Abstract|Pain 1| Volume 357, SUPPLEMENT 1, e91, October 15, 2015

Bedside neuromodulation of persistent pain and allodynia using caloric vestibular stimulation: an effectiveness trial

      Background: Caloric vestibular stimulation (CVS) is widely applied for neurological diagnosis but is also a safe, inexpensive, non-invasive neuromodulation technique. Case studies report short and sustained therapeutic effects of CVS in persistent pain (PP).
      Objective: Conduct an effectiveness trial of CVS in phantom limb pain (n = 8), spinal cord injury pain (n = 12), complex regional pain syndrome (CRPS; n = 14) and non-specific PP (n = 4).
      Patients and methods: Thirty-eight participants (19 males; mean age = 45.6 years) underwent 1–3 sessions of iced-water CVS. All but four also underwent a cold-arousal control (ice-pack to forehead). Subjective pain and light touch allodynia numerical rating scores (NRS) were collected pre- and post-CVS. The study was IRB-approved.
      Results: MANOVA showed significant interaction of time by intervention (F[2,32] = 3 · 99, p < 0.05). Univariate tests revealed pain scores differed significantly between CVS and control (F[1,33] = 17.30, p < 0.01). Pain was significantly lower 30 minutes post-CVS (M = 3.44, SD = 2.62) than post-control (M = 4.25, SD = 2.79; t(33) = −3.77, p < 0.01). Average reductions were 24.8% for CVS (1.13 NRS points, SD = 1.67) and 6.4% for control (0.29 points, SD = 1.21). The strongest CVS PP responses lasted up to one week. Importantly, CVS induced clinically significant allodynia reductions in three of nine CRPS patients with allodynia (10/10 to 2/10; 6/10 to 3/10; 2/10 to 0/10), lasting 24 hours to one month. CVS was well-tolerated (one patient had vomiting).
      Conclusion: Examination is required of repeated CVS (several times/week for several weeks) to increase PP reductions from statistically to clinically significant, increase the proportion of clinically significant allodynia responders, and assess other allodynia conditions (e.g. post-herpetic, trigeminal and occipital neuralgia).