Laryngeal Anatomy and Embryology

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Laryngeal Anatomy and Embryology

Laryngology, Voice and Swallowing
Author Credentials 

Abie Mendelsohn, MD
Assistant Professor
Department of Head and Neck Surgery
UCLA School of Medicine
200 Medical Plaza, Suite 550
Los Angeles, CA 90095
Amendelsohn@mednet.ucla.edu

Thomas Heineman, MD
Otolaryngology Resident
Department of Head and Neck Surgery
UCLA School of Medicine
10833 Le Conte Avenue, 62 -132 CHS
Los Angeles, CA 90095
TEHeineman@mednet.ucla.edu

Module Summary

The larynx is a complex anatomic structure that functions in phonation, respiration, and deglutition. By understanding the innervation and musculature of the larynx, the function of the larynx can be preserved in cases of surgical excision of tumors, clefts and other lesions. The superficial lamina propria of the vocal fold should be preserved if at all possible to allow for optimal vocal function. Furthermore, the function of the larynx can be augmented in cases with voice, airway or swallowing dysfunction. Otolaryngologists should be familiar with embryologic abnormalities of the larynx including laryngeal clefts and anatomic conditions leading to a non-recurrent laryngeal nerve. An intimate knowledge of the anatomy and embryology is required for precise evaluation of functional and structural pathology as well as surgical planning.

Module Learning Objectives 
  1. Explain the development of larynx relating to the brachial arches and pouches.
  2. Describe laryngeal innervation and musculature, as it relates to laryngeal function.
  3. Recognize the most common modalities of laryngeal structure and function evaluation.
  4. Identify laryngeal malformation conditions and their basis in embryology.
  5. Describe the reconstruction and treatment options for congenital laryngeal malformations.
  6. Appreciate the cellular basis of the cover-body theory as it relates phonation.

Embryology

Learning Objectives 
  1. Order the steps of laryngeal development in utero.
    1. Formation and contribution of the branchial arches and pouches.
    2. Timing of intrinsic laryngeal musculature innervation.
  2. Describe the embryologic conditions which lead to non-recurrent laryngeal nerve.
  3. Predict when in development arrest occurs to cause laryngeal atresia.
    1. Classify congenital glottic web within the spectrum of laryngeal atresia.
    2. Locate the site of developmental failure which produces laryngeal cleft.
References 
  1. Alli O, Berzofsky C, Sharma S, Pitman MJ. Development of the rat larynx: a histological study. Laryngoscope. 2013 Dec;123(12):3093-8.
  2. Pitman MJ, Berzofsky CE, Alli O, Sharma S. Embryologic innervation of the rat laryngeal musculature--a model for investigation of recurrent laryngeal nerve reinnervation. Laryngoscope. 2013 Dec;123(12):3117-26.
  3. Cannon CR. The anomaly of nonrecurrent laryngeal nerve: identification and management. Otolaryngol Head Neck Surg. 1999 May;120(5):769-71.
  4. Bent JP, Manaligod J, Smith RJ. Unilateral laryngeal dysgenesis. Otolaryngol Head Neck Surg. 1998 Dec;119(6):712.
  5. Zaw-Tun HI. Development of congenital laryngeal atresias and clefts. Ann Otol Rhinol Laryngol. 1988 Jul-Aug;97(4 Pt 1):353-8.

Anatomy

Learning Objectives 
  1. Understand the extrinsic and intrinsic laryngeal musculature in regards to adduction, abduction, vocal fold length and tension.
  2. Appreciate the sensory and motor innervation of the larynx.
  3. Describe the cartilaginous skeleton and landmarks of the larynx.
References 
  1. Armstrong WB, Netterville JL. Anatomy of the larynx, trachea, and bronchi. Otolaryngol Clin N Am. 1995 Aug;28(4):685-99.

Basic Science

Learning Objectives 
  1. Be familiar with the cover-body theory of vocal fold vibration in phonation.
  2. Describe the cellular and extracellular matrix which comprises the cover layer.
References 
  1. Hirano M, Kakita Y. Cover-body theory of vocal fold vibration. Speech science. San Diego: College-Hill Press; 1985.
  2. Soliman AM, Jones RM, Flint PW. Cell adhesion molecules in normal laryngeal development. Otolaryngol Head Neck Surg. 1999 Jan;120(1):73-7.

Genetics

Learning Objectives 

Review known genetic syndromes which are associated with laryngeal abnormalities.

  1. Velocardiofacial syndrome (chromosome 22q11.2 deletion)
  2. Familial congenital bilateral vocal fold paralysis
  3. Congenital familial subglottic stenosis
  4. Cri du chat syndrome
References 
  1. Miyamoto RC, Cotton RT, Rope AF, Hopkin RJ, Cohen AP, Shott SR, Rutter MJ. Association of anterior glottic webs with velocardiofacial syndrome (chromosome 22q11.2 deletion). Otolaryngol Head Neck Surg. 2004 Apr;130(4):415-7.
  2. Hsu AK, Rosow DE, Wallerstein RJ, April MM. Familial congenital bilateral vocal fold paralysis: a novel gene translocation. Int J Pediatr Otorhinolaryngol. 2015 Mar;79(3):323-7.
  3. Manickavasagam J, Yapa S, Bateman ND, Thevasagayam MS. Congenital familial subglottic stenosis: a case series and review of literature. Int J Pediatr Otorhinolaryngol. 2014 Feb;78(2):359-62.
  4. Virbalas JM, Palma G, Tan M. Obstacles to communication in children with cri du chat syndrome. J Voice. 2012 Nov;26(6):821.e1-3.

Patient Evaluation

Learning Objectives 
  1. Discuss in-office non-invasive methods of laryngeal examination
    1. Targeted patient history, including birth history
    2. Perceptual voice evaluation
    3. Clinical swallow evaluation
  2. Describe in-office invasive methods of laryngeal examination
    1. Flexible laryngoscopy
    2. Rigid laryngoscopy
    3. Videostroboscopy
    4. Functional Endoscopic Evaluation of Swallowing (FEES)
    5. Laryngeal Electromyography
  3. Explain laryngeal examination under general anesthesia
    1. Pediatric Laryngoscopy and Bronchoscopy (L&B)
    2. Suspension direct microlaryngoscopy
References 
  1. Hillel A. The study of laryngeal muscle activity in normal human subjects and in patients with laryngeal dystonia using multiple fine-wire electromyography. Laryngoscope. 2001;111:1–47.
  2. Woo P. Objective measures of laryngeal imaging: what have we learned since Dr. Paul Moore. J Voice. 2014 Jan;28(1):69-81.

Imaging

Learning Objectives 
  1. Laryngeal findings with Computed tomography (CT)
  2. Laryngeal findings with Magnetic resonance imaging (MRI)
References 
  1. Sarikaya B. Radiological aspects of laryngoceles. Otolaryngol Head Neck Surg. 2007 Oct;137(4):691-2; author reply 692.
  2. Lee YS, Son EJ, Chang HS, Chung WY, Nam KH, Park CS. Computed tomography is useful for preoperative identification of nonrecurrent laryngeal nerve in thyroid cancer patients. Otolaryngol Head Neck Surg. 2011 Aug;145(2):204-7.

Pathology

Learning Objectives 

Understand the histological layers of the vocal cord from the epithelium to the vocalis muscle.

References 
  1. Kotby MN, Kirchner JA, Kahane JC, Basiouny SE, el-Samaa M. Histo-anatomical structure of the human laryngeal ventricle. Acta Otolaryngol 1991;111:396–402.

Treatment

Learning Objectives 
  1. Appreciate the different types of speech therapy for functional voice disorders
  2. Appreciate the different types swallow therapy for muscle weakness dysphagia
References 
  1. Cohen MS, Zhuang L, Simons JP, Chi DH, Maguire RC, Mehta DK. Injection laryngoplasty for type 1 laryngeal cleft in children. Otolaryngol Head Neck Surg. 2011 May;144(5):789-93.
  2. Mangat HS, El-Hakim H. Injection augmentation of type I laryngeal clefts. Otolaryngol Head Neck Surg. 2012 May;146(5):764-8.

Medical Therapies

Learning Objectives 

Describe the state of the art of regenerative medicine for congenital defects of the larynx.

References 
  1. Lange P, Fishman JM, Elliott MJ, De Coppi P, Birchall MA. What can regenerative medicine offer for infants with laryngotracheal agenesis? Otolaryngol Head Neck Surg. 2011 Oct;145(4):544-50.

Surgical Therapies

Learning Objectives 
  1. Understand role of posterior CO2 laser cordotomy
  2. Understand endoscopic and open approaches of laryngeal cleft repair
References 
  1. Balakrishnan K, Cheng E, de Alarcon A, Sidell DR, Hart CK, Rutter MJ. Outcomes and Resource Utilization of Endoscopic Mass-Closure Technique for Laryngeal Clefts. Otolaryngol Head Neck Surg. 2015 Jul;153(1):119-23.

 

Staging

Learning Objectives 
  1. Illustrate the structural differences of laryngeal cleft classifications.
  2. Diagram the courses of all branchial cleft anomalies.
References 
  1. PMID: 2729823 Benjamin B, Inglis A. Minor congenital laryngeal clefts: diagnosis and classification. Ann Otol Rhinol Laryngol. 1989;98:417-420.
  2. PMID: 25442127 Prosser JD, Myer CM. Branchial cleft anomalies and thymic cysts. Otolaryngol Clin North Am. 2015 Feb;48(1):1-14.

Case Studies

  1. A 12-year-old girl presents with a left neck swelling that has been recurrent since she was an infant. She has been treated with multiple courses of antibiotics and aspirations as well as attempted excisions. On physical examination she has a mass of the anterior left neck, approximately 2 cm. She was taken to the operating room for direct laryngoscopy and noted to have a sinus tract starting in the left pyriform sinus apex. What is the course of this entity in relationship to important structures such as the superior and recurrent laryngeal nerves, internal carotid artery, and hypoglossal nerve?
  2. A 65-year-old complains of hoarseness for several years which has progressed to the point of dyspnea on exertion. He is an avid trumpet player. On examination he is noted to have a mass of the left neck, approximately 4 cm in size. The mass is soft, painless, reducible, and vibrates during phonation. There are no overlying skin changes. What is the etiology of such masses and what defines internal, external and combined mixed types?

Review

Review Questions 
  1. What is the cover-body theory of voice production?
  2. What are the clinical signs of laryngeal clefts?
  3. What are the clinical signs of vocal fold paralysis?
  4. What are the common in-office modalities for assessment of laryngeal function?
  5. What is the only abductor muscle of the larynx along with its innervation?
  6. Name the muscle supplied by the external branch of the superior laryngeal nerve as well as its subparts.
Resources 

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