Dr S Sooriakumaran FRCP FRCS
Consultant in Rehabilitation Medicine
Among the wide-ranging presentations of chronic pain, phantom limb pain is considered to be the most curious and challenging to overcome. In the United States, about 1.7 million individuals were estimated to be living with limb loss and this number is projected to increase to 3.6 million by the year 2050.
Up to 98% of amputees experience phantom limb in the form of a sensation or pain at some stage in their lifetime. In addition to the profound physical and psychological aftermath of limb amputation, phantom limb pain can be quite debilitating, affecting health-related quality of life. Hence it is crucial for the treating clinicians to be skilled in evidence based recent management.
Over the years, researchers have brought forward different theories to explain phantom limb pain. It is now widely accepted as a form of neuropathic pain involving peripheral, spinal and supraspinal levels. Functional MRI scans have shown cortical reorganisation following amputation with strong correlation with phantom limb pain severity.
Phantom pain can vary in severity and manifest as paraesthesiae – pins and needles; dysaesthesiae – burning/stabbing; and/or allodynia – stimulus that normally does not result in pain.
A multidisciplinary approach to enable amputees to cope better with pain and to improve their function and quality of life should be the goal.
Assessment and treatment
A thorough assessment, including history, physical examination and specific investigations, is crucial to identify treatable causative factors. Adversities in the residual limb, poorly fitting prostheses, general physical and mental health can all trigger phantom pain.
A holistic approach targeting peripheral – desensitisation techniques, transcutaneous electric nerve stimulation, sonographically-guided steroid or botulinum toxin injection, radiofrequency ablation, surgical excisions and targeted muscle reinnervation; spinal cord stimulation; and central neural mechanisms – pharmacotherapy, mirror reflection-induced feedback, virtual and augmented reality are being practiced with varying efficacy.
Perioperative and intermediate to long-term pharmacological treatment is widely used. Medications prescribed include NMDA receptor antagonists, opioids, anticonvulsants, antidepressants and local anaesthetics. Functional prosthetic feedback is known to be an effective therapeutic tool to reduce phantom limb pain.
Up to 98% of amputees experience phantom limb in the form of a sensation or pain at some stage in their lifetime.
Further studies and a multi-disciplinary approach are crucial
Considering the projected increase in global prevalence of amputation, effective management of acute and chronic phantom limb pain is of paramount importance. Further studies are needed to elucidate the peripheral and central mechanisms responsible. Effectiveness of pharmacological, surgical and virtual reality methods need robust evaluation. A multidisciplinary approach to enable amputees to cope better with pain and to improve their function and quality of life should be the goal.