History
See the list below:
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The onset of pain in brachial neuritis (BN) is often abrupt and may follow recent illness, surgery, [8] immunization, or even trauma (see Causes, below). Up to two thirds of cases begin during the nighttime.
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The pain usually is localized to the right shoulder region, but it may be bilateral in 10-30% of cases.
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The pain's intensity is very high (9+/10) and is maximal at onset.
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Usually, the pain is described as sharp or throbbing in nature.
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The pain usually is constant, but it is exacerbated by movements of the shoulder. Movements of the neck, coughing, and/or sneezing usually do not worsen the pain.
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Intense pain can last from a few hours to several weeks and requires opiate analgesia.
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Low-grade pain may persist for up to a year.
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As the pain subsides, weakness becomes apparent.
In most cases of BN, this weakness manifests within about 2 weeks of onset.
Weakness is maximal at onset but can progress over 1 or more weeks.
A wide variety of muscles is affected, particularly those innervated by the upper trunk. The supraspinatus, infraspinatus, serratus anterior, and deltoid muscles are particularly susceptible, but many different single and multiple combinations of muscle involvement, including a pure distal form, have been reported.
The patient may notice considerable atrophy and wasting, as well as a deep aching in the affected muscles.
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Numbness may occur, depending on the particular nerves affected, and usually is found in the nerve distribution corresponding to maximal muscle weakness. However, numbness is rarely a prominent complaint.
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Variants of BN can present with isolated or multiple cranial neuropathies (IX, X, XI, XII). [33]
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In 25-50% of patients, the medical history indicates a viral illness or vaccination that occurred days or weeks prior to the onset of symptoms. Some patients also may note recent trauma or severe exercise, surgery, infection, or immunization.
Physical
See the list below:
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Due to the extreme pain involved, patients with brachial neuritis usually present acutely. Typically, the affected arm is supported by the uninvolved arm and is held in adduction and internal rotation.
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Atrophy of the affected muscles becomes prominent after approximately 2 weeks.
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Considerable muscle pain may be noted on palpation.
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Passive and active attempts at shoulder and scapular movement result in a significant increase in pain. Movements of the neck are relatively pain free.
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Muscle strength in affected muscles often is reduced severely (to 2 or less on the Medical Research Council [MRC] grading scale).
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Reflexes may be reduced or absent, depending on which nerves are involved.
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Sensory loss is not prominent but may be detectable (in particular, loss of axillary nerve sensation), depending on the specific nerves affected.
Causes
The exact cause of brachial neuritis is unknown, but the condition is thought to be associated with an immune-mediated response to an as yet poorly understood trigger. Brachial neuritis has been linked to many antecedent events or illnesses, as follows:
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Viral infection (particularly of the upper respiratory tract)
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Bacterial infection (eg, pneumonia, diphtheria, typhoid)
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Parasitic infestation
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Surgery [8]
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Trauma (not related to shoulder)
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Vaccinations (eg, influenza, tetanus, diphtheria, tetanus toxoids, pertussis [DPT], smallpox, swine flu)
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Childbirth
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Miscellaneous medical investigative procedures (eg, lumbar puncture, administration of radiologic dye)
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Systemic illness (eg, polyarteritis nodosa, lymphoma, systemic lupus erythematosus, temporal arteritis, Ehlers-Danlos syndrome)
A rarer, hereditary form of BN has been localized to the SEPT9 gene on chromosome arm 17q and should be considered a distinct disorder. This entity presents in a younger age group, affects males and females equally (autosomal-dominant inheritance), and is characterized by recurrent, often bilateral attacks. Dysmorphic facial features (eg, hypotelorism, long nasal bridge, facial asymmetry) can also be present.
A study from England and the Netherlands found that in samples of British and Dutch patients with brachial neuritis, about 10% had hepatitis E. In the combined retrospective (British)/prospective (Dutch) study, van Eijk et al found hepatitis E virus (HEV) infection in five out of 47 patients. Clinical and electrophysiologic examination indicated that the brachial neuritis was bilateral in all of the patients with hepatitis E. [34, 35]
A study by Ripellino et al found that of 141 cases of acute HEV infection in southern Switzerland, 43 patients (30.5%) had neurologic symptoms, with 28 patients (19.9%) having myalgia, and 15 patients (10.6%) having brachial neuritis. [36]
The French National Agency for the Safety of Medicines and Health Products (ANSM) reported evidence of brachial neuritis as an adverse effect of mRNA vaccinations for coronavirus disease 2019 (COVID-19). For example, serious brachial neuritis cases were found in six individuals who received the Pfizer/BioNTech vaccine, with symptoms developing within 50 days post-vaccination; three cases occurred after the first vaccine dose, and three were reported after the second. The patients were aged 19 to 69 years. Two cases developed less than 18 days post-vaccination in patients who received the Moderna vaccine, with brachial neuritis arising after the first dose in one patient and after the second dose in the other. A third case associated with the Moderna product occurred a number of weeks following vaccination. There is also some evidence of brachial neuritis arising in a small group in association with AstraZeneca’s viral vector vaccine. [37]
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The patient is a 43-year-old farmer, shown 6 months after presenting with severe right shoulder pain and weakness. Note severe wasting of the right infraspinatus and deltoid and winging of the scapula.
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Same patient as above. Note again severe supraspinatus and infraspinatus wasting on the right.
