What is the appropriate diagnostic work‑up and management for a patient with diaphragmatic denervation (phrenic‑nerve injury)?

Management of Diaphragmatic Denervation (Phrenic Nerve Injury)

For symptomatic unilateral diaphragmatic paralysis from phrenic nerve injury, phrenic nerve reconstruction surgery should be the primary treatment option after 6 months of conservative management, as it restores functional diaphragmatic activity rather than simply repositioning a paralyzed muscle. 1, 2

Diagnostic Work-Up

Initial Imaging

• Start with chest X-ray (anteroposterior and lateral views) to identify hemidiaphragm elevation, which is the hallmark finding of diaphragmatic paralysis 3, 4
• Look specifically for: elevated hemidiaphragm, paradoxical motion on fluoroscopy, and mediastinal shift 5

Confirmatory Testing

• CT scan with contrast enhancement of chest and abdomen if diagnosis is uncertain or to evaluate for structural defects versus pure denervation 3, 4
• Fluoroscopic sniff testing to document paradoxical upward motion of the paralyzed hemidiaphragm during inspiration 1, 2

Essential Electrodiagnostic Assessment

• Phrenic nerve conduction studies and electromyography are critical to quantitate the nerve deficit and determine the extent of denervation atrophy 6, 7
• Measure compound muscle action potentials (CMAPs) to assess nerve viability and guide surgical planning 2, 7
• These studies distinguish between complete nerve transection, partial injury, and conduction block—information that directly determines surgical approach 1, 7

Pulmonary Function Testing

• Spirometry measuring forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) to quantify respiratory impairment 2, 7
• Maximal inspiratory pressure (MIP) to assess inspiratory muscle strength 2
• Expect 25-50% decrease in pulmonary function with unilateral paralysis 5

Ultrasound Evaluation

• Diaphragmatic ultrasound can detect abnormal contractile patterns and measure diaphragm thickness 8
• Useful to distinguish between flutter, paralysis, and eventration 8

Management Algorithm

Conservative Management (First 6 Months)

• Observe for minimum 6 months before considering surgical intervention, as some phrenic nerve injuries may spontaneously recover 1, 9
• Medical therapies and nocturnal positive airway pressure may provide symptomatic benefit during observation period 6
• Monitor with serial pulmonary function tests and quality-of-life assessments 2

Surgical Decision-Making

For symptomatic patients after 6 months of conservative management:

Primary Option: Phrenic Nerve Reconstruction

• Phrenic nerve reconstruction is superior to diaphragm plication because it restores functional diaphragmatic activity rather than simply repositioning a paralyzed muscle 1, 6, 2
• Surgical planning based on preoperative and intraoperative electrodiagnostic testing 1, 7
• Techniques include: neurolysis (for conduction block), interpositional nerve grafting (for nerve gaps), or neurotization (for proximal injuries) 1, 6

Expected outcomes from phrenic nerve reconstruction:

• 10% improvement in FEV1 and 8% improvement in FVC at 1 year 2
• 22% improvement in FEV1 and 18% improvement in FVC at 2 years 2
• 63-71% improvement on fluoroscopic sniff testing 2
• 59% improvement in physical functioning on SF-36 quality-of-life survey 2
• Recovery continues to improve from 1 to 2 years, supporting incremental recovery with longer follow-up 2

Alternative: Diaphragm Plication

• Consider plication only when nerve reconstruction is not feasible (e.g., complete nerve loss with no proximal stump, very delayed presentation with severe muscle atrophy) 6, 7
• Plication provides static repositioning but no functional restoration 7
• Use non-absorbable interrupted 2-0 or 1-0 monofilament or braided sutures in two layers for the plication technique 3

Common Etiologies to Identify

• Iatrogenic injury during cardiac surgery or neck surgery (most common) 1, 6
• Interscalene nerve blocks (17% of cases) 2
• Cervical trauma including chiropractic manipulation 1, 9
• Neuralgic amyotrophy 6
• Idiopathic (many cases have no identifiable cause) 6

Critical Pitfalls to Avoid

• Do not confuse diaphragmatic paralysis (denervation) with diaphragmatic hernia—hernias require immediate surgical repair due to risk of bowel obstruction and strangulation, while denervation allows for 6 months of observation 4
• Do not skip electrodiagnostic testing—this is essential to determine nerve viability and guide surgical approach, yet it is often not obtained 7
• Do not assume all elevated hemidiaphragms are paralysis—eventration (congenital thinning) and hernia must be distinguished, as management differs 3, 4
• Do not delay referral beyond 6 months in symptomatic patients—earlier surgical intervention (after the 6-month observation period) may improve outcomes before severe denervation atrophy occurs 1, 2
• Do not offer plication as first-line surgery—nerve reconstruction should be attempted first in properly selected patients, as it provides functional restoration 6, 2

Multidisciplinary Approach

• Referral to specialty centers combining diagnostic evaluation, surgical treatment, and rehabilitation is required to achieve optimal long-term outcomes 6
• Coordination between pulmonology, neurology, and peripheral nerve surgery specialists 6, 7