IT is well known that phantom limb pain can reappear or be exacerbated transiently during spinal anesthesia in amputees.1However, to the best of our knowledge, the reappearance of phantom limb pain immediately after nonamputation surgery in an amputee has not been reported. We herein present a patient with chief complaint of reactivation of phantom limb pain the day immediately after cervical myelopathy surgery.
Case Report
A 65-yr-old man was scheduled to undergo surgery for cervical myelopathy resulting from spondylotic canal stenosis. Past medical history revealed four previous surgeries under general anesthesia, one of which required amputation as a result of a railway accident at the age of 49 yr. The injuries sustained from his fall from the railway platform required amputation below the left shoulder, below the right knee and at the midmetacarpal bones of the right first, second, and third fingers. Approximately 1 month after the amputation he began to suffer from severe and painful phantom limb sensations localized to the right below-knee and the left below-shoulder regions. The sensations were described as cramped pain and were greater in the right below-knee region than in the left below-shoulder region. The patient had complained of intractable cramp pain for approximately 6 months, but the treatments administered during this period are not known. As a result of gradual decrease of phantom limb pain, the sensation changed from pain to numbness. The painless phantom limb sensation from the left below-shoulder and the right below-knee regions described as numbness gradually decreased in intensity and area of involvement during the past 15 yr but still persisted up to the present time. The patient had also complained of telescoping phenomenon of his left hand (a gradual transposition towards the stump) and that the location of his left hand gradually moved superiorly from his left waist region towards the thoracic region, whereas he did not experience telescoping of his right lower limb.
The patient was hospitalized in our hospital to undergo surgery for cervical degenerative myelopathy because of spondylotic canal stenosis with calcification of the posterior longitudinal ligament that was not directly attributed to the railway accident. The preoperative symptom was neck and back pain untreatable with medications accompanied by nausea and chest discomfort. Preoperative magnetic resonance imaging revealed flattening of the cervical spinal cord at the level of C5–6 and C6–7, where the herniated disc extruded towards the left anterior side of the cord. The operation was performed with a left anterior approach by subtotal corporectomy of C5/C6 and discectomy of C4/C5/C6/C7 with iliac strut graft fusion. The symptoms of cervical myelopathy improved postoperatively. Postoperative magnetic resonance imaging revealed improvement of the cord flattening.
The morning immediately after surgery the patient was aware of the presence of pain in his left upper arm, which gradually extended to the left elbow, wrist, and fingers during the day. He felt as if his left hand had moved away from his left thoracic region inferiorly towards his left waist region. Pain intensity gradually increased during the day, and by night the patient recognized it to be the same as the phantom limb pain that he had previously experienced. The reactivated pain was of the same quality and in the same location. It was an intractable, continuous, spontaneous cramp pain localized to the whole region of the left below-shoulder and was exacerbated with mobilization of the shoulder or application of pressure to the stump. The pain resulted in daily sleep disturbance while the pain intensity fluctuated. His initial treatment for the pain was with oral lornoxicam, a nonsteroidal antiinflammatory drug that brought no pain relief. He was first consulted by our pain clinic staff at day 6 after surgery. Sensory examination of the well-healed scar of the stump revealed the presence of hypoesthesia and hypoalgesia. No palpable neuromas could be detected in the stump. He was treated with oral amitriptyline (20 mg per day) and dextromethorphan (45 mg per day) by our pain clinic staff. The phantom limb pain gradually subsided with this combination of drugs and completely subsided by the 15th day after surgery. At the same time the patient felt that his left hand had gradually returned from the thoracic region to the original location, the left waist region, as before surgery. The nonpainful phantom limb sensation of the left below-shoulder and the right below-knee regions persisted as numbness, described in text. The drugs were discontinued by the patient’s own judgment 1 month after the operation. Follow-up evaluation revealed that the patient has been free of phantom limb pain for 6 consecutive months without any analgesics.
Discussion
The phantom limb pain that had once been completely relieved and remained asymptomatic for approximately 15 yr was reactivated after surgery for cervical myelopathy. The mechanisms involved in the reactivation are postulated to be associated with surgery. The surgical site of the cervical spine in this patient was close to the left dorsal horn neurons of the cervical spinal cord where the primary afferent nerves of the left upper limbs terminate in and where the secondary afferent nerves originate. Phantom limb pain of this patient was reactivated and limited only to the left upper limb. It is probable that mechanical stimuli or inflammatory responses resulting from the surgical stress to the cervical spine resulted in functional changes in the afferent pathway of the left upper limb. Several animal studies have revealed that injury-producing tissue damage increases excitability of the central nervous system2,3and reduces inhibitory pain modulation.4Moreover, it was demonstrated that electrical stimulation to the region of the thalamus in amputees that originally represented the missing limb could evoke phantom sensations including pain, in which it was indicated that the thalamic representation of the amputated limb remains functional in amputees with phantoms.5Therefore, it is a possible explanation that functional changes in the central nervous system caused by surgical noxious stimuli to the cervical spine resulted in the reactivation of the phantom limb pain.
Electrophysiological improvement in the decompressed cervical spinal cord might have contributed to the reappearance of pain. Several studies revealed that evoked potentials in the spinal cord suppressed by cervical cord compression recovered promptly after surgical decompression.6–8Although we did not investigate this patient electrophysiologically, we could hypothesize the normalization of neural activities by marked improvement of the symptoms and findings in the postoperative magnetic resonance imaging. A similar case was described by Brihaye in 1958, in which painless phantom phenomenon from a right lower limb extinguished itself progressively, paralleling the aggravation of cervical radiculopathy because of a herniated disc and reappeared upon slow recovery from radiculopathy 6 months after excision of the herniated disc.9For our patient, the electrophysiological improvement after cervical decompression probably influenced the neural activities of the central nervous system that might have contributed to the reappearance of phantom limb pain.
The phantom limb pain was relieved with oral amitriptyline and dextromethorphan. Both amitriptyline and dextromethorphan have antagonistic potencies for N -methyl-d-aspartate receptors in the central nervous system.10–12Oral dextromethorphan was reported to effectively attenuate postamputation phantom limb pain, in which it was discussed that dextromethorphan interrupted sensitization in the central nervous system by antagonizing N -methyl-d-aspartate receptors.12This is included as a possible explanation for our patient: that central sensitization induced by surgical stimuli was interrupted by the combined administration of these two drugs and remained suppressed even after discontinuation of these drugs.
In summary, the phantom limb pain that had once been completely relieved and remained asymptomatic for approximately 15 yr was reactivated after cervical spinal decompression. This case suggests that phantom limb pain suppressed for some length of time can be reactivated by surgery that involves aggravating stimulation involving the pain pathway. The possibility of reactivation of phantom limb pain may be taken into consideration when the balance of advantages and disadvantages of surgery is evaluated.