| Conversion disorder | |
|---|---|
| Classification and external resources | |
| ICD-10 | F44 |
| ICD-9 | 300.11 |
| DiseasesDB | 1645 |
| eMedicine | emerg/112 med/1150 |
| MeSH | D003291 |
Conversion disorder is a neurosis marked by the appearance of physical symptoms such as partial loss of muscle function without physical cause but in the presence of psychological conflict. Symptoms include numbness, blindness, paralysis, or fits without a neurological cause. It is thought that these problems arise in response to difficulties in the patient's life, and conversion is considered a psychiatric disorder in the Diagnostic and Statistical Manual of Mental Disorders 4th edition (DSM-IV).[1] Formerly known as "hysteria", the disorder has arguably been known for millennia, though it came to greatest prominence at the end of the 19th century, when the neurologists Jean-Martin Charcot and Sigmund Freud and psychiatrist Pierre Janet focused their studies on the subject. The term "conversion" has its origins in Freud's doctrine that anxiety is "converted" into physical symptoms.[2] Though previously thought to have vanished from the west in the 20th century, some research has suggested it is as common as ever.[3]
The DSM-IV classifies conversion disorder as a somatoform disorder while the ICD-10 classifies it as a dissociative disorder.
Contents |
DSM-IV defines conversion disorder as follows:
The nature of the association between the psychological factors and the neurological symptoms remains unclear. Earlier versions of the DSM-IV employed psychodynamic concepts, but these have been incrementally removed from successive versions.
The tenth revision of the World Health Organization's International Classification of Diseases uses the term "conversion" as an alternative descriptor for the dissociative disorders class of mental and behavioural disorders (i.e. the F44 class), with the explicit suggestion that dissociative and conversion symptoms probably share common psychological mechanisms.[4] In ICD-10, the dissociative [conversion] disorders class includes 10 disorders that, in addition to specific criteria for each individual disorder, must each meet the following general criteria:
In the 19th century, physicians such as Silas Weir Mitchell in the US and Paul Briquet and Jean-Martin Charcot in France developed ideas about patients sharing unexplained neurological symptoms. Charcot specialised in treating patients who were suffering from a variety of unexplained physical symptoms including paralysis, contractures (muscles which contract and cannot be relaxed) and seizures. Some of these patients sporadically and compulsively adopted a bizarre posture (christened arc-de-cercle) in which they arched their body backwards until they were supported only by their head and their heels.
The term "Conversion disorder" originated with Freud. He viewed these apparently neurological symptoms as a result of the conversion of intrapsychic distress into physical symptoms. This distress was thought to cause the brain to unconsciously disable or impair a bodily function as a side effect of the original repression, which served to relieve the patient's anxiety.[5] However, recent evidence suggests that patients do remain distressed by their symptoms in the long term[6] It has also been suggested that at least some of the classic psychoanalytic cases of hysteria, such as "Anna O.",[7] may actually have suffered from organic illness. In fact, in Studies On Hysteria in which Breuer's Anna O. case was first presented, Freud wrote this: "Others of the patient's symptoms were not of a hysterical nature at all. This is true, for example, of the neck cramps, which I consider a modified version of migraine and which as such are not to be classified as a neurosis but as an organic disorder. Hysterical symptoms, however, regularly become attached to these." Freud believed that all hysterical symptoms ultimately have some organic components.[8]
Conversion disorder can present with any motor or sensory symptom including any of the following:
The DSM-IV-TR does not have specific diagnosis for Mass Psychogenic Illness but the text describing conversion disorder states that "In 'epidemic hysteria,' shared symptoms develop in a circumscribed group of people following 'exposure' to a common precipitant."
The diagnosis of conversion disorder involves three elements: the exclusion of neurological disease, the exclusion of feigning, and the determination of a psychological mechanism. Each of these has difficulties.
Conversion disorder presents with symptoms that typically resemble a neurological disorder such as stroke, multiple sclerosis, epilepsy or hypokalemic periodic paralysis. The neurologist must carefully exclude neurological disease, through examination and appropriate investigations.[9] However, it is not uncommon for patients with neurological disease to also have conversion disorder[10].
In excluding neurological disease, the neurologist has traditionally relied partly on the presence of positive signs of conversion disorder — certain aspects of the presentation that were thought to be rare in neurological disease, but common in conversion. The validity of many of these signs has been questioned, however, by a study showing that they also occurred in neurological disease.[11] One such symptom, for example, is La belle indifférence, described in DSM-IV as "a relative lack of concern about the nature or implications of the symptoms". In a later study no evidence was found that patients with "functional" symptoms are any more likely to exhibit this than patients with a confirmed organic disease.[12] Another feature thought to be important was that symptoms would tend to be more severe on the non-dominant (usually left) side; there were a variety of theories such as the relative involvement of cerebral hemispheres in emotional processing, or more simply just that it was "easier" to live with a functional deficit on the non-dominant side. However, a literature review of 121 studies established that this was not true, with publication bias the most likely explanation for this commonly held view.[13] Although agitation is often assumed to be a positive sign of conversion disorder, release of epinephrine is a well-demonstrated cause of paralysis from hypokalemic periodic paralysis[14].
The process of exclusion is not perfect, so misdiagnoses will occur. However, in a highly influential[15] study from the 1960s, Eliot Slater demonstrated that misdiagnoses had occurred in one third of his 112 patients with conversion disorder.[16] Later authors have argued that the paper was flawed, however,[6][17] and a meta-analysis has shown that misdiagnosis rates since that paper are around 4%, the same as for other neurological diseases.[18]
Conversion disorder is unique in DSM-IV in explicitly requiring the exclusion of deliberate feigning. Unfortunately, this is only likely to be demonstrable where the patient confesses, or is "caught out" in a broader deception, such as a false identity.[19] One neuroimaging study suggested that feigning may be distinguished from conversion by the pattern of frontal lobe activation;[20] however this is a research, rather than a clinical technique. True rates of feigning in medicine remain unknown, though neurological presentations of feigning may be among the more common.[21]
The psychological mechanism can be the most difficult aspect of the conversion diagnosis. DSM-IV requires that the clinician believe preceding stressors or conflicts to be associated with the development of the disorder, though how this might come about is still the subject of debate.
The original Freudian model[2] suggested that the emotional charge of painful experiences would be consciously repressed as a way of managing the pain, but this emotional charge would be somehow "converted" into the neurological symptoms. Freud later argued that the repressed experiences were of a sexual nature.[22] As Peter Halligan comments, conversion has 'the doubtful distinction among psychiatric diagnoses of still invoking Freudian mechanisms'[23] Janet, the other great theoretician of hysteria, argued that symptoms arose through the power of suggestion, acting on a personality vulnerable to dissociation.[24] In this hypothetical process, the subject's experience of their leg, for example, is split-off from the rest of their consciousness, resulting in paralysis or numbness in that leg. Later authors have attempted to combine elements of these models, but none of them has a firm empirical basis.[25] Some support for the Freudian model comes from findings of high rates of childhood sexual abuse in conversion patients[26] and from a recent neuroimaging study showing abnormal emotion processing of a traumatic event linked to motor processing of the affected limb, in a patient with conversion.[27] Support for the dissociation model comes from studies showing heightened suggestibility in conversion patients,[28] and in abnormalities in motor imagery.[29] There has been much recent interest in functional neuroimaging in conversion. As researchers identify the mechanisms which underlie conversion symptoms it is hoped these will allow the development of a neuropsychological model. A number of such studies have been performed, including some which suggest that blood flow in patients brains may be abnormal while they are unwell. These have all been too small to be confident of the generalisability of their findings, however, so no neuropsychological model has been clearly established.
A 2007 review stated that conversion disorder and dissociative disorders are statically associated, share features such as a history of abuse and high suggestability, and likely have common underlying causes. It recommended that DSM should follow ICD-10 and reclassify conversion disorder from a somatoform disorder to a dissociative disorder.[30]
An evolutionary psychology explanation for conversion disorder is that the symptom may have been evolutionarily advantageous during warfare. A non-combatant with these symptoms signals non-verbally, possibly to someone speaking a different language, that she or he is not dangerous as a combatant and also may be carrying some form of dangerous infectious disease. This can explain that conversion disorder may develop following a threatening situation, that there may be a group effect with many people simultaneously developing similar symptoms (as in Mass Psychogenic Illness), and the gender difference in prevalence.[31]
Information on the prevalence of conversion disorder in the West is limited, in part due to the complexities of the diagnostic process. In neurological settings, rates of unexplained symptoms are very high, at between 30 and 60%,[32][33][34] which suggests conversion to be more common than most neurological diseases. However, the diagnosis of conversion typically requires an additional psychiatric evaluation, yet few patients will see a psychiatrist[35] so an unknown fraction of those unexplained symptoms will be due to conversion. Large scale psychiatric registers in the US and Iceland found rates of 22 and 11 per 100,000 per year, respectively,[36] but it is unclear what proportion of unexplained symptoms these represent.
It is often thought that rates are higher outside of the West, perhaps related to cultural and medical attitudes, though evidence for this is again limited.[3] A community survey of urban Turkey found a rate of 5.6%.[37] Many authors have found rates to be higher in rural and lower socio-economic groups where technological investigation of patients is limited.[38][39][40]
'Hysteria' was originally understood to be a condition exclusively affecting women, though it has increasingly been recognised in men. In recent, larger studies,[32][41] women continue to predominate, with between 2 and 6 female patients for every male.
Conversion disorder may present at any age but is rare in children younger than 10 years or in the elderly. Studies suggest a peak onset in the mid-to-late 30s.[32][42][43]
Treatment may include the following:[44]
There is little evidence-based treatment of conversion disorder.[46] Other treatments such as cognitive behavioral therapy, hypnosis, EMDR, and psychodynamic psychotherapy need further trials.
The DSM-IV-TR states that conversion symptoms will in most cases disappear within 2 weeks in those hospitalized. One-fifth to one-quarter will have a recurrence within a year with this also predicting future recurrences. Acute onset, clearly identifiable stress at this time, and short time between onset and treatment are associated with a favorable prognosis.
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||