Virtual Reality and Cranial Nerve Neuromodulation to Manage Chronic Pain

Virtual Reality and Cranial Nerve Neuromodulation in the Management of Chronic Pain in Veterans: a Pilot Study

In Canada, veterans suffer from chronic pain at twice the rate of the general population. This pain is often linked to post-traumatic stress disorder (PTSD), and both have a major impact on their quality of life. The autonomic nervous system (ANS) plays a key role in these pathologies, making its modulation a promising therapeutic target. Virtual reality (VR) is already being used to alleviate pain and PTSD in veterans, mainly by modulating ANS reactivity. Two types of VR exist: prolonged exposure (desensitization) and the calming effect, the latter being better tolerated and more suitable for rebalancing the ANS. However, its effects on pain remain modest and temporary. To reinforce these benefits, it is proposed to combine VR with a new approach called cranial nerve non-invasive neuromodulation (CN-NINM), an innovative technique that allows the generation of a direct flow of neuronal impulses via the stimulation of the tongue. The goal of this project is therefore to document the efficacy of VR and the combination of VR and CN-NINM on pain and ANS in veterans suffering from chronic pain and PTSD. VR, CN-NINM and the combination of the two will be applied for 20 minutes. Clinical pain, experimental pain and ANS reactivity will be assessed before and after the interventions. At the end of this study, it is expected that the investigators will be able to document the type of effect CN-NINM could have, and that it could become a complementary therapeutic option.

In Canada, many veterans suffer from chronic pain, with a prevalence twice as high as that of the general population. Chronic pain is often linked to post-traumatic stress disorder(PTSD). Together, these two conditions impact on the functioning and quality of life of veterans. Recent studies suggest that the autonomic nervous system (ANS) plays a central role in the pathophysiology of chronic pain and PTSD, making it a prime therapeutic target.

Virtual reality (VR) is already being used with veterans, and its effectiveness in relieving pain and PTSD is well documented in veterans, notably by modulating ANS reactivity. Two types of VR approaches are commonly used: VR with prolonged exposure (desensitization) and VR with a calming effect (aimed at normalizing the stress response and SNA reactivity).The latter is better tolerated than prolonged-exposure VR and remains better suited to rebalancing ANS reactivity and relieving symptoms. It calms the ANS and relieves pain (acute and chronic) when combined with traditional rehabilitation, but its effects on pain intensity remain modest and limited in time.

To optimize the benefits of VR, it is proposed to combine VR with a non-pharmacological method, as suggested by experts. This non-pharmacological approach is cranial nerve non-invasive neuromodulation (CN-NINM). CN-NINM is an innovative approach that stimulates the cranial nerves via electrodes placed directly on the tongue; the impulses reach and modulate the activity of ANS structures located in the brainstem. These structures are linked to autonomic functions and pain modulation. This combination could reinforce and prolong the positive effects of VR on veterans' pain.

Objectives: 1) To document the effect of VR (an intervention currently provided) on pain and ANS reactivity in veterans with PTSD, 2) to assess the ability of CN-NINM (vs sham CN-NINM) to potentiate the effects of VR on pain and on ANS reactivity.

Methods: In this within-subjects factorial crossover design, 15 veterans will be recruited. Sociodemographic, pain and PTSD-related variables will be collected to confirm participant eligibility. Prior to the interventions, participants will undergo an assessment of both clinical pain (intensity and unpleasantness of pain, numerical scale 0-10) and experimental pain. The tonic thermal experimental pain paradigm involves the application of a thermode (hotplate) to participants' forearms. Thermal nociceptive stimuli will be induced for 2 minutes on the participants' forearm using the thermode. Although the temperature remains constant for the entire 2 minutes, the participant will be informed that the temperature may increase, decrease, or remain stable during the procedure. The participant will then, at all times, evaluate the intensity of the pain with a visual analogue scale connected to a computer(CoVAS: visual analogue scale from 0 to 100).

Additionally, participants will complete clinical questionnaires assessing anxiety, pain and PTSD-related symptoms. Various autonomic measures (blood pressure, heart rate reactivity [HRV], electrodermal response) will also be taken to characterize ANS reactivity before and after each intervention. Participants will receive the 3 interventions (VR, VR+CN-NINM and VR+ sham CN-NINM) randomly assigned. The VR headset will broadcast calming images for 20 minutes. CN-NINM will be applied, using a portable stimulator, placed directly on the tongue of the participants for 20 minutes simultaneously with VR.

Inclusion Criteria:

1. Be a veteran;
2. Be ≥30 years old;
3. Have a diagnosis of chronic musculoskeletal pain (pain > 6 months);
4. Have been diagnosed with PTSD by a health professional and/or have a PTSD Checklist for DSM-5 (PCL-5) score > 30/80 and
5. Speak English or French.

Exclusion Criteria:

1. Bipolar disorder, psychosis;
2. Neuropathic pain (based on the Neuropathic Pain Diagnosis and Questionnaire (DN4));
3. Visual disorders or photosensitivity, color blindness;
4. Epilepsy, motion sickness and
5. Any containdications to CN-NINM.