This study looks at a non-invasive ear stimulation treatment to better understand nerve pain in people living with HIV. The study aims to assess how the body and nervous system respond to this treatment, including changes in heart function and pain signals. The goal is to learn how future treatments for nerve pain may be improved.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
SINGLE
Enrollment
70
Transcutaneous auricular vagus nerve stimulation (taVNS) will be administered at the cymba concha using hydrogel electrodes and a Digitimer DS8R biphasic constant-current stimulator. Participants will receive 90-minute stimulation sessions consisting of monophasic pulses (pulse width: 500 microseconds; frequency: 25 Hz; duty cycle: 50%). Stimulation intensity will be set at 200% of the participant's sensory perception threshold and may be adjusted up to 5 milliamperes (mA) while remaining below the pain threshold.
Christine E Lynn Rehabilitation Center
Miami, Florida, United States
Change in Short Interval intraCortical Inhibition (SICI)
Short-interval intracortical inhibition (SICI) will be assessed using paired-pulse transcranial magnetic stimulation (TMS) with a MagPro X100 stimulator. Change in SICI will be calculated as the difference between post-intervention and pre-intervention measurements. Negative values indicate increased intracortical inhibition.
Time frame: Baseline (Day 0), Post-trial (Day 14)
Change in Root Mean Square of Successive Differences (RMSSD)
The root mean square of successive differences (RMSSD), will be assessed using a three-lead electrocardiogram (ECG). Change in RMSSD will be calculated as the difference between post-intervention and baseline measurements. Higher RMSSD values indicate greater parasympathetic (vagal) activity and heart rate variability.
Time frame: (Days 1-13), Post-trial (Day 14)
Change in Neuropathic Pain Symptom Severity (NPSI)
Neuropathic pain symptom severity will be assessed using the Neuropathic Pain Symptom Inventory (NPSI), a patient-reported questionnaire that evaluates 10 neuropathic pain symptoms on an 11-point numeric scale ranging from 0 (no symptom) to 10 (worst symptom severity imaginable). The NPSI also includes 2 items assessing the duration of ongoing pain and the frequency of pain attacks. Higher scores indicate greater neuropathic pain symptom severity.
Time frame: Baseline (Day 0), post-trial (Day 14)
Change in Neuropathic Symptom Intensity (Numeric Rating Scale)
Neuropathic symptom intensity will be assessed using the 0-10 Numeric Rating Scale (NRS). Participants will rate the average severity of HIV-associated peripheral neuropathy symptoms from 0 (not bothersome) to 10 (worst imaginable). Higher scores indicate greater symptom intensity.
Time frame: Baseline (Day 0), pre/post each treatment session (Days 1-13), post-trial (Day 14), and at follow up (Day 45)
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Change in Serum Neurofilament Light Chain (NfL)
Serum neurofilament light chain (NfL) will be measured from non-fasted venous blood samples. NfL concentrations (pg/mL) will be quantified using enzyme-linked immunosorbent assay (ELISA). Change in NfL will be calculated as the difference between post-intervention and baseline serum concentrations. Higher concentrations indicate greater neuroaxonal injury.
Time frame: Baseline (Day 0), Post-trial (Day 14)
Change in Serum Interleukin-1 Beta (IL-1β)
Serum interleukin-1 beta (IL-1β) will be measured from non-fasted venous blood samples. IL-1β concentrations (pg/mL) will be quantified using enzyme-linked immunosorbent assay (ELISA). Change in IL-1β will be calculated as the difference between post-intervention and baseline serum concentrations. Higher concentrations indicate greater systemic inflammation.
Time frame: Baseline (Day 0), Post-trial (Day 14)
Change in Serum Tumor Necrosis Factor-Alpha (TNF-α)
Serum Tumor Necrosis Factor-Alpha (TNF-α) will be measured from non-fasted venous blood samples. TNF-α concentrations (pg/mL) will be quantified using enzyme-linked immunosorbent assay (ELISA). Change in TNF-α will be calculated as the difference between post-intervention and baseline serum concentrations. Higher concentrations indicate greater systemic inflammation.
Time frame: Baseline (Day 0), Post-trial (Day 14)
Change in Wind-Up Ratio (WUR)
Wind-up ratio (WUR), will be assessed using responses to repeated pinprick stimuli. Change in WUR will be calculated as the difference between post-intervention and baseline measurements. Lower WUR values indicate reduced temporal summation and decreased central sensitization.
Time frame: Baseline (Day 0), Pre/post each treatment session (Days 1-13), Post-trial (Day 14)
Change in Conditioned Pain Modulation (CPM)
Conditioned pain modulation (CPM), will be assessed using a cold pressor conditioning stimulus (1 to 4°C for 60 seconds) and pressure pain threshold (PPT) testing on the forearm. The CPM effect will be calculated as the percent change in PPT from before to after the conditioning stimulus (%ΔPPT). Higher CPM values indicate greater endogenous pain inhibition.
Time frame: Baseline (Day 0), Post-trial (Day 14)