Dr. Haguki's Knowledge Notes ⑤ 🔵 Visualizing the 'Back of the Throat' with Endoscopic Evaluation of Swallowing (Part 1)

🌱 Introduction

In a previous article (Knowledge Note ④) I mentioned that specialized evaluation may be necessary to check the condition of the back of the throat in detail.

"Would you like to have an examination?"

When your primary care physician or dentist suggests this, if you can already imagine what kind of examination it is, what it checks, and how much it can tell you, it will make it easier for you to prepare yourself mentally.

Starting with this issue, I will introduce the Videoendoscopic Evaluation of Swallowing (VE), which is widely used for evaluating feeding and swallowing in children, in two parts: Part 1 and Part 2. In Part 1, I will focus on "What is VE and what can it reveal?", and in Part 2, I plan to cover "Differences from VF (Videofluoroscopic Swallowing Study) and how to utilize the results."

I have also touched upon an image of an actual VE procedure in Field Guide ① (a case involving support for eating while using nasal high flow), so please take a look at that as well to get a more concrete idea.

🔵 Why is an objective examination necessary?

Before diving into VE, let's briefly organize the position of such examinations.

The process of understanding a child's feeding and swallowing function is broadly composed of the accumulation of the following three steps.

🔹 Medical Interview

First, as a major premise, it begins by confirming the current method of nutritional intake and the route used. In addition to oral intake, there are several other methods for delivering nutrition.

• Nasal tube (NG tube): A method of passing a tube through the nose to deliver nutrition to the stomach

• ED tube: Similar to passing a tube through the nose, but it reaches beyond the stomach to the duodenum or jejunum. This is sometimes chosen when using elemental diet formulas that place less burden on digestion

• Gastrostomy/Jejunostomy: A method of delivering nutrition directly to the stomach (gastrostomy) or intestine (jejunostomy) through a small hole (stoma) made in the abdomen

• Intravenous nutrition: A method of delivering nutrition directly through blood vessels. There is peripheral intravenous nutrition using blood vessels in the arm, etc., and central venous nutrition performed by placing a tube in a large blood vessel

Whether or not the child is taking food orally, a precise evaluation of swallowing is performed if necessary. For children who are taking food orally, it is done to check the risk of aspiration and the suitability of food texture; for children who are not taking food orally, it may be done to assess the state of saliva management and the possibility of future oral intake. It is not the case that only one or the other is the subject of evaluation.

Based on that, we carefully listen to the history, including the situation at birth, ease of choking or sucking strength during the nursing period, progress of weaning, current meal situation, changes in weight and growth, effects of medications (such as changes in saliva secretion due to anticonvulsants), and history of gastroesophageal reflux. At the same time, we also grasp medical backgrounds such as stability of posture maintenance, fluid restrictions due to heart disease, or food restrictions due to allergies, as well as the presence of gastrointestinal symptoms, interest and motivation for meals, the degree of psychomotor development and oral function/oral sensory development, and the status of medical care such as breathing and suctioning.

🔹 Observation of actual meal scenes

We check the stability of posture, how the mouth opens, how well the lips close (presence of food spills), how the child chews, tongue movement (forward/backward, side-to-side, elevation), timing of swallowing, time taken for meals, and how long concentration lasts, while observing the actual meal scene.

🔹 Objective examination

The two methods discussed so far are, so to speak, 'information visible from the outside.' However, there is a limit to how accurately one can grasp how food actually moves once it enters the throat—the phase known as the pharyngeal phase—through interviews and observation alone. This is because a reaction like coughing is not enough to determine what is truly happening deep in the throat.

Therefore, objective examinations like VE are performed when necessary. In other words, VE is not a magical tool that 'reveals everything on its own,' but rather a part of an evaluation built upon the foundation of previous interviews and observations; understanding it this way makes the significance of the examination easier to convey.

🔵 What is VE?

VE is an examination in which a thin endoscope (fiberscope) is inserted through the nose to directly observe the back of the throat (pharynx and larynx) in real-time while displaying the view on a monitor.

You might imagine 'endoscopy' to be a major procedure, but the scope used is actually very thin, and in most cases, it does not require sedation or anesthesia. Because of this thinness, it is an examination that can be performed even on infants. Furthermore, since it does not require large-scale special equipment, it can be performed in the same way in outpatient clinics, during home visits, or at the bedside. Unlike VF, which uses X-rays (discussed in detail in Part 2), it also has the feature of involving no radiation exposure.

During the examination, the patient actually eats or drinks the food they usually consume or specially colored test food and beverages, and we check the process in real-time. Coloring the food makes it easier to distinguish its movement on the endoscopic screen.

The ability to perform this anywhere is not just 'convenient'; it means we can evaluate the patient in their usual living environment, in their accustomed posture, using their own tableware, and with their usual caregiver. This leads to obtaining information closer to the child's 'actual mealtime scene'.

(*Whether the examination can be performed, the specific method, and the necessity of sedation depend on the child's condition and the medical institution's policy. Please check with your primary physician or the specialist in charge for details.)

🔵 What are we looking at with VE?

By observing the back of the throat through an endoscope, the following information can be obtained. I will introduce them one by one, including their significance.

🔹 Structure of the throat (morphology)
We directly check the morphology of parts such as the posterior pharyngeal wall, the base of the tongue, the arytenoid region, and the vocal cords. Characteristics of the innate shape and the presence of left-right differences are also among the information that can be grasped here.

🔹 Movement of the throat (function)
We look at functional aspects, such as whether the vocal cords move to close tightly and whether the pharynx contracts properly. Vocal cord movement is involved in the role of preventing food and saliva from entering the trachea, and pharyngeal contraction is involved in the force that smoothly sends food into the esophagus.

🔹 State of saliva and secretions
We check how much secretion (such as saliva) has accumulated in the back of the throat and whether the individual is able to process (swallow) it well. If there is a large amount of secretion retention, it can lead to the risk of saliva itself entering the trachea, so this is an important observation item.

🔹 Movement of the epiglottis during swallowing
The epiglottis is a tissue that acts as a lid for the entrance to the trachea the moment food is swallowed. We check whether this movement occurs with good timing by observing the state before and after swallowing.

(*Actually, the exact moment swallowing occurs cannot be seen directly with VE. This is because a phenomenon called 'whiteout' occurs, where the screen turns completely white for an instant as the tissues at the back of the throat approach the endoscope lens during the swallow. Therefore, the contraction of the pharynx, the movement of the epiglottis, and the moment of aspiration itself are, in some respects, inferred and evaluated from findings visible before and after the swallow—such as how much food remains after swallowing or whether food can be seen inside the trachea. If you want to check the moment of swallowing itself in more detail, it is sometimes evaluated in combination with VF (videofluoroscopic swallowing study), which will be introduced in Part 2.)

🔹 Pharyngeal residue after swallowing
After swallowing, we check whether food remains in the recessed parts of the throat called the piriform sinus or the vallecula. If there is a lot of residue, it can lead to 'post-swallow aspiration,' where food enters the trachea during subsequent breathing.

🔹 Presence and degree of aspiration
We check whether food or saliva has entered the trachea, and if so, to what extent, based on the state before and after swallowing.

🔹 Degree of laryngomalacia
We look to see if the tissues supporting the larynx are soft and if there is any movement where parts are drawn inward when inhaling. It is known that laryngomalacia can easily affect the coordination of breathing and swallowing (Irace et al., 2019).

The ability to confirm all this information in real-time while overlapping it with the actual eating scene is a major feature of the VE examination.

🟠 The perspective of silent aspiration

One of the important roles of VE is the detection of silent aspiration (aspiration without coughing).

While there is a common misconception that 'aspiration equals coughing,' it has been reported that in many cases, even in children, food or saliva enters the trachea without triggering a cough reflex (Weir et al., 2011; Arvedson et al., 1994). Just because there is no coughing does not mean there is no aspiration.

This can occur due to various factors, such as how sensory information is received or how the nerves function, and it cannot be captured by the simple logic that 'no coughing means it is safe' or 'coughing means it is dangerous.' Being able to actually look at the back of the throat to confirm these conditions, which are difficult to notice just by looking at appearance or mealtime behavior, is one of the great values of the VE examination.

🌱 Summary of Part 1

So far, I have introduced what kind of examination VE is and what it looks at. You might feel apprehensive when you hear 'endoscope,' but in reality, it is an examination that does not require special preparation, can be performed in environments close to daily life, and does not require sedation.

In the second part, I will introduce the differences between VE and VF (videofluoroscopic swallowing study), which is often compared to it, and how the results of VE are utilized in daily care.

References
📕Weir KA, McMahon S, Taylor S, Chang AB. Oropharyngeal aspiration and silent aspiration in children. Chest. 2011;140(3):589-597.
📕Arvedson J, Rogers B, Buck G, Smart P, Msall M. Silent aspiration prominent in children with dysphagia. Int J Pediatr Otorhinolaryngol. 1994;28(2-3):173-181.
📕Irace AL, Dombrowski ND, Kawai K, et al. Evaluation of Aspiration in Infants With Laryngomalacia and Recurrent Respiratory and Feeding Difficulties. JAMA Otolaryngol Head Neck Surg. 2019;145(2):146-151.