Background: Effective interventions are needed for individuals with persisting post-concussion symptoms. High-resolution, relational, resonance-based, electroencephalic mirroring (HIRREM®) is an allostatic, closed-loop, acoustic stimulation neurotechnology, designed to facilitate relaxation and self-optimization of neural oscillations.
Methods: Fifteen athletes (seven females, mean age 18.1 years, SD 2.6) with persisting post-concussion symptoms received 18.7 (SD 6.0) HIRREM sessions over a mean of 29.6 (SD 23.2) days, including 11.3 (SD 4.6) in office days. Pre- and post-HIRREM measures included the Rivermead Post-Concussion Symptoms Questionnaire (RPQ, n = 12), the Insomnia Severity Index (ISI, n = 15), the Center for Epidemiologic Studies Depression Scale (CES-D, n = 10), short-term blood pressure and heart rate recordings for measures of autonomic cardiovascular regulation (n = 15), and reaction time by the drop-stick method (n = 7). All participants were asked about their physical activity level and sports participation status at their post-HIRREM data collection visit and 1 to 3 months afterward.
Results: At the post-HIRREM visit, subjects reported improvements in all three inventories (RPQ mean change 19.7, SD 11.4, Wilcoxon p = 0.001; ISI mean change -4.1, SD 4.1, Wilcoxon p = 0.003; CES-D mean change -12.0, SD 10.0, Wilcoxon p = 0.004), including statistically significant reductions in 14 of the 16 individual items of the RPQ. There were also statistically significant improvements in baroreflex sensitivity, heart rate variability in the time domain (SDNN), and drop-stick reaction testing (baseline mean distance of 23.8 cm, SD 5.6, decreased to 19.8 cm, SD 4.6, Wilcoxon p = 0.016). Within 3 months of the post-HIRREM data collection, all 15 had returned to full exercise and workouts, and ten had returned to full participation in their athletic activity.
Conclusions: The use of HIRREM by a series of athletes with persisting post-concussion symptoms was associated with a range of improvements including, for the majority, return to full participation in their sport. The findings do not appear to be consistent with constituents of the placebo effect. A larger controlled trial is warranted.
Keywords: Allostasis; Baroreflex sensitivity; HIRREM; Heart rate variability; Neurotechnology; Persisting post-concussion symptoms; Post-concussion syndrome; Reaction time; Return to play; Sports concussion.