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].