The science behind phantom limb pain

Losing a limb does not always mean losing the sensations associated with it.

Key points

• The condition can affect a person well beyond the physical sensation itself.
• The sensation can feel particularly different from one person to another and may not always be straightforward to describe.
• A number of factors can influence how a person experiences pain after an amputation, making each case different.
• The nervous system can continue responding to changes after an amputation.

Losing a limb does not always mean losing the sensations associated with it. For some amputees, pain can continue to be felt in a hand, arm, leg, or foot that is no longer physically present. Known as phantom limb pain (PLP), the condition can affect everyday life in ways that are often tough for others to understand. With September observed as Pain Awareness Month, understanding the science behind this experience can support those living with it recognise the condition and seek the right backing.

Notably, the condition can affect a person well beyond the physical sensation itself. Dr Amarnath Reddy B, consultant in pain management at Yashoda Hospitals, highlights its wider impact on everyday life. "After amputation, approximately two-thirds of individuals experience PLP, with pooled estimates of 64 percent. PLP can interfere with sleep, mobility, prosthetic employ, employment, and social activities, and can additionally cause physical pain in the missing limb. This can lead to anxiety, depression, and a lower quality of life, " notes Dr Amarnath.

Meanwhile, the sensation can feel particularly different from one person to another and may not always be straightforward to describe. Dr Joy Mounica, consultant neurologist at Renova Hospitals, Langar Houz, explains the different ways it can be experienced. "PLP is described as the perception of pain originating from a limb that has been amputated or is otherwise absent. PLP can vary in intensity, duration, and quality, ranging from throbbing or stabbing sensations to burning or cramping feelings. PLP typically occurs within six months after limb loss. High prevalence rates are seen in lower limb amputations, " shares Dr Joy.

Notably, a number of factors can influence how a person experiences pain after an amputation, making each case different. Dr Amarnath outlines the range of treatments available depending on the individual's needs. "Gabapentinoids, antidepressants, opioids, NMDA receptor antagonists, physical and occupational therapy, mirror therapy, nerve blocks, neuromodulation (rTMS, tDCS, spinal cord or peripheral nerve stimulation), and, in certain situations, surgical interventions are among the options available today. Conventional medications frequently provide little to no relief, " he notes.

For context, the nervous system can continue responding to changes after an amputation. It may contribute to the pain experienced by some patients. Dr Joy explains, "PLP may arise from maladaptive changes in the neuromatrix, which can generate internal patterns of pain that the brain then localises to the amputated limb."

One approach that has gained attention is mirror therapy. It uses visual feedback to support the brain adapt to the loss of a limb. Dr Amarnath describes, "Mirror therapy creates a straightforward visual illusion in which the brain 'sees' both limbs moving painlessly by placing the reflection of the intact limb where the missing limb would be. Through neuroplasticity, this visual-motor feedback reduces pain signals and recalibrates maladaptive brain maps. Studies show significant pain reductions in plenty of patients, including an RCT where 89 percent of upper-limb amputees improved. It is most useful for post-amputation PLP and is additionally employed in complex regional pain syndrome (CRPS), " notes Dr Amarnath.

Dr Joy points to the importance of combining different forms of care. "Treatment of PLP involves a multimodal approach that combines pharmacotherapy, physical therapy, psychological interventions and adjuvant therapies such as transcutaneous electrical nerve stimulation (TENS), mirror therapy, biofeedback, acupuncture, massage and electroconvulsive therapy (ECT), " she adds.

PLP should therefore not be dismissed as something a person has to live with. With timely care, rehabilitation, psychological backing and appropriate treatment, relief and a better quality of life are feasible.

For now, the science behind phantom limb pain remains the part of the story worth watching, and further updates are likely as more details are confirmed.