Hysterical Conversion, Consciousness and the Brain

It played a great role in medical history, from Hippocrates in the 3rd century BCE to the French neurologists Charcot and Janet, and finally Sigmund Freud. It was part of the scientific discovery of hypnosis and placebo effects, entangled with trauma and sexuality. It convinced 19th century medicine that the mind could sometimes override the known nervous system. Even today, it may be responsible for some of the suffering in mystery illnesses like Gulf War Syndrome and even back pain. Of all neurological disorders, only this one changes the patient’s consciousness with no visible damage to the nervous system.

It is of course conversion hysteria, the mysterious malady that can change from day to day, making physically healthy people feel ill, leading to temporary blindness, tunnel vision, paralysis, false pregnancy, imagined pain or numbness to touch. From 1 to 3% of neurological patients still receive this diagnosis. (*)

William James wrote in 1896, “Poor hysterics. First they were treated as victims of sexual trouble … then of moral perversity and mediocrity … then of imagination. Among the various rehabilitations which our age has seen, none are more deserving or humane. It is a real disease, but a mental disease.”

Today, after two millenia of debate, we can finally see what happens in the brain in this “disorder of the imagination,” as it is still sometimes called. A recent article by Vuillieumier et al studied seven patients who came to a hospital in Geneva complaining of one-sided weakness or paralysis in one arm. Most also felt numbness in the affected arm. All patients had very recent onset of the symptoms, and almost all recovered in a few months. (Ordinarily, recovery from local nerve damage is extremely rare). No physical basis could be found.

Choosing patients with one-sided paralysis was important, because it allowed very close comparisons between the healthy arm and the paralyzed one. Brain scans could then compare the left and right sides of the Conversion hysteria convinced 19th century medicine that the mind could sometimes override the known nervous system same person, at the same time and in the same brain. Patients were also compared during their period of hysterical paralysis and afterwards, so that each subject served as his or her own control. Such close comparisons are essential, because human beings and their brains are so variable.

All patients were facing stressful life events when they came down with their paralytic symptoms, just as one might expect. But none had major psychiatric or neurological disorders. MRI scans showed no detectable physical impairment. Dozens of other tests confirmed the absence of other diagnoses. All these careful selection criteria allowed the researchers to focus just on the hysterical impairment and minimize extraneous influences.

Thus twenty-three centuries after Hippocrates, one could begin to ask what was happening in the brain regions involved in hysterical limb paralysis. In each patient, brain images were recorded to vibration applied to both arms. Such vibration is known to stimulate the sensorimotor regions responsible for feeling and movement of the hands. (Since hands and arms are connected to the opposite sides of the brain, the tested side was in the “contralateral” hemisphere).

What about the results? Surprisingly, almost no differences were found between the two hemispheres of the seven subjects. The “paralyzed” and normal sides did not seem to be different at the level of the cortex. What happens in the brain during hysterical limb paralysis? Rather, unusually low blood flow was found in two regions: The thalamus — the “gateway to the cortex” — and the basal ganglia. (See here for image and details of thalamus and basal ganglia).

It seems that voluntary commands to move the affected limb were blocked from activating the pathways that control the paralyzed arm. This blockage could happen in the thalamus (the “gateway”), but also in the basal ganglia, which involve automatic muscle control.

It is helpful to try this yourself. Put your hand on a table that will not move if you push it. Now push very hard. Notice the conscious experience of effort, as well as the feeling in your hand. Effort and conscious touch are cortical events, requiring the front half of cortex. Thus we can be conscious of an effort to move an arm, especially if it occurs against resistance. The table is one kind of resistance, but imagine what would happen if your right arm were suddenly paralyzed. You would probably also try and try to move it, even against internal resistance. It would also feel like effort, and would involve cortex.

In contrast, the detailed movement of your arm is controlled unconsciously, by basal ganglia, cerebellum and motor nerves going down to the muscles. If you want to illustrate this to yourself, just try to be conscious of which muscles you use to pronounce the words “hysterical paralysis!” Nobody can tell, because our brains and nerves are normally unconscious in their control of detailed movements. Thus conversion patients could feel (in the cortex) that they were trying very hard to move their arm, but all their efforts to move were blocked in the output pathway to the muscles.

The brain is a very complicated place, and this study by Vuillieumier and colleagues is not likely to be the last word. Yet it tells a coherent story. In these patients control of the “paralyzed” arm was blocked, not in cortex itself, but rather in the cortical gateway (the thalamus) going to the motor nerves, and in the basal ganglia, which control unconscious details of movement. If these results hold up we will finally know a little bit more than Hippocrates did in the 3rd century BC.

© 2003 Bernard J. Baars

References

1. James, W. (1896) On exceptional mental states: The 1896 Lowell lectures. NY: Charles Scribner’s Sons, 1896.
2. Vuilleumier, P., C. Chicherio, F. Assal, S. Schwartz, D. Slosman & T. Landis (2001) Functional neuroanatomical correlates of hysterical sensorimotor loss. Brain, 124, 1077-1090.

Footnote:

(*) The term “hysteria” is controversial because its root, “hysteros” is the Greek word for uterus. Physicians thought for many years that only women could have conversion symptoms. However, Jean Charcot discovered in the mid-19th century that some men suffering from trauma after train accidents showed conversion disorders as well. Hysterical conversion is not an exclusively female disorder. Because there is no universally accepted substitute, the term is still used in diagnostic manuals.

Abstract

Vuilleumier, P., C. Chicherio, F. Assal, S. Schwartz, D. Slosman & T. Landis (2001) Functional neuroanatomical correlates of hysterical sensorimotor loss. Brain, 124, 1077-1090.

Hysterical conversion disorders refer to functional neurological deficits such as paralysis, anaesthesia or blindness not caused by organic damage but associated with emotional “psychogenic” disturbances. Symptoms are not intentionally feigned by the patients whose handicap often outweighs possible short-term gains. Neural concomitants of their altered experience of sensation and volition are still not known. We assessed brain functional activation in seven patients with unilateral hysterical sensorimotor loss during passive vibratory stimulation of both hands, when their deficit was present and 2-4 months later when they had recovered. Single photon emission computerized tomography using 99m Tc-ECD revealed a consistent degree of regional cerebral blood flow in the thalamus and basal ganglia contralateral to the deficit. Independent parametric mapping and principal components statistical analyses converged to show that such subcortical asymmetries were present in each subject. Importantly, contralateral basal ganglia and thalamic hypoactivation resolved after recovery. Furthermore, lower activation in contralateral caudate during hysterical conversion symptoms predicted poor recovery at follow-up. These results suggest that hysterical conversion deficits may entail a functional disorder in striatothalamocortical circuits controlling sensorimotor function and voluntary behavior. Basal ganglia, especially the caudate nucleus, might be particularly well situated to modulate motor processes based on emotional and situational cues from the limbic system. Remarkably, the same subcortical premotor circuits are also involved in unilateral motor neglect after organic neurological damage, where voluntary limb use may fail despite a lack of true paralysis and intact primary sensorimotor pathways. These findings provide novel constraints for a modern psychobiological theory of hysteria.