Notalgia paresthetica

Notalgia paresthetica is a chronic localised sensory neuropathy of the mid-back, characterised by itching, burning or tingling between the shoulder blades, usually within the T2 to T6 dermatomes, often with a hyperpigmented patch produced by chronic scratching.

It belongs with the neuropathic itch disorders alongside brachioradial pruritus, and current evidence links it to degenerative change or compression of the thoracic spinal nerves rather than to primary skin disease.

Terminology and classification

• Notalgia paresthetica is a chronic localized sensory neuropathy characterised by itching, burning or tingling in the mid-back, usually between the shoulder blades.
• The name combines a Greek root meaning back pain with a second root meaning abnormal sensation, and it describes the two dominant qualities of the disorder.
• It has also been called hereditary localized pruritus, posterior pigmented pruritic patch and subscapular pruritus in older dermatological literature.
• It is a form of neuropathic itch in the same category as brachioradial pruritus, and it is not a primary dermatosis.
• ICD-10 has no dedicated code, so the condition is usually recorded under codes for pruritus or peripheral neuropathy, whereas ICD-11 includes an entity for notalgia paresthetica.
• The Human Phenotype Ontology term for pruritus, HP:0000989, captures the dominant phenotype and is used when phenotyping affected patients.
• It must be distinguished from psychogenic pruritus and from primary skin disease that has produced secondary pigmentation.

History

• The term notalgia paresthetica was introduced in the 1930s, and Astwazaturow is usually credited with the early clinical description.
• In 1978 Pleet and Massey published a clinical series in Neurology that established the entity in the English-language dermatology and neurology literature.
• Savk and colleagues published a pathogenesis study in 2000 that linked the localization to degenerative changes of the thoracic spine.
• In 2006 Weinfeld and colleagues reported successful treatment with intradermal botulinum toxin type A, and later series described prolonged relief.
• High-concentration capsaicin patches were tested for neuropathic itch in the 2010s, and Andersen reported variable responses in a small series published in 2016.
• The pigmented patch was long regarded as the primary lesion, but it is now understood as a consequence of chronic scratching.
• Recognition of neuropathic itch as a distinct mechanism has reframed the condition as a nerve disorder rather than a skin disorder.

Epidemiology

• Notalgia paresthetica is common in dermatology practice, and clinic-based series report it in roughly 1 to 2 percent of patients with chronic pruritus, making it one of the more frequent causes of unexplained itch referred to specialist clinics.
• It affects mainly middle-aged and older adults, with most series reporting a peak between 40 and 60 years of age.
• Women are affected more often than men in most case series, although referral bias may contribute to this pattern, and the female predominance is consistent across dermatology and neurology series.
• Familial cases have been described under the label hereditary localized pruritus, suggesting a genetic contribution in a minority of patients.
• The condition is probably underdiagnosed because the itching is often attributed to dry skin or to a primary dermatosis.
• There is no associated mortality, but sleep disruption, irritability and impaired quality of life are common.
• Population-based prevalence estimates are lacking, and most figures come from tertiary dermatology clinics with selected referral populations.

Pathophysiology

• The favoured mechanism is focal compression or irritation of the posterior rami of the spinal nerves from T2 to T6.
• These posterior rami pass at a right angle through the multifidus muscle, a course that may make them vulnerable to otherwise trivial mechanical insults.
• Cervical and thoracic spondylosis, disc protrusion and vertebral compression fractures have been reported in a large proportion of patients, and these changes are most often seen at the levels that correspond to the affected skin.
• Neuropathic itch arises from sensitization of cutaneous C fibres and from loss of small nerve fibres, and intraepidermal nerve fibre density is reduced in some biopsies.
• The notalgia component refers to a deep aching quality, while paresthesia reflects spontaneous firing in irritated nerve fibres.
• The hyperpigmented patch is secondary to repeated scratching and is not a primary pigmentary disorder.
• An association with multiple endocrine neoplasia type 2A has been suggested in case reports but is not established.

Clinical features

• The cardinal symptom is itching between the shoulder blades, usually on one side and more often on the left, and the itch is often most intense in the evening and at night.
• Burning, tingling, numbness or hyperesthesia may accompany the itch and can be more troublesome than the itch itself.
• A well-circumscribed hyperpigmented patch is present in many patients, sometimes with lichenification and excoriations.
• There is no primary rash, vesicle or scale, which helps distinguish it from inflammatory dermatoses.
• The course is chronic and relapsing, and heat, stress and friction often worsen the symptoms.
• Sleep disturbance, impaired concentration and reduced quality of life are common consequences of persistent itch, and the resulting sleep deprivation may itself worsen the itch.
• Bilateral or more widespread involvement occurs occasionally and should prompt a search for another cause.

Diagnosis

• Diagnosis is clinical and rests on the characteristic location, the quality of the itch and the absence of primary skin lesions, and a clear response to topical treatment or to a nerve block can provide supportive evidence.
• Examination should include sensory testing for light touch, pinprick and temperature and a careful search for the pigmented patch.
• Dermoscopy may show a reticulated pigment network, but this finding is not diagnostic on its own.
• Differential diagnosis includes brachioradial pruritus, lichen simplex chronicus, prurigo nodularis, allergic and irritant contact dermatitis, tinea corporis, herpes zoster and xerosis.
• Delusions of parasitosis and other psychocutaneous disorders must be excluded, particularly when the itch is described as crawling.
• Spinal imaging is indicated when neurological signs, radicular pain or a history of trauma are present.
• Skin biopsy with intraepidermal nerve fibre quantification can support a neuropathic origin, and systemic causes of pruritus such as renal, hepatic, thyroid and haematological disease should be excluded.

Management

• There is no curative treatment, and management aims to break the itch-scratch cycle and to treat any underlying spinal disease, and patients should be told that complete and permanent relief is uncommon.
• Topical capsaicin 8 percent patches, available as Qutenza, reduce neuropathic itch in some patients but cause transient burning and the benefit varies.
• Topical lidocaine and short courses of topical corticosteroids may relieve symptoms, although the evidence for both is limited.
• Gabapentin, pregabalin and oxcarbazepine have been reported to reduce itch severity in small series.
• Intradermal botulinum toxin type A produced prolonged relief in case reports, and the effect may outlast the usual three to six months of neuromuscular blockade.
• Paravertebral nerve blocks with bupivacaine and methylprednisolone acetate have been used for refractory cases.
• General measures include emollients, avoidance of scratching and irritants, and physiotherapy for postural and spinal contributors.

Research and controversies

• Evidence is limited to small trials and case series, and no large randomized trial has established a standard of care, with most published studies including fewer than 50 patients.
• The response to capsaicin is inconsistent, and a 2016 series found considerable variability even with the 8 percent patch.
• Whether botulinum toxin acts on sensory nerve endings or on muscle spasm remains uncertain, and the long duration of benefit is unexplained.
• The association with spinal degeneration is supported by imaging series but is not universal, and some patients have no structural abnormality.
• Some authors question whether notalgia paresthetica is a distinct neuropathy or a regional variant of neuropathic itch.
• Validated outcome measures for neuropathic itch are being developed, and future trials will need better endpoints than a global patient impression.
• Patient education about the benign nature of the condition and about pigmentation caused by scratching is an important unmet need.