Introduction 

Every once in a while, almost everyone gets an itchy skin. This could be due to allergies caused by new skincare products, medications, and food. Itching of the skin could also be caused by dryness, stress, and as a warning sign of a silent systemic disease. This itching can subside once the root cause is addressed. However, it can become irritating and a tad worrisome when the itching persists.  

This persistent itching is referred to as Notalgia paresthetica. In this condition, the skin of the upper back (either left or right) becomes chronically itchy. Thus, repeated scratching of the itch is difficult to withstand.  

As a result, this overstimulates the cells of the affected area. Subsequently, this could cause brownish patches of skin compared to the surrounding unaffected skin, called hyperpigmentation. But why and how does this happen? This article simplistically unravels the mechanism and triggers of chronic itching in notalgia paresthetica. 

Understanding notalgia paresthetica

According to the American Osteopathic College of Dermatology, nostalgia paresthetica (NP) is a chronic neuropathic condition characterised by intense itching of the skin in the middle of the upper back. NP occurs at the inferior or medial aspect of the scapula (i.e., your shoulder blade) and is usually one-sided.

This condition was first described in 1934 by a Russian neurologist, Michail Astwazaturow, as a sensory neuropathy with pruritus as the hallmark symptom.¹ NP can be accompanied by pain, paresthesia, and hyperesthesia. Notalgia indicates pain in the back, while paresthesia denotes burning pain or itch.

NP doesn’t have a racial predilection and is usually encountered worldwide. However, it occurs more in women than in men between the ages of 54-62 years old.² Additionally, an individual's family history can increase the risk of developing NP. For hereditary cases, NP can start at an early age in infants, teens, and, less frequently, young adults.³

Notalgia paresthetica, also called cutaneous nerve syndrome, can occur with or without hyperpigmented macules. NP can worsen with time and can last for months to years. Other symptoms of NP apart from pruritus (i.e., itching) include burning sensation, numbness, soreness, tingling, and discomfort. 

Why does itching occur in notalgia paresthetica?

The itching sensation in NP stems from some type of injury or dysfunction to the sensitive neurons and cellular mechanisms that regulate it. Typically, the thoracic nerves are made up of 12 pairs of spinal nerves (numbered T1-T12) that originate from the thoracic segment of the spinal cord and innervate the motor and sensory neurons. This implies that these nerves control movement and sensation in the back, chest, and abdomen.⁴

The specific aetiology of NP is not well elucidated. However, the following are the possible mechanisms that describe the pathogenesis of NP;

• Damage to sensory branches of thoracic nerves (T2 and T6): The spinal nerves T2-T6 pass through the spinal muscles at a right angle after coming out of the spinal cord. This makes them vulnerable to injury and entrapment by spinal muscles, resulting in notalgia paresthetica⁴
• Aberrant firing of itch-transmitting neurons: The abnormal firing of itch-transmitting nerve fibres is primarily attributed to nerve irritation and a dysfunctional itch control mechanism in the nervous system.⁵ Specifically, nerve damage or irritation in the area of the thoracic spinal nerves (T2-T6) can cause the unprovoked stimulation of these fibres

This can be caused by nerve root compression, often due to degenerative conditions in the spine. The resulting nerve damage can then trigger the release of neurotransmitters such as histamine and other neurotransmitters. Consequently, these excite histamine-sensitive nerve fibres called C-fibres, leading to the itching sensation.⁵

• Disrupted itch-control mechanism: Similar to the activation of itch-transmitting nerve fibres, nerve injury or damage can disrupt the normally regulated itch-control mechanism.  This nerve impingement could be caused by chronic nerve trauma, musculoskeletal problems, etc. Dysregulation of this mechanism can also lead to a disorder called alloknesis⁶

Other signs and triggers of NP

NP is mostly unilateral, but in some cases, both sides of the back can be involved (i.e., bilateral). Fascinatingly, NP occurs on the opposite side of the dominant hand.² For instance, if the individual uses the right hand dominantly, NP will occur on the left side of the back. Notaliga paresthetica can evoke the following symptoms;

• Pruritus, which can be chronic and persist for years
• Alloknesis 
• Pain 
• Allodynia 
• Fluctuating heat and cold sensations
• Hyperesthesia 
• Secondary skin lesions due to chronic scratching of the area⁷
• Lichenification and excoriations

Some predisposing factors and triggers of NP include; 

• Degenerative disc disease
• Intense exercise
• Prolonged bed rest 
• Disc herniation 
• Paraspinal muscle spasm⁸
• Spinal stenosis
• Accidents or trauma that affect the nerves⁸
• Neurotoxicity of certain chemicals 

Other less common triggers of NP include genetic predisposition, especially in people with conditions like MEN2A, metabolic disorders such as type 2 diabetes, and infectious etiologies such as herpes zoster.⁹

Treatment options and management of NP

Several techniques have been used for the treatment and management of people with NP, but they show conflicting results and varying levels of success. Hence, no single intervention has proven to be the mainstay procedure for treating this benign but stubborn condition. Fortunately, patients with mild or intermittent NP may require no treatment.¹⁰

Thus, the treatment options for NP include the following; 

• Use of topical agents such as capsaicin, lidocaine, and botulinum toxin A
• Oral medications such as gabapentin, oxcarbazepine and amitriptyline
• Transcutaneous electrical nerve stimulation (TENS)¹¹
• Cervical traction
• Exposure to narrow-band ultraviolet-B radiation¹²

Certain procedures that could help relieve the symptoms include acupuncture and spinal nerve block (with an anti-inflammatory agent like methylprednisolone)¹¹

Physical therapy specifically targeting the paraspinal muscles, accompanied by repetitive back exercises and stretches, is effective in some cases. These types of exercises reduce the angle at which cutaneous nerves interfere and injure the paraspinal muscles. As a result, there is a significant reduction in irritation and itching.¹³

Summary

Notalgia paresthetica is a chronic and overlooked sensory neuropathy characterised by abnormal sensation of the skin with pruritis as the hallmark symptom. This condition is also associated with burning pain, heightened sensitivity to sensory stimuli, numbness, and tingling. NP can persist for months to years and is more common in middle-aged people assigned female at birth  (AFAB).

Three basic mechanisms have been postulated to cause NP, which include: damage or trauma to the sensory branches of the thoracic nerve (T2 and T6), abnormal firing of itch-transmitting neurons, and a malfunctioning itch-control mechanism. The main trigger for NP is nerve injury or some sort of pressure on the nerve root. Additionally, intense exercise, herniated discs, and minor trauma to the thoracic nerves can also trigger the onset of NP.

The treatment options involve the use of topical and/or oral agents, physical therapy, massage, etc. However, these interventions have generated conflicting results in different studies. Therefore, collaborative multidisciplinary approaches must be incorporated by dermatologists, pharmacists, radiologists, orthopaedic surgeons, and neurologists for the successful management of this condition.

FAQs

Can home remedies help with notalgia paresthetica?

Yes, exercises can be used to stretch the pectoral muscles and strengthen the thoracic spinal extensor muscles.  This can help decrease postural stress and reduce pressure on the cutaneous nerves. 

What are the long-term complications of NP?

Potential complications that could be associated with notalgia paresthetica can include secondary skin infection, hyperpigmentation due to intense rubbing, lichen amyloidosis, lichen simplex chronicus, and prurigo nodules.

Can NP go away on its own without treatment? 

Yes, notalgia paresthetica can go into remission in some patients. Although Notalgia paresthetica isn't life-threatening, the symptoms can affect your quality of life and cause discomfort and skin conditions. 

How is NP diagnosed? 

Notalgia paresthetica is primarily diagnosed through a thorough investigation of medical history and physical examination of the patient. A doctor will assess the patient's clinical features, such as chronic itching, and examine the back for signs of skin changes such as hyperpigmentation. Additionally, a skin biopsy or imaging scans may be done to rule out other differential diagnoses or assess for an underlying spinal problem.