What is a laryngeal cleft?

Anatomy basics

A laryngeal cleft is a rare anatomical defect that is difficult to diagnose. Because this airway anomaly is hidden deep within the throat, it cannot be seen by looking into a patient’s mouth or nose. Viewing this type of cleft is possible by using a special rigid scope to examine the patient’s throat while they are asleep in an operating room. To fully understand a laryngeal cleft, it helps to be familiar with the organs involved: the larynx, trachea, and esophagus.

The larynx, also known as the voice box, is an important organ located in the neck. It’s made up of cartilage, ligaments, muscle, and mucus membranes. It’s about the size of a marble in infants and a plum in adults. The larynx sits on top of the trachea and contains specialized tissue including vocal cords and a protective flap called the epiglottis. If you put your palm on the front of your neck and hum, you can feel the vocal cords vibrating within the larynx. 

The larynx

The trachea is a tube that is part of the respiratory system. The trachea sits below the larynx in the lower throat and upper chest. Air passes through the trachea to get to the lungs. The trachea has cartilage rings, which give it structure to remain open.

The trachea

The esophagus is a tube that is part of the digestive system. The esophagus lies behind the trachea (towards the spine) and transports food and liquid from the mouth to the stomach. 

The esophagus

Anatomy of the Larynx

Think of the larynx as a gatekeeper that enables three big jobs to safely occur in the body: swallowing, breathing, and speaking. The larynx controls each of these important functions and allows only one at a time. For example, you cannot breathe and swallow at the same time.

  • Breathing: the vocal cords open to allow air to pass through the trachea and into the lungs.

  • Speaking: air is expelled from the lungs through the vocal cords as they vibrate, creating sound.

  • Swallowing: the epiglottis covers the opening of the trachea and allows food, liquids, and saliva to safely travel through the esophagus into the stomach.

The gatekeeper

Breathing

Swallowing

The larynx controls the movement of air, food, and water through the trachea and the esophagus.

Normally, the larynx is completely separate from the esophagus. This separation ensures food and liquid go straight into the stomach through the esophagus. A laryngeal cleft is an abnormal opening in the tissue that separates the larynx from the esophagus. When there is a gap or division in this tissue, food and liquids are able to leak into the trachea and lungs when swallowing occurs. This is called aspiration. The cleft can also cause a variety of other symptoms.

What is a laryngeal cleft?

Laryngeal clefts are classified according to how deep the gap extends downward towards the lungs. Two commonly used classifications systems are:

  • Benjamin and Inglis Classification - developed in 1989

  • Philippe Monnier Classification - developed in 2006

Types

A laryngeal cleft being palpated with a probe.

The Benjamin and Inglis Classification System 

This system categorizes laryngeal clefts into four types according to how deep the gap extends between the esophagus and the larynx (and sometimes also the trachea). It can be complicated to classify clefts, but the basics are:

  • Type 1: the gap is above the vocal cords. This is the most mild cleft.

  • Type 2: the gap is below the vocal cords, but still within the larynx.

  • Type 3: the gap extends below the larynx into the trachea.

  • Type 4: the gap extends deeper into the trachea, past the collar bone (thoracic inlet), and may reach the bottom. This is the most severe type of cleft. 

Benjamin and Inglis Classification System. Image provided by Otoscape website.

The Philippe Monnier Classification System 

This system expanded the Benjamin and Inglis system to include subcategories for types 3 and 4:

  • Type 1: the gap is above the vocal cords. This is the most mild cleft.

  • Type 2: the gap is below the vocal cords, but still within the larynx.

  • Type 3a: the gap extends through the entire larynx.

  • Type 3b: the gap extends through the larynx and into the trachea, but does not extend past the thoracic inlet.

  • Type 4a: the gap extends deep into the trachea and past the thoracic inlet.

  • Type 4b: the gap extends through the entire trachea and into a main bronchi (large tube in the lungs). This is the most severe type of cleft.

The cause of laryngeal clefts is unknown. It can occur randomly, as a part of a genetic syndrome, or may be inherited. Early during normal fetal development, one tube develops. Eventually, this tube separates into two completely separate tubes: the esophagus and the trachea. Sometimes this separation does not fully occur, resulting in a laryngeal cleft.

What causes a laryngeal cleft?

How common is this birth defect?

Laryngeal clefts are considered a rare congenital anomaly. Studies commonly state that laryngeal clefts occur in 1 out of every 10,000 - 20,000 live births, affecting more boys than girls. However, more recent studies suggest type 1 laryngeal clefts may be more common than previously thought. More research is needed to learn the true incidence rate for each type of laryngeal cleft. 

MAB approved: September 2024