Somatosensory Loss Research Articles

A multi-modal evaluation of experimental pain and psychological function in women with carpometacarpal osteoarthritis

ObjectiveThumb carpometacarpal osteoarthritis (CMC1 OA) is a prevalent and debilitating condition that lacks effective treatments. Understanding the multidimensional pain experience across CMC1 OA disease stages is crucial to improving treatment outcomes. This study examined how radiographic CMC1 OA severity is associated with physical, psychological, and somatosensory function. MethodThirty-one women with early-stage (Eaton-Littler 1–2) or end-stage (Eaton-Littler 3–4) radiographic CMC1 OA completed validated questionnaires to assess pain, disability, and psychological function. Additionally, experimental pain was measured in each participant using quantitative sensory testing (QST) (mechanical, pressure, vibratory, thermal) at seven body sites (thenar, hypothenar, brachioradialis bi-laterally; quadriceps on affected side). Cohort differences (early-vs. end-stage) across all variables were analyzed using a multivariable modeling approach that included fixed effects and interactions; notably, age was controlled as a confounder. ResultsEnd-stage CMC1 OA participants had higher scores in the pain (p ​= ​0.01) and function (p ​= ​0.02) portions of the AUSCAN assessment, self-reported disability of the DASH questionnaire (p ​= ​0.04), and painDETECT scores (p ​= ​0.03), indicating greater pain and disability compared to early-stage participants. Additionally, end-stage CMC1 OA participants demonstrated reduced vibratory detection and heat pain thresholds at multiple body sites (p's ​< ​0.05), with significant interactions observed across the mechanical and cold stimuli. ConclusionFindings revealed women with end-stage CMC1 OA exhibited increased neuropathic pain characteristics and somatosensory loss compared to those with early-stage CMC1 OA. These results underscore the importance of addressing both peripheral and centralized pain mechanisms and the need for multimodal approaches in the treatment of CMC1 OA.

The effect of foot somatosensory loss in postural control during Functional reach test in patients with diabetic polyneuropathy: A controlled study

BackgroundIn patients with diabetic polyneuropathy (DPN), differences in postural control due to losing the lower limb somatosensory information were reported. However, it is still unclear by which mechanisms the dynamic postural instability is caused. ObjectivesThis study aimed to investigate postural control differences and neuromuscular adaptations resulting from foot somatosensory loss due to DPN. MethodsIn this controlled cross-sectional study, fourteen DPN patients and fourteen healthy controls performed the Functional Reach Test (FRT) as a dynamic task. The postural control metrics were simultaneously measured using force plate, motion capture system, and surface electromyography (sEMG). The main metrics including reach length (FR), FR to height ratio (FR/H), displacement of CoM and CoP, moment arm (MA), and arch height ratio. Also, kinematic (range of motion of ankle, knee, and hip joints), and sEMG metrics (latencies and root mean square amplitudes of ankle and hallux muscles) were measured. To compare variables between groups, the independent sample T-test for (normally distributed) and the Mann-Whitney U test (non-normally distributed) were used. ResultsThe subjects' reach length (FR), FR to height ratio, absolute MA, and displacement of CoM were significantly shorter than controls, while displacement of CoP was not significant. Arch height ratio was found significantly lower in DPN patients. We observed that CoM was lagging CoP in patients (MA = + 0.89) while leading in controls (MA = -1.60). Although, the muscles of patients showed significantly earlier activation, root mean square sEMG amplitudes were found similar. Also, DPN patients showed significantly less hip flexion, knee extension, and ankle plantar flexion. ConclusionsThis study presented that decreasing range of motion at lower limbs’ joints and deterioration in foot function caused poor performance at motor execution during FRT in DPN patients.

Abstract TP86: Stroke-Impaired Proprioception Limits Motor Recovery With BCI-FES Device

Introduction: Non-invasive brain-computer interface (BCI) therapy with contingent (i.e., closed-loop) functional electrical stimulation (FES) shows efficacy improving motor function. However, it is not well understood why some stroke survivors respond better to closed-looped BCI-FES intervention than others. Contingent BCI-FES intervention drives neuroplastic change toward adaptive functional connectivity in stroke-impaired sensorimotor brain areas by enriching the afferent feedback environment. The interruption of afferent-efferent feedback circuits is a neural correlate of long-term acquired disability and intactness of functional connections predicts recovery capacity. Studies suggest that proprioception is essential for motor learning and performance. Therefore, we hypothesize that proprioceptive intactness is essential for recovery of motor performance when using a BCI-FES. Methods: Participants with upper extremity motor loss resulting from stroke (n=35) completed up to 30 hours of closed-loop BCI-FES. Results: Change in ARAT scores over the course of the control period were compared to ARAT change scores over the intervention period at a one-month follow up assessment. On average, participants in the intervention realized greater change in ARAT (M = 2.11, SD = 4.68) than during the control phase (M = 0.294, SD = 3.53). An independent-samples t-test indicated this difference, 1.82, 95%CI [-4.17, 0.534], was not statistically significant, t (40.901) = -1.56, p = 0.126. Preliminary results indicate that Proprioceptive sensory loss has a greater limiting effect on recovery than cutaneous somatosensory loss. Discussion: Rehabilitating motor capacity after stroke depends on the intactness of sensorimotor neural circuits. If afference signals are missing or degraded due to stroke, motor recovery is poor. When the stroke spares afferent connectivity to the peripheral muscles, the sensorimotor cortex can leverage plasticity-based motor rehab strategies such as BCI-FES. Conclusion: Intactness of sensorimotor circuits is related to baseline severity of motor impairment as well as recovery of motor function. Efficacious prescription of BCI-FES intervention is best suited for patients with stroke-spared proprioception.

A pilot study: effect of somatosensory loss on motor corrections in response to unknown loads in a reaching task by chronic stroke survivors.

Despite recent studies indicating a significant correlation between somatosensory deficits and rehabilitation outcomes, how prevailing somatosensory deficits affect stroke survivors' ability to correct their movements and recover overall remains unclear. To explore how major deficits in somatosensory systems impede stroke survivors' motor correction to various external loads, we conducted a study with 13 chronic stroke survivors who had hemiparesis. An inertial, elastic, or viscous load, which was designed to impose perturbing forces with various force profiles, was introduced unexpectedly during the reaching task using a programmable haptic robot. Participants' proprioception and cutaneous sensation were also assessed using passive movement detection, finger-to-nose, mirror, repositioning, and Weinstein pressure tests. These measures were then analyzed to determine whether the somatosensory measures significantly correlated with the estimated reaching performance parameters, such as initial directional error, positional deviation, velocity deviations, and speed of motor correction were measured.Of 13 participants, 5 had impaired proprioception, as they could not recognize the passive movement of their elbow joint, and they kept showing larger initial directional errors even after the familiarization block. Such continuously found inaccurate initial movement direction might be correlated with the inability to develop the spatial body map especially for calculating the initial joint torques when starting the reaching movement. Regardless of whether proprioception was impaired or not, all participants could show the stabilized, constant reaching movement trajectories. This highlights the role of proprioception especially in the execution of a planned movement at the early stage of reaching movement.

Association of Balance with Somatosensory Loss of Lower Limb in Diabetic Patients

Background: Diabetes, a prevalent global health issue, notably in Pakistan, poses significant challenges in healthcare management due to its complications, including impaired balance and increased fall risk. Objective: This study aimed to investigate the association between balance impairment and somatosensory loss in diabetic patients, focusing on the impact of aging and gender differences. Methods: A cross-sectional study was conducted over six months at Akhtar Seed Trust Teaching Hospital, Lahore, involving 600 participants. The Berg Balance Scale (BBS) and Rivermead assessments were used to evaluate balance and somatosensory loss. Participants included males and females aged above 25, with stratification into positive and negative cases based on their balance and somatosensory status. Results: Of the 600 participants (224 males, 376 females), 150 were categorized as positive cases, showing significant balance impairment. The BBS assessment revealed that two-point discrimination was more affected compared to vibratory sense and proprioception. The study found a statistically significant association between somatosensory loss and balance impairment, irrespective of age and gender. Conclusion: The study concludes that there is a significant correlation between somatosensory loss and balance impairment in diabetic patients, with aging and gender playing a lesser role. These findings underscore the need for targeted balance and sensory training in diabetic care to reduce fall risks.

Functional Outcomes of Motor Learning Interventions in Anterior Cruciate Ligament Injuries

Anterior cruciate ligament injury is one of the pathologies that affect the daily and professional life of the majority of athletes. When the treatment options are examined, there are two options surgical treatment and conservative treatment. Rehabilitation is essential in both cases, with or without surgery. Especially for returning to sports, long-term rehabilitation after surgery has become essential. While many different exercise methods have been tried in the prevention of anterior cruciate ligament injury and rehabilitation after reconstructive surgery, many have focused on strength training. The abnormal movement pattern that occurs with the somatosensory loss seen after anterior cruciate ligament injury results in a functional loss in the injured extremity and the contralateral extremity in the long term. Considering the incidence of injury, studies to establish the normal movement pattern and restore motor control are very important. For this reason, motor learning-based interventions that support neuroplasticity are of great interest today. This review aims to examine the functional results of current motor learning-based interventions in anterior cruciate ligament rehabilitation in line with the literature.

Characterizing Touch Discrimination Impairment from Pooled Stroke Samples Using the Tactile Discrimination Test: Updated Criteria for Interpretation and Brief Test Version for Use in Clinical Practice Settings.

Somatosensory loss post-stroke is common, with touch sensation characteristically impaired. Yet, quantitative, standardized measures of touch discrimination available for clinical use are currently limited. We aimed to characterize touch impairment and re-establish the criterion of abnormality of the Tactile Discrimination Test (TDT) using pooled data and to determine the sensitivity and specificity of briefer test versions. Baseline data from stroke survivors (n = 207) and older neurologically healthy controls (n = 100) assessed on the TDT was extracted. Scores were re-analyzed to determine an updated criterion of impairment and the ability of brief test versions to detect impairment. Updated scoring using an area score was used to calculate the TDT percent maximum area (PMA) score. Touch impairment was common for the contralesional hand (83%) but also present in the ipsilesional hand (42%). The criterion of abnormality was established as 73.1 PMA across older adults and genders. High sensitivity and specificity were found for briefer versions of the TDT (25 vs. 50 trials; 12 or 15 vs. 25 trials), with sensitivity ranging between 91.8 and 96.4% and specificity between 72.5 and 95.0%. Conclusion: Updated criterion of abnormality and the high sensitivity and specificity of brief test versions support the use of the TDT in clinical practice settings.

Huzurevindeki Geriatrik Diyabetli Bireylerde Proprioseptif Egzersizin Denge ve Duyusal Fonksiyona Etkisi: Randomize Kontrollü Çalışma

Objective: Diabetes is a chronic disease whose prevalence increases with age and causes severe damages in all systems of the body. The aim of our study was to assess the effects of proprioceptive exercises on balance and sensory function in the geriatric adults with Type 2 diabetes mellitus. Material and Methods: Forty individuals aged 65 and over with Type 2 diabetes mellitus were divided as a study group (n=20) and as a control group (n=20). All patients were evaluated at the baseline and after 8 weeks training. Balance was measured using Berg Balance Scale and Nintendo Wii system. Balance and gait were evaluated by Tinetti Balance and Gait Test. Semmes-Weinstein monofilament test was used for assessing tactile sensory, diapason for vibration and active matching test for joint position sense. Study group received 45 minutes long proprioceptive exercise training 3 times/week for 8 weeks and the control group only received diabetic patient education. Results: Study group demonstrated significant differences in Berg Balance Scale, Wii Fit balance age and Tinetti Balance and Gait Test scores (p<0.05). Vibration perception duration yielded a higher duration in the study group after treatment (p<0.05). Active matching movement and tactile sensory of the sole showed statistically improvement in the study group (p<0.05). Conclusion: Proprioceptive exercises recommended to individuals with geriatric diabetes can be a beneficial approach to increase balance ability to prevent falling and somatosensory loss.

IS THERE A RELATIONSHIP BETWEEN PAIN, LIMITS OF STABILITY AND SENSORY INTERACTION BALANCE IN PATIENTS WITH LUMBAR DISC HERNIATION? A CROSS-SECTIONAL STUDY

Objectives: Lumbar Disc Herniation (LDH) is a disorder causing pain and somatosensory loss. Although the association between pain and postural control in chronic low back pain is known, the relationship between pain and sensory problems with postural control is unknown in LDH, which is one of the most serious conditions among diseases. The purpose of the study was to determine the relationship between pain severity, Limits of Stability and Sensory Interaction Balance in patients with LDH. &#x0D; Methods: A total of 119 LDH patients, 64 of whom were women and 55 were men, were included in this cross-sectional study. Pain severity and postural control of the patients was measured by using Visual Analog Scale and Biodex Balance Device, respectively. Limits of Stability and Clinical Test of Sensory Interaction Balance tests were used for postural control evaluation.&#x0D; Results: The results of our study indicated that pain and disability were positively correlated with sensory interaction balance (p0.05).&#x0D; Conclusions: In patients with LDH, the sensory interaction balance was negatively affected by the increased pain and disability level, while LOS was not. Therefore, in addition to reducing pain and disability, approaches to increase the balance of sensory interaction should be adopted in physiotherapy programs of these patients.

What is “usual care” in the rehabilitation of upper limb sensory loss after stroke? Results from a national audit and knowledge translation study

Purpose To characterise the assessments and treatments that comprise “usual care” for stroke patients with somatosensory loss, and whether usual care has changed over time. Materials and methods Comparison of cross-sectional, observational data from (1) Stroke Foundation National Audit of Acute (2007–2019) and Rehabilitation (2010–2018) Stroke Services and (2) the SENSe Implement multi-site knowledge translation study with occupational therapists and physiotherapists (n = 115). Descriptive statistics, random effects logistic regression, and content analysis were used. Results Acute hospitals (n = 172) contributed 24 996 cases across audits from 2007 to 2019 (median patient age 76 years, 54% male). Rehabilitation services (n = 134) contributed organisational survey data from 2010 to 2014, with 7165 cases (median 76 years, 55% male) across 2016–2018 clinical audits (n = 127 services). Somatoensory assessment protocol use increased from 53% (2007) to 86% (2019) (odds ratio 11.4, 95% CI 5.0–25.6). Reported use of sensory-specific retraining remained stable over time (90–93%). Therapist practice reports for n = 86 patients with somatosensory loss revealed 16% did not receive somatosensory rehabilitation. The most common treatment approaches were sensory rehabilitation using everyday activities (69%), sensory re-education (68%), and compensatory strategies (64%). Conclusion Sensory assessment protocol use has increased over time while sensory-specific training has remained stable. Sensory rehabilitation in the context of everyday activities is a common treatment approach. Clinical trial registration number: ACTRN12615000933550 IMPLICATIONS FOR REHABILITATION Only a small proportion of upper limb assessments conducted with stroke patients focus specifically on sensation; increased use of standardised upper limb assessments for sensory loss is needed. Stroke patients assessed as having upper limb sensory loss frequently do not receive treatment for their deficits. Therapists typically use everyday activities to treat upper limb sensory loss and may require upskilling in sensory-specific retraining to benefit patients.

Anticipation and compensation for somatosensory deficits in object handling: evidence from a patient with large fiber sensory neuropathy.

The purpose of this study was to determine the contributions of feedforward and feedback processes on grip force regulation and object orientation during functional manipulation tasks. One patient with massive somatosensory loss resulting from large fiber sensory neuropathy and 10 control participants were recruited. Three experiments were conducted: 1) perturbation to static holding; 2) discrete vertical movement; and 3) functional grasp and place. The availability of visual feedback was also manipulated to assess the nature of compensatory mechanisms. Results from experiment 1 indicated that both the deafferented patient and controls used anticipatory grip force adjustments before self-induced perturbation to static holding. The patient exhibited increased grip response time, but the magnitude of grip force adjustments remained correlated with perturbation forces in the self-induced and external perturbation conditions. In experiment 2, the patient applied peak grip force substantially in advance of maximum load force. Unlike controls, the patient's ability to regulate object orientation was impaired without visual feedback. In experiment 3, the duration of unloading, transport, and release phases were longer for the patient, with increased deviation of object orientation at phase transitions. These findings show that the deafferented patient uses distinct modes of anticipatory control according to task constraints and that responses to perturbations are mediated by alternative afferent information. The loss of somatosensory feedback thus appears to impair control of object orientation, whereas variation in the temporal organization of functional tasks may reflect strategies to mitigate object instability associated with changes in movement dynamics.NEW & NOTEWORTHY This study evaluates the effects of sensory neuropathy on the scaling and timing of grip force adjustments across different object handling tasks (i.e., holding, vertical movement, grasping, and placement). In particular, these results illustrate how novel anticipatory and online control processes emerge to compensate for the loss of somatosensory feedback. In addition, we provide new evidence on the role of somatosensory feedback for regulating object orientation during functional prehensile movement.

Does rTMS Targeting Contralesional S1 Enhance Upper Limb Somatosensory Function in Chronic Stroke? A Proof-of-Principle Study

Background Somatosensory deficits are prevalent after stroke, but effective interventions are limited. Brain stimulation of the contralesional primary somatosensory cortex (S1) is a promising adjunct to peripherally administered rehabilitation therapies. Objective To assess short-term effects of repetitive transcranial magnetic stimulation (rTMS) targeting contralesional (S1) of the upper extremity. Methods Using a single-session randomized crossover design, stroke survivors with upper extremity somatosensory loss participated in 3 rTMS treatments targeting contralesional S1: Sham, 5 Hz, and 1 Hz. rTMS was delivered concurrently with peripheral of sensory electrical stimulation and vibration of the affected hand. Outcomes included 2-point discrimination (2PD), proprioception, vibration perception threshold, monofilament threshold (size), and somatosensory evoked potential (SEP). Measures were collected before, immediately after treatment, and 1 hour after treatment. Mixed models were fit to analyze the effects of the 3 interventions. Results Subjects were 59.8 ± 8.1 years old and 45 ± 39 months poststroke. There was improvement in 2PD after 5-Hz rTMS for the stroke-affected (F(2, 76.163) = 3.5, P = .035) and unaffected arm (F(2, 192.786) = 10.6, P < .0001). Peak-to-peak SEP amplitudes were greater after 5-Hz rTMS for N33-P45 (F(2, 133.027) = 3.518, P = .032) and N45-P60 (F(2, 67.353) = 3.212, P = .047). Latencies shortened after 5-Hz rTMS for N20 (F(2, 69.64) = 3.37, P = .04), N60 (F(2, 47.343) = 4.375, P = .018), and P100 (F(2, 37.608) = 3.537, P = .039) peaks. There were no differences between changes immediately after the intervention and an hour later. Conclusions Short-term application of facilitatory high-frequency rTMS (5Hz) to contralesional S1 combined with peripheral somatosensory stimulation may promote somatosensory function. This intervention may serve as a useful adjunct in somatosensory rehabilitation after stroke.

Reorganization of motor modules for standing reactive balance recovery following pyridoxine-induced large-fiber peripheral sensory neuropathy in cats.

Task-level goals such as maintaining standing balance are achieved through coordinated muscle activity. Consistent and individualized groupings of synchronously activated muscles can be estimated from muscle recordings in terms of motor modules or muscle synergies, independent of their temporal activation. The structure of motor modules can change with motor training, neurological disorders, and rehabilitation, but the central and peripheral mechanisms underlying motor module structure remain unclear. To assess the role of peripheral somatosensory input on motor module structure, we evaluated changes in the structure of motor modules for reactive balance recovery following pyridoxine-induced large-fiber peripheral somatosensory neuropathy in previously collected data in four adult cats. Somatosensory fiber loss, quantified by postmortem histology, varied from mild to severe across cats. Reactive balance recovery was assessed using multidirectional translational support-surface perturbations over days to weeks throughout initial impairment and subsequent recovery of balance ability. Motor modules within each cat were quantified by non-negative matrix factorization and compared in structure over time. All cats exhibited changes in the structure of motor modules for reactive balance recovery after somatosensory loss, providing evidence that somatosensory inputs influence motor module structure. The impact of the somatosensory disturbance on the structure of motor modules in well-trained adult cats indicates that somatosensory mechanisms contribute to motor module structure, and therefore may contribute to some of the pathological changes in motor module structure in neurological disorders. These results further suggest that somatosensory nerves could be targeted during rehabilitation to influence pathological motor modules for rehabilitation.NEW & NOTEWORTHY Stable motor modules for reactive balance recovery in well-trained adult cats were disrupted following pyridoxine-induced peripheral somatosensory neuropathy, suggesting somatosensory inputs contribute to motor module structure. Furthermore, the motor module structure continued to change as the animals regained the ability to maintain standing balance, but the modules generally did not recover pre-pyridoxine patterns. These results suggest changes in somatosensory input and subsequent learning may contribute to changes in motor module structure in pathological conditions.

Patterns of neurological deficits and recovery of postoperative C5 nerve palsy.

Paresis of the C5 nerve is a well-recognized complication of cervical spine surgery. Numerous studies have investigated its incidence and possible causes, but the specific pattern and character of neurological deficits, time course, and relationship to preoperative cord signal changes remain incompletely understood. Records of patients undergoing cervical decompressive surgery for spondylosis, disc herniation, or ossification of the longitudinal ligament, including the C4-5 level, were reviewed from a 15-year period, identifying C5 palsy cases. Data collected included age, sex, diabetes and smoking statuses, body mass index, surgical levels, approach, presence of increased cord signal intensity, and modified Japanese Orthopaedic Association (mJOA) scores. Narrative descriptions of the patterns and findings on neurological examination were reviewed, and complications were noted. The minimum follow-up requirement for the study was 12 months. Of 642 patients who underwent cervical decompressive surgery, 18 developed C5 palsy (2.8%). The incidence was significantly lower following anterior surgery (6 of 441 [1.4%]) compared with that following cervical laminectomy and fusion (12 of 201 [6.0%]) (p < 0.001). There were 10 men and 8 women whose mean age was 66.7 years (range 54-76 years). The mean preoperative mJOA score of 11.4 improved to 15.6 at the latest follow-up examination. There were no differences between those with and without C5 palsy with regard to sex, age, number of levels treated, or pre- or postoperative mJOA score. Fifteen patients with palsy (83%) had signal changes/myelomalacia on preoperative T2-weighted imaging, compared with 436 of 624 (70%) patients without palsy; however, looking specifically at the C4-5 level, signal change/myelomalacia was present in 12 of 18 (67%) patients with C5 palsy, significantly higher than in the 149 of 624 (24%) patients without palsy (p < 0.00003). Paresis was unilateral in 16 (89%) and bilateral in 2 (11%) patients. All had deltoid weakness, but 15 (83%) exhibited new biceps weakness, 8 (44%) had triceps weakness, and 2 (11%) had hand intrinsic muscle weakness. The mean time until onset of palsy was 4.6 days (range 2-14 days). Two patients (11%) complained of shoulder pain preceding weakness; 3 patients (17%) had sensory loss. Recovery to grade 4/5 deltoid strength occurred in 89% of the patients. No patient had intraoperative loss of somatosensory or motor evoked potentials or abnormal intraoperative C5 electromyography activity. Postoperative C5 nerve root dysfunction appears in a delayed fashion, is predominantly a motor deficit, and weakness is frequently appreciated in the biceps and triceps muscles in addition to the deltoid muscle. Preoperative cord signal change/myelomalacia at C4-5 was a significant risk factor. No patient had a detectable deficit in the immediate postoperative period or changes in intraoperative neuromonitoring status. Neurological recovery to at least that of grade 4/5 occurred in nearly 90% of the patients.

Assessment of somatosensory changes in Chinese temporomandibular disorders arthralgia patients by quantitative sensory testing.

Somatosensory changes in Chinese temporomandibular disorders (TMD) arthralgia patients have not been fully studied by the latest technologies. This study aims at assessing somatosensory changes in Chinese TMD arthralgia patients quantitatively. Standardised quantitative sensory testing (QST) was performed on the pain sites and contralateral sites of 40 patients diagnosed with TMD arthralgia according to the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) before and after medication; similar measures were taken in 40 age- and gender-matched healthy controls. Differences within and between groups were assessed through Z-scores, two-way ANOVA and loss/gain coding system. The pain sites of patients presented increased sensitivity to thermal stimuli and mechanical pain stimuli together with decreased sensitivity to mechanical tactile stimuli before medication (P<.001). Before treatment, 100% of patients had somatosensory abnormalities at the pain sites; the most frequent abnormalities were somatosensory gain to cold nociceptive, pinprick and pressure stimuli, and the most frequent loss/gain score was L0G3 (no somatosensory loss with a gain of thermal and mechanical somatosensory function; 70.0%). After treatment, although the clinical symptoms and signs of 40 patients disappeared, 80.0% of the patients' pain sites still showed multiple phenotype abnormalities. The most frequent loss/gain score was L0G2 (no somatosensory loss with a gain of mechanical somatosensory function; 35.0%). Multiple phenotypes of facial somatosensory abnormalities were detected in Chinese TMD arthralgia patients before and after treatment, despite the disappearance of clinical signs and symptoms. Individual variations indicate a possible need for subgroup classification, individualised management and mechanism-based treatment.

Brain and Body: A Review of Central Nervous System Contributions to Movement Impairments in Diabetes.

Diabetes is associated with a loss of somatosensory and motor function, leading to impairments in gait, balance, and manual dexterity. Data-driven neuroimaging studies frequently report a negative impact of diabetes on sensorimotor regions in the brain; however, relationships with sensorimotor behavior are rarely considered. The goal of this review is to consider existing diabetes neuroimaging evidence through the lens of sensorimotor neuroscience. We review evidence for diabetes-related disruptions to three critical circuits for movement control: the cerebral cortex, the cerebellum, and the basal ganglia. In addition, we discuss how central nervous system (CNS) degeneration might interact with the loss of sensory feedback from the limbs due to peripheral neuropathy to result in motor impairments in individuals with diabetes. We argue that our understanding of movement impairments in individuals with diabetes is incomplete without the consideration of disease complications in both the central and peripheral nervous systems. Neuroimaging evidence for disrupted central sensorimotor circuitry suggests that there may be unrecognized behavioral impairments in individuals with diabetes. Applying knowledge from the existing literature on CNS contributions to motor control and motor learning in healthy individuals provides a framework for hypothesis generation for future research on this topic.

Blocking tactile input to one finger using anaesthetic enhances touch perception and learning in other fingers.

Brain plasticity is a key mechanism for learning and recovery. A striking example of plasticity in the adult brain occurs following input loss, for example, following amputation, whereby the deprived zone is “invaded” by new representations. Although it has long been assumed that such reorganization leads to functional benefits for the invading representation, the behavioral evidence is controversial. Here, we investigate whether a temporary period of somatosensory input loss to one finger, induced by anesthetic block, is sufficient to cause improvements in touch perception (“direct” effects of deafferentation). Further, we determine whether this deprivation can improve touch perception by enhancing sensory learning processes, for example, by training (“interactive” effects). Importantly, we explore whether direct and interactive effects of deprivation are dissociable by directly comparing their effects on touch perception. Using psychophysical thresholds, we found brief deprivation alone caused improvements in tactile perception of a finger adjacent to the blocked finger but not to non-neighboring fingers. Two additional groups underwent minimal tactile training to one finger either during anesthetic block of the neighboring finger or a sham block with saline. Deprivation significantly enhanced the effects of tactile perceptual training, causing greater learning transfer compared with sham block. That is, following deafferentation and training, learning gains were seen in fingers normally outside the boundaries of topographic transfer of tactile perceptual learning. Our results demonstrate that sensory deprivation can improve perceptual abilities, both directly and interactively, when combined with sensory learning. This dissociation provides novel opportunities for future clinical interventions to improve sensation.

Somatosensory Profiling of Patients with Burning Mouth Syndrome and Correlations with Psychologic Factors.

To compare somatosensory function profiles and psychologic factors in patients with primary burning mouth syndrome (BMS) and healthy controls and to evaluate correlations of subjective pain ratings with somatosensory and psychologic parameters. A quantitative sensory testing (QST) protocol-including cold detection threshold (CDT), warmth detection threshold (WDT), thermal sensory limen (TSL), paradoxical heat sensation (PHS), cold pain threshold (CPT), heat pain threshold (HPT), mechanical pain threshold (MPT), wind-up ratio (WUR), and pressure pain threshold (PPT)-was performed at the oral mucosa of the tongue, buccal, and palatal sites in 30 Chinese patients (25 women and 5 men, mean age 50.9 ± 9.2 years) with primary BMS and in 18 age- and gender-matched healthy controls (15 women and 3 men, mean age 53.2 ± 7.0 years). For each BMS patient, z scores and loss/gain scores were computed. Psychologic status was evaluated in both groups using the Self-Rating Anxiety Scale and Self-Rating Depression Scale. Correlations of BMS patients' subjective pain ratings with somatosensory and psychologic profiles were assessed with the use of Pearson or Spearman correlations and multiple linear regression. In BMS patients, 53.3% had somatosensory abnormalities according to z scores vs 22.2% of healthy controls (P = .033). The abnormalities in BMS patients were somatosensory loss to thermal nonnoxious stimuli (TSL = 20.0%, CDT = 13.3%, WDT = 13.3%), mechanical pressure stimuli (PPT = 16.7%), pinprick stimuli (MPT = 6.7%), and thermal pain stimuli (CPT = 3.3%), and somatosensory gain to repetitive pinprick stimuli (WUR = 6.7%), pressure stimuli (PPT = 6.7%), and thermal pain stimuli (HPT = 3.3%). The most frequent loss/gain score was 13.3% for loss of thermal somatosensory function with no somatosensory gain; 13.3% for loss of thermal and mechanical somatosensory function with no somatosensory gain; and 13.3% for gain of mechanical somatosensory function with no somatosensory loss. Mild elevations in anxiety scores were seen in 30% of the BMS patients, and 50% and 36.7% had mild and moderate elevations, respectively, in depression scores. No anxiety or depression was detected in the control group. QST results, but not psychologic scores, were significantly correlated with patients' subjective pain ratings (PHS, Spearman coefficient -0.384, P = .029; CPT, Pearson coefficient -0.370, P = .034; MPT, Pearson coefficient -0.376, P = .032; PPT, Pearson coefficient 0.363, P = .037). The present findings documented distinct differences in somatosensory function in patients with primary BMS compared to controls, indicating a complex pathophysiology and interaction between impairments in nociceptive processing and psychologic functioning.

Somatosensory Loss Influences the Adoption of Self-Centered Versus Decentered Perspectives.

The body and the self are commonly experienced as forming a unity. Experiencing the external world as distinct from the self and the body strongly relies on adopting a single self-centered perspective which results in integrating multisensory sensations into one egocentric body-centered reference frame. Body posture and somatosensory representations have been reported to influence perception and specifically the reference frame relative to which multisensory sensations are coded. In the study reported here, we investigated the role of somatosensory and visual information in adopting self-centered and decentered spatial perspectives. Two deafferented patients who have neither tactile nor proprioceptive perception below the head and a group of age-matched control participants performed a graphesthesia task, consisting of the recognition of ambiguous letters (b, d, p, and q) drawn tactilely on head surfaces. To answer which letter was drawn, the participants can adopt either a self-centered perspective or a decentered one (i.e., centered on a body part or on an external location). The participants’ responses can be used, in turn, to infer the way the left-right and top-bottom letters’ axes are assigned with respect to the left-right and top-bottom axes of their body. In order to evaluate the influence of body posture, the ambiguous letters were drawn on the participants’ forehead, left, and right surfaces of the head, with the head aligned or rotated in yaw relative to the trunk. In order to evaluate the role of external information, the participants completed the task with their eyes open in one session and closed in another one. The results obtained in control participants revealed that their preferred perspective varied with body posture but not with vision. Different results were obtained with the deafferented patients who overall do not show any significant effect of their body posture on their preferred perspective. This result suggests that the orientation of their self is not influenced by their physical body. There was an effect of vision for only one of the two patients. The deafferented patients rely on strategies that are more prone to interindividual differences, which highlights the crucial role of somatosensory information in adopting self-centered spatial perspectives.

Trigeminal nociceptive function and oral somatosensory functional and structural assessment in patients with diabetic peripheral neuropathy

This case-control study primarily compared the trigeminal nociceptive function, the intraoral somatosensory profile and possible structural nerve changes between diabetic peripheral neuropathy (DPN, n = 12) patients and healthy participants (n = 12). The nociceptive blink reflex (nBR) was recorded applying an electrical stimulation over the entry zone of the right supraorbital (V1R), infraorbital (V2R) and mental (V3R) and left infraorbital (V2L) nerves. The outcomes were: individual electrical sensory (I0) and pain thresholds (IP); root mean square (RMS), area-under-the-curve (AUC) and onset latencies of R2 component of the nBR. Furthermore, a standardized full battery of quantitative sensory testing (QST) and intraepidermal nerve fibre density (IENFD) or nerve fibre length density (NFLD) assessment were performed, respectively, on the distal leg and oral mucosa. As expected, all patients had altered somatosensory sensitivity and lower IENFD in the lower limb. DPN patients presented higher I0, IP, RMS and AUC values (p < 0.050), lower warm detection thresholds (WDT) (p = 0.004), higher occurrence of paradoxical heat sensation (PHS) (p = 0.040), and a lower intraoral NFLD (p = 0.048) than the healthy participants. In addition, the presence of any abnormal intraoral somatosensory finding was more frequent in the DPN patients when compared to the reference group (p = 0.013). Early signs of trigeminal nociceptive facilitation, intraoral somatosensory abnormalities and loss of intraoral neuronal tissue can be detected in DPN patients.