Volumetric investigation of brain regions in patients with conversion disorder

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Abstract

Preliminary evidence revealed a decrease of regional cerebral blood flow in the thalamus and basal ganglia contralateral to the deficit and suggested that hysterical conversion deficits might entail a functional disorder in striatothalamocortical circuits. However, there is no systematic structural magnetic resonance imaging (MRI) study in the literature in patients with conversion disorder (CD). Therefore, we aimed to perform structural MRI to evaluate the brain regions of interest in first applying patients with CD. Morphometric MRI was used to compare regional brain volumes in ten women with CD and same number of healthy comparison subjects. Intracranial volume (ICV), whole brain volume, gray and white matter volumes did not differ between the patient and control groups. Patients with CD had significantly smaller mean volumes of the left caudate nucleus, lentiform nucleus (p < 0.01 for caudate nucleus and p < 0.05 for lentiform nucleus) and right caudate nucleus and lentiform nucleus (p < 0.05 for both structures). In patients, the right thalamus was significantly smaller, and the left thalamus rendered to be smaller compared to healthy controls. Age at onset showed a significant relation with left caudate, and a near-significant trend with right thalamus volumes. In conclusion, our findings suggest that patients with CD have significantly smaller mean volumes of the left and right basal ganglia and smaller right thalamus, with a trend toward to smaller left thalamus compared to healthy controls and that these findings provide novel constraints for a modern psychobiological theory of hysteria.

Introduction

Conversion disorder (CD) is defined as loss or distortion of neurological function that cannot be fully explained by a known organic neurological disease (American Psychiatric Association, 1994). Yet, their symptoms are not intentionally feigned, not adequately explained by malingering, and may result in significant distress and handicap (Merskey, 1995). In clinical neurological practice, conversion symptoms represent a common disorder, accounting for 1–3% of diagnoses in general hospitals (Marsden, 1986), or even more in some neurological settings (Binzer and Kullgren, 1998, Ron, 1994). Though CD is not very frequent in western societies, it is very common in eastern societies (Pierloot and Ngoma, 1988, Chandrasekaran et al., 1994). The region differs from Western societies and even from Western Turkey in terms of more frequently encountered CD which constitutes an important psychiatric disorder in the region.

Hysterical symptoms long raised questions about mind–body relationships. Described in early medical writings as psychic disorders caused by bodily disturbances, they were later regarded as the physical effect of violent impressions or passions (Merskey, 1995). A role of neurobiological factors is suggested by the fact that symptoms are more frequent on left-side limbs, pointing to possible right-hemisphere involvement (Stern, 1983), and seem occasionally facilitated by a real coexisting brain disease (Eames, 1992). However, specific functional brain correlates of conversion symptoms have not been demonstrated, except for a few recent pioneering studies (Spence et al., 2000). Physicians, like philosophers, still often call upon a ‘disease of the will’ or ‘of the imagination’ (Merskey, 1995), yet little is known about the neural functioning of motor will or imagination, and how it may be affected in hysterical patients (Marshall et al., 1997, Spence et al., 2000). Demonstrating objective brain correlates of hysterical symptoms may therefore help to understand the mechanisms that underlie a subjective experience of abnormal neurological function in these patients. Also, it may provide unique insights into mechanisms that subserve normal conscious experience of sensation and volition. A variety of neuropsychological findings (Flor-Henry et al., 1981) and neurophysiological abnormalities (Tiihonen et al., 1995, Lorenz et al., 1998, Spence et al., 2000) have been reported in patients with hysterical conversion. However, many of these studies included only a few or single patients, and provided relatively conflicting or inconclusive results overall. Vuilleumier et al. (2001) evaluated seven patients with conversion disorder using by single photon emission computerized tomography using 99mTc-ECD and revealed a decrease of regional cerebral blood flow in the thalamus and basal ganglia contralateral to the deficit and suggested that hysterical conversion deficits might entail a functional disorder in striatothalamocortical circuits controlling sensorimotor function and voluntary motor behaviour. However, there is no systematic structural magnetic resonance imaging (MRI) study in the literature. Therefore, taken together, we aimed to use structural MRI to evaluate the brain regions of interest in first applying patients with CD.

Section snippets

Subjects and clinical evaluation

Twelve female patients with unilateral motor symptoms meeting DSM-IV criteria for CD, as determined by the Structured Clinical Interview for DSM-IV (SCID; Spitzer et al., 1997) who consecutively applied to the Firat University School of Medicine Emergency Unit or to directly Department of Psychiatry and 12 healthy female controls were studied. The mean (± S.D.) age of the CD patients was 28.1 (5.1) years and the mean age of the normal subject group was 29.2 (5.6) years. All subjects were

Demographic variables

There were no significant differences in demographic variables of age, gender composition, educational level, and handedness between patients with CD and healthy controls (p > 0.05).

Interrater reliability measurements

All interrater and intrarater reliability scores were equal to or above 0.82, demonstrating sufficient inter- and intra-reliability.

Unadjusted whole brain and regional brain volumes

Table 1 presents the unadjusted volumes of the structures evaluated. ICV, whole brain volume, gray and white matter volumes did not differ between the patient and control groups (p > 0.05).

Discussion

The father of modern psychology, William James remarked long ago (James, 1986): ‘Poor hysterics. First they were treated as victims of sexual trouble…then of moral perversity and mediocrity…then of imagination. Among the various rehabilitation which our age has seen, none are more deserving or humane. It is a real disease, but a mental disease.’ As mentioned in Williams James saying, CD is a real disease but a mental disorder seems to involve some brain volumetric differences when compared to

Conclusion

In conclusion, our findings suggest that patients with CD have significantly smaller mean volumes of the left and right basal ganglia and smaller right thalamus, with a trend toward to smaller left thalamus compared to healthy controls and that these findings provide novel constraints for a modern psychobiological theory of hysteria. Although this reduction may be important in understanding the pathophysiology of CD, its functional and psychopathologic consequences are still unclear. Future

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