Pediatric Immune Mediated Brachial Plexopathy

Author(s): Glendaliz Bosques, MD, Kemly M Philip, M.BioE, and Kelly Pham, MD

Originally published:12/02/2013

Last updated:04/05/2017

1. DISEASE/DISORDER:

Definition

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

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 infiltrates2 and reported antecedent immunization or viral/bacterial infection.3 INA has also noted to been associated with triggers including the perioperative and peripartum stage in addition to demanding exercise. 1 HNA, autosomal dominant in inheritance, is linked to a mutation in the septin 9 (SEPT9) gene on chromosome 17q25.4

Epidemiology including risk factors and primary prevention

Both forms are rare, with estimated overall incidence of INA of 2 to 3 per 100,000 people a year.5 However, a recent 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 proposing that NA may in fact be underdiagnosed by physicians due to limited familiarity with the disorder. 6 Male to female predominance is 2:1, with median age of onset at 3 years old.3 No differences in side at onset have been reported. This epidemiologic information is limited in children because of clinical similarities to poliomyelitis, resulting in misdiagnosis. HNA is extremely rare and has been described in approximately 200 families worldwide.4 Usually, there is a parent affected, and the incidence of new mutations is unknown. Onset of HNA occurs during the second or third decade of life, primarily affecting males.7

Patho-anatomy/physiology

There is a genetic predisposition (HNA); however, the pathophysiology has not been elucidated. Autoimmune-inflammatory and mechanical processes (repetitive activity to limb) have been described in case reports. In both INA and HNA, local trauma can lead to weakening of the perineurium, resulting in focal damage of individual fascicles leading to a scattered pattern of motor and sensory involvement (pain).9 Furthermore, van Alfen et al proposes that weakening of the upper trunk through overuse compromises the blood-nerve barrier making the brachial plexus susceptible to immunocyte damage.9 Other areas involved include the lumbosacral plexus, phrenic nerve, recurrent laryngeal nerves, cranial nerves, and distal autonomic nervous system.4 Electron microscopy of biopsied brachial plexi has shown inflammatory infiltrates and demyelination. Electrodiagnostics may reveal denervation of affected muscles because of axonal damage and/or demyelination findings.2,3

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

NA presents in two thirds of children with severe neuropathic pain in 1 shoulder/arm. The other third presents with painless weakness.3 The initial pain lasts approximately 2 to 3 weeks.10 Bilateral brachial plexus is involved 10 to 30% of the time although symptoms may be asymmetric1, 11,12 and females have more frequent involvement of the middle and lower brachial plexus with poorer functional outcomes.13 Patchy paralysis and sensory deficits subsequently develop after the resolution of pain. Paresis can be associated with musculoskeletal pain related to paretic muscles or compensatory muscle use.4 Recovery is conflicting because evidence shows less/more favorable outcomes in children than adults; 47% to 63% completely recover in 6 to 8 months.3,14 Classical HNA is relapsing remitting with 1 exacerbation every 6.5 years; a portion of patients suffer from chronic symptoms.8 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,1 dysphonia (recurrent laryngeal nerve),8 and diaphragm dysfunction (phrenic nerve).4 Musculoskeletal complications include muscle atrophy, scapular instability/winging, and pain related to paresis and compensatory mechanisms.4 Chronic pain, both musculoskeletal and neuropathic, may develop.

2. 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. Inquire about recent infections or immunizations and history of cancer with radiotherapy. A family history, specifically questions about similar episodes in family members, is important for diagnosis of HNA. The child’s ability to tolerate and function in school and additional age appropriate activities/hobbies should be noted.

Physical examination

Physical examination includes neurologic examination with mental status, motor, sensory, coordination, among others in order to rule out other etiologies, such as compression, trauma, hereditary neuropathy with liability to pressure palsies, or other central nervous system affection. This should be followed by a shoulder examination, including inspection, palpation, range of motion, strength, and special tests to rule out shoulder pathology. Look for additional signs of peripheral nerve involvement, such as leg paresis and dysesthesias (lumbosacral plexus), dysphonia (recurrent laryngeal), paradoxical breathing (phrenic nerve), and vasomotor symptoms, which have been shown to affect 15% of 246 patients, such as edema, nail/hair changes, and temperature dysregulation.1 Look for dysmorphic features associated with HNA including hypotelorism, cleft palate, short stature, unusual skin folds, and facial asymmetry.10

Functional assessment

Functional assessment may include Shriner’s Hospital for Children Upper Extremity Evaluation,16 Toronto Active Movement Scale,17 Melbourne Assessment of Unilateral Upper Limb Function,18 Quality of Upper Extremity Skills Test,18 and the Box and Block Test,19 all measures of upper extremity functional mobility and strength. Reliability and sensitivity in NA patients will need to be established because this has yet to be done.

Laboratory studies

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.4 If HNA is suspected, genetic testing for the SEPT9 mutation is warranted.

Imaging

In many patients, initial evaluation includes chest radiograph to rule out pancoast tumor or other space-occupying lesions. Radiographs may also reveal diaphragm elevation with phrenic nerve involvement. 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.11 The suprascapular nerve is involved in almost all cases, followed by the axillary nerve, in about half of the cases, followed by the musculocutaneous, long thoracic, and radial nerves; muscles commonly affected include the infraspinatus, supraspinatus, serratus anterior, biceps, deltoid, and triceps.7 T1 images may show muscle atrophy and fatty infiltration.11,20

Supplemental assessment tools

Electrodiagnostics, two weeks after onset of paresis to avoid false negatives, may support the diagnosis of NA in children. Nerve conduction studies may show normative or prolonged conduction velocity with/without decreased amplitudes of both compound motor and sensory nerve action potentials. Electromyography (EMG) may show signs of acute denervation and axonal damage, including fibrillations and positive sharp waves.21 EMG performed three to four months after symptom onset may show chronic denervation and early reinnervation with polyphasic motor unit potentials.13,22 Early predictions of outcomes is not well documented in children. Female sex, presence of distal vasomotor dysfunction, joint contracture, recurrent pain with no signs of motor recovery after 3 months13, 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 and 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 may have been to many practitioners prior to diagnosis, resulting in frustration, and must be handled delicately.

3. REHABILITATION MANAGEMENT AND TREATMENTS

At different disease stages

Only anecdotal evidence for treatment of NA exists.22

In the acute period, oral prednisolone may lead to quicker pain relief, improved strength, and better recovery at 1 year when compared with historical controls in an observational study of adults and children with NA.23 Symptom management with a long-acting nonsteroidal anti-inflammatory drug and a sustained-release opiate is appropriate and effective.4

During the subacute and chronic phases, persistent neuropathic pain may be treated with gabapentin, carbamazepine, or amitriptyline.4 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.24

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 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-90.25 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,26 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.22,23

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.

4. CUTTING EDGE/EMERGING AND UNIQUE CONCEPTS AND PRACTICE

Cutting edge concepts and practice

Recent case reports described improvements after intravenous immunoglobulin (IVIG) in half of the treated adults with antiganglioside antibody-positive NA; however, 1 patient developed aseptic meningitis.27 Another case series reported the use of pulsed IVIG with methylprednisolone versus methylprednisolone only in 10 patients with subacute or chronic NA with resultant improvements in function.28 Further studies about the use of immunomodulatory therapy in these patients, or the use of antiganglioside antibodies as a marker or predictor for therapy response, is warranted. In a small cohort of five cases of brachial neuritis, Pan et al recently 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.29

5. GAPS IN THE EVIDENCE-BASED KNOWLEDGE

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

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Original Version of the Topic

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

Author Disclosures

Glendaliz Bosques, MD
Nothing to Disclose

Kemly M Philip, M.BioE
Nothing to Disclose

Kelly Pham, MD
Nothing to Disclose

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