The vicious cycle of itch-scratch that is caused by neurodermatitis can lead to a variety of complications like skin thickening-damage and discomfort. In this article we will be addressing those aspects in simple terms so it can be easily understood. 

Overview

Neurodermatitis, also known as Lichen simplex chronicus, is a form of eczema that is presented as a patchy dry area that is thick and scaly, which often occurs alongside other skin conditions such as psoriasis. This is due to numerous amounts of scratching and rubbing of certain parts of the skin.¹ Lichen simplex can be differentiated from any other dermatological condition by examination. A fully mature plaque will appear hyperpigmented or hypopigmented and will show skin lines and a thick, leathery appearance.² Neurodermatitis usually occurs in approximately 12% of the population; ages range from 30 to 50 year olds. This is typically due to the stress situations that face the individual at some point in their life. It's known to be more common in females than males, with a ratio of 2:1.¹

Causes 

The scratch process may occur due to certain factors, which includes,

• Anxiety 
• Obsessive-compulsive disorder (OCD)
• Depression 
• Stress
• Emotional disturbances
• Trauma 
• Dry skin
• Tight clothing^3,1

It's been shown that genetic predisposition is a huge contributor towards neurodermatitis, which basically means that if you suffer from neurodermatitis, there may be someone in the family that also does as well.⁴ Neurodermatitis (Lichen simplex chronicus) can also be triggered by environmental factors such as

• Humidity and temperature 
• Skin irritants (wool, tight clothing, polyester)
• Tobacco smoke 
• Certain Types of food 
• Frequent use of soap^4,5

Pathophysiology

The itching sensation is encoded by neurons that are recognizable both in the peripheral and central nervous systems, which lead to a response of scratching. There are various locations where itch can come into contact with sensory modalities, from its initiation in a particular area on the skin to the brain where it's finally perceived.⁶ The pathophysiology of neurodermatitis has many factors involved, which are neurological, immunological and psychological.¹⁰ 

The itch-scratch cycle is a crucial mechanism of neurodermitis because it is the key aspect of worsening the condition.

Start of the itch

The cycle is initiated with an itch sensation that is caused by stress, irritation of the skin or any form of skin condition

Scratching response 

To respond to the itchiness, the affected area will be scratched by the individual in order to alleviate the discomfort; this will cause the release of pro-inflammatory mediators such as histamine and cytokines (IL-1), (TNF-α) and (IL-6)

Inflammation and skin damage 

Due to numerous scratches, the protective layer of the skin will be damaged, which will lead to the further release of inflammatory mediators that will increase the sensation of itching. 

Nerve fiber sensitisation 

Constant scratching excites the fibers that are present in the affected area, making them respond faster to the itch stimuli, which means even minor irritants can cause very intense itching.

Lichenification (skin thickening)

Thickening of the skin due to chronic scratching is more susceptible to itching. 

Worsening of the condition 

Over a certain period of time, the cycle will cause neurodermitis, which will lead to further skin damage and further inflammation and secondary infections that will lead to more complexities of the condition.^7,10

Symptoms

Neurodermatitis is characterized by the following symptoms:

• The most common feature is intense itching, and it's mostly localized in an area where repeated itching occurs on the skin
• Thickening of the skin (lichenification)
• Hyperpigmentation or hypopigmentation, where the affected area will appear darker or lighter than the rest of the skin tone color
• Plaques (thick and hard patches) 
• Discomfort 
• secondary infections 
• Psychological impact¹ 

Diagnosis

Clinical evaluation

Physical examination is essential because the dermatologist will check the affected area if there are signs of LSC like thickening, plaque, hyperpigmentation, or hyperpigmentation and skin line. This usually occurs on the neck, lower leg, forearm, genitals, and wrist. Patient history is taken to ask about the onset of action of itching and tries to identify the causes such as anxiety, stress, irritants, or trauma, and medical history if there are any other atopic conditions.⁸

Differential diagnosis

Differentiating between conditions is essential because neurodermatitis (LSC) has common characteristics with other dermatological conditions. Psoriasis can be identified by having silver scales. Contact dermatitis when exposed to irritants frequently. Atopic dermatitis starts in childhood and is widely spread on the body. Laboratory tests are used to gain skin samples and do a biopsy; this will identify if there is any thickening or inflammation.⁸

Treatment and management

Treatment of lichen simplex chronicus may include topical anti-inflammatory therapies like corticosteroids (high potency may be applied for three weeks at a time for thicker plaques); topical emollients such as antibiotics if infection is highly likely or present, especially if immunosuppressant drug therapy is being used; and antihistamines can be used to prevent exacerbation by allergic mediators. Anxiolytics or antidepressants can be used for the management of stress. Cognitive-behavioral therapy (CBT) can be used in order to break the cycle of itch-scratch. Doing meditation and relaxation to relieve stress. UVA or UVB and photochemotherapy exposure therapies can be used for severe cases, excluding genitale involvement. The involvement of psychological treatment is also essential, as is psychotherapy and anti-anxiety medications in drug therapy. Surgical intervention known as cryosurgery.¹

Complications

Neurodermatitis does not fade away on its own; treatment for it is essential to avoid the following complications: 

• Sleep problems: harsh scratching will sometimes lead to insomnia at night 
• Scars: Continuous scratching can lead to permanent scars, which will be visible marks 
• Infections: Other parts of the skin might be infected due to exposure and the breaking of the skin protective layer 
• Long-term recurrence: Neurodermatitis is known to be a chronic condition so long-term management is needed to avoid moments of remission and flaring 
• Emotional distress: The skin alteration can lead to anxiety, stress, and social withdrawal due to embarrassment⁹

Summary

The pathophysiology of lichen simplex chronicus (neurodermatitis) has many factors associated with it, from neurological to psychological impacts. By the demonstration of the itch-scratch cycle, we can see that continuous itching can lead to frequent scratching, resulting in hyper or hypopigmentation of the affected area and thickening of the skin. The harsh scratching due to a very intense itch can lead to inflammations, which are caused by the interactions between the skin cells and nerve fibers. The high exposure to secondary infections is ultimately because of the skin integrity disruption caused by chronic scratching due to the dysfunction of the skin barrier and dysregulation of the immune system. Nevertheless, continuous advancements in comprehending the pathophysiology of neurodermatitis are very essential in order to develop useful treatments that are effective in breaking the itch-scratch cycle, addressing the neurological and psychological factors, and most importantly, restoring the skin integrity.