Relief from intractable phantom pain by combining psilocybin and mirror visual-feedback (MVF)

Introduction

Phantom limb phenomena are extremely common after amputation, with about 95% of amputees experiencing phantom sensations and roughly two-thirds reporting severe phantom limb pain (PLP). Earlier experimental work has linked these phenomena to cortical reorganisation—such as invasion of the deafferented foot area by neighbouring thigh representations in primary somatosensory cortex—and to failures of visuo-motor feedback that can produce a 'learned paralysis' of the phantom. Mirror visual feedback (MVF), in which a mirror superimposes the intact limb's reflection onto the felt location of the phantom, has previously been shown to restore a visuo-motor loop and relieve pain in many patients. The authors also situate their work within the literature on mirror systems, including touch- and pain-related mirror responses in secondary somatosensory and cingulate regions, and suggest these systems may contribute to inter-personal referral of sensation when afferent veto signals are absent. Ramachandran and colleagues present a single-case series of informal experiments in a 35-year-old man (‘‘AL'') with a right lower-leg amputation and intractable PLP. The report focuses on several phenomena: topographic referral of sensation to the phantom, MVF effects including relief of pain and of dysuria-associated pain, referral of warmth from an artificial flame, evocative re-experiencing of implanted nails with a telescoping-nail illusion, and most centrally the effects of psilocybin alone and in combination with MVF. The authors aim to describe these observations, consider mechanisms (notably 5-HT2A-mediated plasticity and cross-modal facilitation), and to raise hypotheses for further controlled work.