Laryngeal Paralysis

Introduction to Laryngeal Paralysis

Laryngeal paralysis is a condition where the vocal cords fail to move normally. It affects breathing, voice, and swallowing. The two main types are unilateral and bilateral vocal fold paralysis, depending on whether one or both vocal cords are affected. While the condition may seem rare, it frequently follows surgical procedures, especially those involving the thyroid or chest.

Understanding Laryngeal Nerve Supply

The larynx receives both motor and sensory innervation from the recurrent laryngeal nerve (RLN) and the superior laryngeal nerve (SLN).

• Motor supply. All the intrinsic muscles of the larynx are supplied by the recurrent laryngeal nerve, except for the cricothyroid muscle, which is supplied by the external branch of the superior laryngeal nerve.
• Sensory supply. Below the vocal cords, the sensory supply is provided by the recurrent laryngeal nerve. Above the vocal cords, the sensory supply is provided by the internal branch of the superior laryngeal nerve.

Course of Laryngeal Nerves

1. Recurrent laryngeal nerve. The course of the right and left recurrent laryngeal nerves are not symmetrical.

• The right recurrent laryngeal nerve arises from the vagus at the level of the subclavian artery. It then loops around it and then ascends into the neck in the tracheo-oesophageal groove and enters the larynx at the level of the cricothyroid joint. As it nears the thyroid gland, it runs close to the bifurcation of the right inferior thyroid artery. Here, it takes an oblique and more lateral path than the left RLN, which makes it more vulnerable to iatrogenic injury during thyroid surgery or dissection.
• The left recurrent laryngeal nerve has a longer course than the right. It arises from the vagus in the mediastinum at the level of the arch of aorta. It then loops around it and then ascends into the neck in the tracheo-oesophageal groove and enters the larynx at the level of the cricothyroid joint. The left recurrent laryngeal nerve is more susceptible to pathological injury as it has a much longer course, which makes it more prone to paralysis compared to the right one.

2. Superior laryngeal nerve. It arises from the inferior ganglion of the vagus, descends behind the internal carotid artery and divides at the level of the greater cornua of the hyoid bone into the external laryngeal nerve and internal laryngeal nerve.

• Internal branch. The internal branch travels with the superior laryngeal artery, pierces the thyrohyoid membrane and provides sensory supply to the mucosa of the larynx above the vocal cords (epiglottis, pharynx, vallecula). It pierces the inferior constrictor muscle and unites with an ascending branch of RLN to form Galen’s anastomosis.
• External branch. The external branch travels with the superior thyroid artery to provide motor supply to the cricothyroid muscle.

Types of Laryngeal Nerve Supply

1. Unilateral Vocal Fold Paralysis (UVFP). In Unilateral Vocal Fold Paralysis (UVFP), one vocal cord stops moving. This immobility creates a gap between the vocal folds during phonation. As a result, excessive air escapes while speaking, which causes hoarseness, a breathy voice, and swallowing difficulties, especially with liquids. UVFP occurs more frequently in men due to their higher incidence of thoracic tumours. The left vocal fold becomes paralysed more often than the right in about a 60:40 ratio.

Causes of Unilateral Vocal Fold Paralysis. Injury to the nerve during thyroid surgery is the most common cause of UVFP. Other causes include:

• Iatrogenic injury
• Neck trauma or accidents
• Tumours in the neck or skull base
• Viral or inflammatory infections
• Neurological disorders like stroke, Wallenberg syndrome, or Arnold-Chiari malformation
• Idiopathic causes (unknown origin)

Surgeries That May Cause UVFP. Many surgeries risk damaging the laryngeal nerves, leading to vocal cord paralysis. These include: Thyroidectomy or parathyroidectomy, Anterior cervical spine surgeries, Carotid endarterectomy, Cricopharyngeal myotomy or Zenker diverticulum repair, Pneumonectomy and lobectomy, Aortic aneurysm repair, Coronary artery bypass graft (CABG), Aortic valve replacement, Esophageal surgery, Tracheal surgery, Thoracoscopy, Thymectomy, PDA ligation, Heart or lung transplants, Skull base or brainstem surgery, Central venous catheter placement and Endotracheal intubation.

Clinical Features of UVFP. 

• Breathy and weak voice
• Persistent hoarseness
• Difficulty speaking long sentences
• Choking or coughing while eating or drinking

Nerve-Specific Vocal Cord Paralysis Symptoms

• Recurrent Laryngeal Nerve Palsy
  • All intrinsic muscles except the cricothyroid become paralysed.
  • Patients show abductor cord paralysis, with hoarseness, breathiness, reduced loudness, and low pitch.
• Superior Laryngeal Nerve Palsy
  • Rare and usually occurs during thyroid surgery.
  • Only the cricothyroid muscle becomes paralysed, and the voice at high pitch is affected.
  • Patients lose high-pitched vocal ability, mainly noticeable in professional voice users.
• Combined Recurrent and Superior Laryngeal Nerve Palsy
  • Caused by high vagal lesions.
  • Patients have a breathy voice, air wastage, difficulty with long sentences, dysphagia, coughing, and aspiration.

Clinical Evaluation of Vocal Cord Paralysis

• Perform a head and neck examination, including palpation of the thyroid gland and cranial nerve examination to rule out neck pathology for vocal fold paralysis.
• Fibreoptic laryngoscopy to observe vocal cord movement and glottic gap during adduction.
• CT scan from skull base to diaphragm to detect lesions or nerve compression.

Treatment Options for Unilateral Vocal Fold Paralysis

1. Observation and Speech Thearpy. If UVFP occurs without aspiration, clinicians may adopt a watchful waiting approach. They monitor the patient for 6 to 9 months, allowing time for spontaneous recovery or compensation by the opposite vocal fold. Early surgery can be done if the patient suffers from:

• Significant aspiration and dysphagia
• High vagal lesions
• Terminal illness, where improving communication matters

2. Injection Laryngoplasty. Vocal fold injection laryngoplasty is a minimally invasive procedure aimed at medializing a paralysed vocal cord temporarily, thereby improving voice quality and swallowing. This technique is particularly beneficial for patients when recovery of the vocal fold is expected.

Indications:

• • Expected recovery of vocal cord function
  • Small glottic gap (2–3 mm)
  • Absence of posterior gap
  • Terminal illness with aspiration or voice loss

Common Injectables:

• • Calcium hydroxyapatite: Preferred, provides effects lasting around one year.
  • Autologous fat: Natural option, though partially absorbed over time.
  • Carboxymethylcellulose gel: Offers variable longevity and is well-tolerated.
  • Micronised human dermis
  • Hyaluronic acid
  • Bovine collagen
  • Glycerine: Temporary solution with shorter duration.
  • Silicone: Limited use
  • Teflon paste (done for permanent medialisation but rarely used now due to granuloma risk)

Procedure of Injection Laryngoplasty: Vocal fold injections can be performed under local anaesthesia under flexible laryngoscopy control. Local anaesthesia allows for real-time voice assessment during the procedure, which can be advantageous for precise placement. It may also be performed via direct laryngoscopy under general anaesthesia. The material is injected laterally to the vocal ligament in the thyroarytenoid muscle bulk. It should not be injected superficially, which may cause stiffening of the lamina propria (superficial mucosal layer) and disruption in the mucosal wave critical for normal voice.

Approaches include transcutaneous and transoral techniques, selected based on patient anatomy and surgeon preference. Techniques include:

• • Transcricothyroid membrane
  • Trans-thyroid cartilage
  • Trans-thyrohyoid membrane
  • Per-oral or transnasal endoscopic routes

3. Laryngeal Framework Surgery. Type I Thyroplasty (Medialization Thyroplasty) can be done for patients with permanent vocal cord paralysis with a large glottic gap or bowing (prebylaryngis). Typically performed under local anaesthesia, these procedures allow for intraoperative voice monitoring. 🔗 Types of Thyroplasty

Indications: Dysphonia or aspiration due to vocal cord paralysis or atrophy (presbylarynx)

Benefits: Improves glottic closure, restores the mucosal wave and enhances voice quality.

Procedure: An implant (e.g., silicone, Gore-Tex®, or calcium hydroxylapatite) is inserted into the paraglottic space through a window made in the thyroid ala to push a paralysed vocal fold towards the midline, enhancing glottic closure. Position the window below the midpoint of the thyroid cartilage’s vertical height. Avoid false cord medialization and poor voice outcomes. Use the Koufman formula to calculate the window, which typically measures 10–12 mm wide and 4–6 mm high. Arytenoid adduction may be added for better results when there is a poorly supported arytenoid or a posterior gap, but the surgery is more complex and carries higher risks. The implant size depends on laryngeal anatomy. Men usually need a larger window than women.

2. Bilateral Vocal Fold Paralysis (BVFP). BVFP occurs when both vocal cords are immobile, usually in a midline or paramedian position, resulting in severe breathing difficulty. Despite a normal-sounding voice, airway compromise is the key concern.

Causes of BVFP

• Thyroidectomy, tracheal resection, or oesophagectomy surgeries
• Mediastinal tumors
• Neurological diseases (Amyotrophic lateral sclerosis, Guillain-Barré, post-polio syndrome)
• Congenital conditions (Arnold-Chiari malformation)
• Idiopathic in some cases

Other Causes of Bilateral Cord Fixation

• Cricoarytenoid joint fixation (due to trauma or arthritis)
• Interarytenoid scarring from prolonged intubation

Symptoms of BVFP. Patients present with:

• Stridor
• Shortness of breath
• Exercise intolerance
• Noisy breathing

If vocal folds lie close together, the airway is blocked, but voice remains relatively normal.

Diagnosis of BVFP

• Endoscopy shows both cords are immobile (midline or paramedian position).
• Imaging helps exclude masses or neurological lesions.
• Laryngeal EMG may help distinguish between paralysis and joint fixation.

Treatment for BVFP

1. Airway Management
   • Tracheostomy: Immediate airway, but no voice.
   • Posterior cordotomy (Kashima’s procedure): Widens the airway using coblation.
   • Vocal fold lateralisation (Type II thyroplasty): Improves breathing but sacrifices voice.
   • Reinnervation: Using phrenic-accessory nerve graft to restore posterior cricoarytenoid muscle activity.
2. Joint Fixation Management. Laser cordectomy + arytenoidectomy: Relieves joint fixation.
3. Interarytenoid Scar Management. Posterior cricoid split + cartilage grafting: Restores airway space.

 

———— End of the chapter ————

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Reference Textbooks.

• Scott-Brown, Textbook of Otorhinolaryngology-Head and Neck Surgery.
• Cummings, Otolaryngology-Head and Neck Surgery.
• Stell and Maran’s, Textbook of Head and Neck Surgery and Oncology.
• Ballenger’s, Otorhinolaryngology Head And Neck Surgery
• Susan Standring, Gray’s Anatomy.
• Frank H. Netter, Atlas of Human Anatomy.
• B.D. Chaurasiya, Human Anatomy.
• P L Dhingra, Textbook of Diseases of Ear, Nose and Throat.
• Hazarika P, Textbook of Ear Nose Throat And Head Neck Surgery Clinical Practical.
• Mohan Bansal, Textbook of Diseases of Ear, Nose and Throat Head and Neck Surgery.
• Hans Behrbohm, Textbook of Ear, Nose, and Throat Diseases With Head and Neck Surgery.
• Logan Turner, Textbook of Diseases of The Nose, Throat and Ear Head And Neck Surgery.
• Arnold, U. Ganzer, Textbook of  Otorhinolaryngology, Head and Neck Surgery.
• Ganong’s Review of Medical Physiology.
• Guyton & Hall Textbook of Medical Physiology.

Author:

Dr. Rahul Bagla
MBBS (MAMC, Delhi) MS ENT (UCMS, Delhi)
Fellow Rhinoplasty & Facial Plastic Surgery.
Renowned Teaching Faculty
Mail: msrahulbagla@gmail.com
India

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