Vagus nerve palsy occurs when the tenth cranial nerve or one of its branches is damaged, producing dysfunction in the structures it supplies. Because the vagus nerve controls swallowing, voice production, airway protection, heart rate, and gut motility, even partial injury can significantly impair daily life. The most common clinical presentation is vocal cord paralysis caused by damage to the recurrent laryngeal nerve, a branch of the vagus that loops through the chest before ascending to the larynx. Understanding where and how the vagus nerve can be injured is essential for accurate diagnosis and targeted treatment.
Anatomy of Vulnerability
The vagus nerve follows a long and exposed path from the brainstem to the abdomen, making it susceptible to injury at multiple levels. It exits the skull through the jugular foramen, descends through the neck within the carotid sheath alongside the internal jugular vein and carotid artery, passes through the thorax near the aortic arch and pulmonary hilum, and distributes branches to the heart, lungs, oesophagus, and abdominal organs.
The recurrent laryngeal nerve (RLN) deserves special attention because its anatomy predisposes it to injury. The left RLN loops beneath the aortic arch, while the right RLN hooks under the subclavian artery. The left nerve’s longer course through the thorax exposes it to compression from mediastinal masses, aortic aneurysms, and enlarged left atrium in mitral valve disease. Both RLNs pass close to the thyroid gland, placing them at risk during thyroid surgery.
Causes of Vagus Nerve Palsy
Iatrogenic injury during surgery is the single most common cause of vagus nerve palsy, accounting for roughly 40 percent of cases. Thyroidectomy carries a 1 to 2 percent risk of permanent RLN injury, while anterior cervical spine surgery, carotid endarterectomy, and cardiac operations (particularly those involving cardiopulmonary bypass) also pose risk. The nerve can be stretched, compressed, devascularised, or transected during these procedures.
Tumours account for approximately 20 to 25 percent of cases. Skull base tumours (glomus jugulare, schwannoma), lung cancer involving the mediastinum, and thyroid malignancy can directly invade or compress the vagus nerve or its branches. Idiopathic vagal palsy, where no cause is identified despite thorough investigation, represents about 15 to 20 percent of cases and is presumed viral in many instances.
Other causes include neck trauma, radiation therapy to the head and neck, neurological conditions such as Guillain-Barre syndrome and multiple sclerosis, and diabetic autonomic neuropathy affecting vagal fibres. Christopher Honey’s 2025 description of cervicovagopathy in Frontiers in Neurology identified chronic vagal compression at the cervical level as another mechanism, presenting with the HELPS syndrome (headache, ear pain, laryngeal symptoms, pharyngeal symptoms, and syncope/pre-syncope) and the VANCOUVER syndrome (vagus-associated neurogenic cough occurring due to vagal entrapment or compression).
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Recognising the Symptoms
Unilateral vagus nerve palsy most commonly presents with hoarseness, breathiness, or vocal fatigue due to paralysis of one vocal cord. Swallowing difficulty (particularly with liquids), a sensation of food sticking in the throat, and coughing or choking during meals indicate pharyngeal and laryngeal involvement. The uvula deviates away from the affected side when the patient says “ahh,” because the functioning palatopharyngeal muscles on the healthy side pull it across.
Bilateral vagus nerve palsy is a medical emergency when it affects both RLNs, because both vocal cords can fall to the midline, obstructing the airway. Stridor, severe dyspnoea, and respiratory distress require immediate intervention, often including tracheostomy. Bilateral palsy from high vagal lesions also impairs the gag reflex bilaterally, creating aspiration risk that may necessitate enteral feeding.
Autonomic features of vagal palsy can include resting tachycardia (loss of parasympathetic cardiac braking), gastroparesis (delayed gastric emptying from impaired vagal motor input to the stomach), and reduced heart rate variability on HRV testing.
Diagnostic Workup
Flexible nasolaryngoscopy is the primary diagnostic tool, allowing direct visualisation of vocal cord movement. A paralysed cord is typically fixed in the paramedian position and may show wasting of the vocalis muscle over time. The examination also assesses pharyngeal sensation and the symmetry of palatal movement.
Imaging should cover the entire course of the vagus nerve from skull base to thorax. CT of the neck and chest with contrast can identify masses, vascular abnormalities, or post-surgical changes. MRI of the brainstem and skull base is indicated when a central lesion (stroke, demyelination, tumour) is suspected. Laryngeal electromyography (LEMG) can distinguish between neurological paralysis and mechanical fixation of the cricoarytenoid joint, and may provide prognostic information about the likelihood of recovery.
Treatment Options
Treatment depends on the cause, severity, and whether recovery is expected. When the nerve is intact but injured (neuropraxia from surgical retraction, for instance), spontaneous recovery occurs in up to 60 percent of cases within 6 to 12 months. During this waiting period, speech therapy focusing on vocal cord compensation techniques can significantly improve voice quality.
If recovery does not occur, surgical options include injection laryngoplasty (injecting a filler material like calcium hydroxylapatite into the paralysed cord to push it to the midline, improving closure) and medialization thyroplasty (inserting a permanent silicone or Gore-Tex implant through the thyroid cartilage to reposition the cord). For bilateral paralysis causing airway obstruction, procedures like posterior cordotomy or arytenoid abduction lateralise one cord to open the airway, though this trades airway patency for voice quality.
Laryngeal reinnervation is an emerging surgical technique where a functioning nerve (typically the ansa cervicalis) is anastomosed to the RLN stump. While it does not restore vocal cord movement, it maintains muscle bulk and tone, producing a more stable long-term voice outcome than injection or implant alone. Current research is exploring selective reinnervation techniques that may eventually restore both adductor and abductor function.
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