the affected limb or the patient struggles to maintain a steady rhythm with the unaffected limb while the affected limb tremors, can also be observed.
- Gait Disorder: Functional gait disorders are characterized by patterns inconsistent with neurological disorders. Unilateral leg weakness may present as dragging the leg, with the hip internally or externally rotated, causing the foot to point outwards or inwards. Other features include sudden knee buckling without falls, a “walking on ice” pattern (stiff knees and ankles, slow, broad gait, abducted arms), excessively slow gait initiation, feet appearing to stick to the ground, and pseudoataxia (unsteady gait, crossed legs, sudden side-stepping). Examination may reveal uneconomic postures that shift the center of gravity unnaturally.
- Dystonia: Functional dystonia features include severe limb pain, adult onset, fixed posture (even during sleep), clenched fist, or inverted foot. Inconsistent movements and multiple somatic complaints are common. Symptom remission after placebo, suggestion, or general anesthesia can occur.
- Myoclonus: Organic myoclonus involves jerking movements due to muscle contractions or decreased tone. Functional myoclonus is inconsistent in frequency and amplitude and may resolve with placebo or suggestion. Patients may be stimuli-sensitive but exhibit a prolonged and variable latency to stimuli, unlike typical reflex responses.
Anesthesia or Sensory Loss: Functional sensory loss is a less specific FND manifestation. It often does not follow dermatomal patterns or patterns of neurological disorders. Patients may describe a sharp demarcation of sensory loss, often at a joint or the extremity’s end, shoulder, or groin. “Hemisensory syndrome,” with sensory loss on one side of the body, sometimes accompanied by a “cut in half” sensation or ipsilateral hearing/vision issues, may also occur. Midline splitting can be assessed using a tuning fork placed on the sternum or frontal bone. Healthy individuals will feel vibrations equally on both sides, as these bones vibrate as a unit. Patients with functional sensory loss may 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: Common in FND. Complete blindness is more suggestive of factitious symptoms. In FND, the pupillary reflex is intact. True blindness onset usually leads to difficulties in maneuvering and increased minor injuries, which are absent in FND. Diagnostic tests include:
- Mirror Test: Moving a mirror in front of the patient; tracking their reflection indicates they are not truly blind.
- Fingertip Test: Difficulty touching index finger tips together suggests functional blindness, while truly blind individuals use proprioception to perform this task.
- Signature Test: Inability to sign their name is common in functional blindness, whereas truly blind individuals can sign without difficulty.
- Optokinetic Test: Observing optokinetic nystagmus when a rotating drum with stripes is presented indicates visual processing.
- Menace Reflex: Blinking or flinching to a perceived threat (hand moved quickly towards the face) suggests vision.
- Tearing Reflex: Tearing up in response to a bright light indicates intact vision.
- Olfactory or Hearing Disturbances: Less common, typically presenting as anosmia or deafness. Patients reporting anosmia usually have a normal sense of taste. True anosmia often involves decreased taste and signs of nutritional deficiencies. Loud sounds may elicit a blink or startle response in patients with functional deafness.
Swallowing Symptoms: Globus sensation or globus pharyngeus, a lump or tightness in the throat, is a functional esophageal disorder with no physiological cause. It occurs between meals and lacks odynophagia or dysphagia. It can occur in individuals without FND but is often associated with psychiatric comorbidities.
Speech Symptom: Functional dysphonia (hoarseness or whispering) is the most common, but slurred speech, articulation issues, stuttering, foreign accent syndrome, and mutism can also occur. Patients with functional dysphonia can often cough or sing normally during a lung exam, while those with true dysphonia struggle. Vocal cord examination is typically normal.
Evaluation and Diagnostic Procedures for Conversion Disorder
Conversion diagnosis primarily relies on a detailed history and physical examination. However, laboratory studies or imaging may be necessary to exclude underlying medical conditions, depending on the presenting symptoms. For example, patients with suspected psychogenic nonepileptic seizures might undergo an electroencephalogram (EEG) to rule out epileptic activity, or blood tests like prolactin or creatine phosphokinase to differentiate from epileptic seizures. Patients presenting with weakness may undergo electromyography (EMG) or magnetic resonance imaging (MRI). Further investigations may be ordered to assess for potential comorbid conditions.
Treatment and Management Strategies for Functional Neurologic Disorder
The initial step in treating Functional Neurologic Disorder is effectively communicating the diagnosis to the patient. It is generally advised not to disclose the diagnosis during the first encounter. Building a strong therapeutic alliance is paramount. Engage the patient by asking about their understanding of their symptoms and encouraging them to express their feelings. In subsequent sessions, focus on the following key points:
- Validate Symptom Reality: Emphasize that their symptoms are real and acknowledge the impact they have on the patient’s life.
- Avoid Dismissal: Do not suggest that “nothing is wrong” or that it is “just psychological.”
- Use Analogies: Provide examples of organic conditions worsened by stress, such as irritable bowel syndrome or peptic ulcer disease, and common physical manifestations of stress like sweating, shaking, or palpitations during anxiety.
- Explain Diagnostic Process: Clearly explain how the diagnosis was reached, highlighting the exam and history findings that differentiated FND from organic neurological disease.
- Emphasize Reversibility: Explain that symptoms are potentially reversible because there is no underlying structural damage, although function is impaired.
- Promote Diagnosis Acceptance: Stress that accepting the diagnosis is crucial for effective treatment, allowing the patient to engage fully rather than seeking alternative explanations.
- Coordinate Care: Communicate with other healthcare providers involved to ensure a unified approach to diagnosis and treatment.
Psychotherapy is the cornerstone of FND treatment. Cognitive-Behavioral Therapy (CBT) has demonstrated the most robust evidence of effectiveness. CBT addresses the relationship between thoughts, feelings, and behaviors. It helps patients analyze predisposing factors, improve communication, and develop healthier ways to express emotions. Studies have shown CBT can significantly reduce the frequency of dissociative seizures. Other beneficial therapies include psychodynamic psychotherapy (particularly for those who accept psychological contributions to their symptoms), group therapy (for peer support and learning), and family therapy (to improve communication). Hypnotherapy can also be beneficial, even in severe cases, particularly for comorbid chronic pain. Hypnosis may be considered a second-line treatment, especially for speech symptoms or sensory loss.
Physical therapy is another first-line treatment, especially for motor symptoms. It reinforces the clinical team’s recognition of the patient’s symptoms as real. Physical therapists can help reduce motor symptoms by encouraging normal movements and progressively increasing task complexity. Physical therapy can also prevent secondary weakness or deficits arising from functional motor symptoms.
Pharmacotherapy is most effective when comorbid mental health conditions, such as anxiety or depression, are present. Medications like antidepressants, anxiolytics, or mood stabilizers should be chosen based on the underlying condition. Some studies suggest antidepressants, particularly serotonin-norepinephrine reuptake inhibitors (SNRIs) targeting pain, may alleviate certain FND symptoms even without a clear comorbid mental illness. Antipsychotics, like quetiapine and haloperidol, have been investigated. Quetiapine appears to be comparably effective to haloperidol in managing FND symptoms but with fewer extrapyramidal side effects.
Transcranial magnetic stimulation (TMS) may offer benefits, although controlled studies are limited. TMS is hypothesized to have neuromodulatory effects that can alter symptom-related beliefs and expectations. Paradoxical intention treatment, where patients intentionally engage in unwanted behaviors eliciting FND symptoms, has mixed reviews. Some criticize its potential to harm the patient-clinician relationship, while others believe it can help patients identify symptom triggers. Frequent follow-up appointments with all members of the care team are crucial to prevent symptom relapse and reduce unnecessary emergency department or urgent care visits.
Differential Diagnosis: Distinguishing FND from Other Conditions
Several psychiatric disorders need to be considered in the differential diagnosis of Functional Neurologic Disorder:
- Factitious Disorder: Patients intentionally feign or induce symptoms to assume the sick role and receive medical care, without seeking external rewards like financial gain. Factitious disorder by proxy involves inducing illness in someone under their care. In contrast, FND symptoms are not intentionally produced.
- Somatic Symptom Disorder: Characterized by distressing somatic symptoms that disrupt daily life, accompanied by excessive thoughts, feelings, and behaviors related to these symptoms. While there can be overlap, FND symptoms are typically inconsistent with medical diagnoses, and the patient response is less exaggerated than in somatic symptom disorder.
- Illness Anxiety Disorder: Previously hypochondriasis, this involves preoccupation with having or acquiring a serious illness, with minimal somatic symptoms. Patients display excessive health-related behaviors or maladaptive avoidance. FND patients typically do not exhibit the same level of preoccupation.
- Malingering: Not a psychiatric disorder, but a behavior where patients feign or exaggerate symptoms for personal or financial gain, such as avoiding work or legal obligations or obtaining medications. Unlike factitious disorder, malingerers are often non-compliant with exams and treatment.
Numerous general medical and neurological conditions can mimic FND, depending on the presenting symptom. Common conditions in the differential diagnosis include:
- Multiple Sclerosis (MS): A demyelinating central nervous system disease presenting with CNS dysfunction signs like spinal cord syndrome, brainstem syndrome, or optic neuritis, typically with a relapsing-remitting course and corresponding neurological deficits. MRI findings are diagnostic.
- Epilepsy: Key differences between psychogenic nonepileptic seizures and epileptic seizures have been discussed. Serum prolactin levels, often elevated after epileptic seizures but not PNES, can be helpful. Video-EEG monitoring can also aid in differentiating the conditions.
- Myasthenia Gravis: A neuromuscular transmission disorder characterized by weakness in bulbar, ocular, respiratory, and extremity muscles. Serologic testing for acetylcholine receptor antibodies (AChR-Ab) and muscle-specific tyrosine kinase antibodies (MuSK-Ab), and electrodiagnostic tests, are diagnostic.
- Stroke: Characterized by motor, sensory, or generalized neurological changes with anatomical patterns.
- Spinal Disorders: Cervical myelopathy, spinal stenosis, and other spinal cord disorders can cause motor and sensory disturbances that may resemble FND.
- Movement Disorders: Distinguishing features between functional and organic movement disorders have been described above.
In strokes, spinal disorders, and movement disorders, the key differentiating factor from FND is the inconsistency of exam findings with anatomical or neurological patterns in FND.
Prognosis and Outcome of Functional Neurologic Disorder
The general prognosis for Functional Neurologic Disorder can be variable, often described as guarded, but depends on several factors. Positive prognostic factors include sudden symptom onset, early diagnosis, short symptom duration, absence of comorbid psychiatric disorders (especially personality disorders), identifiable stressors, and a positive patient-clinician relationship. A greater number of physical symptoms and poorer pre-diagnosis physical functioning are associated with a less favorable outcome.
Complications Associated with Conversion Disorder
Complications of Functional Neurologic Disorder can include persistent disability and reduced quality of life. Some patients may be lost to follow-up, and treatment adherence can be challenging. Disability rates and quality of life impairment in patients with functional movement symptoms have been found to be comparable to those with Parkinson’s disease. Patients with paralysis symptoms may experience disability levels similar to those with multiple sclerosis. Overall, patients with psychogenic symptoms experience comparable physical disability and higher psychological disability rates than those with organic neurological disorders.
Deterrence and Patient Education Strategies
Patient education is a crucial component of FND management. Providing patients and their families with educational resources is essential. National support groups for conversion disorder are available. Clinicians should meet with family members separately to discuss positive reinforcement strategies, encouraging them to focus on validating the reality of the patient’s symptoms rather than dismissing them. Families can offer significant support, help identify symptom triggers, ensure follow-up appointment attendance, and participate in family therapy. It is also important to recognize the potential stress the diagnosis places on families and encourage them to access support groups for families of individuals with mental illness.
Enhancing Healthcare Team Outcomes for Improved Patient Care
An interprofessional team approach is essential for managing Functional Neurologic Disorder. Interprofessional chronic pain rehabilitation programs, incorporating multidimensional and tailored interventions, have shown effectiveness for chronic pain and are applicable to FND. Effective communication among primary care physicians, psychiatrists, and psychologists is crucial. Psychiatric nurses play a vital role in patient monitoring and education, avoiding confrontation. Pharmacists ensure medication appropriateness, verify dosages, and educate patients and families on medication adherence and side effects. Nursing and pharmacy staff should promptly communicate any concerns to the clinical team. This collaborative interprofessional approach enhances patient outcomes and minimizes adverse effects.
Neurologists and other specialists may also be involved depending on the specific symptoms. A consensus among providers on diagnosis presentation and a clear, multifaceted treatment plan is vital. Ineffective communication can weaken the patient-clinician relationship, worsen prognosis, and increase symptom relapse risk. Physical therapists are crucial for patients with motor symptoms. Inpatient interprofessional treatment may benefit patients with severe, debilitating FND or those unresponsive to initial treatments.
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