Efficacy and Mechanisms of Virtual Reality Treatment of Phantom Leg Pain

After amputation of an arm or leg, up to 90% of subjects experience a "phantom limb", a phenomenon characterized by persistent feelings of the missing limb. Many subjects with a phantom limb experience intense pain in the missing extremity that is often poorly responsive to medications or other interventions. The proposed work will contrast the efficacy of two virtual reality treatments for phantom limb pain: a 'Distractor' and an Active VR treatment. In the Distractor treatment, participants are engaged in a visually immersive virtual reality experience that does not require leg movements (REAL i-Series® immersive VR experience). In the Active VR treatment, subjects play a series of VR games using the virtual rendering of both legs.

Almost 2 million people in the US have had an amputation and up to 90% of people with limb amputation experience the persistent sensation of the missing extremity, a phenomenon known as a "phantom limb" (Weeks et al., 2010). Additionally, a significant proportion of individuals with a phantom limb - up to 85% in some studies - experience persistent and debilitating pain in the missing limb, a condition known as phantom limb pain (hereafter PLP). Although existing therapies provide pain relief in some cases, there is widespread agreement that current approaches fall short of bringing relief to most individuals with PLP (Weeks et al., 2010).

The investigators recently completed a proof-of-concept study (Ambron et al., 2021) in which eight subjects with below knee amputations (BKA) underwent two virtual reality (VR) treatments for PLP. In an Active VR treatment, subjects played a variety of active games requiring leg movements while receiving high-quality visual feedback of the missing lower leg. Feedback about leg position was provided via an electromagnetic system using leg sensors (trackSTAR, Ascension Technologies Inc), and the program generated an image of the missing lower leg, visible as a first-person avatar. This treatment was contrasted with a "Distractor" treatment, in which participants were engaged in a visually immersive virtual reality experience that did not require leg movements (Cool!TM). Both treatments were associated with significant reductions in pain intensity, but the Active VR treatment was also associated with reductions in pain interference, depression, and anxiety.

The specific aims of the current study are (i) to replicate our prior observations of efficacy of VR treatment in a larger sample of individuals with BKA; (ii) to test VR therapy in patients with above knee amputations; (iii) to compare the efficacy of Active VR treatment to Distractor VR treatment for PLP on measures of pain as well as psychological health and quality of life.

Eligibility Criteria:
Inclusion Criteria:

1. Age 18 - 100 years
2. Capacity to provide Informed Consent
3. Unilateral above or below knee amputation more than 3 months prior to enrollment
4. Absence of cognitive impairment, operationally defined as a Montreal Cognitive Assessment score of 18 or greater
5. Pain averaged over the preceding 1 month in the phantom limb rated as greater than 4 on a scale of 0-10.

Exclusion Criteria:

1. History of significant medical or neurological disorder such as stroke or moderate to severe traumatic brain injury (operationally defined as loss of consciousness for more than 30 minutes)
2. History of significant or poorly controlled psychiatric disorders
3. Current significant depression or anxiety as judged by the Hospital Anxiety and Depression Scale (HADS) (Zigmond \& Snaith, 1983).
4. Current abuse of alcohol or drugs, prescription or otherwise
5. Nursing a child, pregnant, or intent to become pregnant during the study