summary Brachial neuritis (Parsonage-Turner syndrome) is an uncommon disorder characterized by severe shoulder pain followed by patchy muscle paralysis and sensory loss involving the shoulder girdle and upper extremity. Diagnosis is made clinically with a through neurological exam that may vary from moderate motorsensory changes to flaccid paralysis of the upper extremity and can be confirmed by EMG/NCS. Treatment is observation and pain control with recovery taking up to 3 years. Operative nerve exploration, neurolysis, nerve transfer or tendon transfer be be indicated if there is no evidence of EMG recovery by 9-12 months. Epidemiology Incidence 1.6-3 cases per 100,000 persons reported per year likely at least 30 cases per year (underdiagnosed) Demographics males > females (range 1.5:1 to 11.5:1) middle-age (4th decade) ages 20-60 most common (average age 41), though any age can be affected (range 3-81 years old) unilateral involvement bilateral in 10-30% of patients (16% simultaneously) Etiology Two clinical types idiopathic neuralgic amyotrophy (INA) (this topic) hereditary neuralgic amyotrophy (HNA) (see associated conditions) Various eponyms for this syndrome include: scapular winging (when long thoracic nerve involved) neuralgic amyotrophy (NA) or idiopathic neuralgic amyotrophy (INA) Parsonage-Turner syndrome (PTS) acute brachial neuropathy / neuritis / plexopathy / plexitis idiopathic brachial plexus neuropathy / neuritis Pathophysiology pathoanatomy any nerve or branch within the brachial plexus can be involved login to view 1 more bullet nerves most commonly affected login to view 6 more bullets pathophysiology unclear etiology for idiopathic type, likely multifactorial with autoimmune, genetic, infectious, environmental and biomechanial processes all playing a role login to view 7 more bullets ultimately, a constellation of processes results in an inflammatory response involving the brachial plexus and its branches risk factors infection login to view 4 more bullets immunizations (15%) login to view 1 more bullet stress login to view 3 more bullets drugs login to view 1 more bullet iatrogenic login to view 1 more bullet Associated conditions hereditary neuralgic amyotrophy (HNA) very rare login to view 1 more bullet autosomal dominant mutations in the gene septin 9 on chromosome 17q24 login to view 1 more bullet differs from idiopathic form by login to view 11 more bullets Classification Idiopathic Neuralgic Amyotrophy (INA) vs. Hereditary Neuralgic Amyotrophy (HNA) Factor INA HNA Incidence 1-30/100,000/yr Rare Gene Septin 9 (chromosome 17) Age at Onset Middle-age (20-60 y/o) Young (20s) Recurrence Uncommon (~1.5 episodes) More frequent (3.5 episodes) Appearance Normal features Dysmorphic Involvement of Nerves outside Brachial Plexus Uncommon (17%) Common (56%) Presentation History phase I: sudden onset of severe, unrelenting shoulder pain primary symptom in 90% of cases radiates to the proximal arm and/or neck awakens people from sleep lasts days to weeks login to view 1 more bullet phase II: painless flaccid paralysis after the onset of pain, a period of weakness begins within 24 hours (33%) to 4 weeks (80%) most commonly involves the upper brachial plexus and usually more than one nerve branch login to view 3 more bullets phase III: slow recovery slow and steady return of motor function over 6-18 months duration over the recovery phase is often directly proportional to duration of pain phase at onset Physical examination fasciculations and atrophy may be seen signs of dennervation during the painful phase, the pain is not particularly affected by motion or palpation severe weakness of shoulder external rotation and abduction supraspinatus, infraspinatus and deltoid dysfunction hypotonia and areflexia login to view 1 more bullet medial scapular winging serratus anterior (long thoracic nerve) involvement sensory changes occur in 78% of patients paresthesias and hypoesthesias most common over deltoid, lateral arm and radial forearm may go unnoticed by patient due to overlying pain and weakness autonomic dysregulation occur in 15% of patients trophic skin changes temperature dysregulation increased sweating altered nail/hair growth Evaluation Diagnostic tests can help rule out other conditions and thus support the diagnosis of INA Laboratory CBC and ESR are usually normal labs are largely inconclusive, but may show elevated liver enzymes positive antiganglioside antibodies positive antinuclear antibody (ANA) test Imaging plain radiographs often normal evaluate for calcific tendinitis of the rotator cuff login to view 1 more bullet magnetic resonance imaging (MRI) early findings login to view 2 more bullets late findings login to view 1 more bullet Other studies electromyography (EMG) helpful to confirm the diagnosis login to view 1 more bullet findings login to view 4 more bullets sensory nerve conduction studies (NCS) less useful than EMG findings login to view 3 more bullets cerebrospinal fluid (CSF) analysis findings login to view 2 more bullets Differential Cervical spine radiculopathy pain and weakness follows a specific nerve root distribution INA involves multiple nerve roots and peripheral nerve distributions starts in the neck and radiates down the arm INA involves the shoulder and occasionally radiates to the neck and proximal arm pain is aggravated by movement in the acute pain phase, motion does not tend to worsen pain Rotator cuff pathology shoulder pain persists despite development of shoulder weakness in INA, shoulder weakness tends to develop after acute pain phase and is often painless impingement signs are often present pain usually resolves or improves with subacromial lidocaine injection subacromial lidocaine injection does not affect INA pain, as the pain is neuropathic and not related to impingement Entrapment neuropathy shoulder pain with progressive weakness in a specific peripheral nerve distribution (ex. supraspinatus and infraspinatus weakness with suprascapular nerve entrapment) INA usually involves the upper brachial plexus, affecting muscles from multiple peripheral nerve distributions (ex. supraspinatus, infraspinatus, deltoid and biceps weakness) EMG shows involvement of an isolated peripheral nerve EMG in INA shows involvement of nerve roots and peripheral nerves Idiopathic hypertrophic brachial neuritis (IHBN) rare disorder characterized by weakness in upper limb muscles and hypertrophy of the brachial plexus brachial plexus hypertrophy can be seen on MRI typically painless INA begins with acute painful phase, followed by painless weakness EMG and NCS exhibit demyelination (slowed velocity, prolonged distal sensory latencies) NCS in INA shows reduced amplitude related to axonal loss, but preserved conduction velocity and distal sensory latencies (no demyelination) Treatment Nonoperative observation and pain control indications login to view 1 more bullet technique login to view 7 more bullets outcomes login to view 4 more bullets physical therapy indications login to view 1 more bullet technique login to view 2 more bullets outcomes login to view 1 more bullet oral corticosteroids indications login to view 1 more bullet technique login to view 1 more bullet outcomes login to view 1 more bullet Operative nerve exploration, neurolysis, neurorrhaphy, nerve grafting, nerve transfer or muscle/tendon transfers indications login to view 1 more bullet technique login to view 10 more bullets outcomes login to view 2 more bullets Prognosis Recurrence is rare in non-hereditary cases Factors associated with poor prognosis female gender lower trunk involvement upper trunk has best prognosis persistent pain and no motor function recovery by 3 months hereditary cases Age has no effect on prognosis Timing of recovery 66% have recovery of motor function within 1 month recovery rated "excellent" in 36% at 1 year, 75% at 2 years and 89% at 3 years may take up to 8 years for full recovery of strength