Advancing innovative techniques for managing post-limb loss pain

The American Congress of Rehabilitation Medicine (ACRM) 2022 annual conference featured several limb loss or amputation-focused presentations. In this article, I focus on the latest techniques for managing phantom limb pain.

What is phantom limb pain?

Phantom limb pain is a perception of pain that can occur in any part of the body that no longer exists. Phantom limb pain is perceived to originate from the lost limb, beyond the level of the amputation.

There is a spectrum of phantom limb symptoms from non-painful to painful. Non-painful symptoms include tingling, numbness, itchiness and heat. Painful symptoms, on the other hand, encompass burning, cramping, throbbing and shooting or stabbing pain.

Why do amputees suffer from phantom limb pain?

There are various theories as to what causes phantom limb pain. The concept of neuromatrix representation is based on the representation of one’s body. Following an amputation, an individual’s cerebral and peripheral body representations mismatch, therefore causing pain. Further, the lack of visual feedback or cue from the lost limb adds to the pain.

Cortical reorganisation theory also offers a hypothesis as to the mechanism of phantom pain. According to this theory, neurons that previously received stimulus before a limb was amputated now respond to new signals from other nearby neurons, causing the brain to perceive sensations in the amputated limb.

Treatments for phantom limb pain

Non-invasive treatments

One presenter noted that proprioception and visualisation can lower phantom limb pain, as evidenced by visualisation techniques such as using mirrors or looking at footage of the limb before it was amputated. Research suggests that these techniques can help ease phantom pain by ‘tricking’ the brain into thinking that the lost limb is present. Similarly, virtual reality therapy allows the patient to visualise the lost limb by relying on visual feedback.

Transcutaneous electrical nerve stimulation (TENS) has been recommended as a non-invasive treatment option for phantom limb pain and muscle spasm. It involves the use of low-voltage electric currents to prevent signals reaching the brain. It can also be used to increase blood flow and increase the patient’s level of endorphins.

For some amputees, phantom limb pain can be eased by using relatively inexpensive over the counter creams and oils with cooling and warming properties.

Residual limb covers aimed at preventing exposure of nerve endings to the residual limb to electric fields have been claimed to reduce phantom limb pain and were also discussed at the conference.

Invasive treatments

Although a patient may have undergone an amputation, the brain still creates signals that go to the nerves. Researchers have therefore focused on whether these signals can be targeted in order to both control an artificial limb and reduce, if not eradicate, phantom and neuroma pain. Randomised control trials have shown that targeted muscle reinnervation (TMR) can be highly effective in reducing pain.

Comment

In the context of an amputation claim, rehabilitation for an amputee can set the tone for how the claim progresses. If the treating clinicians, amputee and legal teams get it right then it can maximise recovery, improve quality of life and potentially avoid claims inflation due to medical complications.

Amputees face many challenges in their recovery and, as such, it is important that the rehabilitation programme offers solutions. Phantom limb pain is one such challenge; for example, one presenter referred to studies which suggested that 95% of amputees suffered from either residual limb pain or phantom limb pain.

The symptoms can vary drastically but, in some cases, it can be a potential barrier to prosthetic rehabilitation and therefore limit mobility and independence. The presentations at the ACRM conference confirm that studies into the root causes and potential cures for phantom limb pain are continuing but also that there are potential solutions available that can reduce phantom limb pain and thereby limit the impact on an amputee's rehabilitation.

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