From the Guidelines
Phrenic nerve paralysis can cause severe respiratory morbidity, particularly if bilateral, and may lead to significant respiratory compromise, including shortness of breath, reduced exercise tolerance, and sleep-disordered breathing. When the phrenic nerve is damaged or impaired, it disrupts the normal function of the diaphragm, which is the primary muscle responsible for breathing. This can result in various respiratory complications, as noted in a study published in the Journal of Thoracic Oncology 1. The condition may be unilateral, affecting one side of the diaphragm, or bilateral, which is more serious and can cause significant respiratory compromise.
Symptoms and Diagnosis
The severity of symptoms depends on whether one or both phrenic nerves are affected and the patient's underlying lung function. Phrenic nerve paralysis can be diagnosed through:
- Chest X-rays showing an elevated hemidiaphragm
- Fluoroscopy demonstrating paradoxical diaphragm movement
- Nerve conduction studies
- Pulmonary function tests showing reduced lung volumes, especially in the supine position. A recent study published in the European Respiratory Review 1 highlights the importance of considering phrenic nerve paralysis in patients with severe respiratory symptoms, even in the absence of obvious lung parenchyma damage.
Clinical Implications
In severe cases, patients may experience atelectasis (lung collapse), recurrent pneumonia, and respiratory failure requiring ventilatory support. The use of diaphragm pacing, as described in a study published in the American Journal of Respiratory and Critical Care Medicine 1, may be considered in some cases to support ventilation. However, the primary concern remains the prevention of severe respiratory morbidity, particularly in cases of bilateral phrenic nerve paralysis, as emphasized in the study published in the Journal of Thoracic Oncology 1.
From the Research
Phrenic Nerve Paralysis Causes
- Respiratory failure due to diaphragmatic paralysis, as seen in patients with high cervical spinal cord injury 2
- Exertional dyspnea and orthopnea, as presented in a case of bilateral phrenic nerve palsy 3
- Respiratory failure secondary to unilateral phrenic nerve injury, which can be improved with respiratory training 4
- Dyspnea after coronary artery bypass grafting, as a rare complication of cardiac surgery 5
- Iatrogenic phrenic nerve paralysis from interscalene block, leading to dyspnea and requiring emergent diagnosis in the Emergency Department 6
Associated Symptoms
- Shortness of breath
- Orthopnea
- Paradoxical movement of the epigastrium
- Elevation of the hemidiaphragm on chest X-ray
- Respiratory insufficiency
- Tachypnea
- Sinus tachycardia
- Chest pain
- Pneumonia
- Fever
Diagnostic Methods
- Fluoroscopic sniff test to demonstrate diaphragmatic dysfunction
- Pulmonary function tests to reveal restrictive pulmonary disease with evidence of neuromuscular etiology
- Nerve conduction studies to confirm phrenic neuropathy
- Ultrasonographic assessment to confirm diaphragmatic paralysis
- Point-of-care ultrasound to evaluate diaphragmatic movement
- Chest X-ray to reveal elevation of the hemidiaphragm