It has been suggested that hysteria has disappeared and is only an old, stigmatizing and pejorative, even erroneous concept, reflecting the inability of the medical community to sometimes make a diagnosis. Currently, these disorders, called dissociative disorders, conversion disorders or functional neurological disorders, remain a frequent and disabling clinical reality for patients. Several studies and reviews have tried to better describe the clinical presentation, but also to better understand the neurobiological mechanisms involved in these disorders through the development of certain brain imaging techniques. If the neurobiological correlates are better understood, effective treatments are still lacking and only multidisciplinary care (general practitioners, neurologists, psychiatrists, physiotherapists etc …) and individualized can bring a benefit to the patient.
Introduction
Every doctor is confronted during his career with a number of patients for whom an accurate diagnosis cannot be made. For some of them, time makes it possible to obtain a diagnosis with the appearance of clearer symptoms and signs. For others, the cause of the symptoms remains unknown and if the disorders persist for at least six months, the terminology that is most often required is that of undifferentiated somatoform disorders (table). When the clinical presentation is neurological (that is, it includes a motor, sensory or sensory disorder), it is called conversion disorders, again according to the DSM-IV. So far, we remain in a descriptive register, although the term “conversion” refers to Freudian theories of a transformation of psychic conflicts into physical symptoms.
Clinical presentation: “pseudo-neurological” symptoms and signs
Dissociative disorder is a “pseudo-neurological” syndrome that can mimic motor, sensory or sensory impairment, seizures of the epileptic type or abnormal movements, including gait disorders. The diagnosis is not based only on the absence of pathological signs related to the symptoms; if a patient has hemiparesis, it is understood that cortico-spinal signs on the same side will be exclusive of a conversion disorder. On the other hand, it is possible to find other abnormalities on neurological examination and this does not exclude a diagnosis of conversion syndrome; a patient may have sequellar cortico-spinal signs of a previous stroke and meet the clinical criteria for dissociative tremor.
On the other hand, the diagnosis is based on the presence of so-called “positive” signs which, when present, strongly suggest the diagnosis of dissociative disorder. While some of these signs (some examples of which are described below) have been validated, most have no established specificity or sensitivity. It is therefore the entire clinical picture that allows the neurologist to establish the diagnosis, avoiding restricting it to a diagnosis of exclusion. Recently, a review of all studies was able to establish that the diagnostic error rate was 4%, which is comparable to other neurological diseases such as motor neuron diseases (6%), or psychiatric diseases such as schizophrenia (8%).
Dissociative motor disorders
Dissociative motor disorder is retained when signs of inconsistency are observed: for example, a patient is paralyzed in his right leg during the examination in bed but is able to stand on this leg when he puts his pants back on at the end of the examination. The presence of releases, during the examination, of the force is also suggestive: the patient can develop a good force, but it is not supported and, against resistance, the loose force (without pain or pathology being the cause).
Dissociative sensory disorders
Dissociative sensory disorders are also suggested when there are inconsistencies: a patient with complete anesthesia in all modes in the legs (including direction of position) should not have a normal Romberg test or normal walking. The presence of a sensory deficit in a non-organic territory also suggests the diagnosis: for example, anesthesia on a hemi leg, which corresponds neither to the territory of a nerve root nor to that of a nerve trunk (such as sciatica), nor to the cerebral cortical representation of the territory of the leg.
Dissociative convulsive disorders
Convulsive dissociative disorders (psychogenic non-epileptic seizures or CNEP) can be diagnosed when they are recorded simultaneously with an electroencephalogram and the electroencephalogram shows no epileptic activity during the seizure. Some clinical signs are very strongly suggestive such as swaying of the pelvis; lateral movements of the head (non-no type); the arc of a circle in type of contraction; the slow and gradual onset as well as the long duration of the seizure and finally with their eyes closed (they remain open during a generalized seizure). This last sign has been validated and shows a positive predictive value of 0.94 (sensitivity 96% and specificity 98%).
Dissociative gait disorders
Dissociative gait disorders are recognized when there is a typical feature, such as “the skater’s walk”, the patient slipping his feet as on ice, or when there is an inefficiencies position: the patient maintains his center of gravity in a position requiring additional effort (e.g. walking bent knees that requires, in addition to a good balance, a considerable strength of the quadriceps).
Tremor and dissociative sensory disorders
Dissociative tremor (the most common of the dissociative abnormal movements) is recognized when it is variable, changes when the subject is distracted , or is driven by another frequency (during a rhythmic movement of the other hand, for example). Finally, we can mention dissociative sensory disorders: deafness, blindness for which the assistance of ophthalmologist and ENT specialists is often necessary.
Hysteria: a historical concept?
In antiquity, Hippocrates devoted several chapters of his Treatises on Medicine to describing the symptoms of hysteria and their treatments. It was not until the nineteenth century that an interest was reborn in the medical community for this intriguing clinical presentation through Jean-Martin Charcot, who established his fame, in part, by presenting patients in “great hysterical crisis” during his legendaryTuesday Lessons. Subsequently, one of his students, Sigmund Freud, developed the concept of psychic conflict into a somatic symptom. Then we witness in the last century a sidelining of this pathology, both by psychiatrists and neurologists, to the point where it is even suggested that hysteria no longer exists.The broadening of the spectrum of psychiatric diagnoses, such as personality disorders, also brings confusion with the concept of histrionic personality.
With the advent of new techniques such as electrophysiology and brain imaging, interest has reborn in recent decades and it has recently been established that hysteria, renamed conversion disorders or dissociative disorders, or more simply in the language used with the patient, functional disorders (function is disturbed, but the organ is healthy), remains today a frequent and disabling pathology. It is estimated that up to 30% of patients in a general neurology consultation have medically unexplained symptoms and their follow-up shows that more than half (55%) are not improved at eight months of progression. Long-term follow-up of patients with dissociative motor and/or sensory syndrome showed that twelve years later, 83% of them remain symptomatic and nearly 30% have ceased all professional activity at an average age of 44 years.
Medically Unexplained Neurological Symptoms: A Missed Diagnosis?
One of the reasons why a school of thought that hysteria had disappeared was established is that it was understood that these were simply diagnostic errors. In 1965, a study suggested that if these patients were followed long-term, an organic disease was actually discovered in two cases over three to ten years.A recent meta-analysis of 27 studies from 1965 to 2005 showed that the rate of diagnostic error seems to decrease over the years but this is explained by the improvement of the methodology of the studies and not advances in medicine (such as the appearance of the brain scan for example). It is currently estimated that the diagnostic error rate in conversion disorders is 4%, which is comparable to other psychiatric (schizophrenia: 8%) and neurological (motor neuron disease: 6%) diseases.
If we now know that a diagnosis can be made as certainly as for other diseases, it is obvious that it is based on criteria that must be as objective as possible, knowing that it is a clinical diagnosis and that no biological marker is available. In this sense, a major effort to validate clinical and paraclinical signs (the most important of which are reported below) has been made and continues to spark research.
To support the diagnosis of convulsive dissociative disorder (or psychogenic non-epileptic seizure – CNEP) the fact that the eyes are closed during the seizure is an excellent clinical sign bringing a positive predictive value (specificity of 98% and sensitivity of 96%). When the clinician suspects a CNEP, for example because of an atypical presentation (very long duration, asynchronous movements, etc.), the practice of an electroencephalographic recording of 24 to 72 hours makes it possible to obtain a diagnosis of certainty in 73% of cases.The dosage of blood prolactin 20-30 minutes after the attack makes it possible to differentiate between a CNEP and an epileptic seizure with loss of contact (generalized or partial complex, specificity of 60% and 46% respectively and sensitivity of 96% for both).The presence of stertorous breathing, when well documented, also makes it possible to decide in favor of an epileptic seizure.
For dissociative motor disorders, we clinically look for Hoover’s sign (automatic extension movement of the diseased leg that is felt by the examiner during a forced flexion movement of the healthy leg; based on the walking reflex), one version of which showed that the involuntary automatic movement was significantly more marked during dissociative paresis than during organic paresis.
Regarding abnormal movements, clinical diagnostic criteria have recently been modified and, despite a retrospective study drawing, their validation showed a specificity of 100% and a sensitivity of 83% to detect an abnormal psychogenic movement “certain” or “probable”. These criteria are based on the characteristics of abrupt onset, distractibility, inconsistency, weakness or associated sensory disorder, associated somatization, pain or fatigue, potential secondary benefit and potential pattern (prior exposure to neurological disease). Psychogenic tremor has been separately validated demonstrating that the most reliable sign to differentiate it from essential tremor would be the presence of distractibility (specificity and sensitivity of 73%); the tremor will change or even disappear when the patient has to focus on another task, for example the finger-nose test.
For gait disorders and sensory disorders, it is the clinician’s experience that takes precedence since there is not yet a clearly validated sign, although there is a current to formally test observations, such as the recent “sign of the chair”: a group of patients with psychogenic walking disorder could better propel a chair on which they were sitting than a group of patients with organic damage. For sensory disorders, it is the atypical presentation (not respecting a neurological territory) which is a classic index suggesting a non-organic deficit. The renewed interest in dissociative neurological disorders is therefore well reflected in the plethora of recently published scientific articles that seek to better characterize and describe these signs known for several centuries and, in parallel with the development of evidence – based medicine , to obtain reproducible and reliable signs.
Dissociative/conversion disorders: a psychiatric illness?
If these disorders are therefore better and better characterized, their cause is still not established with certainty. According to the Freudian concept, it was accepted that it was a psychiatric illness with the resolution of the psychic conflict by the production of the somatic symptom. Studies have established that there are more traumatic psychological events in these patients, more history of physical and sexual abuse and that they are more prone to other psychiatric disorders, such as depression and anxiety.However, it is also known that the evidence of such a history is not reliable, especially because of the subjective assessment of the extent of the possible trauma, and an anamnesis of a “stressful event” is in fact often reported also before the onset of an organic neurological disease.
Dissociative/conversion disorders: a neurobiological correlate?
If we accept that the primary cause lies in a psychic dysfunction, the fact remains that the very particular clinical presentation, which sometimes mimics very closely a neurological deficit, suggests a cerebral dysfunction. As early as 1995, PET and functional MRI brain imaging studies highlighted different patterns of abnormal activation of certain cortical and subcortical regions. No clear model is currently established due to methodological problems; most of these studies could only be carried out in small groups of patients, the clinical presentation of dissociative disorders being very heterogeneous (different types of convulsions, paresis or sensory disorders of various distribution, etc.). However, it appears that hyperactivity of the frontal regions, secondary to emotional phenomena, could in turn inhibit the regions responsible for the symptom, such as the motor precentral cortex during motor disorders or parietal during sensory disorders. These frontal regions are involved in the will, so a disruption of their activity could prevent a voluntary movement. A seven-subject study, carried out when the symptom (hemi sensitivo-motor syndrome) was present and when it had recovered, showed that there was hypo activation of the thalamus and basal ganglia, including the caudate nucleus, which recovered concomitantly with the resolution of the symptom. This suggests that crucial loops in the regulation of movement, are also involved in the production of the dissociative somatic symptom. It is therefore possible that these loops are themselves under the influence of the limbic system (involved in emotional regulation). Indeed, it is well known that the caudate nucleus and thalamus are connected with the amygdala (emotional process) and the orbitofrontal cortex (willpower).A recent study focused on demonstrating this potential link between emotional regulation and the production of a neurological symptom: a patient suffering from dissociative motor hemi syndrome was subjected, during the acquisition of functional MRI images, to a task forcing her to remember a traumatic event (announcement of rupture by the spouse); in parallel with tonsillar hyperactivation (witness of the involvement of emotional memory), it was observed a hypo activation of the motor cortex located on the side opposite to its deficit.
These “active” inhibitions of certain brain regions could then correspond to very old protective mechanisms from the point of view of evolution since similar behaviors have been observed in the animal kingdom.The reaction of astonishment, for example, generated by fear, where the animal no longer moves, would have the function of masking any potential clues about its location to a predator while waiting for the danger to disappear. Another example of a deficit was observed in ducks that appeared sick and lame, while slowly moving a predator away from their nest. These behaviors aimed at ensuring survival could be found in humans where deficits, incomprehensible according to the laws of organicity, would be produced unconsciously in order to ensure a better balance of the internal system of the body and, not far from Freudian theories, to put aside a psychic danger or to face an external situation (secondary benefit of being sick).
What potential for a treatment?
As demonstrated so far, much progress and effort has been made to better understand both the clinical and neurobiological aspect of this disease, but what about treatments? Since no definitive model has been established, targeted therapy is not yet possible. Several studies, often uncontrolled or on too small groups of patients, have shown an interest in cognitive behavioral therapies, physiotherapy or antidepressant drugs.
Currently, it seems reasonable to offer the patient multidisciplinary care adapted to each individual situation. It is important to explain to the patient that he or she is suffering from a known and recognized disease. It has been shown that the term is best accepted by patients and that of functional neurological disorder.We can then, by explaining that the function is disturbed (the voluntary control of the force, for example) but that the organ is intact (the brain and the nerves), reassure the patient about other serious pathologies that he might fear, and consider a reversibility of the symptoms. It is then useful to involve the patient in the care and to explain the benefit of a psychiatric evaluation and follow-up. It is essential that the patient understands that he is referred to psychiatry, precisely because the diagnosis is positive (no organic lesions) requires the intervention of this specialty and not because by exclusion, or even out of spite, we turn to another specialty.
Finally, it should always be borne in mind that if the diagnosis of functional neurological disorder is a positive diagnosis and not exclusion, the coexistence of an organic pathology is possible; we often observe patients suffering from epilepsy and psychogenic non-epileptic seizures or patients suffering from multiple sclerosis and functional disorders, such as psychogenic tremor for example. The management of these two pathologies in parallel will then be necessary.
Conclusion
Hysteria still exists, even if this stigmatizing term has been abandoned in favor of more descriptive terms (dissociative disorders, conversion disorders, functional disorders) and represents a frequent and disabling pathology. Although in some situations the establishment of a diagnosis of certainty remains difficult, more and more clinical and paraclinical signs are developing to help with the diagnosis and the error rate is low. Thus, the clinician must currently make a positive diagnosis of conversion and no longer, as unfortunately often in the past, evoke by default this possibility in front of an atypical table accompanied by an extended negative paraclinical assessment. The most likely causes concern triggering factors of a psychiatric nature (traumatic episode or psychological stress, vulnerability with a field of abuse in childhood, comorbidity of anxiodepressive disorders), which can in turn lead to changes in brain function. The management of these patients requires a thorough and specialized examination, if possible with the help of a neurologist, then psychiatric care, combined with somatic follow-up. In the future, a better understanding of the mechanisms and causes of the disease will make it possible to develop more specific treatments.
Practical implications
> An association between dissociative disorder and trauma has been demonstrated
>There are positive neurological signs: lack of agreement between what is experienced, aware and expressed or fluctuation of the clinical situation
> Joint neurologist-psychiatrist care with restitution of the diagnosis in terms of functional disorder makes it possible to establish a therapeutic alliance
> The treatments have not been studied but the unanimity of the doctors retain a treatment by psychotherapy