Discussion
Phantom limb pain and stump pain, which are considered to occur in 50%
to 80% of limb amputees, are intractable conditions [1]. A study by
Kooijman et al. evaluating the association between phantom limb pain and
stump pain in 124 subjects with upper extremity amputations found a
significant association between these 2 types of pain [2]. Phantom
limb pain is thought to be caused by several factors, including abnormal
impulses from neuromas caused by peripheral nerve damage, and neuronal
hyperexcitability at the level of the spinal cord [3]. Phantom limb
pain includes pain associated with motor or deep sensation, and pain
associated with cutaneous superficial sensation [4]. Phantom limb
pain is different from stump pain, which is caused by pain local to the
stump, but these amputation-associated pain symptoms are often difficult
to distinguish in clinical practice. Our present patient was also
considered to have a mixture of these 2 types of pain.
There are several treatments for these types of pain, including
antidepressants, antiepileptic drugs, opioids, and other medications, as
well as surgical treatments, such as nerve blocks, but no standard
treatment has been developed to date [5]. Therefore, it is necessary
to select an appropriate treatment for each patient. In our case, the
patient’s pain could not be controlled using medication alone, so nerve
blocks were additionally performed. Mirror therapy is said to be
effective for phantom limb pain [6], although it was not performed
in our patient. There are also reports that transcutaneous electrical
nerve stimulation (TENS) is effective for both phantom pain and stump
pain [7]. However, there has been no systematic review of evidence
for the therapeutic effects of TENS. Therefore, the efficacy of TENS for
phantom and stump pain remains unclear at present [8]. In the
present patient, we also investigated the possibility of brachial plexus
block as an interventional treatment. However, because the pain was
localized to the annular finger, and because a brachial plexus block
would cause residual nerve damage in the thumb to the index finger,
which could affect his job performance, we chose peripheral ulnar nerve
block and median nerve block. In fact, the pain was markedly improved by
the nerve blocks, and hence the pain was thought to be caused by pain in
the ulnar and median nerve regions. Following the nerve blocks, his pain
was controlled with oral medication alone, indicating that peripheral
nerve blocks are effective for pain associated with cutaneous
sensations, such as electrical shock pain and allodynia. There are few
reports to date of the improvement of phantom limb pain or stump pain in
the hand using peripheral nerve blocks, and our present case suggests
that peripheral nerve block is a useful therapy for mixed phantom limb
and stump pain.
Previous reports in the literature have demonstrated that intravenous
lidocaine is effective for stump pain [9], and pulsed radiofrequency
is effective as an interventional treatment [10-12]. If the
patient’s pain relapses in the future, these therapies are an option. In
addition, it is important to treat refractory phantom limb pain and
stump pain using a variety of approaches, including psychotherapy and
cognitive behavioral therapy [13].