Background
Functional neurological symptom disorder (conversion disorder) is classified as one of the somatic symptom and related disorders in the Diagnostic and Statistical Manual of Mental Disorders of the American Psychiatric Association, Fifth Edition, Text Revision (DSM-5-TR); [1, 2] these were formerly known as somatoform disorders. [3] Although defined as a condition that presents as an alteration or loss of a physical function suggestive of a physical disorder, conversion disorder is traditionally taken to be the expression of an underlying psychological conflict or need.
Conversion symptoms are presumed to result from some unconscious process. The precipitating psychological conflict or stressor may not be apparent initially, but may become evident in the course of obtaining a patient’s history: ideally, it is a psychological issue related symbolically and temporally to symptom onset. Conversion symptoms are not considered to be under voluntary control, and, should not be due to any physical disorder or known pathological mechanism (after appropriate medical evaluation). NB: Conscious/intentional production of physical symptoms is classified as factitious disorder or malingering.
Though classified with somatic symptom/somatoform disorders in DSM-III through DSM-5-TR, conversion disorder is classified as a dissociative disorder in ICD-10, keeping its long association with hysteria (Dissociative Disorders in DSM). [4, 5] Clinical descriptions of conversion disorder date to almost 4000 years ago; the Egyptians attributed symptoms to a "wandering uterus." In the 19th century, Paul Briquet described the disorder as a dysfunction of the CNS. [6, 7] Freud first used the term conversion to refer to the development of a somatic symptom to help bind anxiety around a repressed conflict. [8] In current practice, the term has made it into the popular press. [9, 10]
Pathophysiology
Presenting symptoms can range far across the field of clinical neurology. Conversion reactions usually approximate lesions in the nervous system’s voluntary motor or sensory pathways. Symptoms most commonly reported are weakness, paralysis, pseudoseizures, involuntary movements (eg, tremors), and sensory disturbances. These losses or distortions of neurologic function cannot adequately be accounted for by organic disease.
Functional MRI (fMRI) and transcranial magnetic stimulation (TMS) studies have shown different activation patterns in patients with conversion symptoms and healthy control subjects; this is in keeping with the "involuntary" nature of conversion symptoms. [11, 12, 13, 14, 15]
Patients whose symptoms are limited to pain or sexual functioning are not classified under conversion disorder; likewise, patients already classified as demonstrating somatization disorder or schizophrenia are also not classified under conversion disorder.
The DSM-5-TR diagnostic criteria for conversion disorder are as follows: [1]
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One or more symptoms of altered voluntary motor or sensory function.
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Clinical findings provide evidence of incompatibility between the symptom and recognized neurological or medical conditions.
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The symptom or deficit is not better explained by another medical or mental disorder.
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The symptom or deficit causes clinically significant distress or impairment in social, occupational, or other important areas of functioning or warrants medical evaluation.
According to psychodynamic theory, conversion symptoms develop to defend against unacceptable impulses. [8] The primary gain, that is to say the unconscious purpose of a conversion symptom is to bind anxiety and keep a conflict internal. A fairly transparent example would be leg paralysis after an equestrian competitor is thrown from his or her horse. The symptom has a symbolic value that is a representation and partial solution of a deep-seated psychological conflict: to avoid running away like a coward, and yet to avoid being thrown again.
According to learning theory, conversion disorder symptoms are a learned maladaptive response to stress. Patients achieve secondary gain by avoiding activities that are particularly offensive to them, thereby gaining support from family and friends, which otherwise may not be offered. [16]
Epidemiology
Frequency
True conversion reaction is rare. [17, 18] Predisposing factors include extreme psychosocial stress, and perhaps, rural upbringing. Some psychiatrists suspect that western society has incorporated Freudian notions of unconscious motivations and conflicts: conversion reactions have become too obvious to serve their purpose.
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The incidence of individual persistent conversion symptoms is estimated to be 2-5/100,000 per year. [1]
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Cultural factors may play a significant role. [19] Symptoms that might be considered a conversion disorder in the United States may be a normal expression of anxiety in other cultures.
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One study reports that conversion disorder accounts for 1.2–11.5% of psychiatric consultations for hospitalized medical and surgical patients.
At the National Hospital in London, the diagnosis was made in 1% of inpatients. [20] Iceland's incidence of conversion disorder is reported to be 15 cases per 100,000 persons.
Mortality/Morbidity
Patients diagnosed with conversion disorder may go on to demonstrate serious, traditional medical illness. This has been happening less and less often over the years (29% in 1950s down to 4% in 1990s). Unfortunately, emergency physicians may find themselves sorting out new neurologic symptoms in settings of terrible time pressure: populations statistics may be of little reassurance for any specific individual.
Sex- and age-related demographics
Sex ratio is not known although it has been estimated that women patients outnumber men by 6:1. According to DSM-5, conversion disorder is two to three times more common in females. [1]
Conversion disorder may present at any age but is rare in children younger than 10 years or in persons older than 35 years. [21]
In a University of Iowa study of 32 patients with conversion disorder, however, the mean age was 41 years with a range of 23–58 years. [22]
An Australian study estimated a pediatric incidence of 2.3/100,000 based on 194 cases of conversion disorder found among those reported to the Australian Pediatric Surveilance Unit from 2002–2003. Family loss (death/separation), followed by family violence, were the most commonly identified stressors (precipitants). [23] Prior opinion has been that incidence of conversion is increased after physical or sexual abuse, and that incidence also increases in those children whose parents are either seriously ill or have chronic pain. [24]
Prognosis
Prognostic studies differ in outcome, with recovery rates ranging from 15-74%. Factors associated with favorable outcomes are male gender, acute onset of symptoms, precipitation by a stressful event, good premorbid health, and an absence of organic or psychiatric disorder. [39]
Many patients with conversion reactions have spontaneous remission or demonstrate marked or complete recovery after brief psychotherapy.
