Phantom limb experience after brachial plexus anaesthesia

There are more than two million amputees in the USA, and almost all will experience phantom limb sensations (PLS), describing the missing limb as still present. They may also experience intense pain, known as phantom limb pain (PLP), a considerable factor in poor quality of life. In some upper extremity amputees and following brachial plexus avulsion injury (BPAI), hand digits can be detected and mapped to distinct facial skin areas, termed hand-to-face remapping. In this study, we analysed PLS following brachial plexus anaesthesia (BPA) administered prior to upper limb surgeries. Our 39 participants had planned shoulder, wrist or hand surgery. We sought to determine the time course for the emergence of phantom limb experiences after BPA up to the following 24 hours in participants with intact limbs. We also investigated whether there was hand-to-face remapping, suggesting potential cortical reorganization, or changes in proprioception before and after the induction of BPA. Twenty (54%) participants reported PLS immediately after the onset of BPA (T2), and 28 (72%) participants altered proprioception (AP) after surgery (T3). However, neither PLP nor hand mapping onto the face was reported or evoked. PLS were seen earlier than AP. We conclude that PLS arise rapidly after BPA-induced temporary deafferentation of the upper limb and might serve as a model for the permanent deafferentation experienced in individuals with a major upper limb amputation or BPAI. These results contribute to defining a time course for changes after BPA and increase our understanding of how phantom limb phenomena might arise following limb amputation or BPAI.