FEES is a procedure which involves the passing of a thin flexible scope through the nose to the
pharynx to assess the function of a swallow. The FEES exam protocol consists of two parts. The first part consists of pre swallowing tasks and clinical/anatomical observations of the larynx and pharynx, including: volitional airway protection, movement of structures, secretion management, spontaneous swallows and obstructions. These findings inform potential impairments that may be seen during the second part of the FEES protocol. The second part of the FEES protocol involves food, or "bolus" presentation to observe swallow function.
Food coloring is typically given in the food to track the food as it travels along the natural pink-colored tissues of the throat. The timing of the swallow and the efficiency of clearing the bolus is assessed along with the ability to protect the airway before, during and after the swallow. If the food that is given is seen to remain in the throat after the swallow it is called “residue”. Food entering the laryngeal area but not passing below the vocal folds is known as "penetration", food passing below the level of the vocal folds is known as "aspiration". The control of the bolus, or timing, relative to the onset of swallowing gestures and the sensory response is assessed to further understand why the residue, penetration, or aspiration occurred and could indicate a lack of sensation and/or motor movement problems. The addition of a formal sensory test is optional and patient dependent, but use of a sensory test changes the Medicare billing descriptor from FEES to FEESST. The LAR is often included as part of a FEES using the "touch method" as it does not require specialized equipment beyond an endoscope. This was the only method used prior to the invention of the "air pulse" technique feature for FEESST. Clinical use of the "air pulse" method is currently lacking since this specialized equipment is no longer commercially manufactured. The "touch method" is still used during a comprehensive FEES to assess the LAR, however, studies have shown that while it can identify significant sensory deficits,
inter-rater reliability may not always be high. Newer techniques are evolving that may have greater accuracy in assessing sensory responses.
Vagus Nerve Injury When there is damage to the nerve that innervates the throat, the
vagus nerve, both motor and sensory function can be affected since the vagus contains both motor and sensory nerve fibers. However, until sensory testing was developed there was no way to assess sensory loss from a vagus nerve injury. One of the most common symptoms of a vagus nerve injury is chronic cough. If a physician looked into the vocal cords of a patient with chronic cough it would appear they are opening and closing normally, however if sensory testing was performed it would give abnormal results thus indicating that the sensory nerve fibers of the vagus were somehow damaged. This would allow for a more precise diagnosis and treatment. Another clinical situation where assessment of laryngeal sensation is helpful is in patients complaining of throat pain. Again, when examining the throat of such patients, if everything seemed to be moving well, then clinicians are often befuddled as to what the source of the throat pain is. With sensory testing, one can demonstrate that the throat tissues are numb, signifying some damage to the sensory fibers of the vagus and thereby identify vagus nerve injury as the cause of the patient's pain. This is called vagus nerve neuralgia and treatment for neuralgia can then commence. One always sensory tests both the right and left sides of throat and the sensory levels should be symmetric, that is, the right side of the throat should normally equal the left side. However, if during sensory testing it is determined that one side is normal and the other side has a sensory deficit, then likely something has injured the vagus nerve somewhere along it lengthy course from the brain into the neck. As a result, when there is asymmetric sensory nerve loss, imaging of the neck and brain must be done to see where along the course of the vagus nerve a blockage or injury might have taken place. == Indications For Sensory Testing of The Throat ==