Parsonage Turner Syndrome (Brachial Neuritis): A Comprehensive Clinical Review
Parsonage Turner Syndrome (PTS), also known as brachial neuritis or neuralgic amyotrophy, represents a rare but clinically significant neurological disorder affecting the peripheral nervous system. This condition presents a unique challenge for healthcare practitioners due to its sudden onset, variable presentation, and prolonged recovery trajectory. Understanding the multifaceted nature of PTS is essential for optimal patient management and outcomes.
Aetiology
The exact cause of Parsonage Turner Syndrome remains largely unknown, though substantial evidence points to an immune-mediated disorder as the underlying mechanism (1). Research indicates that various risk factors and antecedent events can be identified in approximately 28-83% of presenting patients, suggesting that PTS develops through complex interactions between genetic susceptibility and environmental triggers (12).
Viral infections represent the most commonly identified risk factor, with studies reporting that 25% of patients experience a recent viral illness before symptom onset (12). The second most frequent association involves recent immunization, accounting for approximately 15% of cases (12). This has led to two competing theories regarding PTS development: direct viral involvement of the brachial plexus or an autoimmune response triggered by viral infection or viral antigens present in vaccines (12).
Surgical procedures constitute another significant trigger, with the perioperative period representing a critical timeframe for PTS development (12). Various surgical interventions have been implicated, including orthopedic procedures, coronary artery bypass surgery, hysteroscopy, and oral surgery (12). Interestingly, there appears to be no anatomical correlation between the surgical site and the nerves subsequently affected by PTS (13).
Other documented triggers include bacterial and parasitic infections, trauma remote from the shoulder girdle, strenuous exercise, pregnancy and childbirth, radiation therapy, and various medical procedures such as lumbar puncture (12). Systemic conditions with vasculitic components, including systemic lupus erythematosus, temporal arteritis, and polyarteritis nodosa, have also been associated with PTS development (12).
Additionally, a rare hereditary form of PTS exists, caused by mutations in the SEPTIN-9 (SEPT9) gene in approximately 85% of hereditary cases (20). This genetic variant typically presents at an earlier age (average 25 years) compared to the idiopathic form (average 40 years; 19).
Pathophysiology
The pathophysiological mechanisms underlying Parsonage Turner Syndrome involve complex inflammatory processes targeting specific components of the peripheral nervous system. Available evidence strongly suggests an autoimmune pathogenesis, likely related to genetic susceptibility factors that predispose certain individuals to immune-mediated nerve damage (11).
Histopathologic studies of nerve biopsies from affected patients reveal characteristic changes consistent with inflammatory damage. These findings include perineural thickening, neovascularization, and focal fiber loss, all suggesting an immune-mediated pathogenesis (12). The inflammatory process appears to involve perivascular inflammation and microvasculitis, similar to patterns observed in other autoimmune neurological conditions (11).
The condition demonstrates a marked predilection for motor axons, explaining why pure or predominantly motor nerves are much more frequently involved than sensorimotor or pure sensory nerves (11). This motor axon preference accounts for the characteristic clinical presentation of profound weakness with relatively preserved sensation in many cases.
Ischemic mechanisms may also contribute to the pathophysiology, particularly regarding the sudden onset of severe pain that characterizes the initial phase of PTS (12). Whether this ischemia results from inflammatory or mechanical causes, it may explain the abrupt nature of symptom onset and the intensity of initial pain experienced by patients.
The brachial plexus, being a complex network of nerves extending from the spine through the neck into each armpit and down the arms, becomes the primary target of this inflammatory process (1). The specific pattern of nerve involvement can vary significantly between patients, leading to the wide spectrum of clinical presentations observed in PTS.
Clinical Signs
Parsonage Turner Syndrome typically presents with a characteristic biphasic clinical course consisting of an acute pain phase followed by a weakness phase. The onset of pain is often abrupt and may follow recent illness, surgery, immunization, or trauma, with up to two-thirds of cases beginning during nighttime hours (2).
The initial pain phase is characterized by severe, intense shoulder and upper arm pain, typically described as sharp, throbbing, burning, or stabbing in nature (8, 20). Pain intensity is typically rated as 9+/10 and is maximal at onset (2). The pain usually localizes to the shoulder region, most commonly affecting the right side, though bilateral involvement occurs in 10-30% of cases (2). This intense pain phase can persist from several hours to four weeks, often requiring opiate analgesia for adequate management (2).
As the pain subsides, the weakness phase becomes apparent, typically developing several days to weeks after pain onset. Approximately 70% of patients experience weakness within two weeks of symptom onset (7). The weakness primarily affects the shoulder and upper arm muscles, particularly those innervated by the upper and middle trunks of the brachial plexus (13).
Muscle atrophy and scapular winging frequently develop, with the scapula protruding rather than remaining flat against the chest wall (19). Some patients may present with Kiloh Nevin syndrome, characterized by inability to make the “OK” sign due to anterior interosseous nerve involvement (19).
Sensory symptoms, while present, are typically less prominent than motor deficits. Numbness may occur in nerve distributions corresponding to maximal muscle weakness, but it rarely represents a primary complaint (2). However, studies indicate that some form of sensory symptom, including hypoesthesia or paresthesia, occurs in 89% of patients (13).
Interestingly, approximately 29% of cases present without experiencing typical neuropathic pain, making diagnosis more challenging (13). Additional symptoms may include absent or reduced reflexes, unusual sensations such as burning or tingling, and in severe cases, effects on breathing due to diaphragm involvement or voice changes due to laryngeal nerve effects (8).
Assessment
Accurate diagnosis of Parsonage Turner Syndrome requires a comprehensive clinical assessment combining detailed history-taking, physical examination, and specialized diagnostic testing. The characteristic triad of recognized trigger, shoulder region pain, and subsequent muscle weakness facilitates diagnosis when complete (11).
Clinical evaluation begins with thorough history-taking to identify potential triggering events and characterize the temporal relationship between pain onset and weakness development. Physical examination should assess muscle strength, range of motion, reflexes, and sensory function in the affected limb compared to the contralateral side.
Electrodiagnostic studies represent the cornerstone of PTS diagnosis. Electromyography (EMG) and nerve conduction studies typically demonstrate reduced compound muscle action potential (CMAP) and sensory nerve action potential (SNAP) amplitudes consistent with axonal involvement (13). Needle EMG may reveal denervation changes including fibrillation potentials and positive sharp waves in affected muscles (13). As recovery progresses, polyphasic motor units indicative of reinnervation become apparent (13).
Because PTS commonly affects proximal muscles while sparing distal nerve function, routine distal upper limb nerve conduction studies may appear normal (17). This finding can initially mislead clinicians and delay accurate diagnosis.
Advanced imaging techniques may provide additional diagnostic information. Magnetic resonance neurography, MRI, and ultrasound can help visualize nerve inflammation and rule out structural abnormalities (8). However, electrodiagnostic studies remain the primary confirmatory test.
Laboratory studies are generally indicated only when systemic disease is suspected based on clinical grounds (2). Routine blood work typically yields normal results in idiopathic PTS cases.
The diagnosis can be challenging due to the condition’s rarity and symptom overlap with more common conditions such as cervical radiculopathy or rotator cuff pathology (18). Studies suggest that accurate diagnosis often requires multiple consultations, with median delays of 60-90 days not uncommon (13).
Physiotherapy Management
Physical therapy plays a crucial role in PTS management, though timing and approach must be carefully considered based on the patient’s clinical phase. During the acute pain phase, physical therapy is generally contraindicated until pain levels have decreased sufficiently to allow safe movement (15).
Once pain has adequately subsided, physical therapy should focus primarily on maintaining full range of motion in the shoulder and other affected joints (6). Passive range of motion (PROM) exercises should begin as soon as tolerated, followed by active range of motion (AROM) exercises as strength permits (6). These interventions help prevent contractures and maintain joint mobility during the prolonged recovery period.
The physiotherapy program should progress systematically from basic range of motion maintenance to more complex strengthening and functional activities. Initial interventions may include hot and cold therapy, electrotherapy, and gentle mobilization techniques (5). As patients progress, strengthening exercises targeting the rotator cuff muscles and scapular stabilization become appropriate (6).
Electrical stimulation can be particularly beneficial for neuromuscular re-education and muscle activation in severely weakened muscles (14). This modality helps maintain muscle bulk and promote reinnervation during the recovery process.
Functional conditioning represents an important component of rehabilitation, particularly as patients regain strength. Occupational therapy may be valuable for addressing activities of daily living and workplace modifications (6). Assistive devices and orthotics may be necessary depending on specific functional deficits present (6).
Pain management through passive modalities such as heat, cold, and transcutaneous electrical nerve stimulation (TENS) can serve as useful adjuncts during the rehabilitation process (6,10). These interventions help control residual pain and facilitate participation in active rehabilitation.
The rehabilitation program should emphasize patient education regarding the condition’s natural history, expected recovery timeline, and importance of maintaining activity within tolerated limits. Given the prolonged recovery period often associated with PTS, psychological support and motivation become essential components of comprehensive care (14).
Medication Management
Pharmacological management of Parsonage Turner Syndrome focuses primarily on pain control during the acute phase and supporting the recovery process. Treatment approaches are largely symptomatic, as no specific cure exists for the underlying condition (6).
During the initial acute pain phase, opiate analgesia is often necessary due to the severe intensity of pain experienced by most patients (6,11). Strong analgesics may be required for several days to weeks until the acute pain subsides naturally. However, clinicians must balance effective pain relief with the risks associated with prolonged opioid use.
Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and naproxen can help reduce inflammation and provide pain relief, particularly during the subacute phase (10). These medications offer the advantage of anti-inflammatory effects while avoiding the dependency risks associated with opioids.
Corticosteroids represent a controversial but potentially beneficial treatment option. While immunosuppressive therapy has not been definitively proven beneficial for PTS, emerging evidence suggests that oral prednisolone may be effective for pain treatment and functional recovery (6). A study by van Eijk and colleagues found that prednisolone administration during the acute phase reduced median time for initial pain relief from 20.5 days to 12.5 days (6). Additionally, 18% of prednisolone-treated patients recovered strength within the first month compared to only 6.3% of untreated patients (6).
For neuropathic pain components, specialized medications such as gabapentin or pregabalin may be beneficial(10). These drugs specifically target nerve-related pain and can be particularly useful for managing the burning, tingling, or shooting pain characteristics often associated with PTS.
Some case reports suggest that steroid treatment may be beneficial even when initiated during the weakness phase, though this remains controversial (9). Limited evidence from small case series indicates that corticosteroid injection during the muscle weakness period may improve recovery time and facilitate earlier return to normal activities(9). This is not common practice.
The optimal timing, dosage, and duration of corticosteroid therapy remain subjects of ongoing research. Most protocols suggest early initiation within the first month of symptom onset for maximum potential benefit(16). A typical regimen might involve high-dose oral prednisolone (60mg daily) for one week, followed by gradual tapering over several weeks(9).
Given the current lack of randomized controlled trials, medication decisions should be individualized based on patient factors, symptom severity, and potential risks and benefits of various treatment options(16). Close monitoring for medication side effects and regular reassessment of treatment effectiveness remain essential components of optimal pharmaceutical management.
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