Complex Regional Pain Syndrome: Head and Neck

What Is Complex Regional Pain Syndrome?

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

Does CRPS Impact Anyone?

Adults are more likely than children to suffer from CRPS. The peak onset occurs at roughly 40 years old. Those classified as female at birth are more likely to be affected by CRPS than those identified as male at birth. Individuals with European heritage account for between 66% and 80% of instances.

What Is the Average Incidence of CRPS?

In comparison, CRPS is uncommon. Every year in the US, it impacts approximately 200,000 people.

What Are the Types of Complex Regional Pain Syndrome?

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

• Type 1 - It is associated with reflex sympathetic dystrophy (RSD).

• Type 2 - It is associated with a partial nerve injury (causalgia), though the clinical symptoms of both types are extremely similar.

An autonomic component is usually present in complex regional pain syndrome (CRPS), influencing both the intensity of pain and trophic alterations in the soft tissue layers. Because the sympathetic nerve affects the vasculature, the skin is extremely sensitive to tactile or temperature changes, and its perceptions are altered in these cases.

The inflammation that is diminished after a sympathetic block or due to abnormalities in sudomotor activity is altered by blood flow through the skin. The evidence is that the skin vasculature increases sensitivity to local cold temperature stimuli and catecholamines. This has been shown evidentially through experiments. Sympathetic reflexes are tested for activation and inhibition in response to skin temperature changes and thermoregulation.

Tropical changes, such as abnormal nail growth, abnormally or suddenly increased hair growth, palmar and plantar fibromas, skin turning thin, patchy, or glossy, and hyperkeratosis, have all been hypothesized to occur due to inflammatory pathogenesis, and scintigraphic studies provide compelling evidence that CRPS has an inflammatory component.

What Are the Clinical Features of CRPS?

The term causalgia is now called complex regional pain syndrome (CRPS) which 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 and evoked by continuous, episodic, or paroxysmal stimuli. The regions of the extremities may be affected more by increased pain when the region is elevated. Other abnormal sensations related to the pain that is 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 and several typical abnormalities probably related to autonomic dysfunction are present. These include edema or inflammatory swelling, abnormality of sweating, and skin changes (to tactility or touch, and texture of the skin may be altered). It may be warmer or cooler when comparing the affected side's skin to the other.

How Is Complex Regional Pain Syndrome Diagnosed?

A specific test cannot diagnose CRPS. Medical professionals primarily diagnose it by carefully reviewing symptoms, performing a physical exam, and reviewing the medical history. Their provider will ask individuals if they have had any recent surgery or injuries.

They will search for:

• A shift in the skin's texture, appearance, and temperature in the afflicted region.

• An injury that causes greater pain than anticipated.

• Any further illnesses or ailments that might be the source of the discomfort, skin abnormalities, or other symptoms.

• They could request imaging tests like an MRI (magnetic resonance imaging) or ultrasound to check for underlying nerve injury. However, it is not always easy to identify the nerve injury.

The following diagnostic techniques can be used to validate the diagnosis -

• Quantitative sensory tests.

• Laser doppler flowmetry.

• Infrared thermography.

• Quantitative sudomotor axon reflex test.

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

• Plain radiographs.

• 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 (free nerve endings that send signals to the brain and spinal cord in response to stimuli that cause injury or pain) 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:

• Sensitization of nociceptive fibers.

• Cross-activation between injured afferent fibers (ephaptic crosstalk).

• Sprouting of somatic afferent fibers from adjacent intact nerves.

• Activation of afferent fibers by sympathetic afferents.

• Neuroma formation.

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

• 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.

• Physicians in some patients, physicians have also advised opioid painkiller drugs but should be used with caution as they can be a source of addiction in chronic use.

• Membrane stabilizers acting on sodium channels, such as Phenytoin, Carbamazepine, and local anesthetic agents, have been suggested to reduce the ectopic firing of neurons that causes symptomatic or sudden pain.

• Amitriptyline is the most commonly used drug among tricyclic antidepressants, along with painkillers.

• 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. It has also been used for the treatment of CRPS.

• Topical capsaicin, N-acetylcysteine, has also been documented to show benefit.

• Other methods include administering oxygen-free radical scavengers and deep brain stimulation in the sensory thalamus. Apart from the technique of medial lemniscus, epidural spinal cord stimulation has also been proven to be effective.

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 remains a partially treatable pain syndrome as it is a chronic, painful, and inflammatory disease that affects the head and neck region in the affected individuals.