Cognitive Effects of Complex Regional Pain Syndrome

Living with excruciating pain day in and day out is physically and emotionally taxing. However, that is the reality of complex regional pain syndrome. Complex regional pain syndrome is a chronic pain condition related to the central or peripheral nervous system. With nerve signals sent to incorrect areas of the body, individuals with this condition experience firsthand how the mind and body are interconnected. Although they have a physical ailment, there are extensive cognitive effects of complex regional pain syndrome.

Cognitive Effects of Complex Regional Pain Syndrome
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What is Complex Regional Pain Syndrome?

Known as reflex sympathetic dystrophy syndrome, complex regional pain syndrome is a chronic pain condition resulting from a dysfunction of the central or peripheral nervous systems. The central nervous system consists of the brain and spinal cord, whereas the peripheral nervous system is responsible for sending the nerve signals from the brain and spinal cord to the rest of the body.

In complex regional pain syndrome, increased nerve impulsive is incorrectly transmitted to the wrong area. This creates recurring pain that may be felt as burning pain, stiffness, or swelling. The condition most often begins after an injury and impacts one limb such as an arm, leg, hand, or foot.

Causes of Complex Regional Pain Syndrome

The exact cause of complex regional pain syndrome remains unknown, but experts have identified a few factors that contribute the condition. Most often, complex regional pain syndrome manifests after an injury. Broken bones, surgery, and internal injuries (i.e. blood vessel problems) are common in patients with chronic pain.

Current theories documented in the Journal of Neurology are that injury or trauma to the body alters how the nervous system responds to pain. As the immune system releases cytokines and other inflammatory mediators in response to injury, the nervous system becomes inflames. These changes allow the sensation of pain to continue.  

Additionally, complex regional pain syndrome in families is evidence of a potential genetic link. More women are diagnosed than men, and while it can occur at any age, complex regional pain syndrome is most likely to occur in those between the ages of 20 and 35.

Types of Complex Regional Pain Syndrome

There are multiple types of complex regional pain syndrome. Medical professionals classify the disorder as type 1 or type 2 depending on the presence of an obvious nerve injury. They are both similar in symptoms and treatment.

Type 1 (Reflex Sympathetic Dystrophy)

Type 1 complex regional pain syndrome is also called reflex sympathetic dystrophy. Although a minor injury such as a sprained ankle might have occurred, there is no nerve damage. According to the Mayo Clinic, approximately 90% of people with complex regional pain syndrome have type 1.

Type 2 (Causalgia)

Type 2 is commonly referred to as causalgia. It tends to proceed a severe injury or trauma to the body like surgery, a broken bone, heart attack, or infection. Nerve damage is present.

Symptoms of Complex Regional Pain Syndrome

The symptoms of complex regional pain syndrome can be intermittent or constant. While the pain begins in the area of injury, it can move to various sites on the same limb. In rare cases, the pain migrates to the opposite limb not involved in the injury. Nerve damage impedes the circulation, so the majority of symptoms stem from abnormal blood flow.

  • Pain—The pain is described as a burning, stiffness, aching, stinging, tearing, or throbbing at the site.
  • Sensory loss—The affected area may go “numb” or have a lack of feeling.
  • Heightened sensitivity—Stimuli that should not be painful cause pain.
  • Edema (Swelling)—Fluid buildup in the limb results in swelling.
  • Discoloration of the affected site—Discoloration includes redness or the affected area turning blue, white, or shiny.
  • Decreased mobility—Between pain, weakness, and edema, some have decreased mobility of the limb.
  • Dystonia—Uncontrollable muscle spasms, movements, and tremors
  • Temperature changes—The site becomes hot to the touch or very cold. Abnormal sweating patterns are associated with this symptom.

Stages of Complex Regional Pain Syndrome

Complex regional pain syndrome has three stages. Some experience all stages while others might have symptoms resolve before the condition progresses. Both types of complex regional pain syndrome have the same stages of development.   

  • Stage one is the earliest acute stage. It lasts one to three months and is characterized as an overly sensitive, painful burning sensation with swelling and joint stiffness. The affected limb becomes red and warm to the touch.  
  • Stage two is the dystrophic stage. It lasts three to six months. The pain is more widespread, rather than confined to a small area of the affected limb. There is increase in stiffness and sensitivity to stimuli, as well as temperature. The skin is cooler to the touch.
  • Stage three is the strophic stage. It is typically one year after onset. In stage three, the pain can spread to other limbs. Range of motion is limited.
Cognitive Effects of Complex Regional Pain Syndrome
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Brain Structure and Complex Regional Pain Syndrome

Complex regional pain syndrome impacts the brain. Researchers have reported numerous brain changes in those with the disorder. Multiple studies reveal that chronic pain patients with complex regional pain syndrome have decreased amounts of gray matter in the portion of the brain associated with the limbic system. Structural brain changes are most profound in the early stages. Patients in the later stages do not display the same variances in gray matter. Instead, they have increased activity in the motor cortex involved with pain processing.

Diagnosing Complex Regional Pain Syndrome

There is no single test to confirm complex regional pain syndrome. To diagnose the disorder, a physical first perform a thorough medical history and physical exam. If they confirm that the patient exhibits the signs and symptoms during the exam, other tests can provide evidence of the condition and exclude alternative diagnoses.

These tests include special bone scans and magnetic resonance imaging to detect bone and tissue changes. A bone scintigraphy scan indicates osteoporosis, which is when minerals are leached from the bones in the late-stage complex regional pain syndrome. Tests of the nervous system evaluate the blood flow to the affected limbs, as well as the area’s ability to sweat. An uneven result suggests complex regional pain syndrome.

Psychological Factors of Complex Regional Pain Syndrome

Depression, a persistent feeling of sadness occurring for two or more weeks, is the most prevalent psychological component of complex regional pain syndrome. Chronic pain patients have a higher incidence of anxiety, depression, insomnia, and behavioral changes such as anger. Studies show that these psychological consequences are more related to chronic pain than to complex regional pain syndrome as a whole. Scientists have not identified a connection between psychological distress causing complex regional pain syndrome. Instead, patients are stuck in a cycle. Pain creates emotional distress, and emotional distress contributes to pain. In an attempt to avoid pain, they use their affected limb less frequently. As that limb becomes deconditioned, pain increases.  

Cognitive Impairment In Complex Regional Pain Syndrome

Cognition is the process of thinking. This includes attention, memory, logic, reasoning, and perception. One study reports that 23 percent of patients with complex regional pain syndrome have global cognitive processing impairments without the presence of brain lesions. Perception, as it relates to the affected site, is significant. Patients have deficits in spatial cognition. They experience the loss of awareness of the affected limb like misjudging its size, believing it is smaller or larger than it actually is.

Cognitive impairments arise in the later stages of the disorder. High levels of pain influence how efficient the brain works. Problems with concentration, memory, motor control, and word recall are common. Those deficits are known as “brain fog.”

Treating the Emotional and Cognitive Symptoms of Complex Regional Pain Syndrome

Complex regional pain syndrome has no cure, but there are treatments to manage the physical and the psychological symptoms. A successful treatment is one that reduces pain and increases mobility of the affected limb.

Physical and Occupational Therapy

Physical and occupational therapies are first-line treatments. Trained therapists tailor an exercise regimen to the patient’s needs and abilities. During physical and occupational therapy, patient’s learn coping skills and exercises to implement at home that reduce pain, stiffness, and other symptoms.


Even if the patient is not depressed, tricyclic antidepressants, which are a class of antidepressant drugs, treat neuropathic pain like in complex regional pain syndrome. They target neurotransmitter pathways that alter the perception of pain. Anticonvulsants also treat neuropathic pain from nerve injury. Steroids and NSAIDs are effective in the early stages, as they reduce inflammation. Due to their side effect profile, opioids are reserved as a last resort when other treatment options have failed. On occasion, bisphosphonates decrease the pain of complex regional pain syndrome by inhibiting the breakdown of bones.


Surgery and other procedures are sometimes warranted. Spinal cord stimulation sends electrical pulses to control the pain signals in the spinal cord. A sympathetic nerve blockade has also shown improvements in the pain of complex regional pain syndrome. An injection blocks the nerves of the sympathetic nervous system, so patients cannot feel sensations of pain.

Cognitive Behavioral Therapy

Fear of moving the affected limb is typical in patients with complex regional pain syndrome. Cognitive behavioral therapy is a form of talk therapy founded on the idea that thoughts and emotions influence behavior. A mental health professional assists the patient in identifying unproductive thoughts and cognitive distortions leading to the unwanted behavior. For many cases of complex regional pain syndrome, cognitive behavioral therapy confronts the fears of pain and teachers the patient coping skills.


Hill, R. J., Chopra, P., & Richardi, T. (2012). Rethinking the psychogenic model of complex regional pain syndrome: somatoform disorders and complex regional pain syndrome. Anesthesiology and pain medicine2(2), 54–59.

Mackey, S., & Feinberg, S. (2007). Pharmacologic therapies for complex regional pain syndrome. Current pain and headache reports11(1), 38–43.

Voet, C., le Polain de Waroux, B., Forget, P., Deumens, R., & Masquelier, E. (2014). Spinal cord stimulation for complex regional pain syndrome type 1 with dystonia: a case report and discussion of the literature. F1000Research3, 97.

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