Part 5 · The Diaphragm

Diaphragm Eventration & Paralysis

Eventration vs paralysis, phrenic nerve injury causes, sniff test, and surgical plication.

Surgical relevance

Definitions

Eventration vs paralysis — key distinction
Diaphragmatic eventrationCongenital or acquired permanent elevation of an intact, normally positioned but thinned and attenuated hemidiaphragm — due to absence or deficiency of normal muscular development. The diaphragm retains its continuity. Can be complete (entire hemidiaphragm) or partial (typically the anteromedial segment of the right).
Diaphragmatic paralysisAcquired loss of diaphragmatic movement due to phrenic nerve injury or dysfunction. The diaphragm muscle is structurally normal but denervated. Can be unilateral (common) or bilateral (rare but devastating).

Causes of diaphragmatic paralysis

Causes of phrenic nerve injury and diaphragmatic paralysis
CategoryCauses
Surgical / iatrogenic (most common)
Cardiac surgery — phrenic nerve ice injury or traction · lung resection · mediastinal dissection · radical neck dissection · oesophageal surgery
Malignancy
Mediastinal tumour · apical lung tumour (Pancoast) · lymph node compression of phrenic nerve
Neurological
Guillain-Barré syndrome · motor neurone disease · poliomyelitis · multiple sclerosis · birth injury (cervical nerve traction in shoulder dystocia)
Idiopathic
Viral phrenic neuritis — often follows a viral illness; usually recovers spontaneously over 12–18 months; most common cause of unilateral diaphragm paralysis in young otherwise healthy adults

Clinical features

  • Unilateral paralysis / eventration: often asymptomatic in otherwise healthy individuals with good contralateral lung. Dyspnoea on exertion, orthopnoea (worse when lying supine — contralateral diaphragm drops away, compressing the ipsilateral lung). Recurrent ipsilateral chest infections from poor secretion clearance.
  • Bilateral paralysis: severe orthopnoea, hypercapnic respiratory failure, ventilator dependence. Even mild exertion causes intolerable breathlessness.
  • Children: paradoxical diaphragmatic motion (the affected hemidiaphragm rises on inspiration) causes significant respiratory compromise — lower threshold for surgical intervention than adults.

Investigations

  • CXR: elevated hemidiaphragm — may be subtle; compare serial films if available
  • Fluoroscopy / sniff test: patient sniffs sharply — paradoxical upward movement of the affected hemidiaphragm (normal = moves downward). Gold standard bedside diagnostic test.
  • Ultrasound: dynamic real-time assessment of diaphragm excursion and zone of apposition thickness — increasingly preferred over fluoroscopy; no radiation
  • CT chest: identifies causative lesion — tumour, lymphadenopathy, mediastinal pathology
  • Phrenic nerve conduction studies / EMG: confirms denervation; helps distinguish neuropraxia (recoverable) from axonotmesis or neurotmesis
  • PFT: restrictive pattern; FVC significantly lower in supine vs upright position — a fall of >25% supine is characteristic of bilateral diaphragmatic weakness

Treatment

Conservative management

Observation for 12–18 months is appropriate for idiopathic viral phrenic neuritis — significant spontaneous recovery occurs. Respiratory physiotherapy, positioning advice, and respiratory support (CPAP or NIV at night in bilateral cases).

Surgical plication

Indications:

  • Symptomatic unilateral eventration or paralysis not improving with conservative management
  • Bilateral diaphragm paralysis with ventilator dependence or intolerable breathlessness
  • Neonates and infants — paradoxical motion causes severe respiratory compromise; early plication is well established
  • Post-cardiac surgery phrenic nerve injury with persistent symptomatic elevation
Plication technique

VATS (preferred) or thoracotomy. The attenuated or paralysed hemidiaphragm is plicated — folded on itself in a radial or transverse fashion — using multiple rows of non-absorbable mattress sutures (polyprolene or braided polyester). This creates a taut, flat, non-paradoxical diaphragm surface, pushes the abdominal contents inferiorly, and allows the ipsilateral lung to expand. Results are excellent for eventration; good for paralysis if performed before irreversible muscle atrophy develops.

Outcomes: Immediate improvement in FVC and exercise capacity in the majority. Children with neonatal eventration have excellent long-term results. In adults with paralysis from nerve injury, outcomes depend on the degree of muscle atrophy at the time of plication — earlier is better.

Further reading

All clinical content should be verified against current guidelines before clinical application. This resource is intended for revision and educational purposes only.

Standard textbooks

  • Shields TW, LoCicero J, Reed CE, Feins RH. General Thoracic Surgery. 7th ed. Lippincott Williams & Wilkins.
  • Sellke FW, del Nido PJ, Swanson SJ. Sabiston & Spencer Surgery of the Chest. 9th ed. Elsevier.
  • Pearson FG, et al. Thoracic Surgery. 3rd ed. Churchill Livingstone.

Current guidelines & resources