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Overview of Complex Regional Pain Syndrome

Complex regional pain syndrome (CRPS) is a chronic (lasting greater than six months) pain condition that most often affects one limb (arm, leg, hand, or foot) usually after an injury.  CRPS is believed to be caused by damage to, or malfunction of, the peripheral and central nervous systems.  The central nervous system is composed of the brain and spinal cord; the peripheral nervous system involves nerve signaling from the brain and spinal cord to the rest of the body.  CRPS is characterized by prolonged or excessive pain and changes in skin color, temperature, and/or swelling in the affected area.

CRPS is divided into two types:  CRPS-I and CRPS-II. Individuals without a confirmed nerve injury are classified as having CRPS-I (previously known as reflex sympathetic dystrophy syndrome).  CRPS-II (previously known as causalgia) is when there is an associated, confirmed nerve injury.  As some research has identified evidence of nerve injury in CRPS-I, it is unclear if this disorders will always be divided into two types.  Nonetheless, the treatment is similar.

CRPS symptoms vary in severity and duration, although some cases are mild and eventually go away.  In more severe cases, individuals may not recover and may have long-term disability.

What are the symptoms of CRPS?

The key symptom is prolonged severe pain that may be constant.  It has been described as “burning,” “pins and needles” sensation, or as if someone were squeezing the affected limb.  The pain may spread to the entire arm or leg, even though the injury might have only involved a finger or toe. In rare cases, pain can sometimes even travel to the opposite extremity.  There is often increased sensitivity in the affected area, known as allodynia, in which normal contact with the skin is experienced as very painful.

People with CRPS also experience changes in skin temperature, skin color, or swelling of the affected limb.  This is due to abnormal microcirculation caused by damage to the nerves controlling blood flow and temperature.  As a result, an affected arm or leg may feel warmer or cooler compared to the opposite limb.  The skin on the affected limb may change color, becoming blotchy, blue, purple, pale, or red.

Other common features of CRPS include:

  • changes in skin texture on the affected area; it may appear shiny and thin

  • abnormal sweating pattern in the affected area or surrounding areas

  • changes in nail and hair growth patterns

  • stiffness in affected joints

  • problems coordinating muscle movement, with decreased ability to move the affected body part

  • abnormal movement in the affected limb, most often fixed abnormal posture (called dystonia) but also tremors in or jerking of the limb.

Findings: Effects of Cannabis on Complex Regional Pain Syndrome

Many patients are finding microdosing medical marijuana to be an effective treatment option for their debilitating symptoms. Microdosing is the practice of consuming small amounts of cannabis over an extended period of time, typically a day. By ingesting the THC and other cannabinoids in smaller doses, a patient can still achieve the medical benefits of the cannabis with little or no euphoric “high” effects. This is achieved by taking a small vape hit or just one puff from a joint or pipe periodically throughout the day. It can also be accomplished by consuming the recommended dosage of an edible in smaller portions, or using a tincture drop in herbal tea or hot lemon water.

Researchers from the University of California Davis Medical Center (UCDMC) conducted a study comparing low dose (1.29% THC) and medium dose (3.53% THC) vaporized cannabis to determine if significant analgesic benefits could result without high levels of cognitive side effects. Thirty-nine participants with persistent neuropathic pain completed the study, which involved several interviews and evaluations to rate pain intensity. All patients had used cannabis previously (as required in the inclusion criteria).

Results of the study showed that both the low and medium doses provided significant pain relief, with an average of 30% reduction in pain intensity compared with a placebo. Side effects observed were negligible. It is interesting to note, however, that participants from the medium dose group had worse performance and learning and memory evaluations as compared to those of the placebo and low dose groups.

The authors of the UCDMC study concluded that low and medium doses of vaporized cannabis could be prescribed for treatment of neuropathic pain and provide clinically significant relief; however, in view of the findings, low doses would appear to cause fewer cognitive and psychological side effects.

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