Brachial Plexitis | Diagnosis & Treatment

Brachial plexitis, also known as neuralgic amyotrophy or Parsonage-Turner syndrome, is a rare condition that affects the network of nerves called the brachial plexus, which controls movement and sensation in the shoulders, arms, and hands. This disorder is characterized by sudden and severe pain in the affected area, followed by weakness or paralysis of the affected muscles.

Brachial plexitis can occur at any age, but it most commonly affects young adults. Despite significant research efforts, the underlying cause of brachial plexitis is not well understood, and there is currently no cure for this condition. However, with proper diagnosis and management, most individuals with brachial plexitis can recover some or all of their function over time.

Prevalence

Although it was initially thought to be rare, lack of recognition may have contributed to this belief. It affects between 2 and 3 cases per 100,000 people annually. The condition is more common in males and usually occurs after an illness or environmental factor such as strenuous activity or vaccination (Monteiro et al 2022).

Etiology

There is a fairly broad spectrum of potential causes for brachial neuritis. Infection, whether bacterial, parasitic, or viral, Coxsackie B virus, mumps, variola major and minor, HIV, and parvovirus B19 are some of the more prevalent causes that have been mentioned in the literature (Feinberg and Radecki 2010).

Surgery, anesthesia, rheumatic diseases such Ehlers-Danlos syndrome, systemic lupus erythematosus, temporal arteritis, and polyarteritis nodosa, as well as connective tissue disorders, are other factors that put individuals at risk for brachial neuritis. Other deciding factors include strenuous exercise and injuries to the shoulder girdle.

The injection of radiologic contrast dye, tetanus toxoid and antitoxin, diphtheria, pertussis, and tetanus (DPT) vaccination, smallpox, swine flu, pregnancy, and childbirth, radiation therapy, lumbar puncture, and pneumoencephalogram are additional sources.

There exists a hereditary variant as well, associated with chromosome 17q24. These patients will get recurrent attacks, triggered by the same events as the others such as recent infection (Gonzalez-Alegre et al 2002).

Symptom Course

Brachial neuritis usually includes three phases. Phase 1 involves the patient complaining of severe, typically unilateral pain that is described as aching, sudden in onset, and affects the lateral aspect of the shoulder as seen in axillary nerve involvement, scapular pain as seen in suprascapular nerve involvement, the superolateral thoracic wall as seen in anterior interosseous nerve, antecubital fossa as seen in anterior interosseous nerve, and lateral arm or forearm as seen in musculocutaneous nerve. The pain is worst at night, wakes the sufferer from sleep, and is usually not positional. The interval between the trigger and symptoms ranges from one to twenty-eight days on average, but 66% of patients report the trigger occurring within seven days.

Early detection, in accordance with van Alfen et al., enables medical intervention that can lessen the severity of the clinical course. Over a few days to weeks, the extreme pain self-limits and goes away. In general, the patient’s recovery time will be lengthier the longer the pain lasts. As the pain subsides, patients typically enter phase 2 of the condition and begin to experience painless weakness, such as weakness in the arm and shoulder girdle. The hands and forearm can also be affected, though this is far less common. Muscle atrophy also begins, but after 6 to 18 months, there typically follows a slow, steady recovery of muscle function, defined as phase 3 of the condition (van Alfen and van Engelen 2006).

According to Ferrante et al., 89% of patients made a full recovery after three years, 75% after two years, and 36% after one year. However, according to Van Alfen et al., after a median of 2.5 years, 30% of patients reported persistent discomfort, and 66% reported functional impairments. Highlighting that the condition is not self-limiting.

Diagnosis

A review by Ferrante et al stated the diagnosis is based on NMR and EMG. The syndrome is challenging to diagnose because of its varied conditions, including atypical presentations. The muscular alterations most associated with the syndrome are related to mobility, and pain can also affect the arm, elbow, and cervical spine regions. There is no consensus in the literature on which nerve is the most affected, however, more research is needed to confirm these data (Santos et al 2021). A case report by Abraham et al (2016) even suggested that the inflammation may lay outside of the brachial plexus.

The diagnosis is important because it can prevent unnecessary or unhelpful treatment pathways. Make sure to rule out other diagnoses such as rotator cuff related shoulder pain, frozen shoulder, glenohumeral osteoarthritis, acute poliomyelitis, amyotrophic lateral sclerosis, brachial plexus tumor, cervical disc disease, cervical lesions, mononeuritis multiplex, neoplastic infiltration of the brachial tube, non-traumatic compressive nerve injuries, traction injury to the brachial plexus, and traumatic compressive nerve injury, myocardial infarction, and pulmonary embolism. This list is not exhaustive.

Clinical Examination

On a physical examination, two or more nerves will often be affected. One distinctive feature that sets brachial plexus neuritis apart from other disorders is that it affects various muscles differently even though they are all innervated by the same peripheral nerve (pathy paresis). Later in the illness course, physical examination can reveal lower motor neuron symptoms (hypotonia, areflexia, atrophy, and fasciculations), particularly in the upper brachial plexus (C5,6,7). Shoulder abduction and external rotation will be reduced in cases of weakness that develops following the acute pain phase, indicating involvement of the deltoids, supraspinatus, and infraspinatus muscles. When the serratus anterior muscle is implicated when the long thoracic nerve is affected, you will have medial scapular winging.

Treatment

There is no consensus on ideal treatment modalities. Analgesics are recommended in the painful early phase, as well as immobilization of the affected limb. Nevertheless, corticosteroids do not generally affect the prognosis of brachial neuritis. They may be helpful in the acute phase and have been found to speed up the resolution of acute pain (Gonzalez-Alegre et al 2002). Exercise for the shoulder is recommended if pain allows. Other modalities have been shown to be effective in reducing pain and weakness as well as in regaining muscle trophism and functional status. This includes kinesiotherapy, transcutaneous electrical nerve stimulation, deep dermal therapy, cryotherapy, and/or functional electric stimulation. Note that there are no high quality trials in terms of management for this condition. This is due to the rare nature of the disease.

Disclaimer

The literature is exceptionally scarce on this topic. Interpret these results with caution for clinical practice and intellectual purposes.

References

Monteiro S, Silva Gomes D, Moura N, Sarmento M, Cartucho A. Parsonage-Turner Syndrome Revisited: Four Case Reports and Literature Review. Gaz Med [Internet]. 2022 Feb. 4 [cited 2023 Mar. 28];9(1). https://doi.org/10.29315/gm.v1i1.503

Santos, I. L., & Souza, V. G.. (2021). Musculoskeletal changes and pain in Parsonage Turner syndrome patients: integrative review. Brjp, 4(BrJP, 2021 4(4)), 353–356. https://doi.org/10.5935/2595-0118.20210054

Feinberg, J. H., & Radecki, J. (2010). Parsonage-turner syndrome. HSS journal : the musculoskeletal journal of Hospital for Special Surgery, 6(2), 199–205. https://doi.org/10.1007/s11420-010-9176-x

Gonzalez-Alegre, P., Recober, A., & Kelkar, P. (2002). Idiopathic brachial neuritis. The Iowa orthopaedic journal, 22, 81–85.

van Alfen, N., & van Engelen, B. G. (2006). The clinical spectrum of neuralgic amyotrophy in 246 cases. Brain : a journal of neurology, 129(Pt 2), 438–450. https://doi.org/10.1093/brain/awh722

Abraham, A., Izenberg, A., Dodig, D., Bril, V., & Breiner, A. (2016). Peripheral Nerve Ultrasound Imaging Shows Enlargement of Peripheral Nerves Outside the Brachial Plexus in Neuralgic Amyotrophy. Journal of clinical neurophysiology : official publication of the American Electroencephalographic Society, 33(5), e31–e33. https://doi.org/10.1097/WNP.0000000000000304

Gstoettner C, Mayer JA, Rassam S, et al. Neuralgic amyotrophy: a paradigm shift in diagnosis and treatment. Journal of Neurology, Neurosurgery & Psychiatry 2020;91:879-888.