Sensory and pain modulation profiles of ongoing central neuropathic extremity pain in multiple sclerosis

Electroneuromyography comparison between pre-elderly adult females with and without MS; the potential role of a mind-body therapy in improving neurophysiological profile of MS during pandemic

INTRODUCTION

Imaginary exercises seem to be useful therapeutic approaches to modulate neuromuscular functions due to two main reasons: first, this training would not greatly increase body temperature, and secondly, it can positively affect brain-muscle pathways-which are both primary factors should be considered in rehabilitation programs for patients with multiple sclerosis (MS).

METHOD

32 pre-elderly adult females with relapsing-remitting MS (n = 16 - age M (SD): 56.75 (5.07)) and without MS (n = 16 - age M (SD): 56.56 (4.35)) voluntarily recruited. First, they were assigned into two groups: MS patients and healthy controls, to investigate baseline between-group comparison. Then, MS patients were randomly divided into two groups of eight each, designated as experimental and control groups. Recording the nerve conduction velocity (NCV) of tibial nerve and integrated electromyographic muscle activation (IEMG) of gastrocnemius muscle was conducted twice, before and after a six-week mind-body exercise therapy to evaluate its effectiveness on improving neuromuscular function.

RESULTS

The results showed significant difference in both tibial NCV (P < 0.001) and IEMG (P = 0.001) variables between non-MS group and MS group. Furthermore, there was a significant main effect of intervention (P = 0.05) and time (P < 0.001) on IEMG in the MS group, while there was no significant effect of intervention (P = 0.18) and time (P = 0.23) on NCV (p = 0.89).

CONCLUSION

Neuromuscular dysfunction were apparent in MS patients, and a mind-body therapy of imagery isometric training was found to be useful on improving the neurological deficit in women with MS.

TRIAL REGISTRATION NUMBER

UMIN000046935.

Pain in the Context of Sensory Deafferentation

Pain that accompanies deafferentation is one of the most mysterious and misunderstood medical conditions. Prevalence rates for the assorted conditions vary considerably but the most reliable estimates are greater than 50% for strokes involving the somatosensory system, brachial plexus avulsions, spinal cord injury, and limb amputation, with controversy surrounding the mechanistic contributions of deafferentation to ensuing neuropathic pain syndromes. Deafferentation pain has also been described for loss of other body parts (e.g., eyes and breasts) and may contribute to between 10% and upwards of 30% of neuropathic symptoms in peripheral neuropathies. There is no pathognomonic test or sign to identify deafferentation pain, and part of the controversy surrounding it stems from the prodigious challenges in differentiating cause and effect. For example, it is unknown whether cortical reorganization causes pain or is a byproduct of pathoanatomical changes accompanying injury, including pain. Similarly, ascertaining whether deafferentation contributes to neuropathic pain, or whether concomitant injury to nerve fibers transmitting pain and touch sensation leads to a deafferentation-like phenotype can be clinically difficult, although a detailed neurologic examination, functional imaging, and psychophysical tests may provide clues. Due in part to the concurrent morbidities, the physical, psychologic, and by extension socioeconomic costs of disorders associated with deafferentation are higher than for other chronic pain conditions. Treatment is symptom-based, with evidence supporting first-line antineuropathic medications such as gabapentinoids and antidepressants. Studies examining noninvasive neuromodulation and virtual reality have yielded mixed results.

Paradoxical heat sensation as a manifestation of thermal hypesthesia: a study of 1090 patients with lesions of the somatosensory system

ABSTRACT

Paradoxical heat sensation (PHS) is the perception of warmth when the skin is cooled. Paradoxical heat sensation rarely occurs in healthy individuals but more frequently in patients suffering from lesions or disease of the peripheral or central nervous system. To further understand mechanisms and epidemiology of PHS, we evaluated the occurrence of PHS in relation to disease aetiology, pain levels, quantitative sensory testing parameters, and Neuropathic Pain Symptom Inventory (NPSI) items in patients with nervous system lesions. Data of 1090 patients, including NPSI scores from 404 patients, were included in the analysis. We tested 11 quantitative sensory testing parameters for thermal and mechanical detection and pain thresholds, and 10 NPSI items in a multivariate generalised linear model with PHS, aetiology, and pain (yes or no) as fixed effects. In total, 30% of the neuropathic patients reported PHS in contrast to 2% of healthy individuals. The frequency of PHS was not linked to the presence or intensity of pain. Paradoxical heat sensation was more frequent in patients living with polyneuropathy compared with central or unilateral peripheral nerve lesions. Patients who reported PHS demonstrated significantly lower sensitivity to thermal perception, with lower sensitivity to normally painful heat and cold stimuli. Neuropathic Pain Symptom Inventory scores were lower for burning and electric shock-like pain quality for patients with PHS. Our findings suggest that PHS is associated with loss of small thermosensory fibre function normally involved in cold and warm perception. Clinically, presence of PHS could help screening for loss of small fibre function as it is straightforward to measure or self-reported by patients.

A systematic review and meta-analysis of neuropathic pain in multiple sclerosis: Prevalence, clinical types, sex dimorphism, and increased depression and anxiety symptoms

Chronic pain is the most disability symptom related to multiple sclerosis (MS) brain lesions and can also generate anxiety and depression. There are no updated reports of the general prevalence of neuropathic pain, MS clinical types, sex dimorphism, and its association with depression and anxiety. The protocol was listed in PROSPERO (CRD42022303571). The article selection resulted in 24 studies with a low risk of bias. The prevalence of neuropathic pain in MS patients was 26.8% with higher levels of depression and anxiety. We also observed that female patients (74.2%) have a higher prevalence of neuropathic pain than males (28.9%). We showed the enhanced prevalence of neuropathic pain using the female and male data (58.9%) compared to the total prevalence (26.8%). In addition, the SPMS (40.3%) presented an increased prevalence of neuropathic pain compared to PPMS (15.6%). Thus, we demonstrated the association between neuropathic pain, depression and anxiety symptoms and the influence of diagnosis, age, disease score, and disease duration in the increased prevalence of neuropathic pain in MS patients.