The upper aerodigestive tract: Nasopharynx, oropharynx and hypopharynx

The upper aerodigestive tract is an especially important part of the human anatomy.  It is the common passage through which we breathe and where the food passes through.  Diseases affecting the nasopharynx, oropharynx and/or hypopharynx result in significant disruption of basic daily functions and deterioration in quality of life.  The throat is the area behind the mouth and nasal cavity and is divided into the nasopharynx (area lying behind the nose), the oropharynx (area lying at the back of oral cavity) and the hypopharynx (the lower part of the throat).  Precise reconstruction is especially important in this anatomical region to help individuals recover from functional disability.

Anatomy and function

The pharynx is divided into three segments:

  • This is the upper portion of the throat lying behind the nose and extends from the skull base to the palate.  The nasopharynx is lined by a thin mucous membrane, above which lies the skull bone.
  • This is the middle portion and lies behind the oral cavity is similarly lined by a thin mucous membrane.  It has a unique and complicated geometry and is surrounded by tongue muscles at the front and pharyngeal muscles behind.  These muscles work in a synchronized manner to open and close the throat to regulate the passage of food.
  • Hypopharynx.  This is the lower part of the throat that connects with the airway (anteriorly) and esophagus (posteriorly).  It serves an important function in preventing liquid and food particles from entering the airway, which may result in asphyxiation and pneumonia.

How does it manifest?

Nasopharyngeal cancers are common in Asia and are often treated with chemotherapy and radiation therapy.  Recurrent cancers often require resection of the involved mucous membrane and resurfacing to prevent exposure of the skull bone and carotid artery.

Cancers of the tongue base often result in excision part or all of the oropharynx.  The oropharynx is a shaped like a funnel: wider at the top and narrower at the bottom.  Reconstruction needs to be of similar geometry to permit optimal restoration of function.

Hypopharynx diseases may manifest as defects following tumor resection and may be partial or total circumferential defects.  They may also manifest as circumferential narrowing (stricture) leading to obstruction of the airway and/or food passage.  Individuals with strictures often present with extreme difficulty with eating solids and many such individuals are unable to maintain healthy weight as a result.

How does it arise?

Defects of the nasopharynx often arise from resection of recurrent nasopharyngeal cancers.  Cases in which reconstruction is not previously performed may result in long-term exposure of the skull bone with associated bone infection and foul smell.  The carotid arteries travel along the back wall of the nasopharynx and supply the skull and brain and are also in close proximity.  Lack of soft tissue coverage results in desiccation (drying) of the vessel wall and predisposes to complications.

Defects of the oropharynx also often arise from resection of the tongue base.  Reconstruction is important in restoring the soft tissue barrier between the oral cavity and the neck to prevent leakage of food and saliva.  An inadequate soft tissue bulk of the tongue base also tethers the tongue movement causing speech and swallowing deficits.

Hypopharynx strictures (narrowing) often result from previous radiation therapy or ingestion of alkalis.  Both cause scarring and circumferential narrowing of the hypopharynx.  Hypopharyngeal defects usually arise from tumor resection.

Pharyngeal reconstruction: The art of Reconstructive Surgery

The pharynx serves critical functions of separation of the skull bone from the nasal cavity, separation of the neck from the oral cavity, breathing, speech and swallowing.  Functional restoration in this region is especially important for critical life functions.  This is a challenging part of the human anatomy for reconstruction as it is a small, confined area with complicated geometry and has several different functional considerations.  Successful reconstruction restores tremendous quality of life: it permits individuals to eat and drink normally without the need for tube feeding, permits normal speech and restores normal nasal or mouth breathing without the need for a tracheostomy.

The nasopharynx has a thin mucous membrane lining.  Reconstruction is usually performed using thin flaps raised from the adjacent pharyngeal or nasal walls.  In some cases, prior radiation therapy renders it unfeasible to use such flaps, and distant flaps may be used from the forearm or foot for reconstruction.  The nasopharynx is a small confined space that lies deep within the nasal cavity, the usual approach for such cases is a facial split surgery in which the face is opened and the flap reconstruction performed, before the face is closed up.  Together with some esteemed head and neck surgery colleagues, Dr Yeo has performed pioneering cases in which flap reconstruction was performed through the use of endoscopy without the need for facial split surgery, with the benefit of significantly reduced recovery time and improved aesthetic outcome.

The oropharynx and hypopharynx consist of thin mucous membrane lining circumferentially, with a thin layer of muscle behind and thick, bulky tongue base muscle in front.  It is wide at the top and narrow at the bottom.  Defects may be reconstructed using regional tissue flaps <clickable link to “Reconstructive Services, Reconstruction of the Head and Neck, Treatment, Local and Regional Flaps> or distant flaps <clickable link to “Reconstructive Services, Reconstruction of the Head and Neck, Treatment, Distant Flaps>.  Regional flaps include the pectoralis major flaps and deltopectoral flaps from the chest, and distant flaps include skin flaps harvested from the thigh or forearm, or intestinal flaps harvested from the small or large intestine.  Intestinal flaps are advantageous in selected cases as they are tubular in structure resembling the oropharynx, secrete mucus and lubricate the passage of food and permit a natural voice that skin flaps cannot.  Intestinal flaps are the idea like-for-like reconstruction described by Dr Millard.  Dr Yeo has undergone specific advanced microsurgery training with one of the international pioneers of intestinal flap reconstructive surgery, Professor Hung-Chi Chen and is one of the few plastic surgeons who are able to offer intestinal and skin flap reconstructions in Singapore.

The Picasso Advantage

The upper aerodigestive tract is an especially important part of the human anatomy and has unique and complicated geometry suited for its normal functions.  Precise reconstruction is especially important in this anatomical region to help individuals recover its critical functions.  Successful results necessitate experienced and skilled practitioners.  Dr Yeo has a keen clinical interest in this area and has been at the forefront of delivery of this care.  He completed a fellowship in Advanced Reconstructive Microsurgery as an international fellow under the illustrious Professor Hung-Chi Chen, one of the global leaders for such surgeries.  Dr Yeo is pleased to have the unique distinction of performing intestinal flap reconstruction of the pharynx in Singapore.