Evoked oscillatory cortical activity during acute pain: Probing brain in pain by transcranial magnetic stimulation combined with electroencephalogram.

Temporal dynamics of local cortical rhythms during acute pain remain largely unknown. The current study used a novel approach based on transcranial magnetic stimulation combined with electroencephalogram (TMS-EEG) to investigate evoked-oscillatory cortical activity during acute pain. Motor (M1) and dorsolateral prefrontal cortex (DLPFC) were probed by TMS, respectively, to record oscillatory power (event-related spectral perturbation and relative spectral power) and phase synchronization (inter-trial coherence) by 63 EEG channels during experimentally induced acute heat pain in 24 healthy participants. TMS-EEG was recorded before, during, and after noxious heat (acute pain condition) and non-noxious warm (Control condition), delivered in a randomized sequence. The main frequency bands (α, ß1, and ß2) of TMS-evoked potentials after M1 and DLPFC stimulation were recorded close to the TMS coil and remotely. Cold and heat pain thresholds were measured before TMS-EEG. Over M1, acute pain decreased α-band oscillatory power locally and α-band phase synchronization remotely in parietal-occipital clusters compared with non-noxious warm (all p < .05). The remote (parietal-occipital) decrease in α-band phase synchronization during acute pain correlated with the cold (p = .001) and heat pain thresholds (p = .023) and to local (M1) α-band oscillatory power decrease (p = .024). Over DLPFC, acute pain only decreased ß1-band power locally compared with non-noxious warm (p = .015). Thus, evoked-oscillatory cortical activity to M1 stimulation is reduced by acute pain in central and parietal-occipital regions and correlated with pain sensitivity, in contrast to DLPFC, which had only local effects. This finding expands the significance of α and ß band oscillations and may have relevance for pain therapies.

Deep Brain Stimulation Improves Parkinson's Disease-Associated Pain by Decreasing Spinal Nociception.

Dopamine exerts antinociceptive effects on pain in PD at cortical and spinal levels, whereas only cortical effects have been described for DBS, so far. By assessing the nociceptive flexion reflex (NFR) threshold at medication on, and DBS ON and OFF in two patients, we showed that DBS additionally decreases spinal nociception.

Trans-Spinal Theta Burst Magnetic Stimulation in Parkinson's Disease and Gait Disorders.

BACKGROUND: Gait disorders in patients with Parkinson's disease (PD) can become disabling with disease progression without effective treatment. OBJECTIVES: To investigate the efficacy of intermittent θ burst trans-spinal magnetic stimulation (TsMS) in PD patients with gait and balance disorders. METHODS: This was a randomized, parallel, double-blind, controlled trial. Active or sham TsMS was applied at third thoracic vertebra with 100% of the trans-spinal motor threshold, during 5 consecutive days. Participants were evaluated at baseline, immediately after last session, 1 and 4 weeks after last session. Primary outcome was Total Timed Up and Go (TUG) values comparing active versus sham phases 1 week after intervention. The secondary outcome measurements consisted of motor, gait and balance scales, and questionnaires for quality of life and cognition. RESULTS: Thirty-three patients were included, average age 68.5 (6.4) years in active group and 70.3 (6.3) years in sham group. In active group, Total TUG mean baseline was 107.18 (95% CI, 52.1-116.1), and 1 week after stimulation was 93.0 (95% CI, 50.7-135.3); sham group, Total TUG mean baseline was 101.2 (95% CI, 47.1-155.3) and 1 week after stimulation 75.2 (95% CI 34.0-116.4), P = 0.54. Similarly, intervention had no significant effects on secondary outcome measurements. During stimulation period, five patients presented with mild side effects (three in active group and two in sham group). DISCUSSION: TsMS did not significantly improve gait or balance analysis in patients with PD and gait disorders. The protocol was safe and well tolerated. © 2024 International Parkinson and Movement Disorder Society.

Phenotypical characterization of exteroceptive sensation and pain symptoms on diabetic patients.

BACKGROUD: Diabetic neuropathy (DN) is one of the most common complications of diabetes, affecting about half of individuals with the disease. Among the various symptoms of DN, the development of chronic pain stands out and manifests as exacerbated responses to sensorial stimuli. The conventional clinical treatments used for general neuropathy and associated painful symptoms, still brings uncomplete and unsatisfactory pain relief. Patients with neuropathic pain syndromes are heterogeneous. They present with a variety of sensory symptoms and pain qualities which difficult the correct diagnosis of sensory comorbidities and consequently, the appropriate chronic pain management. AIMS: Herein, we aimed to demonstrate the existence of different sensory profiles on diabetic patients by investigating epidemiological and clinical data on the symptomatology of a group of patients with DN. METHODS: This is a longitudinal and observational study, with a sample of 57 volunteers diagnosed with diabetes from outpatient day clinic of Hospital Universitário of the University of São Paulo-Brazil. After being invited and signed the Informed Consent Form (ICF), patients were submitted to clinical evaluation and filled out pain and quality of life questionnaires. They also performed quantitative sensory test (QST) and underwent skin biopsy for correlation with cutaneous neuropathology. RESULTS: Data demonstrate that 70% of the studied sample presented some type of pain, manifesting in a neuropathic or nociceptive way, what has a negative impact on the life of patients with DM. We also demonstrated a positive association between pain and anxiety and depression, in addition to pain catastrophic thoughts. Three distinct profiles were identified in the sample, separated according to the symptoms of pain: (i) subjects without pain; (ii) with mild or moderate pain; (iii) subjects with severe pain. We also identified through skin biopsy that diabetic patients presented advanced sensory impairment, as a consequence of the degeneration of the myelinated and unmyelinated peripheral fibers. This study characterized the painful symptoms and exteroceptive sensation profile in these diabetic patients, associated to a considerable level of sensory degeneration, indicating, and reinforcing the importance of the long-term clinical monitoring of individuals diagnosed with DM, regarding their symptom profiles and exteroceptive sensitivity.

Development and Validation of the Dystonia-Pain Classification System: A Multicenter Study.

BACKGROUND: Dystonia is associated with disabling nonmotor symptoms like chronic pain (CP), which is prevalent in dystonia and significantly impacts the quality of life (QoL). There is no validated tool for assessing CP in dystonia, which substantially hampers pain management. OBJECTIVE: The aim was to develop a CP classification and scoring system for dystonia. METHODS: A multidisciplinary group was established to develop the Dystonia-Pain Classification System (Dystonia-PCS). The classification of CP as related or unrelated to dystonia was followed by the assessment of pain severity score, encompassing pain intensity, frequency, and impact on daily living. Then, consecutive patients with inherited/idiopathic dystonia of different spatial distribution were recruited in a cross-sectional multicenter validation study. Dystonia-PCS was compared to validated pain, mood, QoL, and dystonia scales (Brief Pain Inventory, Douleur Neuropathique-4 questionnaire, European QoL-5 Dimensions-3 Level Version, and Burke-Fahn-Marsden Dystonia Rating Scale). RESULTS: CP was present in 81 of 123 recruited patients, being directly related to dystonia in 82.7%, aggravated by dystonia in 8.8%, and nonrelated to dystonia in 7.5%. Dystonia-PCS had excellent intra-rater (Intraclass Correlation Coefficient - ICC: 0.941) and inter-rater (ICC: 0.867) reliability. In addition, pain severity score correlated with European QoL-5 Dimensions-3 Level Version's pain subscore (r = 0.635, P < 0.001) and the Brief Pain Inventory's severity and interference scores (r = 0.553, P < 0.001 and r = 0.609, P < 0.001, respectively). CONCLUSIONS: Dystonia-PCS is a reliable tool to categorize and quantify CP impact in dystonia and will help improve clinical trial design and management of CP in patients affected by this disorder. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Site matters: Central neuropathic pain characteristics and somatosensory findings after brain and spinal cord lesions.

BACKGROUND: It is unknown if different etiologies or lesion topographies influence central neuropathic pain (CNP) clinical manifestation. METHODS: We explored the symptom-somatosensory profile relationships in CNP patients with different types of lesions to the central nervous system to gain insight into CNP mechanisms. We compared the CNP profile through pain descriptors, standardized bedside examination, and quantitative sensory test in two different etiologies with segregated lesion locations: the brain, central poststroke pain (CPSP, n = 39), and the spinal cord central pain due to spinal cord injury (CPSCI, n = 40) in neuromyelitis optica. RESULTS: Results are expressed as median (25th to 75th percentiles). CPSP presented higher evoked and paroxysmal pain scores compared to CPSCI (p < 0.001), and lower cold thermal limen (5.6°C [0.0-12.9]) compared to CPSCI (20.0°C [4.2-22.9]; p = 0.004). CPSCI also had higher mechanical pain thresholds (784.5 mN [255.0-1078.0]) compared to CPSP (235.2 mN [81.4-1078.0], p = 0.006) and higher mechanical detection threshold compared to control areas (2.7 [1.5-6.2] vs. 1.0 [1.0-3.3], p = 0.007). Evoked pain scores negatively correlated with mechanical pain thresholds (r = -0.38, p < 0.001) and wind-up ratio (r = -0.57, p < 0.001). CONCLUSIONS: CNP of different etiologies may present different pain descriptors and somatosensory profiles, which is likely due to injury site differences within the neuroaxis. This information may help better design phenotype mechanism correlations and impact trial designs for the main etiologies of CNP, namely stroke and spinal cord lesions. This study provides evidence that topography may influence pain symptoms and sensory profile. The findings suggest that CNP mechanisms might vary according to pain etiology or lesion topography, impacting future mechanism-based treatment choices.

Safety and Outcomes of Dentate Nucleus Deep Brain Stimulation for Cerebellar Ataxia.

Cerebellar symptoms remain orphan of treatment options despite being prevalent and incapacitating. Investigate whether dentate nucleus deep brain stimulation (DN DBS) is safe and leads to improvements in cerebellar symptoms when compared to sham stimulation. This randomized double-blind crossover pilot trial enrolled five patients with spinocerebellar ataxia type 3 or post-lesion ataxia. Active or sham phases were randomly performed three months apart. The primary outcome was ataxia improvement as measured by the Scale for the Assessment and Rating of Ataxia (SARA) after the active compared to the sham period. Secondary outcome measures included safety and tolerability, the Fahn-Tolosa-Marin Tremor Rating Scale (FTMRS), quality of life measurements, and patients' global impression of change. The effects on ataxia were numerically better in four out of five patients after active versus sham stimulation. The composite SARA score did not change after comparing active to sham stimulation (8.6 ± 3.6 versus 10.1 ± 4.1; p = 0.223). The FTMRS showed significant improvement after active stimulation versus sham (18.0 ± 17.2 versus 22.2 ± 19.5; p = 0.039) as did patients' global impression of change (p = 0.038). The quality of life was not modified by stimulation (p = 0.337). DN DBS was well tolerated without serious adverse events. One patient had the electrode repositioned. DN DBS is a safe and well tolerated procedure that is effective in alleviating cerebellar tremor. In this small cohort of ataxic patients, DN DBS did not achieve statistical significance for ataxia improvement.

Motor cortex stimulation for chronic neuropathic pain: results of a double-blind randomized study.

Motor cortex stimulation via surgically implanted electrodes has been used as an off-label treatment for chronic neuropathic pain, but its efficacy has not been fully established. We aimed to objectively study the efficacy of motor cortex stimulation and characterize potential predictors of response. In this randomized, double-blind, sham-controlled, single centre trial, we recruited 18 patients with chronic neuropathic pain who did not adequately respond to conventional treatment and had a numerical pain rating scale (NRS) score ≥6. Patients were initially assigned to receive 3 months of active ('on') or sham ('off') stimulation in a double-blind cross-over phase. This was followed by a 3-month single-blind phase, and 6 months of open-label follow-up. A meaningful response in our trial was defined as a ≥30% or 2-point reduction in NRS scores during active stimulation. Using Bayesian statistics, we found a 41.4% probability of response towards on versus off motor cortex stimulation. The probability of improvement during active stimulation (double-blind, single-blind and open-label phases) compared to baseline was 47.2-68.5%. Thirty nine per cent of the patients were considered long-term responders, 71.4% of whom had facial pain, phantom limb pain or complex regional pain syndrome. In contrast, 72.7% of non-responders had either post-stroke pain or pain associated with brachial plexus avulsion. Thirty-nine per cent of patients had a substantial postoperative analgesic effect after electrode insertion in the absence of stimulation. Individuals with diagnoses associated with a good postoperative outcome or those who developed an insertional effect had a near 100% probability of response to motor cortex stimulation. In summary, we found that ∼40% of patients responded to motor cortex stimulation, particularly those who developed an insertional effect or had specific clinical conditions that seemed to predict an appropriate postoperative response.

Persistent pain is a risk factor for frailty: a systematic review and meta-analysis from prospective longitudinal studies.

Background: pain is prevalent in frail older adults; however, the association of pain and frailty has not been evaluated yet by a systematic assessment of prospective longitudinal studies. Objective: we aimed to assess the association of persistent pain as a risk factor for frailty incidence, using data from longitudinal studies in a systematic review and meta-analysis. Methods: publications were identified using a systematic search on PubMed, Embase, Cochrane Library and clinicaltrials.gov databases from inception to October 2017. Since heterogeneity across studies was high, we used random-effects meta-analysis to calculate the pooled relative risk for the association between persistent pain and the incidence of frailty. We investigated sources of heterogeneity among studies using meta-regression and stratified analyses. Results: we included five prospective longitudinal studies with 13,120 participants (46% women, mean age from 59 to 85 years old). Participants with persistent pain at baseline had twice the risk of developing frailty during the follow-up (pooled RR = 2.22, 95% CI = 1.14-4.29). No variables were related to study heterogeneity in sensitivity analyses. Conclusion: persistent pain was a risk factor for the development of frailty in a meta-analysis of longitudinal studies. Better understanding of the association between pain and frailty with proper evaluation of potential confounders could allow the development of targeted interventions.

Pregabalin for the Prevention of Oxaliplatin-Induced Painful Neuropathy: A Randomized, Double-Blind Trial.

LESSONS LEARNED: Pregabalin is a medication that can decrease neuronal hyperexcitability, relieve neuropathic pain, and reach stable plasma levels after a titration period of only a few days.Its use during oxaliplatin infusions was not able to decrease the incidence of chronic, oxalipaltin-related neuropathic pain, compared with placebo. BACKGROUND: Patients with colorectal cancer (CRC) receiving oxaliplatin (OXA) develop acute and chronic painful oxaliplatin-induced peripheral neuropathy (OXAIPN). Acute and chronic OXA-related neuropathies have different pathophysiological bases, but both lead to a common phenomenon: central sensitization (CS) of nociceptive neuronal networks, leading to increased sensitivity (hyperlgesia, allodynia) in the somatosensory system, the common ground of chronic neuropathic pain. Because CS is related to increased risk of painful OXAIPN, we hypothesized that preemptive use of the anti-hyperalgesic drug pregabaline (known to decrease CS) during OXA infusions would decrease the incidence of chronic OXAIPN. METHODS: Pain-free, chemotherapy-naïve CRC patients receiving at least one cycle of modified-FLOX [5-FU(500 mg/m2)+leucovorin(20 mg/m2)/week for] 6 weeks+oxaliplatin(85 mg/m2) at weeks 1-3-5 every 8 weeks] were randomized (1:1) into the study. Patients received either pregabalin or placebo for 3 days before and 3 days after each OXA infusion and were followed for up to 6 months. Clinical assessments were performed at baseline, at the end of chemotherapy, and after the follow-up period. The main outcome was average pain at the last visit assessed by the visual analogic scale (0-10) item of the Brief Pain Inventory (BPI). Secondary endpoints were presence of neuropathic pain according to the Douleur Neuropathique-4 (DN-4), pain dimensions (short- form McGill Pain Questionnaire [MPQ]), Neuropathic Pain Symptom Inventory (NPSI), and changes in nerve conduction studies (NCS) and side effect profile. RESULTS: One hundred ninety-nine patients (57.0 ± 10.7 years old, 98 female, 101 male) were randomized. Data from 56 patients were not included in the analyses (as they did not receive at least one full cycle of modified FLOX). Data from 78 patients in the pregabalin group and 65 patients in the placebo group were retained for analyses. At the last visit, pain intensity in the pregabalin group was 1.03 (95% confidence interval [CI] = 0.79-1.26), and 0.85 (95% CI = 0.64-1.06) in the placebo group, which did not reach significance. Scores from the BPI, MPQ, DN-4, NPSI, and NCS and side-effect profiles and incidence of death did not differ between groups. Quality of life (QoL) score did not differ between groups (placebo = 76.9 ± 23.1, pregabalin group 79.4 ± 20.6). Mood scores were not significantly different between groups (placebo 9.7 [8.1-11.2]; pregabalin 6.8 [5.6-8.0]). CONCLUSION: The preemptive use of pregabalin during OXA infusions was safe, but did not decrease the incidence of chronic pain related to OXAIPN.

Neuropathic pain after brachial plexus avulsion--central and peripheral mechanisms.

REVIEW: The pain that commonly occurs after brachial plexus avulsion poses an additional burden on the quality of life of patients already impaired by motor, sensory and autonomic deficits. Evidence-based treatments for the pain associated with brachial plexus avulsion are scarce, thus frequently leaving the condition refractory to treatment with the standard methods used to manage neuropathic pain. Unfortunately, little is known about the pathophysiology of brachial plexus avulsion. Available evidence indicates that besides primary nerve root injury, central lesions related to the abrupt disconnection of nerve roots from the spinal cord may play an important role in the genesis of neuropathic pain in these patients and may explain in part its refractoriness to treatment. CONCLUSIONS: The understanding of both central and peripheral mechanisms that contribute to the development of pain is of major importance in order to propose more effective treatments for brachial plexus avulsion-related pain. This review focuses on the current understanding about the occurrence of neuropathic pain in these patients and the role played by peripheral and central mechanisms that provides insights into its treatment. Pain after brachial plexus avulsion involves both peripheral and central components; thereby it is characterized as a mixed (central and peripheral) neuropathic pain syndrome.

Correlation between impulsivity and executive function in patients with Parkinson disease experiencing depression and anxiety symptoms.

BACKGROUND: Depression and anxiety are comorbidities often associated with Parkinson disease (PD). Recent studies debate on how affective disorders can influence the cognition of patients with PD. This study sought to investigate how depression and anxiety affect specific executive functions and impulsivity traits in these patients. METHODS: Twenty-eight patients with advanced PD and 28 closely matched healthy volunteers (HV) were assessed for depressive and anxiety symptoms, impulsivity, executive function and control attention and behavioral response. RESULTS: Compared to the HV group, the PD group showed significantly higher perseverative responses and slowness to adapt to changes in environmental stimuli and longer reaction time for inter-stimulus interval change. Depression symptoms were significantly correlated to motor impulsivity score and total Barratt Impulsiveness Scale (BIS -11) score. Moreover, there was also significant correlation between anxiety symptoms and attentional impulsivity score and total BIS-11 score. Correlation analysis between impulsivity and control attention indicated a positive correlation in commission and a negative correlation in reaction time and detectability in the PD group. CONCLUSIONS: The present results suggest that depression and anxiety were highly correlated to impulsivity but not to executive functions changes in these PD patients.

Repetitive transcranial magnetic stimulation in chronic pain: a review of the literature.

OBJECTIVE: To review the literature on the analgesic effects of repetitive transcranial magnetic stimulation (rTMS) in chronic pain according to different pain syndromes and stimulation parameters. DATA SOURCES: Publications on rTMS and chronic pain were searched in PubMed and Google Scholar using the following key words: chronic pain, analgesia, transcranial magnetic stimulation, neuropathic pain, fibromyalgia, and complex regional pain syndrome. STUDY SELECTION: This review only included double-blind, controlled studies with >10 participants in each arm that were published from 1996 to 2014 and written in English. Studies with relevant information for the understanding of the effects of rTMS were also cited. DATA EXTRACTION: The following data were retained: type of pain syndrome, type of study, coil type, target, stimulation intensity, frequency, number of pulses, orientation of induced current, number of session, and a brief summary of intervention outcomes. DATA SYNTHESIS: A total of 33 randomized trials were found. Many studies reported significant pain relief by rTMS, especially high-frequency stimulation over the primary motor cortex performed in consecutive treatment sessions. Pain relief was frequently >30% compared with control treatment. Neuropathic pain, fibromyalgia, and complex regional pain syndrome were the pain syndromes more frequently studied. However, among all published studies, only a few performed repetitive sessions of rTMS. CONCLUSIONS: rTMS has potential utility in the management of chronic pain; however, studies using maintenance sessions of rTMS and assessing the effects of rTMS on the different aspects of chronic pain are needed to provide a more solid basis for its clinical application for pain relief.

Interdigital direct neurorrhaphy for treatment of painful neuroma due to finger amputation.

BACKGROUND: Painful neuroma following amputation is a disabling condition for which treatments are not usually satisfactory. The aim of this study is to retrospectively evaluate the results of interdigital neurorrhaphy after neuroma resection as an option for the surgical treatment of painful digital neuroma. METHOD: We retrospectively analyzed data from seven patients submitted to interdigital neurorrhaphy for treatment of digital neuroma. For evaluation of the results, the visual analog scale (VAS) for pain assessment, measurements with Simmens-Weinstein filaments and a handgrip dynamometer, and quantification of the Disabilities of the Arm, Shoulder and Hand (DASH) score were all performed. The mean improvements on the VAS and DASH scores were calculated. RESULTS: The mean follow-up was 28.3 months. All patients presented some degree of improvement in upper limb functionality and pain, and handling the affected finger was possible in all cases. The mean improvement on the VAS and DASH scores was 29.8 and 55.5 %, respectively. No patients presented long-term complications. CONCLUSION: Although this study was based on a small number of patients, it indicates that interdigital neurorrhaphy seems to be a feasible surgical treatment for painful digital neuroma.

Dopamine transporter imaging using 99mTc-TRODAT-1 SPECT in Parkinson's disease.

BACKGROUND: Although the decrease in striatal dopamine transporter (DAT) density has been described in North American, European, and Asian Parkinson's disease (PD) patients, studies on this issue are required in the rest of the world. This study examined the diagnostic utility of DAT imaging in Brazilian PD patients. MATERIAL/METHODS: Twenty PD patients (13 males, 7 females, median age: 62 years, median age at disease onset: 56 years, median disease duration: 5 years, and median UPDRS-III score: 29) and 9 age- and sex-matched healthy subjects underwent single-photon emission computerized tomography (SPECT) using 99mTc-TRODAT-1. RESULTS: PD patients showed a significant decrease in the striatum, caudate nucleus, and putamen DAT densities compared with data from healthy subjects. Striatal 99mTc-TRODAT-1 bindings had the highest diagnostic accuracy compared to those estimates from caudate nucleus and putamen. For the diagnosis of PD, a striatal 99mTc-TRODAT-1 binding cut-off value of 0.90 was associated with a sensitivity of 100% and a specificity of 89%. There was no significant difference between striatal 99mTc-TRODAT-1 binding values provided by different readers, contrary to 99mTc-TRODAT-1 binding estimates in the caudate nucleus. CONCLUSIONS: Striatal DAT imaging using 99mTc-TRODAT-1 can be considered a marker for differentiating PD patients from healthy individuals, with a good interobserver reproducibility.

The deep and the deeper: Spinal cord and deep brain stimulation for neuropathic pain.

Neuropathic pain occurs in people experiencing lesion or disease affecting the somatosensorial system. It is present in 7 % of the general population and may not fully respond to first- and second-line treatments in up to 40 % of cases. Neuromodulation approaches are often proposed for those not tolerating or not responding to usual pharmacological management. These approaches can be delivered surgically (invasively) or non-invasively. Invasive neuromodulation techniques were the first to be employed in neuropathic pain. Among them is spinal cord stimulation (SCS), which consists of the implantation of epidural electrodes over the spinal cord. It is recommended in some guidelines for peripheral neuropathic pain. While recent studies have called into question its efficacy, others have provided promising data, driven by advances in techniques, battery capabilities, programming algorithms and software developments. Deep brain stimulation (DBS) is another well-stablished neuromodulation therapy routinely used for movement disorders; however, its role in pain management remains limited to specific research centers. This is not only due to variable results in the literature contesting its efficacy, but also because several different brain targets have been explored in small trials, compromising comparisons between these studies. Structures such as the periaqueductal grey, posterior thalamus, anterior cingulate cortex, ventral striatum/anterior limb of the internal capsule and the insula are the main targets described to date in literature. SCS and DBS present diverse rationales for use, mechanistic backgrounds, and varying levels of support from experimental studies. The present review aims to present their methodological details, main mechanisms of action for analgesia and their place in the current body of evidence in the management of patients with neuropathic pain, as well their particularities, effectiveness, safety and limitations.

The incidence, characteristics, impact and risk factors of post-COVID chronic pain in Thailand: A single-center cross-sectional study.

The COVID-19 pandemic has affected millions of individuals worldwide. Pain has emerged as a significant post-COVID-19 symptom. This study investigated the incidence, characteristics, and risk factors of post-COVID chronic pain (PCCP) in Thailand. A cross-sectional study was conducted in participants who had been infected, including those hospitalized and monitored at home by SARS-CoV-2 from August to September 2021. Data were collected for screening from medical records, and phone interviews were done between 3 to 6 months post-infection. Participants were classified into 1) no-pain, 2) PCCP, 3) chronic pain that has been aggravated by COVID-19, or 4) chronic pain that has not been aggravated by COVID-19. Pain interference and quality of life were evaluated with the Brief Pain Inventory and EuroQol Five Dimensions Five Levels Questionnaire. From 1,019 participants, 90% of the participants had mild infection, assessed by WHO progression scale. The overall incidence of PCCP was 3.2% (95% CI 2.3-4.5), with 2.8% (95% CI 2.0-4.1) in mild infection, 5.2% (95% CI 1.2-14.1) in moderate infection and 8.5% (95% CI 3.4-19.9) in severe infection. Most participants (83.3%) reported pain in the back and lower extremities and were classified as musculoskeletal pain and headache (8.3%). Risk factors associated with PCCP, included female sex (relative risk [RR] 2.2, 95% CI 1.0-4.9) and greater COVID-19 severity (RR 3.5, 95% CI 1.1-11.7). Participants with COVID-19-related exacerbated chronic pain displayed higher pain interferences and lower utility scores than other groups. In conclusion, this study highlights the incidence, features, and risk factors of post-COVID chronic pain (PCCP) in Thailand. It emphasizes the need to monitor and address PCCP, especially in severe cases, among females, and individuals with a history of chronic pain to improve their quality of life in the context of the ongoing COVID-19 pandemic.

Intra-operative transdural electric stimulation in awake patient: target refining for motor cortex stimulation.

INTRODUCTION: Most authors perform the implantation of epidural electrodes for motor cortex stimulation (MCS) under general anesthesia, using navigation merely based on anatomic landmarks or in combination with intra-operative sensory evoked potentials (SEP) for functional localization. However, intra-operative SEP can only provide the localization of central sulcus in patients who present sensory pathways which are at least partially preserved. Conversely, there are massive deafferentation pain syndromes (e.g., brachial plexus avulsion or amputation) in which the peripheral sensory pathways are severely or totally injured, precluding the use of intra-operative SEP. Objective. The authors present a simple technique for functional localization and intra-operative mapping of motor cortex by the implementation of transdural electrical stimulation of cerebral cortex for target refining of motor cortex during cortical electrode implantation procedures. METHODS: Thirteen patients with complete brachial plexus root avulsion suffering from severe neuropathic pain in the affected limb were included in this report. First, the anatomical location of the motor cortex of the hand was stereotactically determined by the hand knob within the central sulcus. Functional mapping of cortex was performed by transdural bipolar electrical stimulation under local anesthesia, so patients were fully awake during the whole time of cortical mapping. The cortical mapping oriented the placement of epidural electrodes for chronic cortical stimulation for treatment of neuropathic pain. RESULTS: Stereotactic MR images of the hand knob were considered a satisfactory landmark for the motor area of the hand in all patients. On top of the anatomical landmark, transdural electrical stimulation (4.0-6.0 mA, 30-60 Hz and pulse width of 1 ms) gave vivid sensations of movement in the deafferented hand, forearm, and arm. The phantom sensation was elicited with lower current than usual motor mapping in patients with intact limbs. It was possible to delineate the spatial map of the phantom hand on the cortical surface with acceptable resolution. The sensation of wrist flexion was elicited in all; most of the patients had clear distinction of the thumb and index. The remaining fingers were not perceived individually. The cortical area responsive to the thumb tended to occupy a lateral position related to the areas of the other fingers, following the maps of the normal homunculus. The evoked sensation was restricted to the period of stimulation, and it stopped as soon as that was discontinued. The stimulation also evoked emotional responses related to sensation of limb movement. CONCLUSION: The proposed technique was useful for target refining in implantation of epidural electrode for motor cortex stimulation. Further studies are required to investigate if target refining by intra-operative mapping will significantly improve the results in the treatment of refractory pain.

Development and validation of a Brazilian version of the short-form McGill pain questionnaire (SF-MPQ).

The aim of this study was to develop and validate a short form of the Brazilian version of McGill Pain Questionnaire (SF-MPQ). Three hundred two patients with chronic pain filled out the validated Brazilian long form of the McGill Pain Questionnaire (LF-MPQ). Words chosen by ≥25% of the patients were selected to comprise the SF-MPQ. The Brazilian SF-MPQ consisted of 15 descriptors (8 sensory, 5 affective, and 2 evaluative) rated on a binary mode (present or absent). Four pain scores were derived by counting the words chosen by the patients for sensory, affective, evaluative, and total descriptors. The SF-MPQ showed poor internal consistency (KR-20 = 0.52) but possibly acceptable because it showed discriminant validity to discriminate patients presenting different levels and mechanisms of pain, and it was strongly correlated with the LF-MPQ. The low KR-20 coefficient could result from the small number of items. The Brazilian version of the SF-MPQ proved to be a useful instrument to evaluate the different qualities of pain. It is a reliable option to the long-form MPQ.