Severe arm pain following radiation

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Over the years, Mr. C had had no pain or other known sequelae from the injury. He was single, lived alone, and was unemployed. Just three weeks prior to his visit, he had completed radiation therapy for prostate cancer.

Mr. C appeared calm and was alert and oriented to person, place, and time. Nonpitting edema caused his right hand to become tightly swollen. His fingers had a “sausage tube” look, with mottled, shiny skin that was cool to the touch. There was hair loss over the dorsal aspect of the right hand. The nail beds blanched well with less than a two-second capillary refill. The radial pulse was full, and sensation was intact to a 10-g monofilament. His forearm was pale and cool, with marked muscle atrophy. The upper arm was similar in appearance. Mr. C's vital signs were normal. He was afebrile. Besides the pain, he complained of fatigue, which he attributed to his recent radiation therapy.

Laboratory evaluation revealed  normal complete blood count and differential, blood urea nitrogen, creatinine, electrolytes, and liver enzymes. Testing for antinuclear antibodies was negative. His complement levels were very elevated, with C3 at 172 mg/dL (normal: 75-140) and C4 at 38.1 mg/dL (normal: 0-34). Westergren sedimentation rate (WSR) was 114 mm/hr (normal: 0-20), and C-reactive protein (CRP) was 10.6 mg/dL (normal: 0-1). Plain-film x-rays showed mild osteopenia in the humeral, radial, and ulnar shafts. A three-phase bone scan failed to show any sort of lesion but did confirm the osteopenia. Mr. C had limited use of his right arm, with no grip strength or active range of motion of the hand, wrist, or elbow. Active range of motion at the shoulder was weak and elicited intense pain.

Differential diagnoses included rheumatoid arthritis, metastatic disease, upper-extremity neurovascular compromise, or reflex sympathetic dystrophy (RSD). Mr. C was placed on a four-week, 80-mg prednisone taper, hydrocodone/acetaminophen as needed, gabapentin 400 mg t.i.d., and amitriptyline 50 mg at bedtime for his pain. Nevertheless, his pain remained at an 8/10 most of the time. His arm and hand showed no changes in appearance. Repeat WSR, CRP, and complement determinations at six weeks showed resolution of the elevations in spite of the continued pain and swelling. These findings led to the assumption that the laboratory aberrations had been due to the recent radiation therapy rather than the arm pathology.

With physical therapy, Mr. C experienced a slow resolution of his symptoms of approximately 75
percent after six months. He was ultimately diagnosed with RSD. Electromyography confirmed the diagnosis.

Analysis

Reflex sympathetic dystrophy, also known as “complex regional pain syndrome,” involves sensory, autonomic, and motor features. It usually occurs in the extremities, often after an injury or insult. The symptoms can resolve spontaneously but frequently remain to some degree indefinitely. Presenting features are intense and out of proportion to the initial injury. Causality appears to be based on a pathologic sympathetically maintained reflex arc that generates and perpetuates the pain.

Diagnosis is often one of exclusion. Classic presentation of RSD includes pain that is often debilitating, loss of function, and sympathetic dysfunction. Soft-tissue swelling, dystrophy, trophic changes, vasomotor instability, joint stiffness, and patchy osteoporosis are more specific findings. Most patients have an identifiable injury or trauma that precedes the onset of symptoms. Though Mr. C had no recent traumatic event involving his arm or shoulder, his presentation was otherwise classic.

There are no specific diagnostic tests, although several have been shown to be useful. Electrodiagnostics rule out neuropathies or entrapment syndromes. Radiographic studies exclude bone pathology; osteoporetic changes have been found as early as two weeks after symptoms appear. Blood tests may identify any infectious or rheumatologic process. However, as in this case, they may also confuse the picture.   

Once the diagnosis is established, physical therapy is the most basic and beneficial treatment. With the main goal being restoration of function, concomitant pain management is a necessity. Tricyclic antidepressants have significant analgesic effects. Gabapentin is also useful. Corticosteroids have a definite anti-inflammatory effect and are helpful in short-term administration. Opioid usage is questionable; neuropathic pain has not been proven to be highly responsive to these agents. However, addition of an opioid is often necessary to facilitate adequate pain control for physical therapy and rehabilitation.

Sympathetic and/or somatic blocks may prove useful, though there are no large-scale controlled clinical trials that support their use. Spinal-cord stimulation and intrathecal analgesia show promise in both clinical experience and controlled trials.

Overall, RSD is considered a temporary condition. Occasionally, however, patients develop refractory chronic pain and dysfunction. Physical therapy, pain management, and antidepressant support are essential in those cases.

At follow-up one year later, Mr. C's right hand and arm were at 90 percent function, and he no longer required medications for pain control. He is continuing periodic physical therapy appointments and routine oncology and primary-care follow-up visits.

Ms. Sego is a primary-care nurse practitioner at the Department of Veterans Affairs Medical Center in Kansas City, Mo.

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