Drug-Free Noninvasive Thermal Nerve Block: Validation of Sham Devices

Abstract

Headache is a leading cause of disability and suffering. One major challenge in developing device treatments is demonstrating their efficacy given devices' often-high placebo rate. This paper reviews the importance of validating sham devices as part of finalizing the design for larger-scale prospective randomized controlled trials in patients with chronic headache as well as the results of a prospective, single-blind trial to validate two potential sham noninvasive thermal nerve block devices. Study participants were trained to self-administer thermal nerve block treatment using sham devices in an office visit. Two different sham systems with different temperature profiles were assessed. Devices were offered for patients to use daily at-home for one week to assess the durability of sham placebo effects before participants were given active treatment in a second office visit followed by another optional week of self-administered active treatment at-home use. Sham treatments reduced pain scores by an average of 31% from 6.0 ± 2.3 to 4.3 ± 3.3, including two participants who fell asleep during the in-office treatment and woke up with no pain, but whose pain recurred after returning home during at-home use of the sham system. In-office active treatments reduced pain scores by 52% from 6.7 ± 2.1 to 3.3 ± 2.9 with sustained pain relief during optional at-home use. Successful blinding for the study was confirmed with an ideal Bang's Blinding Index of 0 and an ideal James' Blinding Index of 1. Both the sham and active treatments were viewed by participants as highly credible, and credibility increased from the beginning to end of sham treatments on average.

Keywords: chronic pain; drug-free nerve block; sham device; thermal nerve block.

Figure 1

Trial flow diagram. Pink circles represent female participants, blue circles represent the male participant, X indicates the treatment was not conducted because of scheduling difficulties, and # indicates that the patient’s pain scores were excluded from the primary analysis due to taking a triptan (subject #3) or falling asleep (subjects 5 and 7).

Figure 2

Responses to 5-point blinding scale. Error bars show one standard deviation.

Figure 3

Responses to the credibility/expectancy questionnaire administered at the beginning and end of each in-office treatment. Error bars show one standard deviation.

Figure 4

Average DVPRS pain scores before sham and active treatment. Error bars show one standard deviation. * excludes subjects who fell asleep (n = 2) or used acute headache treatment (n = 1).