Author(s): Joslyn Gober, DO, Sandra De Mel, MD
Originally published: December 2, 2013 Last updated: January 3, 2024
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Disease/Disorder

Definition

Immune mediated brachial plexopathy, aka neuralgic amyotrophy (NA), is a disease process often characterized by severe neuropathic pain followed by paresis and paresthesia along the distribution of the peripheral nerves of the brachial plexus. Two forms exist: idiopathic neuralgic amyotrophy (INA), also known as Parsonage-Turner syndrome (PTS), and hereditary neuralgic amyotrophy (HNA). HNA may also affect other nerves, such as the lumbosacral plexus and phrenic nerve. 1

Etiology

Though little is known, an inflammatory-immune mechanism is suspected for both INA and HNA. This is supported by biopsies of affected brachial plexi containing inflammatory infiltrates and reported antecedent immunization or viral/bacterial infection. 2,3 Frequently associated infections include smallpox, coxsackievirus, influenza, Borrelia burgdorferi, typhoid, Epstein-Barr Virus, poliovirus, and Human Immunodeficiency Virus.4,5 Recent years have also shown the emergence of Covid-19 related NA. 4 In infancy, NA has been commonly associated with osteomyelitis or septic arthritis.5 INA has been linked to the perioperative and peripartum stage, trauma, radiation, or demanding exercise.1 HNA, which is autosomal dominant in inheritance, is linked to a mutation in the septin 9 (SEPT9) gene on chromosome 17q25.6

Epidemiology including risk factors and primary prevention

Both forms of NA are rare, with estimated INA overall incidence (pediatric and adult) of 1.64 per 100,000 people a year.5 However, a prospective one-year cohort by van Alfen et al suggests that the incidence of classical NA may actually be higher at 1 per 1000 people, hypothesizing that NA may be underdiagnosed by physicians due to limited familiarity with the disorder. 7 Male to female predominance is 2:1 to 11.5:1, with median age of onset at 3 years old.3,5 Biphasic age distribution has been observed with peaks in newborns (younger than 8 weeks) and adolescents (7-15 years of age).5,8 No differences in laterality of onset have been reported. Of note, the pediatric epidemiologic information is limited due to clinical similarities to poliomyelitis, resulting in misdiagnosis.3

Compared to INA, patients with HNA may suffer recurrent “attacks”.1,6 HNA is extremely rare and has been described in approximately 200 families worldwide.6 Usually, there is a parent affected, yet the incidence of new mutations is unknown. 10% of patients may report a positive family history of HNA.9 Onset of HNA occurs during the second or third decade of life, and it primarily affects males.10

Patho-anatomy/physiology

There is a genetic predisposition to HNA, however, little is known regarding the implicated mutations. Although the SEPT9 gene is known to be involved, only 55% of North American families with HNA displayed this mutation, pointing towards secondary mutations that have yet to be identified. Rarely, deletion of the PMP22 gene has been implicated.5

Autoimmune, inflammatory and mechanical processes (repetitive activity to limb) have been described in case reports. In both INA and HNA, local trauma can cause weakening of the perineurium, resulting in focal damage of individual fascicles leading to a scattered pattern of motor and sensory involvement (pain).11 Biopsy findings have found lymphocytic, inflammatory infiltrates in affected nerves with signs of axonal degeneration, supporting the theory of an autoimmune-inflammatory process.2 Furthermore, van Alfen et al proposes that weakening of the upper trunk through overuse and microtrauma compromises the blood-nerve barrier making the brachial plexus more permeable and susceptible to immunocyte damage.11 Increased mobility at the shoulder joint makes it vulnerable to these microtraumas following traction on the brachial plexus.11

Although NA may involve any nerve in the brachial plexus, the commonly affected nerves are those of the upper and middle trunk, with possible involvement of the long thoracic and suprascapular nerve. 1 Other areas involved include the lumbosacral plexus, phrenic nerve, recurrent laryngeal nerves, cranial nerves, and distal autonomic nervous system.6 Electron microscopy of biopsied brachial plexi has shown inflammatory infiltrates and demyelination. Electrodiagnostic studies may reveal denervation of affected muscles secondary to axonal damage and/or demyelination findings.2,3  Advances in Magnetic Resonance Imaging (MRI) and High Resolution Ultrasound (HRUS) have shed light on structural pathology of nerve fascicles in NA. Hourglass-like constrictions and rotations of nerves, often with complete axonal discontinuity or rotational entwinement of fascicles, have been associated with NA in multiple studies.4,9 The exact cause of these structural changes is not known, but it has been hypothesized that swelling and adhesion of fascicles may render them susceptible to mechanical trauma and “kinking,” particularly in the mobile shoulder joint.9

Disease progression including natural history, disease phases or stages, disease trajectory (clinical features and presentation over time)

While the majority of adults with NA endorse severe pain as the primary symptom, NA presents in only two thirds of children as neuropathic pain in one shoulder or arm; the other third presents with painless weakness or flaccid paralysis.3 The initial pain lasts approximately 2 to 3 weeks but full recovery may take months to years (i).12 Pain may only be present in 66% of patients, thus lack of pain does not exclude the diagnosis.5 Bilateral brachial plexus is involved 10 to 30% of the time although symptoms may be asymmetric1 and females have more frequent involvement of the middle and lower brachial plexus with poorer functional outcomes.1 Patchy paralysis and sensory deficits subsequently develop after the resolution of pain. Paresis can be associated with musculoskeletal pain related to compensatory muscle use.6 Recovery is conflicting in children with 47% to 63% completely recovering in 6 to 8 months.3,13 Classical HNA is relapsing remitting with a portion of patients suffering from chronic symptoms.1 Nerves outside the brachial plexus are also more frequently involved in patients with HNA, along with more severe paresis and poorer functional outcomes.1

Specific secondary or associated conditions and complications

Complications related to nerve involvement include distal vasomotor dysfunction with temperature dysregulation, edema, sweating and hair/nail changes, dysphonia (recurrent laryngeal nerve), and diaphragm dysfunction (phrenic nerve).1,6 Musculoskeletal complications include muscle atrophy, scapular instability/winging, and pain related to paresis and compensatory mechanisms.6 Chronic pain, both musculoskeletal and neuropathic, may develop.

Essentials of Assessment

History

A thorough history of presenting symptoms is warranted to characterize the nature of pain, location of weakness, and presence of dysesthesias. Pain may be described as deep, sharp, burning, throbbing, or aching. The site of pain is most commonly at the shoulder girdle with worsening over hours, and patients may report symptoms that last days to weeks.5 It is vital to inquire about recent infections, sick contacts, immunizations and history of cancer with radiotherapy. A family history, specifically questions about similar episodes in family members, is important for HNA diagnosis. The child’s ability to tolerate and function in school and additional age-appropriate activities should be noted.

Physical examination

A comprehensive neurologic examination that includes mental status, motor, sensory, reflexes, and gait can help exclude other etiologies such as compression, trauma, hereditary neuropathy with liability to pressure palsies, or other central nervous system afflictions. This should be followed by a shoulder examination with inspection, palpation, range of motion, strength, and special tests to rule out shoulder pathology. Patients may present with their affected arm in internal rotation, flexed at the elbow, and adducted.5 Sensory changes, such as numbness or paresthesia, over the lateral arm or shoulder may be found in over 78% of patients.3,9 Upper extremity muscles, including the deltoid, biceps, supraspinatus, and infraspinatus muscles may show different degrees of weakness, and reflexes are commonly reduced.5 Look for additional signs of peripheral nerve involvement, such as leg paresis and dysesthesias (lumbosacral plexus), dysphonia (recurrent laryngeal), paradoxical breathing (phrenic nerve).Vasomotor symptoms have been shown to affect 15% of 246 patients, and can present as edema, nail/hair changes, and temperature dysregulation.1 Dysmorphic features associated with HNA including hypotelorism, cleft palate, short stature, unusual skin folds, and facial asymmetry.12

Functional assessment

Functional assessment may include Shriners Hospital Upper Extremity Evaluation (SHUEE), Toronto Active Movement Scale, Melbourne Assessment of Unilateral Upper Limb Function, and the Quality of Upper Extremity Skills Test, all measures of upper extremity functional mobility and strength.14,15 Reliability and sensitivity has not yet been established in NA patients.

Laboratory studies

Laboratory tests are not required for diagnosis but may help to differentiate NA from other pathologies. Serum studies may show elevated creatine kinase, elevated liver enzymes, or the presence of antiganglioside antibodies. Slightly increased protein levels, pleocytosis, and oligoclonal bands may be present in cerebrospinal fluid.6 If HNA is suspected, genetic testing for the SEPT9 mutation is warranted.1 Nerve biopsy may show evidence of axonal degeneration but is rarely performed and reserved for ambiguous cases.5

Imaging

In many patients, initial evaluation includes a chest radiograph to rule out a Pancoast tumor or other space-occupying lesions. Radiographs may also reveal diaphragm elevation with phrenic nerve involvement.1 Magnetic resonance imaging, with/without contrast of the brachial plexus/shoulder, may reveal T2 hyperintensities or focal thickening of the plexus and of the involved muscles; however, trauma, inflammation, rhabdomyolysis, exercise, and tumors must be ruled out based on history and physical exam.6 The suprascapular nerve is involved in almost all cases, followed by the axillary nerve (approximately half of cases), musculocutaneous, long thoracic, and radial nerves. The muscles commonly affected include the infraspinatus, supraspinatus, serratus anterior, biceps, deltoid, and triceps.10 T1 images may show muscle atrophy and fatty infiltration at those sites.

Recent studies utilizing MRI have been able to identify specific sites of nerve constrictions and structural pathology, such as fascicle enlargement or torsion, including those at distal nerves branching from the brachial plexus.9 Hourglass-like constrictions have been found at the median nerve, radial nerve, musculocutaneous nerve, suprascapular nerve, and various branches distal to these nerves.16 Multiple studies have validated these findings and the important of MRI and HRUS imaging.9 Specifically, the Magnetic Resonance Neurography (MRN) protocol has emerged as the most sensitive imaging modality for brachial plexopathy as it enables precise visualization of individual nerves comprising the plexus.16

Supplemental assessment tools

Electrodiagnostics, two to four weeks after onset of paresis to avoid false negatives, may support the diagnosis of NA in children. Nerve conduction studies (NCS) may show normative or prolonged conduction velocity with/without decreased amplitudes of compound motor and/or sensory nerve action potentials. However, a recent study showed that 80% of clinically affected nerves did not show abnormalities on sensory NCS; thus, NCS should be interpreted within the appropriate clinical context.5,9

Electromyography (EMG) may show signs of acute denervation and axonal damage, including fibrillations and positive sharp waves.9 EMG performed three to four months after symptom onset may show chronic denervation and early reinnervation with polyphasic motor unit potentials.17 Early predictions of outcomes is not well documented in children. In adults, female sex, presence of distal vasomotor dysfunction, joint contracture, recurrent pain with no signs of motor recovery after 3 months,17 and hereditary disease may be associated with poorer outcomes in muscle strength, sensory, and disability (Rankin) scores.1

Social role and social support system

Inquire about support from family and friends and social roles in school and within the family to better understand the impact of the child’s deficits. Determine whether they have access to and can participate in usual age-appropriate activities. Encourage those that promote bimanual tasks such as swimming, dancing, and martial arts.

Professional issues

Diagnosis of NA is one of exclusion and is known to be delayed because of its rarity and wide spectrum of presentation. Patients and parents may have seen many practitioners prior to diagnosis, resulting in frustration, and must be handled delicately. In pediatric patients it is important to address the diagnosis and treatment options with the parents, while maintaining an age-appropriate level of communication with the patient.

Rehabilitation Management and Treatments

At different disease stages

There is currently no definitive treatment for NA, but various treatments show promise.

In the acute period, oral prednisolone may lead to quicker pain relief, improved strength, and better recovery when compared with historical controls in an observational study of adults and children with NA.5 Studies have shown both intravenous and oral corticosteroids to be effective for earlier recovery of motor function.5 Symptom management with a long-acting nonsteroidal anti-inflammatory drug and a sustained-release opiate is appropriate and effective.6

During the subacute and chronic phases, persistent neuropathic pain may be treated with gabapentin, carbamazepine, or amitriptyline.6 Pregabalin has also been shown to be effective for pain control.

Surgical nerve decompression and reconstruction at the level of individual nerves is being explored in adults but is not fully evaluated for treatment in the pediatric population.12 MRI can be used to identify hourglass-like constrictions of the brachial plexus to plan surgical interventions, such as resection of edematous tissue or epineurectomy.

Rehabilitation strategies include range of motion, stretching, myofascial release (rhomboids, supraspinatus, infraspinatus, and teres minor muscles), and splinting to prevent contractures. To improve proximal muscle weakness, rotator cuff strengthening exercises are beneficial. Although there is little literature about children, the use of neuromuscular electrical stimulation may be valuable for range of motion and assisting in muscle contraction and retraining. If dysesthesias are present, sensory training is useful to augment motor performance by providing sensory cues. Desensitization techniques, focused imagery, or cognitive behavioral therapy may be useful adjuncts in the management of pain. Occupational therapy evaluation for adaptive equipment may be useful. From an educational perspective, a home exercise program, in addition to postural training for appropriate compensatory movements, is pertinent.18

Coordination of care

A useful team approach in the coordination of care includes interdisciplinary involvement of a physiatrist and occupational and physical therapists. Children and their parents are also active members in the treatment team, further stressing the importance of a home exercise program. Additional specialists, such as neurologists, pain management and pediatricians, may be needed.

Patient & family education

The patient and family should be educated on etiology, prognosis, course, and treatment options, including rehabilitation strategies. Genetic counseling may be warranted with HNA. As previously stressed, a home exercise program is of the utmost importance to prevent contractures and maximize function. With the considerable disability resulting from NA, patients may be limited in activities of daily living and functional mobility, necessitating a caregiver. In children, one must also consider how this affects school attendance, relations with peers, and resultant psychologic health.

Emerging/unique interventions

Symptomatic outcomes include monitoring the duration and severity of pain using the McGill Pain Questionnaire, the presence of fatigue using the Checklist Individual Strength test, and psychological distress using the Symptom Checklist-90.19 Quality of life may be measured using the Pediatric Quality of Life Inventory. General function and disability may be evaluated with the Overall Disability Sum Score, the Modified Rankin Scale, or the WeeFIM and Pediatric Evaluation of Disability Inventory,20 for caregiver burden. The Disabilities of the Arm, Shoulder and Hand scale is upper extremity specific. Adverse outcomes or side effects of treatment are also pertinent outcome measures.

More research is being conducted on immunotherapy treatment in NA. Multiple studies are available in adults being treated with intravenous immunoglobulin (IVIG), methylprednisolone, or even plasmapheresis; reports in pediatric patients are few. A recent case series in pediatric patients evaluated the efficacy of IVIG with or without methylprednisolone (n=4) and determined immunotherapy to effective. In this study by Hu et al, the authors also performed a literature review of pediatric NA patients (n=22). In patients treated with IVIG, methylprednisolone, or plasmapheresis (or some combination thereof), 40.9% had a full recovery, 50% of patients saw partial to near complete recovery, and 9.1% saw no improvement. More research is needed in this area.10 IVIG with methylprednisolone may also decrease duration of symptoms.5

Translation into practice: practice “pearls”/performance improvement in practice (PIPs)/changes in clinical practice behaviors and skills

Activity-based rehabilitation in the management of NA should be considered to maximize recovery and development in younger children. Functional electrical stimulation of the biceps to facilitate self-feeding, rhomboids for scapular stability, and wrist extensors may facilitate functional positioning of the wrist. Weight bearing across the joints and long bones may be accomplished by lying prone on the elbows or crawling on open hands. Massed practice should include high-volume repetition of grasp and release patterns, elbow flexion (self-feeding), and task-specific practice (upper extremity dressing). Locomotor training should provide neural cues and drive reflexive motor responses in reciprocal patterned activities with bilateral upper extremities.18

Cutting Edge/Emerging and Unique Concepts and Practice

Case reports indicate a possible role of IVIG and methylprednisolone in functional improvements for NA adult patients.21 Further studies about the use of immunomodulatory therapy or the use of antiganglioside antibodies as a marker or predictor for therapy response, is warranted as high quality, prospective, randomized-controlled trials in pediatric patients are not yet published.

In a small cohort of five cases of brachial neuritis, Pan et al demonstrated that hourglass-like constrictions in the absence of external peripheral nerve compression responded better to neurolysis than neurorrhaphy or nerve grafting; their findings ultimately suggest a role for involvement of multifocal terminal branch lesions in patients with severe nerve injuries as opposed to involvement of the brachial plexus alone.22

Targeted next-generation sequencing is being utilized to identify causal mutations in certain inherited peripheral neuropathies and may increase our knowledge of the genes involved in NA.23 Magnetic Resonance Neurography (MRN) is a novel MRI technique that is being used to in both pediatric and adult patients. MRN is quickly becoming the preferred imaging modality in brachial plexopathy as it consistently creates high-quality soft tissue images.16

Gaps in the Evidence-Based Knowledge

There are significant gaps in the evidence-based knowledge on the subject of NA in the areas of etiology, pathophysiology, treatment, and outcome/assessment tools, with room for extensive investigation of all aforementioned areas. Notably, the use of corticosteroids as treatment for NA has no Food and Drug Administration approval and has limited evidence for its use.

References

  1. van Alfen N, van Engelen BG. The clinical spectrum of neuralgic amyotrophy in 246 cases. Brain. 2006;129:438-450.
  2. Suarez GA, Giannini C, Bosch EP, et al. Immune brachial plexus neuropathy: suggestive evidence for an inflammatory-immune pathogenesis. Neurology. 1996;46:559-561.
  3. van Alfen N, Schuuring J, van Engelen BG, Rotteveel JJ, Gabreels FJ. Idiopathic neuralgic amyotrophy in children. A distinct phenotype compared to the adult form. Neuropediatrics. 2000;31:328-332.
  4. Cornea A, Lata I, Simu M, Rosca EC. Patronage-Turner Syndrome Following SARS-CoV-2 Infection: A Systematic Review. Biomedicines. 2023 Mar; 11(3):837.
  5. Rotondo E, Pellegrino N, Di Battista C, Graziosi A, Di Stefano V, Striano P. Clinico-diagnostic features of neuralgic amyotrophy in childhood. Neurological Sciences. 2020 Mar 5:1-6.
  6. van Alfen N. The neuralgic amyotrophy consultation. J Neurol. 2007;254:695-704.
  7. van Alfen N, van Eijk JJJ, Ennik T, Flynn SO, Nobacht IEG, Groothuis JT. Incidence of Neuralgic Amyotrophy (Parsonage Turner Syndrome) in a Primary Care Setting – A Prospective Cohort Study. PLoS ONE 2015; 10(5): 1-9.
  8. Hu X, Jing M, Feng J, Tang J. Four cases of pediatric neuralgic amyotrophy treated with immunotherapy: one-year follow-up and literature review. Journal of International Medical Research. 2020 Mar;48(3):0300060520912082.
  9. Gstoettner C, Mayer JA, Rassam S, Hruby LA, Salminger S, Sturma A, Aman M, Harhaus L, Platzgummer H, Aszmann OC. Neuralgic amyotrophy: a paradigm shift in diagnosis and treatment. Journal of Neurology, Neurosurgery & Psychiatry. 2020 Jun 2.
  10. Sathasivam S, Lecky B, Manohar R, Selvan A: Neuralgic amyotrophy. J Bone Joint Surg Br 2008;90(5):550-553.
  11. van Alfen N. Clinical and pathophysiological concepts of neuralgic amyotrophy. Nat Rev Neurol. 2011;7:315-322.
  12. Tsairis P, Dyck PJ, Mulder DW. Natural history of brachial plexus neuropathy. Report on 99 patients. Arch Neurol. 1972;27:109-117.
  13. Host C, Skov L. Idiopathic neuralgic amyotrophy in children. Case report, 4 year follow up and review of the literature. Eur J Paediatr Neurol. 2010;14:467-473.
  14. Curtis C, Stephens D, Clarke HM, Andrews D. The active movement scale: an evaluative tool for infants with obstetrical brachial plexus palsy. J Hand Surg Am. 2002;27:470-478.
  15. Gilmore R, Sakzewski L, Boyd R. Upper limb activity measures for 5- to 16-year-old children with congenital hemiplegia: a systematic review. Dev Med Child Neurol. 2010;52:14-21.
  16. Upadhyaya V, Upadhyaya DN. Current status of magnetic resonance neurography in evaluating patients with brachial plexopathy. Neurology India. 2019 Jan 1;67(7):118.
  17. Tjoumakaris FP, Anakwenze OA, Kancherla V, and Pulos N. Neuralgic Amyotrophy (Parsonage-Turner Syndrome). J Am Acad Orthop Surg 2012;20: 443-449.
  18. Ramos LE, Zell JP. Rehabilitation program for children with brachial plexus and peripheral nerve injury. Semin Pediatr Neurol. 2000;7:52-57.
  19. van Alfen N, van der Werf SP, van Engelen BG. Long-term pain, fatigue, and impairment in neuralgic amyotrophy. Arch Phys Med Rehabil. 2009;90:435-439.
  20. Msall ME, DiGaudio K, Rogers BT, et al. The Functional Independence Measure for Children (WeeFIM). Conceptual basis and pilot use in children with developmental disabilities. Clin Pediatr (Phil). 1994;33:421-430.
  21. Naito K, Fukushima K, Suzuki S, et al. Intravenous immunoglobulin (IVIg) with methylprednisolone pulse therapy for motor impairment of neuralgic amyotrophy: clinical observations in 10 cases. Intern Med. 2012;51:1493-1500.
  22. Pan YW, Wang S, Tian G, Li C, Tian W, Tian M: Typical brachial neuritis (Parsonage-Turner syndrome) with hourglass-like constrictions in the affected nerves. J Hand Surg Am 2011; 36(7):1197-1203.
  23. Bacquet J, Stojkovic T, Boyer A, Martini N, Audic F, Chabrol B, Salort-Campana E, Delmont E, Desvignes JP, Verschueren A, Attarian S. Molecular diagnosis of inherited peripheral neuropathies by targeted next-generation sequencing: molecular spectrum delineation. BMJ open. 2018 Oct 1;8(10):e021632.

Original Version of the Topic

Glendaliz Bosques, MD, Kelly Dauer, MD. Pediatric immune mediated brachial plexopathy. 12/02/2013.

Previous Revision(s) of the Topic

Glendaliz Bosques, MD, Kemly M Philip, M.BioE, and Kelly Pham, MD. Pediatric immune mediated brachial plexopathy. 4/5/2017.

Glendaliz Bosques, MD, Mani Singh, MD. Pediatric Immune Mediated Brachial Plexopathy. 12/10/2020.

Author Disclosures

Joslyn Gober, DO
Nothing to Disclose

Sandra De Mel, MD
Nothing to Disclose