What are the neurological causes of spontaneous bilateral vocal cord palsy?

Neurological Causes of Spontaneous Bilateral Vocal Cord Palsy

Bilateral vocal cord palsy can result from various neurological disorders affecting the recurrent laryngeal nerve (RLN) innervation, with myasthenia gravis being one of the most significant neurological causes requiring prompt diagnosis to prevent respiratory compromise.

Primary Neurological Causes

Central Nervous System Disorders

• Arnold-Chiari malformation is a significant cause of bilateral vocal cord paralysis in neonates and infants, presenting with high-pitched inspiratory stridor and evidence of airway compromise 1
• Brainstem dysfunction associated with dysmorphic syndromes can lead to bilateral vocal cord paralysis 1
• Cerebrovascular accidents affecting the brainstem nuclei or pathways can result in bilateral vocal cord palsy 1

Neuromuscular Junction Disorders

• Myasthenia gravis can present with bilateral vocal cord palsy as the first manifestation of the disease, potentially leading to acute respiratory distress and stridor requiring intubation 2
• The diagnosis of myasthenia gravis should be considered in patients with unexplained bilateral vocal cord palsy, especially when presenting with acute respiratory symptoms 2

Peripheral Nerve Disorders

• Vagal paragangliomas (PGLs) can cause vocal cord paralysis through compression or infiltration of the vagus nerve, with bilateral lesions potentially leading to bilateral vocal cord paralysis 3
• Surgical intervention on vagal PGLs often results in vocal cord paralysis, and bilateral procedures are generally avoided due to the high risk of requiring tracheostomy 3
• Viral neuronitis accounts for many idiopathic cases of vocal cord palsy 2
• Congenital neurological malformations can cause bilateral vocal cord paralysis in infants 4

Iatrogenic and Traumatic Causes

• Surgical injury to the recurrent laryngeal nerve, particularly during thyroidectomy, is a common cause of vocal cord paralysis 3
• Bilateral recurrent laryngeal nerve injuries during thyroid surgery can lead to catastrophic airway obstruction requiring tracheostomy 3
• Birth trauma can result in vocal cord paralysis in neonates 4
• Endotracheal intubation can cause temporary or permanent vocal cord paralysis due to pressure on sensitive airway tissues 5
• Contributing factors for intubation-related vocal cord paralysis include endotracheal tube size, cuff location, and cuff inflation pressure 5

Diagnostic Approach

• Laryngeal electromyography (LEMG) is valuable in distinguishing neurological from mechanical causes of vocal fold immobility 3
• In symptomatic patients with suspected vocal fold paresis, LEMG studies have shown neurological impairment in 86-92% of cases 3
• LEMG can identify unilateral (60%), bilateral (40%), and contralateral neuropathy (26%) in vocal fold paresis patients 3
• Direct laryngoscopy with flexible fiberoptic nasopharyngolaryngoscopy and video documentation is the best method for diagnosing vocal cord paralysis 1
• Additional diagnostic studies may include CT scan, MRI scan, and laryngeal electromyography 1

Management Considerations

• Patients with bilateral vocal cord palsy have a fixed glottic size, making prevention of airway edema critical as it may precipitate respiratory distress requiring intubation or tracheostomy 5
• Management considerations for bilateral vocal cord palsy include avoiding intubation when possible, using smaller endotracheal tubes when necessary, atraumatic intubation techniques, perioperative corticosteroid administration, and enhanced postoperative monitoring 5
• Tracheotomy is often required to ensure adequate airway during infancy for children with bilateral abductor vocal cord paralysis 1
• Spontaneous recovery occurs in approximately 64% of acquired vocal cord palsies but only 29% of congenital cases 6
• Late spontaneous recovery or compensation is possible, suggesting that permanent surgical interventions to lateralize the vocal cords should not be rushed 6

Special Considerations

• In patients with SDHD-related head and neck paragangliomas (HNPGLs), vagal PGLs rarely should be considered for resection due to the high risk of resultant vocal cord paralysis 3
• Bilateral surgical interventions on vagal PGLs are contraindicated as bilateral vocal cord paralysis often leads to the need for tracheostomy 3
• Patients with bilateral or multifocal lateral skull base disease require careful consideration, as bilateral cranial neuropathy can be devastating 3
• An individualized multidisciplinary approach is recommended for patients with multifocal HNPGLs, with particular attention to avoiding compromise of important neurovascular structures 3