Phantom limb pain (PLP) is
a condition that commonly occurs after an amputation of a major limb. PLP is
described as feeling pain in the limb that is no longer there. Considering the
painful limb no longer exists, scientists and medical professionals have
struggled to design the best treatments for this phenomenon. One up-and-coming
treatment involves virtual reality to alleviate symptoms of PLP. Virtual
reality is a relatively new technology, but it is already beginning to become
widespread and inexpensive which could make this intervention accessible to a
wide range of patients. Another option for treating PLP is a surgical procedure
called target muscle reinnervation (TMR). TMR is currently the only approved
surgery in treating phantom limb pain. There is a possibility that TMR in conjunction
with other types of pain intervention could provide long-term relief for
patients with PLP.
Virtual reality is a newer technology, however, there
have been advancements in the use of this technology way beyond just entertainment.
A group of researchers in Japan designed a program to be used in a virtual
reality headset that could help alleviate PLP (Osumi et al., 2019). When the
patient wears the virtual reality headset, they would be able to look down at two
virtual arms and hands which replicates an existing therapy known as mirror
visual feedback but in a more immersive environment (Osumi et al., 2019). The
results showed relief in patients after using this therapy, but there was only
improvement in the score of kinesthesia-related pain and not in somatosensory-related
pain (Osumi et al., 2019). PLP can arise from many different mechanisms that
are not yet well understood and can cause two different distinct types of pain.
While this type of therapy may help relieve the psychosomatic pain that arises from
the changes in kinesthesia functioning, there are instances where this pain is
caused by the remaining nerve endings and require a more invasive therapy. One
great benefit of this therapy is that it can be relatively inexpensive,
considering a top-of-the-line myoelectric prosthetic arm costs anywhere from
$20,000 to $100,000, whereas an Oculus virtual reality system that is
commercially available has an average cost of $300. While this type of therapy
is a work in progress and cannot relieve all symptoms of PLP, this could be a
good option for low-income patients and could easily be implemented in physical
therapy routines.
Patients suffering from somatosensory-based PLP may have
to go to more invasive treatments, but luckily targeted muscle reinnervation has
had great success in treating these patients. TMR was developed by Dr. Dumanian
to tweak the existing treatment of painful neuromas that commonly develop in
patients with amputations (Dumanian et al., 2019). TMR differs from the
standard neuroma treatment by splicing the nerve into a nearby nerve that is
connected to a muscle, instead of excising the neuroma and burying the exposed
nerve endings in a nearby muscle, which will eventually cause the nerve to
develop a new neuroma (Dumanian et al., 2019). The study discovered that 72% of
patients reported none or mild phantom limb pain after receiving TMR compared
to the control group with standard treatment that only saw this result in 40%
of patients (Dumanian et al., 2019). TMR has been shown to be more successful in
alleviating PLP than the standard treatment and this could be contributed to
being a better treatment for taking care of the painful neuromas that develop at
the end of the excised nerve after amputation. This surgery is now performed all
over the United States and this allows for more access to a critical treatment for
phantom limb pain.
Phantom limb pain appears to be made up of two components,
kinesthesia-related pain, and somatosensory-related pain. The virtual reality
mirror visual feedback theory was able to address kinesthesia-related pain,
whereas targeted muscle reinnervation was able to presumably address somatosensory-related
pain. Considering there was still a 38% of patients suffering from PLP after
TMR, it is possible an intervention addressing kinesthesia-related pain may be
beneficial for these patients. A study using a combination of TMR, and virtual
reality therapy would be an interesting future direction in the treatment of
PLP to discover if there is a further reduction in pain across a wider group of
patients when using a combination of treatment. Patient care after an
amputation often involves a multitude of techniques to allow for a return to
the best quality of life possible after such a significant change in everyday functioning.
A combination of virtual reality therapy and TMR could bring an overall relief
from PLP to patients after amputation.
References
Dumanian,
G.A., Potter, B.K., Mioton, L.M., Ko, J.H., Cheesborough, J.F., Souza, J.M.,
Ertl, W.J., Tintle, S.M., Nanos, G.P., Valerio, I.L., Kuiken, T.A., Apkarian,
A.V., Porter, K. & Jordan, S.W. (2019). Targeted muscle reinnervation
treats neuroma and phantom limb pain in major limb amputees. Annals of Surgery,
270(2). DOI: 10.1097/SLA.0000000000003088
Osumi, M., Inomata, K., Inoue, Y., Otake, Y., Morioka,
S. & Sumitani M. (2019). Characteristics of phantom limb pain
alleviated with virtual reality rehabilitation. Pain Medicine, 20(5),
1038-1046. DOI: 10.1093/pm/pny269
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