Motor conversion disorders reviewed from a neuropsychiatric perspective

Neurocognitive functioning in patients with conversion disorder/functional neurological disorder

Neurocognitive symptoms are common in individuals with somatic symptom and related disorders (SSRD), but little is known about the specific impairments in neurocognitive domains in patients with conversion disorder (CD)/functional neurological disorder (FND). This study examines neurocognitive functioning in patients with CD/FND compared to patients with other SSRD. The sample consisted of 318 patients. Twenty‐nine patients were diagnosed with CD/FND, mean age 42.4, standard deviation (SD) = 13.8 years, 79.3% women, and 289 patients had other SSRD (mean age 42.1, SD = 13.3, 60.2% women). Patients completed a neuropsychological test battery that addressed a broad range of neurocognitive domains, including information processing speed, attention and executive functioning. Patients with CD/FND had clinically significant neurocognitive deficits in all neurocognitive domains based on normative data comparison. Patients with CD/FND also performed significantly worse than patients with other SSRD on information processing speed (Digit Symbol Substitution Test (V = .115, p = .035), Stroop Color–Word Test (SCWT) card 1 (V = .190, p = .006), and SCWT card 2 (V = .244, p < .001). No CD/FND vs. other SSRD differences were observed in other neurocognitive domains. These findings indicate the patients with CD/FND perform worse on information processing speed tests compared to patients with other SSRD.

Diagnosis of Conversion Disorder Using Diffusion Tensor Tractography and Transcranial Magnetic Stimulation in a Patient with Mild Traumatic Brain Injury

We report on a patient with mild traumatic brain injury (TBI) who was diagnosed with conversion disorder for severe weakness of an arm, which was demonstrated using diffusion tensor tractography (DTT) and transcranial magnetic stimulation (TMS). A 23-year-old right-handed female suffered from head trauma resulting from a pedestrian car accident. She underwent rehabilitative management for memory impairment and central pain. At 14 months after onset, she complained of severe weakness of her right arm, which was detected in the morning after sleeping (right shoulder abductor: 3/5, elbow flexor: 3/5, wrist extensor: 1/5, finger flexor: 1/5, and finger extensor: 1/5). Electromyography study for peripheral neuropathy performed at 2 weeks after onset of weakness showed no abnormality. On a 14-month DTT configuration, the integrities of the left corticospinal tract (CST), supplementary motor area-corticofugal tract (SMA-CFT), and dorsal premotor cortex (dPMC)-CFT were well-preserved. Significant differences were not observed for the fractional anisotropy (FA), mean diffusivity (MD), and tract volume (TV) values of the CST, SMA-CFT, and dPMC-CFT in both hemispheres between the patient and ten right-handed age- and sex-matched normal subjects (p > 0.05). On a 14-month TMS study, MEPs obtained at the right abductor pollicis brevis muscle showed no abnormality. Using DTT and TMS, conversion disorder was demonstrated in a patient with mild TBI, who showed severe weakness of an arm. Our results suggest the usefulness of an evaluation of the CST and CFTs from the secondary motor areas using DTT, and the CST using TMS for patients who complain of motor weakness due to conversion disorder.

Imaging psychogenic movement disorders

The neurobiological basis of psychogenic movement disorders (PMDs) has been elusive, and they remain difficult to treat. In the last few years, functional neuroimaging studies have provided insight into their pathophysiology and neural correlates. Here, we review the various methodological approaches that have been used in both clinical and research practice to address neural correlates of functional disorders. We then review the dominant hypotheses generated from the literature on psychogenic paralysis. Overall, these studies emphasize abnormalities in the prefrontal and anterior cingulate cortices. Recently, functional neuroimaging has been used to specifically examine PMDs. These studies have addressed a major point of controversy: whether higher frontal brain areas are directly responsible for inhibiting motor areas or whether they reflect modulation by attentional and/or emotional processes. In addition to elucidating the mechanism and cause, recent work has also explored the lack of agency that characterizes PMDs. We describe the results and implications of the results of these imaging studies and discuss possible interpretations.

An update on psychogenic movement disorders

Psychogenic movement disorders (PMD) and other conversion disorders (CD) with apparent neurologic signs (neurologic CD) plague patients and perplex physicians. Due to a lack of objective evidence of underlying brain lesions, CD were largely abandoned by neurologists and remained poorly understood psychiatric diagnoses throughout most of the 20th century. Modern neuroscience now supports increasingly comprehensive biological models for these complex disorders, definitively establishing their place in both neurology and psychiatry. Although it is often clinically useful to distinguish a movement disorder as either "organic" or "psychogenic," this dichotomy is difficult to defend scientifically. Here we describe the neuroimaging and neurophysiologic evidence for dysfunctional neural networks in PMD, explain the diagnostic potential of clinical neurophysiologic testing, discuss the promising if increasingly complex role of neuropsychiatric genetics, and review current treatment strategies.

Psychogenic movement disorders and motor conversion: a roadmap for collaboration between neurology and psychiatry

BACKGROUND

There are a host of vague terms to describe psychologically-mediated symptoms that mimic neurological disease, such as "functional," "non-organic," "psychogenic," or "medically unexplained." None of these terms has a direct translation in psychiatric classification, and psychiatrists are often faced with patients who do not believe in a psychological origin for their symptoms.

OBJECTIVE

Within the framework of psychogenic movement disorders, we discuss the roadblocks to effective collaboration and treatment in these patients and the current state of the literature regarding diagnosis and treatment.

RESULTS

We describe the approach to these patients from the perspective of neurology and psychiatry, illustrating the differences in terminology and categorization.

CONCLUSION

Psychogenic movement disorders represent a unique opportunity for these fields to collaborate in the care of a potentially curable but significantly disabling disorder.

Motor excitability during movement imagination and movement observation in psychogenic lower limb paresis

BACKGROUND

Patients with a psychogenic paresis have difficulties performing voluntary movements. Typically, diagnostic interventions are normal. We tested whether patients with a psychogenic lower limb paresis exhibit abnormal motor excitability during motor imagery or movement observation.

METHODS

Transcranial magnetic stimulation (TMS) with single and paired pulses was used to explore motor excitability at rest, during imagination of ankle dorsiflexions and during watching another person perform ankle dorsiflexions. Results obtained in ten patients with a flaccid psychogenic leg paresis were compared with a healthy age-matched control group. In addition, results of two patients with a psychogenic fixed dystonia of the leg are presented.

RESULTS

During rest, motor excitability evaluated by motor thresholds, size of motor-evoked potentials (MEP) by single pulse TMS, intracortical inhibition and intracortical facilitation tested by paired-pulse TMS were similar in patients and healthy subjects. MEPs recorded in five patients during movement observation were also comparable across the two groups. During motor imagery, patient MEPs were significantly smaller than in the control group and smaller than during rest, indicating an inhibition.

CONCLUSION

In patients with motor conversion disorder, the imagination of own body movements induces a reduction of corticospinal motor excitability whereas it induces an excitability increase in healthy subjects. This discrepancy might be the electrophysiological substrate of the inability to move voluntarily. Watching another person perform movements induces a normal excitability increase, indicating a crucial role of the perspective and suggesting that focusing the patient's attention on a different person might become a therapeutic approach.

The involuntary nature of conversion disorder

BACKGROUND

What makes a movement feel voluntary, and what might make it feel involuntary? Motor conversion disorders are characterized by movement symptoms without a neurologic cause. Conversion movements use normal voluntary motor pathways, but the symptoms are paradoxically experienced as involuntary, or lacking in self-agency. Self-agency is the experience that one is the cause of one's own actions. The matched comparison between the prediction of the action consequences (feed-forward signal) and actual sensory feedback is believed to give rise to self-agency and has been in part associated with the right inferior parietal cortex. Using fMRI, we assessed the correlates of self-agency during conversion tremor.

METHODS

We used a within-subject fMRI block design to compare brain activity during conversion tremor and during voluntary mimicked tremor in 8 patients.

RESULTS

The random effects group analysis showed that conversion tremor compared with voluntary tremor had right temporoparietal junction (TPJ) hypoactivity (p < 0.05 family-wise error whole brain corrected) and lower functional connectivity between the right TPJ, sensorimotor regions (sensorimotor cortices and cerebellar vermis), and limbic regions (ventral anterior cingulate and right ventral striatum).

CONCLUSIONS

The right TPJ has been implicated as a general comparator of internal predictions with actual events. We propose that the right TPJ hypoactivity and lower TPJ and sensorimotor cortex interactions may reflect the lack of an appropriate sensory prediction signal. The lack of a match for the proprioceptive feedback would lead to the perception that the conversion movement is not self-generated.

Electrophysiological correlates of motor conversion disorder

In patients with a functional (psychogenic) paresis, motor conduction tests are, by definition, normal. We investigated whether these patients exhibit an abnormal motor excitability. Four female patients with a functional paresis of the left upper extremity were studied using transcranial magnetic stimulation (TMS). We investigated motor thresholds, intracortical inhibition and intracortical facilitation at rest. Corticospinal excitability was evaluated by single pulse TMS during rest and during imagination of tonic index finger adductions. Data obtained from the affected first dorsal interosseous muscle were compared with the unaffected hand and with a healthy age-matched control group. Three patients demonstrated a flaccid paresis, one patient had a psychogenic dystonia. Motor thresholds, short interval intracortical inhibition and intracortical facilitation recorded from the affected side were normal. In healthy subjects, movement imagination produced an increase of corticospinal excitability. In the patients, motor imagery with the affected index finger resulted in a decrease of corticospinal excitability compared to rest, being significantly different from the unaffected side and from the control group. We suggest that suppression of corticospinal excitability during movement imagination is an electrophysiological correlate of the patients' inability to move voluntarily and provides some insight into the pathophysiology of this disorder.

Abnormal motor excitability in patients with psychogenic paresis. A TMS study

BACKGROUND

Patients with motor conversion disorders present an inability to execute movements voluntarily, although central and peripheral motor pathways are normal. We speculated that this phenomenon could be due to an abnormal loss of excitatory drive on central motor areas.

METHODS

The effect of motor imagery on motor excitability was tested in a group of eight patients with a functional (psychogenic) hemiparesis and in an age-matched control group (n=8) by using transcranial magnetic stimulation (TMS). TMS pulses were applied at rest and while subjects imagined a tonic index finger adduction. Amplitudes of motor evoked potentials (MEP) recorded from the first dorsal interosseous muscle were used as an indicator of motor excitability.

RESULTS

Motor thresholds and MEP amplitudes at rest were almost identical in the patient group and the control group. During motor imagery, MEP amplitudes increased by 200% in healthy subjects. In the patient group, motor imagery of the "paretic" index finger was associated with a mean MEP amplitude decrease of 37% compared with the MEP size at rest. Motor imagery of the unaffected index finger increased MEPs by 63% which was significantly different both from results in the control group and the "paretic" side.

CONCLUSIONS

We suggest that the paradoxical decrease of motor excitability during motor imagery is the electrophysiological correlate of a disturbed voluntary control in motor conversion disorder. The results further indicate that this abnormality is not restricted to the clinically affected body part.

Evaluation of clinical diagnostic criteria for psychogenic movement disorders

Previous studies showed that there are certain features suggestive of a psychogenic disorder, and Fahn and Williams proposed criteria for psychogenic movement disorders. Data on the sensitivity and specificity of these criteria are lacking. We expanded on the Fahn and Williams criteria to create a new set of diagnostic criteria. We retrospectively reviewed 79 patients in a movement disorders specialty clinic. We applied the proposed diagnostic criteria to both cases and controls and analyzed sensitivity and specificity. The diagnostic criteria correctly identified "clinically probable" (or better) psychogenic movement disorders with a sensitivity of 83% and specificity of 100%. For "clinically possible" or greater, sensitivity was 97% and specificity was 96%. In addition, a significantly higher proportion of patients with psychogenic disease were female and reported either a family history of neurological disease or other exposure to neurological disease (P = 0.001 and 0.01, respectively). The diagnostic criteria are simple to apply and have high sensitivity and specificity for psychogenic movement disorders. Also, we report a correlation between previous exposure to a disease model and psychogenic disease.

General medical and psychiatric perspectives on somatoform disorders: separated by an uncommon language

PURPOSE OF REVIEW

While Diagnostic and Statistical Manual of Mental Disorders-IV provided updated definitions and diagnostic criteria for the diagnoses subsumed under the category of somatoform disorders, various nosological questions are still unresolved. We assessed current research activity on important key concepts related to nosology, validity, and reliability of the Diagnostic and Statistical Manual of Mental Disorders-IV somatoform diagnoses.

RECENT FINDINGS

The initial Medline search for articles from 2000 through 2005 yielded a total of 912 articles. After checking for redundancy and excluding publications using other than Diagnostic and Statistical Manual of Mental Disorders-IV diagnostic criteria, a total of 101 articles was further reviewed. Heterogeneity of papers precluded statistical approaches; thus, a descriptive and narrative review was pursued.

SUMMARY

It appears that applying the specific categories and criteria as proposed by Diagnostic and Statistical Manual of Mental Disorders-IV only captures a small proportion of the phenomena of interest at the interface of medicine and psychiatry. A paradigm shift towards 'general medical/psychiatry interface disorders' in exchange for the current dichotomy of 'mind' vs. 'body' disorders, may reduce stigma associated with current diagnostic labeling, improve user acceptability, and stimulate research in this important but still fragmented clinical area that still lacks agreed-upon diagnostic definitions.

Dissociative and conversion disorders: defining boundaries

PURPOSE OF REVIEW

Although dissociative disorders have been described and diagnosed for some time, their aetiology, pathogenesis, phenomenology and management continues to arouse debate. It is only in recent times that researchers have made some progress by integrating trauma related theories with more contemporary cognitive theories and neurobiology.

RECENT FINDINGS

Dissociation as a phenomenon is reported to occur in a variety of disorders. This widespread occurrence has contributed to a better understanding of dissociation. An expansion of this concept may have contributed to the loss of its original significance. Recent studies in the field of dissociation that pertain to its aetiology, pathophysiology, neurobiology and management are critically reviewed.

SUMMARY

Dissociative disorder is conceptually a difficult disorder to study. Apart from exposure to trauma, certain primary personality attributes may contribute to the propensity to develop dissociative disorder. Recent advances in functional neuroimaging facilitated by enhanced knowledge in the neural representation of body state have helped to improve our understanding of dissociation. There is confusion over the use of various terms such as sexual abuse and physical abuse in explaining causality. Current classificatory systems have not been found suitable when applied across cultures. In spite of all of these limitations, there has been recent progress toward a better understanding of dissociative disorders.