Phantom Limbs

By Nicole Yeung

Many amputees have reported pains that persist for decades - sometimes even for a lifetime. However, these pains exist in limbs that have already been amputated. American physician Silas Weir Mitchell, who visited American Civil War soldiers experiencing such discomfort, coined the term “phantom limb” to refer to these cases. But how can we treat pain in a limb that doesn’t exist?

The “phantom limb” phenomenon occurs when one perceives sensations in a body part that no longer exists. These can be painless, like temperature, pressure, or itching, or painful sensations like burning or tingling. For example, numerous patients with removed bladders still endure intense needs to urinate. Others feel ulcer pains after their ulcer and nerves are extracted. Patients can also experience motions in phantom limbs, such as an amputated arm waving to greet someone or reaching for falling items.

Initially, some researchers believed amputees were denying having lost a limb, causing the sensations there. Others trimmed the amputated limbs and nerves even farther back in hopes of uncovering the root source. They assumed that the pains would vanish after cutting back the limb, but the sensations persisted.

Ramachandran, an MD specialist in neurology, speculated that phantom limbs were a result of merged brain maps. A study by Tim Pons and Edward Taub, which outlined how brain maps for Silver Spring monkeys’ arms processed input from their faces, caught Ramachandran’s attention. The research demonstrated that the face maps were “invading” the arm maps because they were next to each other. This led Ramachandran to suspect that a similar case was occurring with amputees and their phantom limbs. Could their face maps have intruded upon their arm maps?

Ramachandran’s theory was tested when 17-year-old Tom Sorenson (a pseudonym) underwent an amputation above his elbow. Four weeks after his amputation, Sorenson began feeling a phantom limb that replaced his missing arm. A peculiarity soon bothered him: Sorenson had an itch on his phantom limb that he couldn’t scratch. When Ramachandran met Sorenson, he blindfolded him and brushed parts of his body with a Q-tip. As the Q-tip skimmed over Sorenson’s upper lip, not only did he feel it there, but he also felt it in the index finger of his phantom limb. Ramachandran dribbled a drop of water on Sorenson’s cheek, who then felt it trickle down his cheek and phantom limb. This led Ramachandran to discover that he could relieve Sorenson’s itch by scratching his cheek. A magnetoencephalography (MEG) brain scan later confirmed that Sorenson’s hand and face maps overlapped: the map for his hand now processed input from his face. 

Ramachandran’s research proved the plasticity of brain maps. When someone amputates their limb, they may begin to perceive sensations that replace their missing body part. These perceptions are caused by map expansion neuroplasticity, where brain maps that typically process certain regions overtake others. Further studies using mirror boxes indicate that phantom limbs can be manipulated so that amputees can visually “see” and train “movement” in their missing limbs. 

Works Cited:

• Doidge, Norman. The Brain That Changes Itself: Stories of Personal Triumph from the Frontiers of Brain Science. Melbourne, Scribe, 2007.

• Hanyu-Deutmeyer AA, Cascella M, Varacallo MA. Phantom Limb Pain. [Updated 2023 Aug 4]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK448188/

• Rugnetta, Michael. “Phantom limb syndrome | Neurophysiology | Britannica.” Encyclopædia Britannica, 2019, www.britannica.com/science/phantom-limb-syndrome.