Sunday, June 14, 2020

Phantom Limb Pain

How many of you have heard of phantom limb pain? The physiotherapists reading this definitely have, but what about my other readers?

Phantom limb pain (PLP) is the feeling of pain in a body part that does not exist (usually amputated because of an  accident or diabetes). Amputees often get phantom limb pain. After amputating a foot, arm or leg from a person, the brain still has that foot, arm or leg mapped. It is not totally clear how and why a person without the physical limb can still have sensations or pain.

Interestingly, it does not just happen in the arms and legs. Phantom breasts, penises and tongues have been reported too (Davis 1993).

Other than pain, patients say sometimes they feel 'it' tingles or itches too. Often PLP symptoms become worse when the person becomes stressed.

PLP tells us about the representation or map of the limb (the 'virtual limb' inside the brain). This is known as the homunculus. Those of you who attended my Kinesio Taping or Floss Band courses would have already heard of this.
The homunculus
It's been a while since I've treated an amputee, but I read about this very interesting case of a woman with PLP. This woman, named RN in the study was born with only three fingers on her right hand. When she was 18, she got into a car accident and several bones in that right hand was broken. Six months later, her doctors decided to amputate that hand.

After amputation, RN reported having pain as though her hand was still there. You would expect her pain to be in the hand with the three fingers she lost. However, she reported feeling five fingers on her painful phantom hand. And they were not five normal fingers. She said her thumb and index finger felt shorter than the rest, but there was definitely five fingers.

RN lived with this phantom hand for many years before seeking help. She was 57 before she saw Dr Ramachandran (a pioneer for phantom limb research). Like what we learnt from David Butler, Dr Ramachandran treated her with the mirror box. After the mirror training, RN reported that her two smaller fingers had grown to normal size. She now feels that she had a normal right hand, that happened not to exist.
David Butler and the mirror box
Super interesting right? RN never had a normal right hand. You would think that her brain wouldn't have the map (or homunculus) to tell her how it may feel like.

To quote Dr Ramachandran : "The amputation of her hand appears to have disinhibited these suppressed finger representations in her sensory cortex and allowed the emergence of phantom fingers that had never existed in her actual hand."

In other words, the brain has a ready-made map (or homunculus) for a normal hand, that was tweaked to accomodate RN's condition. Once the physical hand was amputated, that map was restored.

*pictures taken with my iPhone XS from David Butler's Explain Pain book.


Davis RW (1993). Phantom Sensation, Phantom Pain And Stump Pain. Archives Phy Med Rehab. 120: 1603-1620.

McGeoch PD and Ramachandran VS (2012). The Appearance Of New Phantom Fingers Post-amputation In A Phocomelus. Neurocase. 18(2): 95-97. DOI: 10.1080/13554794.2011.556128.

No comments:

Post a Comment