Caloric Vestibular Stimulation Reduces Pain and Somatoparaphrenia in a Severe Chronic Central Post-Stroke Pain Patient: A Case Study

Self-touch facilitates the recognition of the dis-owned left hand in somatoparaphrenia: a single case study

We investigated whether self-administered tactile stimulation could act as a temporary restorative mechanism for body ownership disorders, both implicitly and explicitly. We tested this hypothesis in a patient with somatoparaphrenia, who displayed increased accuracy in explicitly recognizing their left hand during self-touch. Furthermore, the patient implicitly perceived their hand and the experimenter's hand as more belonging to their own body compared to conditions where vision was the sole sensory input. These findings highlight the importance of self-touch in maintaining a coherent body representation, while also demonstrating the potential dissociation between the recovery of explicit and implicit perceptions of body ownership.

Modulation of vestibular input by short-term head-down bed rest affects somatosensory perception: implications for space missions

Introduction

On Earth, self-produced somatosensory stimuli are typically perceived as less intense than externally generated stimuli of the same intensity, a phenomenon referred to as somatosensory attenuation (SA). Although this phenomenon arises from the integration of multisensory signals, the specific contribution of the vestibular system and the sense of gravity to somatosensory cognition underlying distinction between self-generated and externally generated sensations remains largely unknown. Here, we investigated whether temporary modulation of the gravitational input by head-down tilt bed rest (HDBR)-a well-known Earth-based analog of microgravity-might significantly affect somatosensory perception of self- and externally generated stimuli.

Methods

In this study, 40 healthy participants were tested using short-term HDBR. Participants received a total of 40 non-painful self- and others generated electrical stimuli (20 self- and 20 other-generated stimuli) in an upright and HDBR position while blindfolded. After each stimulus, they were asked to rate the perceived intensity of the stimulation on a Likert scale.

Results

Somatosensory stimulations were perceived as significantly less intense during HDBR compared to upright position, regardless of the agent administering the stimulus. In addition, the magnitude of SA in upright position was negatively correlated with the participants' somatosensory threshold. Based on the direction of SA in the upright position, participants were divided in two subgroups. In the subgroup experiencing SA, the intensity rating of stimulations generated by others decreased significantly during HDBR, leading to the disappearance of the phenomenon of SA. In the second subgroup, on the other hand, reversed SA was not affected by HDBR.

Conclusion

Modulation of the gravitational input by HDBR produced underestimation of somatosensory stimuli. Furthermore, in participants experiencing SA, the reduction of vestibular inputs by HDBR led to the disappearance of the SA phenomenon. These findings provide new insights into the role of the gravitational input in somatosensory perception and have important implications for astronauts who are exposed to weightlessness during space missions.

The Management of Poststroke Thalamic Pain: Update in Clinical Practice

Poststroke thalamic pain (PS-TP), a type of central poststroke pain, has been challenged to improve the rehabilitation outcomes and quality of life after a stroke. It has been shown in 2.7–25% of stroke survivors; however, the treatment of PS-TP remains difficult, and in majority of them it often failed to manage the pain and hypersensitivity effectively, despite the different pharmacotherapies as well as invasive interventions. Central imbalance, central disinhibition, central sensitization, other thalamic adaptative changes, and local inflammatory responses have been considered as its possible pathogenesis. Allodynia and hyperalgesia, as well as the chronic sensitization of pain, are mainly targeted in the management of PS-TP. Commonly recommended first- and second-lines of pharmacological therapies, including traditional medications, e.g., antidepressants, anticonvulsants, opioid analgesics, and lamotrigine, were more effective than others. Nonpharmacological interventions, such as transcranial magnetic or direct current brain stimulations, vestibular caloric stimulation, epidural motor cortex stimulation, and deep brain stimulation, were effective in some cases/small-sized studies and can be recommended in the management of therapy-resistant PS-TP. Interestingly, the stimulation to other areas, e.g., the motor cortex, periventricular/periaqueductal gray matter, and thalamus/internal capsule, showed more effect than the stimulation to the thalamus alone. Further studies on brain or spinal stimulation are required for evidence.

Diagnosis, Treatment, and Management of Dejerine-Roussy Syndrome: a Comprehensive Review

PURPOSE OF REVIEW

Post-stroke pain represents a complex condition with few standardized diagnostic criteria. As such, the array of symptoms is often difficult to categorize and diagnose. Central post-stroke pain (CPSP), also known as Dejerine-Roussy syndrome, presents as painful paresthesia in any part of the body that is usually coupled with sensory abnormalities.

RECENT FINDINGS

In patients who had experienced a cerebrovascular accident, CPSP typically affects the same areas of the body that are also impacted by the general motor and sensory deficits that result from stroke. Though it is generally debated, CPSP is thought to result from a lesion in any part of the central nervous system. Pain usually presents in the range of 3-6 months after the occurrence of stroke, manifesting contralaterally to the lesion, and most commonly involving the upper extremities. For the most accurate diagnosis of CPSP, a thorough history and clinical examination should be supplemented with imaging. Infarcted areas of the brain can be visualized using either CT or MRI. First-line treatment of CPSP is pharmacologic and consists of a three-drug regimen. Despite this, CPSP is often refractory to medical management producing only modest pain reduction in a limited subset of patients. Adverse effects associated with pharmacologic management of CPSP and frequent recalcitrance to treatment have driven alternative minimally invasive methods of pain control which include transcranial stimulation, deep brain stimulation, and neuromodulation. The aim of this review is to provide a comprehensive update to recent advances in the understanding of the treatment and management of CPSP.

Mirror feedback assisted recovery from hemiparesis following stroke. In Reply to Morkisch et al.: How to perform mirror therapy after stroke? Evidence from a meta-analysis

1 out of 6 people worldwide will have suffered a stroke in their lifetime, 1/3rd of whom will die. Of the 2/3rd who survive, half will be permanently disabled (World Stroke Organization). Given these alarming statistics, it's not surprising that tremendous of amounts of time, resources and funding have been devoted towards research into stroke rehab. In view of this, simple, easy-to-implement procedures are highly sought after. One such procedure is the use of visual feedback conveyed by a mirror, which seems to reactivate some dormant pathways in patients who have suffered a recent stroke (Altschuler et al., 1999; Ramachandran & Altschuler, 2009). This procedure has been validated in several dozen clinical trials, of which a substantial number were conducted rigorously. Morkisch et al. (2019) now present a systematic review and meta-analysis of this dense literature pertaining to this topic. They conclude that "there is a high level evidence for mirror therapy's effectiveness in treating post-stroke hemiparesis". A novel conclusion that emerged from this meta-analysis was that the larger the mirror the more effective the treatment is. Additionally, if an object is manipulated by the normal hand and its reflection viewed in the mirror, the procedure is not as effective, possibly because the discrepancy of signals between the visual feedback (reflection of the object) and the lack of confirmatory somatosensory input from the affected limb leads to inhibition rather than synergy. Lastly, for reasons yet unclear, sending movement commands to the unaffected hand alone (unilateral) is more effective than sending bilateral commands, contrary to the original protocol.Taken collectively, research in this field has two implications - First, the immediate practical utility in the clinic by optimizing mirror therapy's efficacy for hemiparesis after stroke. Second, it leads to a rejection of the model of the brain as made up of isolated, autonomous modules, towards a more dynamic picture, in which the brain is composed of a fluctuating mosaic of neural activity as it adapts to changing sensory inputs. Therefore, dysfunction results not from 'punch out a module - lose a function', but by shifts in equilibria, which can be corrected, perhaps, by hitting a reset button. Even if this turns out to be true for a minority of syndromes, it will be well worth the effort.

Stimulation of the Semicircular Canals or the Utricles by Clinical Tests Can Modify the Intensity of Phantom Limb Pain

Background: After amputation, phantom limb pain may be produced by the multisensory processes underling the experience of an intact body. Clinical evidence has shown that cold caloric vestibular stimulation may modify the perception of phantom limb pain. However, it is yet unknown if this effect can be observed after the mild vestibular stimulation given by the clinical caloric test, or after utricle stimulation by centrifugation. Additionally, there are no studies on the association between the report of altered perceptions or experience of the self or the environment (depersonalization/derealization symptoms) and phantom limb pain.

Objective: To assess the influence of unilateral stimulation of the horizontal semicircular canals by clinical caloric test, and the utricles by unilateral centrifugation on the intensity of phantom limb pain, and to explore the association between phantom limb pain and symptoms of depersonalization/ derealization.

Methods: 34 patients (56 ±7 years old, 23 men) accepted to participate after 3 to 23 months of unilateral supracondylar amputation, secondary to type 2 diabetes mellitus. After assessment of vestibular function and symptoms of common mental disorders, using a cross-over design, in 2 separate sessions with 1 week in between, vestibular stimulation was delivered by right/left caloric test (30 or 44°C) or right/ left centrifugation (3.85 cm, 300°/s peak). Before and after each vestibular stimulus, the intensity of phantom limb pain and depersonalization/derealization symptoms were assessed, with a daily follow-up of pain intensity during 1 week.

Results: Either caloric stimulation or unilateral centrifugation decreased phantom limb pain (p < 0.05), along with decrease of symptoms of depersonalization/derealization (p < 0.05). One third of the patients reporting pain decrease immediately after stimulation also reported no pain at least for 1 day.

Limitations: No sham condition was included.

Conclusions: Vestibular stimulation by the clinical caloric tests or by unilateral centrifugation may decrease the intensity of phantom limb pain, with decrease of perceptions of unreality. These effects might be related to an update of the immediate experience of the body, given by the sensory mismatch induced by asymmetrical vestibular stimulation.

Vestibular and Multi-Sensory Influences Upon Self-Motion Perception and the Consequences for Human Behavior

In this manuscript, we comprehensively review both the human and animal literature regarding vestibular and multi-sensory contributions to self-motion perception. This covers the anatomical basis and how and where the signals are processed at all levels from the peripheral vestibular system to the brainstem and cerebellum and finally to the cortex. Further, we consider how and where these vestibular signals are integrated with other sensory cues to facilitate self-motion perception. We conclude by demonstrating the wide-ranging influences of the vestibular system and self-motion perception upon behavior, namely eye movement, postural control, and spatial awareness as well as new discoveries that such perception can impact upon numerical cognition, human affect, and bodily self-consciousness.

Taxonomising delusions: content or aetiology?

INTRODUCTION

Many theoretical treatments assume (often implicitly) that delusions ought to be taxonomised by the content of aberrant beliefs. A theoretically sound, and comparatively under-explored, alternative would split and combine delusions according to their underlying cognitive aetiology.

METHODS

We give a theoretical review of several cases, focusing on monothematic delusions of misidentification and on somatoparaphrenia.

RESULTS

We show that a purely content-based taxonomy is empirically problematic. It does not allow for projectability of discoveries across all members of delusions so delineated, and lumps together delusions that ought to be separated. We demonstrate that an aetiological approach is defensible, and further that insofar as content-based approaches are plausible, it is only to the extent that they implicitly link content to aetiology.

CONCLUSIONS

We recommend a more explicit focus on cognitive aetiology as the grounds for delusion taxonomy, even when that would undermine traditional content-based boundaries. We also highlight the iterative and complex nature of evidence about aetiologically grounded taxonomies.

Modulation of somatoparaphrenia following left-hemisphere damage

Somatoparaphrenic symptoms after left-hemisphere damage are rare. To verify the potential role of body-related sensory (proprioceptive, visual, and somatosensory) manipulation in patients experiencing sensations of hand disownership, the symptoms of a patient suffering from right-hand somatoparaphrenia were monitored and clinical and neuropsychological variables were controlled. Four types of manipulation were administered: changes in spatial position of the hand, multisensory stimulation, and self-observation using video or mirrors. Multisensory visuo-tactile stimulation was efficacious in terms of reducing somatoparaphrenia, and changes in the position of the hand produced some positive effects. Third-person perspective self-observation did not, however, result in any changes.