Overview

Notalgia Paresthetica (NP) is a common neuropathic condition characterised by a persistent itching sensation on the back, usually on the inner edge of a shoulder blade. Despite manifesting as a skin condition, nerve damage in the mid-back segments of the spinal cord causes NP's signature itch.¹ Due to its unique and often subtle symptoms, NP is both underdiagnosed and underrecognised. The limited data available on diagnosed cases of NP makes it harder to pinpoint its cause.² Still, several studies link NP to back injuries and musculoskeletal diseases. Conventional imaging techniques, like Magnetic Resonance Imaging (MRI) and X-ray imaging, have been crucial in this association, creating new pathways for effective non-dermatological treatments. Specialists are now using MRI and X-ray imaging to both understand and confirm the potential neural and skeletal implications of NP, both aiding in its diagnosis and treatment.^3,4 

Understanding Notalgia Paresthetica

Common signs and symptoms 

NP is chronic but episodic, with symptoms often appearing periodically in patients and lasting for months or even years at a time.⁵ Symptoms of NP are felt mostly on one side of the mid to upper back region, specifically along the inner edge of the shoulder blade. Cases of bilateral NP, where the itching sensation is felt in both shoulder blades, are rare. The itchiness can spread to the wider back, including the shoulder and the general upper back area. 

Here are some signs you might be dealing with NP: 

• Itchiness or burning sensation 
• Pain or tenderness 
• Tingling
• A feeling of heat or cold¹

There are no visible symptoms of NP, but the chronic scratching of the itchy area might produce secondary lesions that can appear as: 

• Bumps 
• Red or brown well-defined patch
• Irritation
• Hemorrhaging⁴

Despite NP not being a serious health concern, these symptoms can severely impact your daily activities, with a third of patients in a large study reporting facing emotional challenges as a result of their condition. NP symptoms can also appear in tandem with other neuropathic conditions, such as brachioradial pruritus (BRP), which manifests with similar symptoms to NP but on the forearms instead.³ However, the condition can affect patients of any age and gender, with some patients as young as six years old.²

What causes Notalgia Paresthetica?

The mechanisms of NP are still being researched. New studies hypothesise it to be related to injury and damage to the spinal nerves. Specifically, the damage tends to be localised to the nerves of the mid-back spinal region, corresponding to rib cage height, known as thoracic nerves. Disc degeneration linked to NP can be of wide-ranging origins, including: 

• Traumatic back injury
• Herniated disc 
• Arthrosis
• Scoliosis 
• Neck problems⁴

Commonly Confused Conditions 

As mentioned earlier, NP is known to be underdiagnosed, and the subtleness of the symptoms can lead those affected to dismiss their condition. When NP patients decide to consult a specialist, misdiagnosis is not uncommon. NP presents similar cutaneous symptoms to other skin conditions, such as: 

• Patchy parapsoriasis 
• Contact dermatitis 
• Tinea versicolor 
• Early cutaneous amyloidosis 
• Neurodermatitis

Regular physical exams and patient history evaluations, in combination with biopsies, can help to rule out some of these conditions. However, in cases where other unrelated signs of musculoskeletal or nerve issues are evident, employing more advanced diagnostic techniques becomes useful.¹

Why Imaging Matters

Even though NP is a benign condition, it becomes vital to investigate further into the underlying condition, especially when it may be related to spinal and nerve issues. Disc degeneration is common and not always symptomatic, but a resulting nerve compression can be a serious health concern. As NP can manifest in association with cervical and spinal issues, examining the spine to reveal any underlying causes and treating the problem at its root rather than soothing a symptom is crucial. 

Imaging serves a three-fold purpose in the evaluation of NP patients:

• Check for disc problems: When present with other symptoms, NP can serve as an alarm bell for disc degeneration and spinal diseases. Imaging these issues can confirm or rule out the presence of these conditions in the patient. 
• Determine the most appropriate treatment plan: NP treatment usually entails multimodal plans, including topical creams, injections, nerve stimulation, and physiotherapy. In cases of detection of back injuries or musculoskeletal issues, treatment can be more targeted, with physiotherapy often being recommended as an appropriate primary treatment. 
• Assess the link between NP and disc degeneration: the causes of NP are still unclear, and understanding them could significantly improve patient care and strengthen diagnostic efficiency. Assessing its link to spine lesions by increasing the number of cases evaluated through imaging techniques would benefit all present and future NP patients.  

Given the importance of identifying underlying spinal issues in NP, imaging techniques like X-rays and MRIs play a central role.

X-rays in Diagnosing Notalgia Paresthetica

What is an X-ray image?

An X-ray is a light ray with a much higher energy than visible light. Due to its very high energy, the ray can pass through some materials that visible light can't go through, such as soft tissue. However, when a material is particularly high in density, such as a bone, even the X-ray is absorbed and mainly reflected off it. X-ray imaging, also referred to as radiography, harnesses the penetration properties of an X-ray to create an image of one's osseous structure. Shining an X-ray through a body part and detecting the light that passes through on the other side reveal a negative impression of the skeletal system.⁶

What an X-ray can reveal about Notalgia Paresthetica

X-ray imaging can reveal the state of a patient's spinal cord, including any alignment issues or degenerative changes. In cases where skeletal issues cause nerve compression related to NP, X-rays can identify degenerative changes in the spines of NP patients, which can be associated with the following diseases:

• Dorsal arthrosis
• Spinal disequilibrium⁷
• Herniated disc 

Unfortunately, because X-rays interact with different tissues distinctly, radiography cannot clearly show soft tissues or nerves. However, since NP is a neuropathic condition, it is important to detect not only the skeletal state but also assess the health of the spinal nerves. For this, other imaging techniques are required.  

MRI in Diagnosing Notalgia Paresthetica

What is an MRI?

MRI creates an image of the internal organs by measuring the collective response of hydrogen in water molecules in our body to a strong magnetic field. Different tissues have different water content, as well as different biomolecular compositions.  These unique environments lead water molecules in each organ to react slightly differently to a magnetic field. This, in turn, means that the hydrogen atoms within water behave differently depending on their anatomical location. An MRI machine detects the hydrogen's reaction to magnetic and electromagnetic impulses, identifying its strength and location. Through this mechanism, an MRI generates a comprehensive image of one's internal anatomy.⁸

What can an MRI reveal about Notalgia Paresthetica?

When focused on your spinal region, an MRI shows the features of your nerves, soft tissue and spinal discs, making it a useful tool to identify neuropathies caused by nerve compression or irritation. Existing studies show that MRI imaging can highlight the following spinal conditions in NP patients: 

• Herniated Nucleus Pulposus 
• Spinal stenosis  
• Cervical degenerative changes  
• Disk protrusion⁹

Other Diagnostic Tools 

You may not have one of the conditions mentioned above. In some cases, MRI and X-rays will not show any disc abnormalities.. For this reason, it is imperative to use multiple diagnostic methods and only include advanced imaging techniques when deemed appropriate by a specialist. Diagnosis of NP will traditionally include: 

• Physical exam 
• Symptom history
• Skin biopsy (if a rash is present)¹
• Electromyography (EMG)

Summary

NP is a common pathology that often hides in plain sight. Despite having the presentation of a skin condition, it arises from nerve-related causes, which can make its diagnosis challenging. Several studies associate NP with spinal nerve compression and irritation, which are often caused by back injury and disc degeneration. MRI and radiographic studies can confirm this nerve irritation or compression and identify the underlying spinal changes that cause the neuropathy. Diagnostic use of MRI and X-rays for NP is still a developing field, but recent studies reveal promising results and open new avenues into understanding the causes of this condition. Identifying and localising the disc degeneration associated with NP can help guide treatment strategies and develop approaches to mitigate other symptoms of the condition.