All about the Phantom Limb Syndrome

Phantom limb syndrome is a very fascinating concept that has intrigued me ever since I first heard about it around 6 months ago in my Introduction to Neuropsychology class. What can we infer from the term ‘phantom limb’? A ghost limb. But what does that mean?

Imagine a soldier loses an arm after a long and tough war. Despite not having the arm, he still experiences sensations as if the arm is still there. These sensations can be shooting pain, the light pressure exerted by clothing, numbness, cramping, or tickling.

The phantom limb syndrome is the ability to feel sensations in a limb or limbs that are missing or have been amputated. It has been found that almost 80-100% of those who have gone through amputation experience phantom limb syndrome. These people might try and feel like they are gesturing, itching, or reaching out for something with their phantom limb. The pain can worsen with stress or anxiety. Most people tend to experience this for almost 6 months after the amputation surgery. For some people, the pain can improve without treatment over time; whereas, for others, the pain may get too difficult to cope up with and can last their whole lifetime.

The symptoms, as mentioned, are felt in a limb that no longer exists. The symptoms usually have an onset within the first week of the amputation of the limb. However, in some cases, the onset can get delayed by months. The pain can be in all forms- shooting, stabbing, pins, and needles, crushing, throbbing, cramping, or burning. This pain can be continuous or can come and go occasionally.

While the exact cause of this syndrome is still not very clear, studies have shown that it is majorly caused due to the changes that occur in the cortex of the brain following the amputation of a limb. The brain continues receiving signals from nerve endings that used to supply signals to and from the now missing limb. Through the use of imaging techniques like Magnetic Resonance Imaging (MRI) and Positron Emission Tomography (PET), parts of the brain that were originally connected to the missing limb gets activated when the individual experiences phantom pain. In order to adjust to the loss of input from the missing limb, the brain and spinal cord rewire themselves and this can trigger pain, the most basic signal from the body indicating that something is not right.

It has also been found that when a part of the body goes missing (a limb, in this case), the brain can remap that part of the body’s sensory circuitry system to another part of the body. For example, if one gets their arm amputated since that area is no longer able to receive sensory information, this information is assigned to another part of the body- say the forehead. So when the forehead is touched, the individual might feel like his or her missing arm is being touched too. This can also result in pain as it is just another form of tangled sensory wiring. Numerous other factors can contribute to phantom pain such as damaged nerve endings, scar tissues at the location of amputation, and the physical memory of the pain in the affected area before amputation was done.

Not everyone who goes through amputation experiences phantom pains. There exist certain risk factors that can make one more likely to develop this syndrome. Some researchers suggest that the presence of pre-amputation pain can increase the chances of one developing phantom pain once the amputation of the limb is done. This is because the brain keeps holding on to the memory of the pain and continues to send pain signals even after the limb is amputated. Other risk factors are the presence of a blood clot at the site of amputation, previous damage to the brain or spinal cord, a traumatic experience of amputation, infection present before amputation, or certain types of anesthesia used during the amputation procedure.

While most people recover from phantom pains soon enough, methods are undertaken to reduce the symptoms and the pains for those who do not. These treatment methods are subjective to the case and the extent of the pain. Some patients find coping techniques such as muscle relaxation, meditation, hypnosis, and biofeedback helpful in relieving pain. Medicines like antidepressants, anticonvulsants, antipsychotics, and muscle relaxers help manage the symptoms. Other times, nonsurgical methods such as acupuncture, shock therapy, transcutaneous electrical nerve stimulation (wherein a tiny electric current is sent through the skin to the neighboring nerves), and transcranial magnetic stimulation (wherein a strong magnetic pulse is sent through the scalp into the brain) are used to reduce symptoms. When non-invasive techniques fail to work, invasive techniques such as spinal cord stimulation (insertion of an electrode near the spinal cord), intrathecal drug delivery, and deep brain stimulation are employed.

Another interesting method of treatment that has had the extent of success is mirror-box therapy. It was developed in the 1990s and helps alleviate pain linked to ‘learned paralysis’. This is often experienced by individuals whose limbs were paralyzed before they were amputated.

The mirror-box is roofless and has a mirror in the middle. The patient is instructed to place their unaffected limb in front of the mirror. The person then looks at the mirror and sees the reflection of the intact limb. This method essentially tricks the brain into ‘seeing’ the phantom limb. The person can try moving the intact arm, causing the brain to believe that the phantom limb is moving as well. This reflection can help reorganize and integrate the mismatch between the proprioception and the visual feedback of the missing part. This causes the brain to relieve the learned paralysis and its associated pain. It has been postulated that a cortical restructuring occurs in the brain through this method and this causes the relieving from pain.

Phantom limb syndrome continues to fascinate researchers worldwide and studies to understand its underlying mechanisms are constantly being conducted.

References:

Phantom pain. (2020, October 29). Retrieved December 14, 2020, from https://www.mayoclinic.org/diseases-conditions/phantom-pain/symptoms-causes/syc-20376272

Phantom Limb Syndrome. (n.d.). Retrieved December 14, 2020, from https://www.winchesterhospital.org/health-library/article?id=96857

Phantom limb syndrome. (n.d.). Retrieved December 14, 2020, from https://www.britannica.com/science/phantom-limb-syndrome

Cheriyedath, S. (2019, February 27). What is a Phantom Limb? Retrieved December 14, 2020, from https://www.news-medical.net/health/What-is-a-Phantom-Limb.aspx

Kim, S. Y., & Kim, Y. Y. (2012). Mirror therapy for phantom limb pain. The Korean journal of pain, 25(4), 272–274. https://doi.org/10.3344/kjp.2012.25.4.272

Phantom limb. (2020, October 28). Retrieved December 14, 2020, from https://en.wikipedia.org/wiki/Phantom_limb

Development, W. (2019, February 28). Mirror Therapy. Retrieved December 15, 2020, from https://www.amputee-coalition.org/resources/mirror-therapy/