3 days ago
Ice Relieves Itch? Think Beyond the Skin
Intense itching of the upper arms following sun exposure is often dismissed as a harmless skin reaction. However, this may indicate a neuropathic condition.
Brachioradial pruritus (BRP) is a rare and frequently overlooked cause of pruritus, typically localised to the arms and triggered by ultraviolet (UV) radiation in patients with underlying radiculopathy. BRP is a subtype of neuropathic pruritus that occurs most often in fair-skinned women.
The Patient and His History
A 41-year-old White woman with a past medical history of generalised anxiety disorder and sunburns presented to her general physician (GP) with complaints of sunburn to the bilateral arms, pins and needles, and extreme itching sensation in the bilateral upper arms.
The patient reported that the rash worsened with heat and improved with ice. She also endorsed changes in colour to the rash, hot to touch, tender, mild swelling, and significant nighttime awakening related to the pain associated with the rash.
Earlier treatments with lotions, over-the-counter cortisone cream, and oral Benadryl failed. Only ice application provided brief relief.
Findings and Diagnosis
The patient's vital signs were stable. Physical examination revealed dark erythema on the sunburned areas of the bilateral upper arms and an atypical skin rash. She was referred for both dermatological and neurologic evaluations.
The dermatologist performed a punch biopsy and allergy test, which showed a nickel allergy. The biopsy report showed sparse lymphohistiocytic, superficial, perivascular inflammatory cell infiltrates; features were non-specific, with suggestions that they may be seen in some drug or viral exanthems, gyrate erythema, urticaria, tumid lupus erythematosus, pigmented purpuric dermatosis, and post-inflammatory pigmentary alteration.
The neurologist recommended an MRI of the cervical spine that was normal. The patient was diagnosed with abnormal skin changes and sensory disturbance in the right lateral upper arm with a C5 dermatomal distribution, with recommendations to have dermatology refill topical pain medication (gabapentin 6%, ketamine 4%, and lidocaine 3% cream) and have the GP titrate up the gabapentin dose.
Based on the overall clinical picture and through exclusion of other causes, the GP diagnosed BRP.
The treatment involved a topical formulation containing gabapentin, ketamine, and lidocaine, with oral gabapentin for neuropathic pain. Within 1 month of initiating therapy, the patient experienced marked improvement in both the rash and associated symptoms.
Discussion
The aetiology of BRP is unknown. It has been attributed to prolonged solar radiation exposure in the summer months, exacerbating underlying cervical spine issues, and is associated with cervical nerve root injury in the setting of osteoarthritis or trauma, resulting in the compression of the nerve root.
Multiple studies have found that BRP is associated with cervical radiculopathy in approximately 57% of patients. The itch and rash associated with BRP are mostly located on the dorsolateral aspect of sun-exposed forearms and are exacerbated by sun exposure. In 75% of cases, both arms were involved.
Other neuropathic conditions, such as notalgia paresthetica, similarly involve spinal abnormalities with dermatomal localisation of itching.
One theory proposes that UV radiation damages peripheral nerve endings and may also lead to neuropathic BRP in individuals predisposed to cervical spinal disease. Most patients describe itch as picking, prickling, burning, or plain itch involving the unilateral or bilateral dorsolateral forearms, which are neuropathic features, suggesting that BRP can be associated with a neurogenic origin.
Patients with BRP report that the application of ice packs provides relief from itching. This is called the ice-pack sign, a key diagnostic indicator of BRP, which is pathognomonic for BRP. This sign was evident in the present case, with itching worsening upon exposure to sunlight and being relieved when ice packs were placed on her forearms bilaterally.
Treatment for BRP has been difficult, but some reported treatments include oral gabapentin, topical capsaicin, oral carbamazepine, cervical spine manipulation, neck traction, physiotherapy, anti-inflammatory medications, surgical resection of the cervical ribs, and sunlight avoidance.
In this patient, symptoms improved significantly within 1 month following treatment with oral gabapentin and a topical containing gabapentin, ketamine, and lidocaine.
Early recognition and diagnosis of BRP by taking a thorough history and physical examination and the utilisation of the ice-pack test are critical for prompt management and avoiding unnecessary workup. Thorough history taking, focused physical examination, and use of the ice-pack test are critical diagnostic steps.
In patients presenting with sunburn to the bilateral arms, pins and needle sensation, extreme itching sensation in the bilateral upper arms, neuropathic dysesthesia of the dorsolateral upper extremities, a visible rash, and stating improvement of pruritus with cold compresses, BRP should be considered as a top differential.
