What is Reflex Sympathetic Dystrophy or RSD or CRPS Type 1? How Common is it and What are its Triggers?

Reflex Sympathetic Dystrophy or RSD is also known as Complex Regional Pain Syndrome (CRPS) Type 1.

RSD or CRPS Type 1 is seen in almost all age group from 2 years to over 90 years with mean age of the illness being 42 years. This disease is 3 times more common in female than male. Reflex Sympathetic Dystrophy or RSD or CRPS Type 1 is often seen following trauma caused by automobile (car) accident, work accident or domestic injuries.¹

Triggers of RSD:  RSD is often seen following peripheral soft tissue injury in 2 to 5% patients. RSD is also observed following stroke and hemiplegia in 13 to 70% patients.

Pain is caused by inflammation and hyper-sensitization of peripheral tissue as well as spinal nerves and central sensitization.

CRPS Type 1 is the chronic illness that follows soft tissue injury and inflammation. Inflammation causes vasodilation resulting in protein exudation and edema. Chronic (long standing) soft tissue inflammation triggers neurogenic irritation involving nerve receptors (nociceptors) and sensory nerve fibers. In contrast, CRPS Type 2 induces primary neurogenic inflammation and secondary soft tissue inflammatory changes.

Inflammatory changes in peripheral soft tissue following non-healing trauma triggers the symptoms of pain in CRPS Type 1 or RSD. Pain is secondary to inflammation during the initial phase. Later neuropathic pain is caused by hypersensitization of pain receptors and nerve fibers by ischemic vascular changes of soft tissue. Pain intensity is severe secondary to hyperactivity of receptors, sensory nerves, sympathetic system, and central nervous system.

Lab studies of peripheral tissue fluid, blood, and cerebrospinal fluid have shown presence of inflammatory neuropeptides such as calcitonin gene-related peptide, substance P, and pro-inflammatory cytokines such as tumor necrosis factor-alpha in patients suffering with chronic CRPS Type 1 and 2. Lab studies also suggest increased endothelin-1 and diminished nitric oxide levels within inflammatory secretions.²

The ischemia (restriction of blood supply) of soft tissue and adjacent bones results in lack of adequate oxygen (hypoxia) to soft tissue and bone. Hypoxia causes secretions of excessive chemical like lactic acid in skin, subcutaneous tissue and muscles resulting in severe pain. Lack of adequate oxygen to peripheral tissue also causes tissue changes like skin color, nail texture, osteoporosis of bones and swelling of soft tissue triggering increased pain.³

Scarring of soft tissue following wound, trauma, extensive burn or inflammation results in destruction of nerve receptors and sensory nerves. Scarring is associated with microscopic pathological destruction and necrosis of peripheral soft tissue. CRPS of Type 1 is observed after soft tissue injury and not any major nerve injury. Peripheral soft tissue inflammation, necrosis and scarring causes peripheral nerve irritation and sensitization of pain receptors, which initiates neuropathic pain resulting in CRPS type 1.

Irritation and hypersensitivity of pain receptors, spinal neurons, and sensory nerve fiber causes continuous severe intractable pain. Hypersensitive pain receptors are spread over skin, muscles, bones and viscera. Severe pain is generated when these hypersensitive receptors are stimulated by simple touch, pressure or irritant. Equally hypersensitive sensory nerves from hypersensitive pain receptors to spinal cord carry pain impulses.

Neuropathic pain is associated with hypersensitivity of peripheral receptors and nerve fibers, nerve cells within spinal cord and central sensitization.

Interneurons in spinal cord exchanges information with different adjacent nerve cells by sending various messenger neurotransmitters. Neurotransmitter productions by spinal and interspinal neuron are erratic in patients suffering with CRPS and often exaggerate intensity of pain impulses. Modified pain impulses (modulation) within spinal cord are transmitted by different sets of ascending sensory nerves from spinal cord to brain and higher pain center. Continuous habitual secretion of neurotransmitters by hypersensitive interneuron in spinal cord, mediate and exchanges information between interneuron. Exaggerated exchanges of neurotransmitter results in sending continuous pain impulses to higher pain centers even after peripheral cause of pain is abolished or restricted.

Several studies had suggested RSD or complex regional pain syndrome (CRPS) is associated with functional reorganization in the primary somatosensory cortex (S1)². Hyperactivities of sensory and motor cortex were observed in patients suffering with CRPS in research studies. Cortical hypersensitivity suggests central sensitization. Chronic neuropathic pain is associated with hyperactivity of pain centers in thalamic neurons and limbic system. Hypersensitive limbic system interferes with sleep, mood and appetite. Central sensitization also triggers autonomic nerves activation.

Autonomic nerve activation results in clinical manifestation of symptoms recognized as autonomic dysfunction. Autonomic dysfunction in CRPS causes initial increase of skin temperature, erythema, tissue edema and later cold skin temperature, dehydration thinning of the skin and bluish discoloration. Autonomic dysfunction is also known as vasomotor changes, sudomotor changes, and atrophic changes.

Vasomotor changes are observed in blood vessels of inflamed soft tissue because of hyper activities of hypersensitive autonomic system. Initially the peripheral blood vessels are dilated causing erythema and pinkish red discoloration of skin. Later blood vessels are constricted resulting in cyanotic purple skin. The changes are predominantly seen in small arteries.

Sudomotor nerves are the efferent nerves of sweat gland. Stimulation of sweat gland by sudomotor nerve causes secretion of sweat. In CRPS the sudomotor nerves are hyperactive.

Trophic changes observed are secondary to ischemia (reduced oxygen supply) of skin, hair, subcutaneous tissue, and bone. The autonomic trophic changes also known as neurogenic atrophy or neurotropic atrophy secondary to vasoconstriction (narrowing of blood vessels) and ischemia (less blood supply).

Also Read:

• Symptoms & Signs Of Complex Regional Pain Syndrome (CRPS) or Reflex Sympathetic Dystrophy (RSD)
• What are the Common Causes of RSD or CRPS Type 1?

References:

1. Demographic and medical parameters in the development of complex regional pain syndrome type 1 (CRPS1):

   prospective study on 596 patients with a fracture.

   Beerthuizen A, Stronks DL, Van’t Spijker A, Yaksh A, Hanraets BM, Klein J, Huygen FJ.

   Pain. 2012 Jun;153(6):1187-92. doi: 10.1016/j.pain.2012.01.026. Department of Medical Psychology and

   Psychotherapy, Erasmus MC, Rotterdam.

2. Increased endothelin-1 and diminished nitric oxide levels in blister fluids of patients with intermediate cold type

   complex regional pain syndrome type 1.

   Groeneweg JG, Huygen FJ, Heijmans-Antonissen C, Niehof S, Zijlstra FJ.

   BMC Musculoskelet Disord. 2006 Nov 30;7:91.

   Department of Anesthesiology, subdivision Pain Treatment Center, Erasmus MC Rotterdam.

3. Bone loss in the contralateral asymptomatic hand in patients with complex regional pain syndrome type 1.

   Karacan I, Aydin T, Ozaras N.J Bone Miner Metab. 2004;22(1):44-7.

   SSK Vakif Gureba Hospital Physical Medicine and Rehabilitation Clinic, Istanbul, Turkey.