PHANTOM LIMB PAIN
Almost every month I have a patient who comes
to me in such severe pain that they ask, "Doctor, can't you just cut
the nerve?" Sometimes their distress is so great that they will suggest
that I amputate the painful limb. This seems to be the logical, if
horrific, end to all their pain. However, phantom limb pain is our
proof that such drastic measures are likely to fail. We can suffer
with severe pain, even when the painful part is no longer part of
the body.
There are hundreds of thousands of patients in
the United States that have undergone amputations and who suffer with
persistent phantom limb pain. This pain can affect mastectomy patients
as well as patients with simple tooth extractions. Phantom sensations
of some kind are almost universal in patients that have undergone
limb amputations. Significant pain occurs in as much as 80% of these
patients, but seems to improve over time in at least half of these
patients.
The cause of phantom pain is not fully understood.
It is important to emphasize that the pain is not imagined, and is
not the result of a psychological or emotional disturbance. We have
learned that the central nervous system (the brain and the spinal
cord) is capable of creating "memories" of pain that can cause the
pain to persist. Furthermore, normal sensation plays an important
role in inhibiting pain. (Notice our tendency to rub an area that
has been injured.) The loss of a limb means that pain sensations can
persist without the brakes of the normal sensations of touch and movement.
Treatment:
Before initiating treatment, it is important that
the clinician carefully distinguish phantom pain from stump pain.
The latter can be caused by neuromas (nerve sprouts from the ends
of damaged or cut nerves), by excessive compression, by infection,
or by a recurrence of the underlying disease.
There are many treatments that can help with phantom
pain, but no single approach is universally successful. In fact the
best approach may be to mix multiple treatments. Phantom pain is the
prime example of neuropathic pain; i.e., pain that is caused by a
damaged or malfunctioning nervous system. Therefore, all the medications
that are used for neuropathic pain can be useful for phantom pain.
This includes anti-convulsant and antidepressant medications. Transcutaneous
electrical nerve stimulation (TENS) of the stump can occasionally
provide relief. Interestingly, stimulation of the intact, opposite
limb is often more effective. In some patients, rehabilitation with
active exercise and use of the stump and a prosthesis can be the most
beneficial treatment. Placement of spinal electrical stimulators has
had mixed results, but if the pain has been refractory to all prior
treatments then this should be considered.
Prevention:
Perhaps even more important than treatment is
prevention. There is some evidence that the chance of developing phantom
pain can be reduced by the use of regional anesthesia to provide thorough
pain relief prior to surgery and for the first few postoperative days.
We clearly have much to learn about phantom pain,
and there is much exciting research in this area. Meanwhile, although
cure is not always possible, careful assessment and treatment can
often bring about significant improvement.
Until next time…Steven Richeimer, M.D.
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Steven Richeimer, MD. All rights reserved.