Introduction

What is “Notalgia Paresthetica”? It sounds like a complicated term, and you may wonder if it’s a rare disease. However, despite sounding so complex, notalgia paresthetica is actually a very common condition. 

This article will discuss the symptoms, causes, pathophysiological mechanisms of Notalgia paresthetica and its treatment. Also, you will learn about physical exercises to improve its symptoms.

‘Notalgia’ means “pain in the back,” and the word ‘Paresthetica’ interprets “ burning pain, tingling or itch.”² It is a common condition affecting middle-aged people assigned female at birth (AFAB). It is characterised by itching on the inner side of our shoulder blade on our back, and usually occurs unilaterally.³ There is no visibility of primary skin lesions, but scratching the area can cause secondary changes. It is a benign condition and is caused by irritation to thoracic nerves 2 to 6.

Symptoms

• It's mainly enclosed in the dermatomes of T2-T6
• Itchiness, burning or tingly feeling in the inner part of the shoulder blade
• Also, patients may complain of pain, heat, cold, a foreign body, tingling and numbness

Skin alteration

• There are no primary skin lesions
• Development of hypopigmentation (brown marks) and hyperpigmentation (white marks) due to constant scratching and a lichenification patch
• Patients tend to scratch the lesions when they are distracted and asleep, which worsens the lesions and leads to scarring
• Alteration in the sensation in the skin is observed when we prick with a pin or touch with a cotton wool and apply heat and cold⁵

Which nerves are involved in notalgia paresthetica, and what are its causes?

• Irritation and damage to the thoracic nerves 2 to 6 are known to be the causative factor, but the exact location and damage are not yet clear. These nerves run a lengthy course through the thick muscles of the back. They make a ninety-degree turn when reaching the skin. These nerves are prone to compression and injury. Even slight compression also leads to these symptoms⁵
• Most studies indicate thoracic polyradiculopathy due to spinal nerve compression as the primary reason for itching.³ The main reason for this conclusion is because of radiographic findings
• The mentioned thoracic nerves can also be impinged due to degenerative changes in vertebrae and herniated intervertebral discs
• Bone lesions, such as Kyphosis and vertebral hyperostosis, are other causes

Peripheral causes of notalgia paresthetica

They are categorised as physical, anatomical, genetic, metabolic and infectious.

The reason for physical causes is muscle spasms due to a back injury.

Some authors suggest that specific nerves pass through the multifidus spinae muscles at a required anatomical angle. The alteration in the angle may make the nerves get irritated more by regular muscle movements or spasms.

Other rare causes are genetic causes like MEN2A, metabolic problems like type 2 diabetes mellitus, and infectious causes like herpes zoster.

 Physical therapy might reduce nerve irritation by altering the angle and changing the tone of the paraspinal muscles. There are also controversial conversations which state that radiculopathy is seen in a dermatomal pattern and not in a localised area, as seen in notalgia paresthetica.

How often does notalgia paresthetica occur?

Notalgia paresthetica comes under the category of chronic neuropathic pruritus, that is, long-term itchy conditions caused by nerve damage, which comprises 8% of all cases of chronic pruritus.

It does not have a racial preference.

It is seen mainly on the opposite side of the dominant hand. 

As most of the population is right-handed, the left-sided itching near the scapula would strongly suggest notalgia paresthetica.

Diagnosis

Normally, diagnosis is done through the patient's history and physical appearance. Sometimes, further imaging is required to rule out other conditions.

Dermatologic, neurologic, orthopaedic examinations⁴, skin biopsy, radiographic image of spine and electrodiagnostic tests are done to come to a conclusion.

Pathophysiological mechanisms

The itching sensation is a complex process which involves sensitive neurons and adjacent cellular mechanisms that help to maintain it. When there is a disruption of this process, there is abnormal activation of itch-transmitting fibres without a definite itch stimulus. This is called alloknesis.

The transmission of itch is at least from 2 types of nerve fibres.

1. The small, unmyelinated C-fibres are believed to be the primary transmitters of itch. They are sensitive to histamine
2. The other nerve fibres transmit both itch and pain

Since there are dual functions of fibres, patients feel different sensations like tingling, pins and needles, Allodynia (a symptom of pain although there is no pain) and itching.

Some itch-sensitive fibres might be associated closely with thermoreceptors (heat sensors), which explains the reason why heat makes itching worse.

Notalgia paresthetica results from a combination of factors, which involve nerve irritation and an abnormal itch control mechanism.

What are the treatments for notalgia paresthetica?

Patients with mild or intermittent itching can be treated by reassurance. They may not require any treatment.

Gabapentin, an oral medication, is used for treatment when necessary.

First-generation antihistamines might be used to reduce scratching during the night as they have a sedative effect.

Capsaicin is the most commonly used topical agent and provides immediate relief. It is recommended when there is inflammation. Anaesthetics, amitriptyline/ketamine and doxepin are rarely used.

Botulinum toxin-A is used, but later studies have shown that it does not bring about much improvement.

TENS (transcutaneous electrical nerve stimulation) has been effective in a few patients, but it has not been very effective in other studies.

Physical therapy and repetition of exercises have proven to be effective

• Crossing our arms and bending forward to stretch the upper back muscles while sitting
• Keeping our arms at our sides, shoulders raised and rotating them forward and backwards
• Keeping our arms straight and rotating at a 360-degree angle
• To rotate our upper body left and right, and hold the stretch
• Massaging the muscles in the affected area also helps⁵

Differential diagnosis

Musculoskeletal pathologies: Osteoarthritis, cervical disc disease, cervical stenosis, osteoarthritis, vertebral fracture, and Malignancies.⁶

Dermatologic pruritic diseases: Contact dermatitis, parapsoriasis and neurodermatitis.

FAQs

What do you mean by alloknesis itch?

Alloknesis itch is a type of itch or itching sensation or scratching behaviour triggered by a stimulus which is non-itching in nature. 

What is Apley’s scratch?

It is a test mainly to diagnose the shoulder's flexibility of movement. It contains three types of hand movements. During these movements, the patients with notalgia paresthetica can easily reach back to the lower angle of the opposite shoulder blade (Scapula).

Summary

Notalgia paresthetica is a benign chronic pruritus condition which is seen mainly in middle-aged AFAB. There is usually an abnormal sensation, like itching, tingling, underneath the shoulder blade. Due to the constant itching, there are hyperpigmented skin lesions. The diagnosis can be easily done with the patient's history and symptoms. Reassurance to patients works with mild symptoms, but necessary oral and topical medicines are advised to control the itch in patients.

It's also advised to do physical exercise, which has proven effective.