Swelling and pain 2 weeks after a dog bite
THE COURSE OF COMPLEX REGIONAL PAIN SYNDROME
Traditionally, type 1 was divided into three stages—an early inflammatory stage, a dystrophic stage, and a late atrophic stage.12 Although there is no evidence to support a consistent three-stage evolution, the severity of symptoms may help determine the best approach to management.13
Patients initially exhibit burning or throbbing pain, diffuse aching, sensitivity to touch or cold (allodynia), localized edema, and vasomotor disturbances of variable intensity that may produce altered color and temperature. Topical capsaicin cream; a tricyclic antidepressant; an anticonvulsant such as gabapentin (Neurontin), pregabalin, or lamotrigine (Lamictal); or a nonsteroidal anti-inflammatory drug should be tried first. Some of these treatments are poorly tolerated in elderly patients. If pain persists, nasal calcitonin may be added. Trigger-point injections with an anesthetic or glucocorticoid may be tried.
The management of early complex regional pain syndrome is sometimes supplemented with systemic corticosteroids, but reviews of randomized controlled trials have failed to show efficacy.14
Later in the course, patients may suffer persistent soft-tissue edema, accompanied by thickening of the skin and periarticular soft tissues, muscle wasting, and the skin changes of brawny edema. Regional blockade of sympathetic ganglions, epidural administration of clonidine, implantable peripheral nerve stimulators, and spinal cord stimulators have all been applied by experts in pain management and may provide benefit. Progression of the syndrome may include cyanosis, mottling, increased sweating, abnormal hair growth, and diffuse swelling in nonarticular tissue.
It is always acceptable to refer to an experienced pain management specialist, and a multidisciplinary approach is recommended at the outset.12
OUR PATIENT’S CARE CONTINUED
Our patient’s forearm and wrist were placed in a sling to keep his left arm elevated when active. This helped control sympathetic vascular edema and throbbing pain. Physical therapy with range-of-motion exercises prevented contracture.
He was discharged home on limited oxycodone as needed, with close follow-up by his primary care physician to monitor his pain symptoms. The pain and swelling slowly improved over the next 2 months, but he suffered a fall, twisting his left wrist. This minor injury was followed by more intense pain and swelling of the forearm, hand, and wrist.
COMORBIDITIES
5. Which of the following statements about conditions associated with complex regional pain syndrome most likely applies to our patient?
- Gout is likely following minor trauma
- Minor trauma or surgical bone biopsy may reactivate complex regional pain syndrome
- Septic hip arthritis due to MRSA may have reemerged and seeded the wrist
- Patients with multiple sclerosis have a propensity for complex regional pain syndrome
- Complex regional pain syndrome type 1 begets type 2
Gout does follow minor injury, but our patient’s uric acid was well controlled on allopurinol (Zyloprim), and gout is unlikely to be causing polyarticular swelling of the hand, wrist, and forearm.
Minor trauma, sometimes inconsequential enough to have been completely forgotten, may either initiate complex regional pain syndrome or, as seen here, reactivate it. Bone changes seen on MRI sometimes trigger surgical bone biopsy, only to reactivate the dysesthesia and sympathetic vascular reaction. Surgery should be avoided. Trauma and surgery are causative rather than associative comorbidities.
Sepsis due to MRSA after total hip arthroplasty may be reactivated, especially in the setting of immunosuppressive treatment. But the diffuse bone changes seen in multiple carpal, radial, and ulnar bones suggest generalized vascular and sympathetic disarray, most consistent with complex regional pain syndrome type 1.
AN ASSOCIATION WITH MULTIPLE SCLEROSIS?
Multiple sclerosis and other central neuropathic conditions such as stroke are associated with complex regional pain syndrome type 1.15,16
A hypothetical cause for the higher prevalence of complex regional pain syndrome in patients with multiple sclerosis may be demyelination resulting in aberrant signaling and overreaction to distal pain receptors. Demyelination of neurons within the autonomic or spinothalamic tracts potentially increases susceptibility to development of the pain syndrome.
Our patient had an apparent stimulus for the development of the syndrome, ie, the initial dog bite, and the wrist injury later may have caused peripheral nerve injury. Such injury may lead to release of vasodilatory neuropeptides including substance P from stimulated cutaneous nerves with cell bodies in the dorsal root ganglia. Excessive vasodilation and increased vascular permeability result in the affected limb becoming edematous and causing cutaneous nerves to be further activated. Stimulated cutaneous neurons normally have an inhibitory influence on sympathetic activity at the level of entry of the dorsal root ganglia in the cord. In complex regional pain syndrome, this inhibition is lost, resulting in a hyperactive somatosympathetic reflex.17 Underlying multiple sclerosis may have contributed to the loss of inhibition by the cutaneous nerves on the sympathetic system.
CASE CONCLUDED
We continued to closely follow this patient, who was on a self-directed program of physical therapy. One year after the original dog bite, the complex regional pain syndrome had completely resolved.
