Super sensitive gag reflex

The gag reflex also known as the pharyngeal reflex, is a reflex contraction of the muscles of the posterior pharynx after stimulation of the posterior pharyngeal wall, tonsillar area, or base of the tongue ¹⁾. The gag reflex is a normal body protective reaction that prevents choking ²⁾. The gag reflex is believed to be an evolutionary reflex that developed as a method to prevent the aspiration of solid food particles from entering the upper airway and your lungs. The gag reflex is started when certain areas of your mouth are touched. These include the roof of your mouth, the back of your tongue, the area around your tonsils and the back of your throat.

Gag reflex is also an essential component of evaluating the medullary brainstem and plays a role in the declaration of brain death ³⁾.

Although the gagging response may be provoked in virtually all humans, the level and type of stimulation necessary to evoke gagging behavior varies across individuals ⁴⁾. In addition to tactile stimulation in the mouth, gagging also may be induced by visual, auditory, or olfactory stimuli ⁵⁾. This behavioral response may be induced only by stimulating the front parts of the oral cavity, suggesting that conditioning (i.e., behavioral learning) and other psychological factors, are an important part of the cause of frequent or “overactive” gagging ⁶⁾.

A hypersensitive gag reflex occurs when this normal reflex has become heightened for some reason. It may be that you have had experiences in the past that have caused particular areas of your mouth to become more likely to trigger the gag reflex. Some people can remember when they were first affected and it is commonly linked to a dental experience, for example, having an impression taken. A hypersensitive gag reflex make dental treatment difficult or impossible. A hypersensitive gag reflex is usually a learned or conditioned response, which occurs following a previous experience. Scientists know this because you are able to tolerate things in your mouth and throat when eating without the gag reflex occurring.

A hypersensitive gag reflex may be either somatogenic or psychogenic in origin ⁷⁾. In dentistry, the gag reflex may be triggered by the dental injection, x-ray sensor/film, rubber dam, or other procedures ⁸⁾. Hypersensitive gag reflex may cause self-consciousness, embarrassment, avoidance of dental treatment, fear, anxiety, and a negative impact on overall quality of life ⁹⁾.

Various behavioral and pharmacological methods have been suggested to reduce hypersensitive gag reflex in dental patients ¹⁰⁾. It has been claimed that nitrous oxide and oxygen sedation (N2O) is able to completely blunt the hypersensitive gag reflex ¹¹⁾. This is clinical study ¹²⁾ showed that nitrous oxide does in fact reduce the hypersensitive gag reflex to varying degrees at various concentrations and allows patients to tolerate a digital x-ray sensor long enough to obtain a dental radiograph.

Gag reflex physiology and neuroanatomy

Control of the gag reflex is by both the glossopharyngeal (cranial nerve 9) and vagus (cranial nerve 10) cranial nerves, which serve as the afferent and the efferent limbs for the reflex arc, respectively. The nerve roots of cranial nerve 9 (glossopharyngeal nerve) and cranial nerve 10 (vagus nerve) exit the medulla through the jugular foramen and descend on either side of the pharynx to finally innervate the posterior pharynx, posterior one-third of the tongue, soft palate, and the stylopharyngeus muscle ¹³⁾.

The stimulus is provided by sensation to the posterior pharyngeal wall, the tonsillar pillars, or the base of the tongue. These sensations are carried by cranial nerve 9 (glossopharyngeal nerve), which acts as the afferent limb of the reflex to the ipsilateral nucleus solitarius also referred to as the gustatory nucleus after synapsing at the superior ganglion located in the jugular foramen. These nuclei, in turn, send fibers to the nucleus ambiguus, which is a motor nucleus present in the rostral medulla. Efferent nerve fibers to the pharyngeal musculature traverse from the nucleus ambiguus through the cranial nerve 10 (vagus nerve). This ultimately results in the bilateral contraction of the posterior pharyngeal muscles.

Contraction of the pharyngeal musculature ipsilateral to the side of the stimulus is known as the direct gag reflex, and contraction of the musculature on the contralateral side is known as the consensual gag reflex.

Testing the gag reflex can also help to assess damage to cranial nerve 9 (glossopharyngeal nerve) and cranial nerve 10 (vagus nerve). Damage to cranial nerve 9 (glossopharyngeal nerve) leads to the absence of the gag reflex on the ipsilateral (same) side. Damage to the cranial nerve 10 (vagus nerve), however, leads to preserved gag reflex on the unaffected side with a lack of response on the affected side. This presentation is because the sensory afferent is intact, regardless of which side is stimulated. If both the glossopharyngeal (cranial nerve 9) and vagus (cranial nerve 10) nerves suffer damage on one side, there would be no consensual reflex on the affected side.

Stimulation of the soft palate can also elicit the gag reflex; however, the sensory limb, in this case, is the trigeminal nerve (cranial nerve 5). Here, sensory stimulation of the soft palate travels through the nucleus of the spinal tract of the trigeminal nerve.

The gag reflex once served as a method to detect dysphagia in the setting of acute stroke. In one study comparing gag reflex to bedside swallowing assessment in 242 patients, the researchers found that the absence of gag reflex was specific for and consistent with the inability to swallow as assessed at the bedside but not sensitive in stroke patients. The study showed that the specificity of the gag reflex in detecting dysphagia was 96%, and sensitivity was to be 39%. However, an intact gag reflex does indicate the presence of protection against long term swallowing issues and predicts a decreased requirement for enteral feeding in the future ¹⁴⁾.

Research has found that the posterior pharyngeal muscles that control the gag reflex are independent of the muscles responsible for swallowing. Therefore, clinicians should not rely upon an absent gag reflex as a predictor for aspiration in stroke patients. Indirect laryngoscopy has demonstrated to be a better alternative to performing the gag reflex to assess airway safety. Researchers have also noted that one out of three people may lack a gag reflex, through habituation, or influenced by emotions through higher centers. Pharyngeal sensation, in contrast, is rarely absent and is thus used as an alternative to gag reflex testing and could prove better at predicting future problems with swallowing ¹⁵⁾.

Before intubating a patient, deep sedation is necessary to confirm the absence of the gag reflex, which is in contrast to when patients receive only minimal and moderate sedation, where the presence of the gag reflex should be confirmed so that the airway is protected ¹⁶⁾.

Finally, performing the gag reflex is a must when assessing brainstem function as part of determining brain death. Confirmation of brain death is done in part by absent brainstem reflexes, which includes absent gag reflex ¹⁷⁾.

Figure 1. Gag Reflex neural pathway

Sensitive gag reflex causes

A hypersensitive gag reflex may be either somatogenic or psychogenic in origin ¹⁸⁾. In dentistry, the gag reflex may be triggered by the dental injection, x-ray sensor/film, rubber dam, or other procedures ¹⁹⁾.

In addition to tactile stimulation in the mouth, gagging also may be induced by visual, auditory, or olfactory stimuli ²⁰⁾. This behavioral response may be induced only by stimulating the front parts of the oral cavity, suggesting that conditioning (i.e., behavioral learning) and other psychological factors, are an important part of the cause of frequent or “overactive” gagging ²¹⁾.

A hypersensitive gag reflex occurs when this normal reflex has become heightened for some reason. It may be that you have had experiences in the past that have caused particular areas of your mouth to become more likely to trigger the gag reflex. Some people can remember when they were first affected and it is commonly linked to a dental experience, for example, having an impression taken. A hypersensitive gag reflex make dental treatment difficult or impossible. A hypersensitive gag reflex is usually a learned or conditioned response, which occurs following a previous experience. Scientists know this because you are able to tolerate things in your mouth and throat when eating without the gag reflex occurring.

What difficulties can a hypersensitive gag reflex cause?

A hypersensitive gag reflex can give rise to a number of difficulties which include:

• Brushing your teeth
• Having dental treatment, impressions and dental x rays
• Using a denture

How can a hypersensitive gag reflex be treated?

Treatment is simple. It is designed to reduce your hypersensitive reflex so that dental treatment can be carried out in the normal way, and for some people to help them wear dentures.

Your dentist will tell you about the two exercises outlined below. Try to carry these out each day and work at your own pace. Some people find they are able to feel an improvement quickly, for others it takes more practice. There may also be times when you have a relapse that may require additional time and effort. If your dentures are causing a gag reflex, your dentist may use a “training appliance” as the next step in the process. Your dentist will arrange a review appointment to monitor your progress.

Alternatively to behavior therapies, various techniques, such as the salt-on-the-tongue, acupuncture, and hypnosis have been used in the treatment of frequent gagging ²²⁾. Whether these strategies truly are efficacious is unknown; however, one of the mechanisms involved is distraction (which itself is a behavioral approach) of the patient, long enough to complete treatment. Such techniques do not eliminate the problem altogether ²³⁾. Other distraction methods include having the patient raise his/her legs, counting up or down from 100, and so on. Distraction techniques that include the use of audiovisual equipment have demonstrated success in reducing fear, anxiety, and pain in the dental clinic and may be useful for some, but not all, patients in addressing problems with gagging that are associated with dental care-related fear ²⁴⁾.

Reviews and recent empirical studies have been published on the myriad techniques available to manage gagging problems in dentistry ²⁵⁾. Future work should address which of these techniques are most effective for reducing problems with gagging and whether certain methods are most appropriate for different severities of gagging.

To be certain, more comprehensive behavioral techniques, which seek to eliminate the association between two stimuli (e.g., dental care and gagging), may be more appropriate for patients who desire longer-lasting reduction of dental care-related fear and associated problems with frequent gagging. A psychologist, other behavioral specialist, or dentist with proper training could treat a problem with frequent gagging using these techniques. Behavioral therapies that target a gagging response are theoretically promising, even though not yet well-studied, and should be further explored in randomized clinical trials to assess their efficacy in reducing the gag response and improving dental treatment-seeking behavior.

Sensitive gag reflex exercise 1

This will help you to relearn how to automatically protect your airway:

1. Relax
2. Breathing through your nose, lift the back of your tongue up to touch the back of your palate. This means you are forming a seal at the back of your mouth.
3. Now try doing this again but open your mouth a comfortable amount.
4. Practice this sequence, increasing the time you are able to hold the position comfortably.

TIP: A good idea is to use this exercise to create a seal at the back when you are brushing your teeth.

Sensitive gag reflex exercise 2

This is a direct desensitization exercise:

1. Relax
2. Take a small soft toothbrush and gently massage your palate just behind your upper front teeth for a few minutes. Practice this at least once a day. It is important to just massage to where you can comfortably tolerate the brush. We do not want you to stimulate your gag reflex as this will simply reinforce your hypersensitive response.
3. When you are comfortable with this, move the brush slightly further backwards over your palate and carry on massaging. Again we do not want you to stimulate your hypersensitive gag reflex, so if it feels too much just move the brush forwards again.
4. Practice this exercise until you are comfortable massaging the front half of your palate.

TIP: It is a good idea to carry out this exercise when you are relaxing in the evening, for example whilst watching TV.

Remember, without practice this treatment will not be effective. Making a simple diary of your exercises can be a useful way of monitoring your progress.