Predicting Post-Stroke Somatosensory Function from Resting-State Functional Connectivity: A Feasibility Study

Accumulating evidence shows that brain functional deficits may be impacted by damage to remote brain regions. Recent advances in neuroimaging suggest that stroke impairment can be better predicted based on disruption to brain networks rather than from lesion locations or volumes only. Our aim was to explore the feasibility of predicting post-stroke somatosensory function from brain functional connectivity through the application of machine learning techniques. Somatosensory impairment was measured using the Tactile Discrimination Test. Functional connectivity was employed to model the global brain function. Behavioral measures and MRI were collected at the same timepoint. Two machine learning models (linear regression and support vector regression) were chosen to predict somatosensory impairment from disrupted networks. Along with two feature pools (i.e., low-order and high-order functional connectivity, or low-order functional connectivity only) engineered, four predictive models were built and evaluated in the present study. Forty-three chronic stroke survivors participated this study. Results showed that the regression model employing both low-order and high-order functional connectivity can predict outcomes based on correlation coefficient of r = 0.54 (p = 0.0002). A machine learning predictive approach, involving high- and low-order modelling, is feasible for the prediction of residual somatosensory function in stroke patients using functional brain networks.

Effects of Textured Insoles on the Balance of Individuals with Knee Osteoarthritis in Dynamic Perturbations

The effectiveness of adding plantar-surface texture to improve balance has been demonstrated in a variety of demographics. It is critical to investigate whether textured insoles can improve balance in people with knee osteoarthritis (OA), who have compromised the somatosensory function of the affected joint and, as a result, are at a higher risk of falling. Thus, this study investigated the degree of benefit from the use of textured insoles for improving balance and compared the balance of people with knee OA to healthy matched peers. This study included eighteen people with knee OA and eighteen healthy, aged, gender, height, weight, and BMI matched controls who were assessed on balance using the sensory organization test and the motor control test. Balance was improved in both groups when the textured insoles were worn, and the healthy knee group demonstrated significantly better balance performance than the knee OA group. The benefits of this study for individuals with knee OA are that it may lead to the development of an evidence-based footwear intervention that is noninvasive, simple to use, and inexpensive, in addition to allowing the user to self-manage and the ability to reduce the risk of falls, thereby improving their quality of life.

Age Differences in Multi-modal Quantitative Sensory Testing and Associations with Brain Volume

Background and Objectives Somatosensory function is critical for successful aging. Prior studies have shown declines in somatosensory function with age; however, this may be impacted by testing site, modality, and biobehavioral factors. While somatosensory function declines are associated with peripheral nervous system degradation, little is known regarding correlates with the central nervous system and brain structure in particular. The objectives of this study were to examine age-related declines in somatosensory function using innocuous and noxious stimuli, across two anatomical testing sites, with considerations for affect and cognitive function, and associations between somatosensory function and brain structure in older adults. Research Design and Methods A cross-sectional analysis included 84 ‘younger’ (n = 22, age range: 19-24 years), and ‘older’ (n = 62, age range: 60-94 years) healthy adults who participated in the Neuromodulatory Examination of Pain and Mobility Across the Lifespan (NEPAL) study. Participants were assessed on measures of somatosensory function (quantitative sensory testing), at two sites (metatarsal and thenar) using standardized procedures, and completed cognitive and psychological function measures, and structural MRI. Results Significant age x test site interaction effects were observed for warmth detection (p=0.018, partial eta 2=0.10) and heat pain thresholds (p=0.014, partial eta 2=0.12). Main age effects were observed for mechanical, vibratory, cold, and warmth detection thresholds (p’s<0.05), with older adults displaying a loss of sensory function. Significant associations between somatosensory function and brain grey matter structure emerged in the right occipital region, the right temporal region, and the left pericallosum. Discussion and Implications Our findings indicate healthy older adults display alterations in sensory responses to innocuous and noxious stimuli compared to younger adults and, furthermore, these alterations are uniquely impacted by anatomical site. These findings suggest a non-uniform decline in somatosensation in older adults, which may represent peripheral and central nervous system alterations part of aging processes.

Drop homotopic effects of masseter-muscle pain on somatosensory sensitivity in healthy participants

Current pain classifications use 1.0-kg palpation of the masseter muscle to distinguish between “pain patients” and “healthy controls” but a thorough understanding of the normal physiological responses to various somatosensory stimuli is lacking. The aim of this study was to investigate somatosensory function of the skin over the masseter muscle in healthy participants that were divided into a masseter pain prone group (MPP) (n = 22) and non-MPP group (n = 22), according to the response to a 1.0-kg palpation. Quantitative sensory testing (QST) was performed at the skin above the right masseter muscle (homotopic). In an additional experiment, 13 individuals each from MPP and non-MPP received application of 60% topical lidocaine tape to the skin over the masseter muscle for 30 min. Immediately after, mechanical pain sensitivity (MPS), dynamic mechanical allodynia, and pressure pain threshold were tested. Homotopic MPS was significantly higher and PPTs significantly lower in MPP than in N-MPP (P < 0.05). Strikingly, no other differences in QST outcomes were observed between the groups (P > 0.05). After lidocaine application, no significant differences in homotopic MPS were observed between groups. The presence or absence of acute provoked pain in masseter muscle is exclusively associated with differences in homotopic MPS which is decreased following topical anesthesia.

Foot and ankle somatosensory deficits in children with cerebral palsy: A pilot study

PURPOSE: To investigate foot and ankle somatosensory function in children with cerebral palsy (CP). METHODS: Ten children with spastic diplegia (age 15 ± 5 y; GMFCS I–III) and 11 typically developing (TD) peers (age 15 ± 10 y) participated in the study. Light touch pressure and two-point discrimination were assessed on the plantar side of the foot by using a monofilament kit and an aesthesiometer, respectively. The duration of vibration sensation at the first metatarsal head and medial malleolus was tested by a 128 Hz tuning fork. Joint position sense and kinesthesia in the ankle joint were also assessed. RESULTS: Children with CP demonstrated significantly higher light touch pressure and two-point discrimination thresholds compared to their TD peers. Individuals with CP perceived the vibration stimulus for a longer period compared to the TD participants. Finally, the CP group demonstrated significant impairments in joint position sense but not in kinesthesia of the ankle joints. CONCLUSIONS: These findings suggest that children with CP have foot and ankle tactile and proprioceptive deficits. Assessment of lower extremity somatosensory function should be included in clinical practice as it can guide clinicians in designing more effective treatment protocols to improve functional performance in CP.