Notalgia Paresthetica

Notalgia paresthetica (NP) is a sensory neuropathic syndrome of the mid back skin, classically described as the unilateral infrascapular area. Notalgia paresthetica is primarily a localized pruritus and dysesthesia syndrome, and it may present with episodic itching or pain on a small patch of the skin around T2-T6, usually an area of skin just past easy reach. Notalgia paresthetica is very common; however, it remains heavily underrecognized and largely underdiagnosed. ^{[1, 2]}

Atypical presentations of notalgia paresthetica have been described, including localized pruritus of the upper back, scalp, and shoulder. ^{[1, 3]} Also described are atypical presentations of an itchy back consistent with notalgia paresthetica accompanied by concurrent or serial presentation of itchy forearms, arms, and/or lower extremities, including the soles. Most recently, notalgia paresthetica has also been described in association with brachioradial pruritus (BRP) in a large number of patients. ^[4] Often, BRP may involve one or both forearms and may be episodic in nature, similar to notalgia paresthetica. 

Accordingly, in 2020 Alai introduced a new term skin-itch-spine-syndrome (SISS), which encompasses notalgia paresthetica and its related spinal paresthesias. Spinal paresthesias, or spinal paresthetica, are neurocutaneous disorders that embody the SISS, including notalgia paresthetica, BRP, meralgia paresthetica, and burning scrotum syndrome. ^[5]

Additional features of notalgia paresthetica may include localized burning, pain, tenderness, hyperalgesia, or dysesthesias. ^[6] Notalgia paresthetica may be associated with a poorly circumscribed tan or hyperpigmented patch in the symptomatic area. Notalgia paresthetica tends to be a chronic condition with periodic remissions and exacerbations. While not life threatening and not generally associated with other comorbidities, notalgia paresthetica frequently decreases quality of life, causing much discomfort and nuisance to the affected patients.

Generally speaking, notalgia paresthetica is described in relatively high association with cervical musculoskeletal disease, particularly at the C5-C6 level. Although radiographically documented cervical spinal disease is not uncommon, it is not a requirement to make the diagnosis of notalgia paresthetica.

Even in the absence of radiographic findings, a significant number of notalgia paresthetica patients have a history of neck pain at some time in their life, painful neck muscle spasm, asymptomatic neck spasm, interscapular pain, arthritis, and neck injuries. Treatment of the underlying neck pathology through nondermatologic modalities often results in temporary improvement of the notalgia paresthetica symptoms. Therapies, including transcutaneous electrical nerve stimulation (TENS) and electrical muscle stimulation (EMS) of the neck, have proved to be some of the most effective and promising treatments for this otherwise refractory condition.

Conversely, topical treatments aimed primarily at the affected back skin are essentially unsatisfactory and ineffective. Traditionally, therapies such as capsaicin have been described as prior mainstays in treatment of notalgia paresthetica; however, therapies aimed at treating the underlying musculoskeletal pathology are likely much more effective than using topical therapies aimed at essentially masking the cutaneous symptoms. ^[7]

Notalgia paresthetica is not seen commonly, if at all, in the pediatric population and is most commonly seen in adults aged 40-80 years. There is a described female predominance for notalgia paresthetica.

Often, these pruritic conditions are observed in the absence of any other skin pathology and the presence of a history of cervical pain or trauma. It is therefore important to consider atypical variants of notalgia paresthetica in patients presenting with refractory, recurrent bouts of localized pruritus in essentially healthy skin and of otherwise undetermined etiology. A review of systems evaluation for relevant cervical disease and a contributory physical examination for palpable cervical muscle spasm and tenderness may be diagnostic for notalgia paresthetica.

Although the etiology of notalgia paresthetica (NP) is unclear. Multiple possible mechanisms have been proposed, including localized increased sensory innervation of the affected skin areas and neuropathy from degenerative cervicothoracic disk disease or direct nerve impingement. ^{[8, 9, 10]}  

Alai et al in 2010 demonstrated a case of notalgia paresthetica with confirmed cervicospinal disease at C4-C6. ^{[1, 11]} Savk et al in 2003 showed that more than half of their patients had significant radiographic changes in the vertebrae corresponding to the dermatome of the cutaneous lesion. Further, all study patients demonstrated normal neurological examination findings and standard electrodiagnostic results. All had skin histopathology compatible with postinflammatory hyperpigmentation. No amyloid deposits or other described pathology were noted upon pathologic examination of the skin. ^[12]  

Alai and Skinner in 2018 reviewed the association of BRP and notalgia paresthetica, and concurrent occurrence in the same patient, with MRI proven C5-C6 disk disease. ^[4]

Springall et al in 1991 concluded that the symptoms of notalgia paresthetica may, in part, be related to an increase in the sensory epidermal innervation in the affected skin areas. ^[9] Histological studies have shown cutaneous changes in a few cases, including lichen amyloid, which may be secondary to the localized chronic scratching and rubbing. ^{[9, 13]}

Some believe a relationship exists between notalgia paresthetica and brachioradial pruritus (BRP), because both are types of localized pruritus syndromes. The recently described association of many cases of BRP and cervical spine disease and descriptions of the disease as a possible neuropathic/neurogenic condition also support a probable neuropathic association with notalgia paresthetica. ^{[12, 14]} In contrast, notalgia paresthetica is generally unilateral, while BRP may involve the unilateral or, less commonly, bilateral upper extremities.

While the exact etiology of the cutaneous findings of notalgia paresthetica (NP) remains unknown, it is largely a dermatologic sign of an underlying systemic disease.

Notalgia paresthetica is not solely a skin disease but a cutaneous sign of an underlying musculoskeletal condition, including degenerative cervical spine disease and muscular spasm. The striking association of notalgia paresthetica with degenerative or traumatic cervicothoracic spine disease suggests that early spinal nerve impingement at the C4-C6 level may contribute to the pathogenesis of the skin symptoms of the disease in some individuals.

Additional studies are needed to further assess the relationship of notalgia paresthetica with cervical musculoskeletal disease. Whether this is a causal or coincidental finding remains to be determined in larger studies. While topical therapies may appear to help decrease the localized symptoms of notalgia paresthetica in a small percentage of patients, systemic or broader-scope cervical examination and a spinal evaluation are warranted to fully evaluate refractory cases. Cervical examination and potential spinal imaging and treatment may be appropriate as primary or first-line therapy in many cases of notalgia paresthetica. ^[15]

Frequency

Notalgia paresthetica (NP) is a relatively common disorder and remains largely underdiagnosed. Therefore, the true frequency may not be accurately reported. Notalgia paresthetica is described worldwide in persons of all races. National variations have not been described.

Race

Notalgia paresthetica may be seen in persons of any race, without any described racial predilection.

Sex

Notalgia paresthetica (NP) may be seen in both males and females. Sexual predilection may tend to favor females; however, large-scale studies are required to define the incidence.

Age

Notalgia paresthetica (NP) is more common in adulthood, typically in persons aged 40-80 years. The exact incidence is unknown.

Notalgia paresthetica (NP) tends to be a chronic disease with periodic remissions and exacerbations. The prognosis for control of the symptoms is good, although the condition has a natural tendency to wax and wane. Notalgia paresthetica generally is not entirely curable, although it is certainly controllable and complete remissions are possible.

While not life threatening, the cutaneous symptoms of notalgia paresthetica frequently decrease quality of life, causing much discomfort and nuisance to the affected patients. In some cases, notalgia paresthetica may become disabling and result in many secondary manifestations of cutaneous disease such as secondary skin infections, prurigo nodules, and lichen simplex.

Some increased morbidity may occur because of the possible underlying cervical and thoracic spine and disk disease. Notalgia paresthetica tends to be a chronic condition with periodic remissions and exacerbations. No increase in mortality is described for notalgia paresthetica.

Although notalgia paresthetica has not generally been described in association with other nonspine comorbidities, Alai et al have described case reports of notalgia paresthetica occurring in patients with conditions such as atopic dermatitis, elevated IgE, hepatitis C, chronic renal insufficiency, and hypereosinophilia. The exact relationship and causation remains to be elucidated.

Patient education involves discussion of possible underlying causes and associations with cervicothoracic spinal disease. Patients need to be advised of potential disease flares with exacerbations of their spinal disease.