Human Studies

Whiplash injury is common following road traffic crashes affecting millions worldwide, with up to 50% of the injured developing chronic symptoms and 15% having a reduced working capability due to ongoing disability. Many of these patients receive treatment in primary care settings based upon clinical and diagnostic imaging findings. Despite the identification of different types of injuries in the whiplash patients, clinically significant relationships between injuries and chronic symptoms remains to be fully established. This study investigated the feasibility of magnetic resonance imaging (MRI) techniques including quantitative diffusion weighted imaging and measurements of cerebrospinal fluid (CSF) flow as novel non-invasive biomarkers in a population of healthy volunteers and chronic whiplash patients recruited from a chiropractic clinic for the purpose of improving our understanding of whiplash injury.

Objective Small area electrodes enable preferential activation of nociceptive fibers. It is debated, however, whether co-activation of large fibers still occurs for the existing electrode designs. Moreover, existing electrodes are limited to low stimulation intensities, for which behavioral and physiological responses may be considered less reliable. A recent optimization study showed that there is a potential for improving electrode performance and increase the range of possible stimulation intensities. Based on those results, the present study introduces and tests a novel planar concentric array electrode design for small fiber activation in healthy volunteers. Approach Volunteers received electrical stimulation with the planar concentric array electrode and a regular patch electrode. Perception thresholds were estimated at the beginning and the end of the experiment. Evoked cortical potentials were recorded in blocks of 30 stimuli. For the patch, stimulation intensity was set to two times perception threshold (PT), while three intensities, 2, 5, and 10 times PT, were applied with the planar concentric array electrode. Sensation quality, numerical-rating scores, and reaction times were obtained for each PT estimation and during each block of evoked potential recordings. Main results Stimulation with the patch electrode was characterized as dull, while stimulation with the planar concentric array electrode was characterized as sharp, with increased sharpness for increasing stimulus intensity. Likewise, NRS scores were higher for the planar concentric array electrode compared to the patch and increased with increasing stimulation intensity. Reaction times and ERP latencies were longer for the planar concentric array electrode compared to the patch. Significance The presented novel planar concentric array electrode is a small, non-invasive, and single-use electrode that has the potential to investigate small fiber neuropathy and pain mechanisms, as it is small fiber preferential for a wide range of stimulation intensities.

Sleep deprivation has been shown to increase pain intensity and decrease pain thresholds in healthy subjects. In chronic pain patients, sleep impairment often worsens the perceived pain intensity. This increased pain perception is the result of altered nociceptive processing. We recently developed a method to quantify and monitor altered nociceptive processing by simultaneous tracking of psychophysical detection thresholds and recording of evoked cortical potentials during intra-epidermal electric stimulation. In this study, we assessed the sensitivity of nociceptive detection thresholds and evoked potentials to altered nociceptive processing after sleep deprivation in an exploratory study with 24 healthy male and 24 healthy female subjects. In each subject, we tracked nociceptive detection thresholds and recorded central evoked potentials in response to 180 single- and 180 double-pulse intra-epidermal electric stimuli. Results showed that the detection thresholds for single- and double-pulse stimuli and the average central evoked potential for single-pulse stimuli were significantly decreased after sleep deprivation. When analyzed separated by sex, these effects were only significant in the male population. Multivariate analysis showed that the decrease of central evoked potential was associated with a decrease of task-related evoked activity. Measurement repetition led to a decrease of the detection threshold to double-pulse stimuli in the mixed and the female population, but did not significantly affect any other outcome measures. These results suggest that simultaneous tracking of psychophysical detection thresholds and evoked potentials is a useful method to observe altered nociceptive processing after sleep deprivation, but is also sensitive to sex differences and measurement repetition.

The aim of this study was to evaluate and compare the effects of extracorporeal shock wave therapy (ESWT) and high-intensity laser therapy (HILT), as outpatient physical therapy modalities, on knee osteoarthritis (KOA) patients. The treatment program was completed by 40 individuals with stage II KOA (according to Kellgren and Lawrence) who were randomly allocated to one of two groups. They have had more than grade 3 pain on the visual analog scale (VAS) during activities for the last 3 months, with body-mass index less than 30 and no history of knee operation, fracture, cancer, or other neuromuscular or musculoskeletal diseases that may affect study results. The ESWT group ( = 20, mean age = 40.12 ± 9.45 years) received ESWT, 0.05 mJ/mm, one session/week for 4 weeks, and the HILT group ( = 20, mean age = 46.62 ± 8.68 years) received HILT, 1500 mJ/cm in each session, three sessions/week for 4 weeks. Both groups received conservative physical therapy programs. Before and after 4 weeks of intervention, pain, physical function, and disability were assessed using a VAS, 6-min walking test, and the Western Ontario and McMaster Universities Osteoarthritis Index. When the pre- and post-treatment mean values of dependent variables of both groups were compared, there were statistically significant improvements in both groups. Significant differences in the measured variables were also discovered in favor of the HILT group compared with the ESWT group. HILT showed a superior effect compared with ESWT on pain, physical function, and disability in chronic KOA patients. Pan African Clinical Trials Registry number: PACTR202007638955907.