Understanding and Treating Complex Regional Pain Syndrome : A Nerve Block Treatment Approach.

There are a variety of treatments with established effectiveness for the management of complex regional pain syndrome (CRPS). However, the distinctiveness and variability of symptoms in patients with CRPS often makes it challenging for therapists to design the most effective personalized treatment approach for their patients. CRPS is an uncommon chronic pain that affects the limbs, and its causes are still not fully comprehended. It usually develops after an injury, a surgery, a heart attack or a stroke and causes an excruciating pain.  The condition is complex in nature, and various terminologies have been used to describe CRPS in the past, resulting in misdiagnosis of the condition, and consequently poor evidence-base regarding available treatment modalities.

When diagnosed at an early stage, an aggressive and interdisciplinary treatment approach can provide healing and sometimes total remission. One of the treatment approaches with effective results is Sympathetic blocks. Several patients have found relief with this treatment consisting of the injection of a local anesthetic to numb the nerves. This technique aims at reducing the over-activity of the sympathetic nerves in CRPS. Such treatment provides pain relief, mood improvement, and improvement of activity level, as proven by many randomized controlled trials, clinical practices and systematic reviews (2).The purpose of this presentation is to discuss the diagnosis, symptoms and treatments approaches of CRPS, with an emphasis on the sympathetic block and its mechanisms.

Definition

Complex regional pain syndrome (CRPS) is a chronic pain condition of the limb (leg, foot, arm or hand) lasting for over six months, and occurs after an injury, a stroke, or a surgery. It is characterized by a group of symptoms resulting from the damage to, or malfunction of, the peripheral and central nervous systems. It can complicate recovery and impair one’s functional and psychological well-being. Initially known as causalgia, complex regional pain syndrome (CRPS) was reported for the first time in 1865 during the American Civil War in soldiers who were affected by neurologic injuries

Characteristics/ Symptoms

• Throbbing pain
• Changes in skin texture on the affected or surrounding area
• Abnormal sweating pattern in the affected area
• Changes in nail and hair growth patterns
• Joint stiffness, swelling and damage
• Muscle spasms, tremors, weakness and atrophy
• Muscle Coordination problems
• Decreased ability to move the affected body part
• Abnormal movement in the affected limb
• Changes in skin temperature — alternation between sweaty and cold
• Changes in skin color- white red or blue
• Changes in skin texture ( may become tender, thin or shiny in the affected area

Sensibility

Types

Complex regional pain syndrome occurs in two types, with similar signs and symptoms, but different causes:

Type 1:  In this category, there is no direct damage to the nerves of the affected limb(s). Type one is also known as reflex sympathetic dystrophy syndrome (RSD). 90% of people with complex regional pain syndrome have type 1.

Type 2. The symptoms in type II are similar to type I, but there is distinct serve injury in this category. It is referred to as causalgia,

Causes

The cause of complex regional pain syndrome isn’t completely understood. It’s believed to be caused by an injury , abnormality of the peripheral and central nervous systems.. This can include a crushing injury, fracture or amputation.

Other major and minor traumas — such as surgery, heart attacks, infections and even sprained ankles — can also lead to complex regional pain syndrome.

No clear understanding of why injuries trigger complex regional pain syndrome.

Possible dysfunctional interaction between the central and peripheral nervous systems

Inappropriate inflammatory responses.

Not everyone with injuries develop complex regional pain syndrome.

Diagnosis

There is no specific test to confirm the diagnosis of CRPS. Qualified physicians often based the diagnosis through observation of signs and symptoms, and study of personal history and a physical exam.

X-rays, and MRI / bone scans are used to check for possible changes in the bones, skin and joints that can be attributed to CRPS.

Early diagnosis and treatment offers more chances for recovery

Treatment options

There is no cure for CRPS. Treatment aims at relieving painful symptoms and improving the patient’s quality of life. There are various treatments options depending on the duration of the condition and the severity of the symptoms. Physicians often use a multidisciplinary approach to treat the condition.

When initiated early and aggressively, the patient has better chances to find relief and remission. An interdisciplinary approach is often needed to achieve optimum results. Below is a list of treatment options.

Occupational/Physical Therapy. Exercise programs can help with motions and preserve mobility.

Nerve Blocks: It is reported that many patients experience major relief from nerve blocks,. It relieves the pain and enables more effective therapy by inhibiting the over-activity of the sympathetic nerves.

Medications: Different drugs are used to treat CRPS and related conditions. associated conditions (such as  anxiety, sleep disorders, and depression)

Medications include topical analgesics, antidepressants, corticosteroids, muscle relaxants, opioids , antiseizures, and sleeping medications.

Psychotherapy: CRPS can have significant psychological effects on patients and their families. They are often depressed, anxious, or suffer from post-traumatic stress disorder.  Psychotherapy can help to improve coping ability.

Surgery:  It is often used in cases where CRPS is caused by a compressed nerve.  It helps release pressure on the

Other options include: Spinal cord stimulation and intrathecal pumps, in which pain medications are injected continuously into the subarachnoid space. Deep brain stimulation and Electrotherapy (ECT) have also been used, and new therapies continue to emerge.

Nerve Block mechanisms

The rationale for using Nerve block to treat CRPS is based on its strong ability to block receptors

^.

Experimental evidence suggests that the symptoms of CRPS are generated by an intense or prolonged painful stimulus that causes increased and prolonged glutamate release.

A randomized, double-blind, placebo-controlled trial showed that sympathetic nerve blocks was beneficial for pain and sensory symptoms in CRPS type I

Calcium channel blockers

A small, uncontrolled case series showed improvement in patients with CRPS using the calcium channel blocker nifedipine. There was no randomized, controlled trials performed The clinical experience and the literature describes significant relief in some patients

Beta-blockers

Poor clinical experience but proven benefits demonstrated in some case reports. A placebo-controlled trial did not demonstrate statistically significant efficacy for some beta-blocker ( example propranolol.

⁾

Oral sympatholytic agents

In theory, oral sympatholytic agents are deemed to provide symptom and pain relief for patients with CRPS and other neuropathic. However, there is no randomized, prospective, controlled study proving their efficacy. But, some benefits were reported for agents like prazosin


^,


phenoxybenzamine and terazosin.

^,

although the clinical use of these drugs is thought to have several adverse side effects.

Sympathetic nerve block is the best treatment option. Sympathetic Nervous System plays a huge role in CRPS.

There is substantial evidence suggesting that the sympathetic nervous system has a role in chronic neuropathic and inflammatory pain states in both animals and humans (3

Patients with CRPS type I have significant impairment of sympathetic nervous system function characterized by decreased sympathetic outflow and increased adrenergic responsiveness. This alteration of sympathetic function can be generalized, suggesting abnormal processing in the central nervous system.

Evidences

Local and regional sympathetic blockade such as stellate ganglion blockade or lumbar sympathetic blockade are widely reported in the many studies   However some studies suggest that the therapeutic response to sympathetic blockade is inconsistent and may only be more effective than placebo at reducing the extent but not the amount of pain

.

According to this review, there is high evidence that intravenous regional blockade with atropine, droperidol and guanethidine is not effective to reduce pain in CRPS, while there is very low evidence that other may be effective. Sympathetic blockade is a relatively invasive modality.

Therapeutic techniques

The techniques used to block sympathetic activity include the following:

Injections of local anesthetic around the sympathetic paravertebral ganglia that project to the affected body part (sympathetic ganglion blocks).

Regional IV applications of guanethidine, beryllium, or reserpine to an isolated extremity

Many uncontrolled surveys in the literature examine the effect of sympathetic interventions on CRPS, and approximately 70% of patients report full or partial responses.



^{(3 )}

One controlled study in patients with CRPS type I found that sympathetic ganglion blocks using local anesthetic had the same immediate effect on pain as a control injection with saline

However, after 24 hours, patients in the local anesthetic group remained noticeably improved relative to the control group, indicating the delayed efficacy of this particular intervention.

Sodium channel blocking agents

The use of IV lidocaine infusion has been shown to be effective in uncontrolled trials for reducing spontaneous and evoked pain with both CRPS types I and II.

Selective sympathetic ganglion nerve blocks

Selective sympathetic ganglion nerve blocks, by their nature, present a variety of difficulties to researchers developing preferred methodological practices.

Although the rationale for using ketamine seems effective and reasonable, and some studies have validated its benefit using objective outcome parameters with double-blind, randomized, controlled methodology.

However, several different research teams have struggled to determine the optimal dosing and duration of infusions, whether the infusions are more effective in an inpatient versus outpatient setting, whether ketamine is best used as an adjunct to regional anesthetic blocks rather than

Sympathetic blocks benefits are visible during the first days following the nerve block.

Patients with a shorter duration of symptoms seem to have a greater response to treatment.

Documentation of a physiologic response (e.g., change in skin temperature of the affected limb or Horner’s syndrome) is important to establish the success of the block .

Blocks should be combined with physical and behavioral therapy within 24 hours of the block.

.An effective block is expected to produce at least 50% improvement in pain and a concomitant increase in function.

Nerve blocks may be repeated only when there is objective evidence of progressive improvement in pain and function. management team communicate regularly about the patient’s treatment plan and progress towards treatment.

Prognosis

Each patient with responds differently to treatment; while spontaneous improvement occurs in some patients, others may not experience effective relief.

Case study 1. 53 years old patient treated with sympathetic blockade with satisfying results.

Case study 2: A 45 years old patient with great relief from sympathetic blocks

Case study 3: A 50 years old patient who didn’t get any relief from sympathetic blocks, but  did get some reliefs using other methods.

Conclusion

The efficacy of some treatments is proven while others remain subject to caution and controversy. The specificity and long-term results, as well as the techniques themselves, have not been satisfactorily evaluated.

Since there is no simple cure for CRPS, it is important to choose the best treatment approach to improve the quality of life of patients and help them resume a normal life. Sympathetic nerves block is the most probable treatment able to achieve such scenario

Bibliography

• 
  Perez R, et al. Treatment of patients with complex regional pain syndrome type 1 with mannitol: A prospective, randomized, placebo-controlled, double blind study. The Journal of Pain. 2008.
  
• Gierthmühlen, J. Binder A. and Baron, R. Machanism-based treatment in complex regional pain syndromes. Nature Reviews. Neurol. 2014
• Mitchell SW, Morehouse GR, Keen WW. Gunshot wounds and other injuries of nerves. 1864. Clin Orthop Relat Res. 2007
• Abdi, S. Complex regional pain syndrome in adults: Pathogenesis, clinical manifestations, and diagnosis. In: UpToDate, Post TW (Ed), UpToDate, Waltham, MA. (Accessed on March 31, 2016.)
• Gungor, Semih et al. “Sympathetic blocks for the treatment of complex regional pain syndrome: A case series.” Medicine vol. 97,19 (2018): e0705. doi:10.1097/MD.0000000000010705
• 
  https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/sympathetic-nerve-blocks-for-pain