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Complex Regional Pain Syndrome: Head and Neck

Published on Oct 22, 2021   -  4 min read

Abstract

This inflammatory dysfunctional pain syndrome, though rare in a few patients, is manageable medically by physicians but is not always curable. Read the article to its clinical features, pathophysiology, diagnostic tests, and management.

What Is Complex Regional Pain Syndrome?

Complex regional pain syndrome is a medical term used for the clinical condition of the patient suffering from chronic and consistent pain of the head and neck region. It would either be post-traumatic sequelae or a painful consequence of a nerve lesion or nerve injury, or irradiation.

What Are the Types of Complex Regional Pain Syndrome?

There are mainly two types of CRPS; type 1 and type 2.

Complex regional pain syndrome (CRPS) always involves an autonomic component affecting pain severity and trophic changes in the soft tissues. The skin is extremely sensitive to tactile or temperature changes because of the vasculature affected by the sympathetic nerve, with its perceptions being altered in these cases.

The inflammation that is diminished after a sympathetic block or due to abnormalities in sudomotor activity is because the blood flow through the skin is altered. The evidence is that the skin vasculature develops an increased sensitivity to local cold temperature stimuli and catecholamines. This has been shown evidentially through experiments. Testing the thermoregulatory response to skin cooling and warming results in inhibition and activation of sympathetic reflexes.

Tropical changes, such as abnormal nail growth, hair growth that is abnormally or suddenly increased, palmar and plantar fibromas, skin turning thin, patchy, or glossy, along with hyperkeratosis have all been hypothesized to occur due to inflammatory pathogenesis, and scintigraphic investigations strongly support an inflammatory component in CRPS.

What Are the Clinical Features of CRPS?

The term causalgia is now called complex regional pain syndrome (CRPS) that is type 2 or nerve-related causalgia. This was first described by Mitchell et al. in 1867 when they reported cases of soldiers suffering from this disorder during the American civil war. The clinical presentation of CRPS patients is heterogeneous, with pain being the common or predominantly prevalent symptom along with substantial variation in its characteristics. The pain can be spontaneous as well as evoked by stimuli, continuous or episodic, or paroxysmal. The regions of the extremities may be affected more with increased pain when the region is elevated.

Other abnormal sensations related to the pain that are found in CRPS patients include mechanical and thermal hyperalgesia (increased sensitivity to pain), hyperesthesia (increased sensations such as touch, smell, sound, and vision), allodynia (presence of pain without any obvious stimulus), hyperpathia (exaggerated pain sensation to a stimulus), and dysesthesia (pain with abnormal sensations such as pricking, burning, itching, stinging or tickling sensations). Additional signs of inflammation are present together with a number of typical abnormalities that are probably related to autonomic dysfunction. These include edema or an inflammatory swelling, abnormality of sweating, and skin changes (to tactility or touch, and texture of the skin may be altered). The skin of the affected side can be either warmer or colder compared to the other side.

How Is Complex Regional Pain Syndrome Diagnosed?

The diagnosis of CRPS is mainly clinical; on the other hand, the following objective diagnostic procedures have been reported in the literature to confirm the diagnostic impression of autonomic, sensory, and motor dysfunction.

  1. Quantitative sensory tests.

  2. Laser Doppler flowmetry.

  3. Infrared thermography.

  4. Quantitative sudomotor axon reflex test.

  5. Bone scintigraphy (gives information about bone vascularity changes).

  6. Plain radiographs.

  7. Sympathetic nerve blocks - This is a therapeutic, as well as a diagnostic modality wherein a local anesthetic, intravenous Phentolamine, or regional intravenous block, is used at the level of the sympathetic ganglion along with an adrenergic blocking agent.

What Is the Pathophysiology of Complex Regional Pain Syndrome?

The mechanism by which pain and other physical abnormalities develop in CPRS is not fully understood. Trauma is understood as the precipitating factor in the pathogenesis causing damage to a peripheral nerve, thereby causing neurobiological changes in both peripheral and central components of the nervous system. This produces an abnormal afferent input that creates a painful sensation in the head and neck as the nociceptors may be affected, and the impact of trauma is indirect or direct on the CNS (central nervous system). The following sequelae may occur relating to the mechanism of pain:

What Are the Available Treatment Modalities For Complex Regional Pain Syndrome?

  1. Many medications have been helpful in evidentially treating this neuropathic pain in CRPS. However, Non-steroidal anti-inflammatory drugs (NSAIDs) have been helpful in some cases as a mainline strategy alongside corticosteroids to address or relieve the peripheral component of the pain.

  2. Opioid painkiller drugs have also been advised by physicians in some patients but should be used with caution as they can be a source of addiction on chronic use.

  3. Membrane stabilizers acting on sodium channels, such as Phenytoin, Carbamazepine along with the use of local anesthetic agents, have been suggested with the purpose of reducing the ectopic firing of neurons that gives symptomatic or sudden pain.

  4. Amitriptyline is the most commonly used drug amongst tricyclic antidepressants along with painkillers.

  5. Gabapentin is a comparatively new drug that is also being used in trigeminal neuralgia and has been suggested for the treatment of other kinds of nerve-related pain, and it has also been used for the treatment of CRPS.

  6. The use of topical capsaicin, N-acetylcysteine, has also been documented evidentially to show benefit.

  7. Other methods that have been used are the administration of oxygen-free radical scavengers, deep brain stimulation in the sensory thalamus. Apart from the technique of medial lemniscus, epidural spinal cord stimulation have also been proved to be effective to an extent.

Conclusion:

CRPS is a complex pain syndrome that is manageable by physicians to a greater extent with the current modalities of drugs available. However, it still remains a partially treatable pain syndrome as it is a chronic, painful, and an inflammatory disease that affects the head and neck region in the affected individuals.

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Last reviewed at:
22 Oct 2021  -  4 min read

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