Body Representation among Adults with Phantom Limb Pain: Results from a Foot Identification Task.

Abstract

BACKGROUND\nImpaired body representation (i.e., disrupted body awareness or perception) may be a critical, but understudied, factor underlying phantom limb pain. This cross-sectional study investigated whether adults with lower-limb loss and phantom limb pain demonstrate impaired body representation as compared to pain-free peers with and without lower-limb loss.\n\n\nMETHODS\nParticipants (n=41 adults with phantom limb pain, n=27 pain-free peers with lower-limb loss, n=39 controls with intact limbs) completed an online foot identification task. Participants judged whether randomized images depicted left or right feet (i.e., left-right discrimination) as quickly as possible without limb movement. Using two Generalized Estimating Equations, effects of group, image characteristics (i.e., side, foot type, view, angle) and trial block (i.e., 1-4) were evaluated, with task response time and accuracy as dependent variables (a≤.050).\n\n\nRESULTS\nAdults with phantom limb pain demonstrated slower and less accurate performance as compared to controls with intact limbs (p=.018) but performed similarly to pain-free peers with lower-limb loss (p=.394). Significant 3-way interactions of group, view, and angle indicated between-group differences were greatest for dorsal-view images, but smaller and angle-dependent for plantar-view images. While all groups demonstrated significant response time improvements across blocks, improvements were greatest among adults with phantom limb pain, who also reported significant reductions in pain intensity.\n\n\nCONCLUSIONS\nAdults with phantom limb pain demonstrate body representation impairments as compared to controls with intact limbs. Body representation impairments, however, may not be unique to phantom limb pain, given similar performance between adults with and without phantom limb pain following lower-limb loss.