References
Gagging – bringing up an old problem part 1: aetiology and diagnosis
From Volume 45, Issue 7, July 2018 | Pages 609-616
Article
Gagging, also widely known as retching and nausea, is a protective physiological response to foreign bodies, or agents, entering the trachea, larynx and/or pharynx. Where an exaggerated form of the gag reflex exists, it is a well-known hindrance to dental procedures and a potential barrier to optimal patient care. Mild gagging problems are a relatively common occurrence in dentistry where, in most instances, various techniques and additional chairside time will allow the clinician to navigate around the issue successfully and arrive at a satisfactory outcome. However, when the affected patient is unable to overcome the gagging sensation, a more severe variation of gagging is present; under these circumstances, even the simplest forms of treatment can prove extremely challenging or may be impossible to execute.
Providing care for patients with a severe gag response can be a very stressful experience for both the clinician and the patient. Furthermore, unsuccessful treatment experiences will serve as a negative reinforcement of any pre-existing dental phobias. Consequently, patients' anticipation of the inevitable distress will (understandably) affect their enthusiasm for routine dental care provision; it is estimated that gagging related issues are responsible for approximately 20% of overall avoidance cases.1 Therefore, those affected by a longstanding history of gagging issues will have an increased risk of poor dental health and extensive treatment requirements. The unsuspecting dentist is eventually greeted by the anxious patient who attends with pain at an emergency appointment. Patients' dental anxiety, combined with the need for a complex restorative rehabilitation approach, often results in radical treatment plans involving numerous extractions, leading to removable appliances (that patients will be unable to wear), which in turn heightens patient anxiety, with a loss of faith in a clinician's abilities and further missed appointments, until they next return with further pain – the term ‘gagging cycle’ seems appropriate (Figure 1).
Therefore, it is clear that the clinician must understand how to identify correctly, diagnose and manage a hyperactive gag reflex. Ideally, this should take place during the first consultation appointment, where the dentist should adopt a holistic approach, aimed at both the psychological and somatic needs of the patient.
Gag reflex physiology
In order to understand the underlying aetiology of the gagging response, we must first look at how it is initiated. This is an inborn defence mechanism which is controlled by the parasympathetic division of the autonomic system. It is more prominent during the early stages of life, thereafter it progressively regresses after the fourth year of life, as the oral functions such as nasal breathing and swallowing begin to mature. Eventually, under normal circumstances, the gag reflex locates to the region of the tonsillar pillars following eruption of the first dentition.
Gagging occurs in order to eject unwanted and toxic material from the upper respiratory tract by contraction of the oropharyngeal muscles. Afferent fibres from the trigeminal, glossopharyngeal and vagus nerves transmit tactile sensory impulses to the vomiting centre, which is located in the medulla oblongata. The centre of the medulla oblongata is in close proximity to the vasomotor, respiratory, salivatory and vestibular centres; this explains why gagging may be associated with hypersalivation, hyperventilation, lacrimation, fainting and/or panic attacks. Subsequently, efferent impulses are relayed to the tongue, oropharynx and upper gastrointestinal tract. This gives rise to unco-ordinated and spasmodic muscular movements, which is characteristic of gagging, and vomiting may then occur. A clinical description of gagging has been outlined in Table 1 and demonstrated in Figure 2. Interestingly, neural pathways from the cerebral cortex to the medulla oblongata (Figure 3) allow the higher centres to influence or even initiate the gagging response.
Aetiological factors
Two main categories of gagging patients have been identified in the literature: namely, the somatogenic group, where gagging is induced by physical stimuli, and the psychogenic group, which is induced by psychological stimuli. Patients are allocated to the relevant group, based on the stimulus thought to be the initiating factor responsible for the reflex.2,3 However, it should be recognized that the distinction between the two groups can be difficult to diagnose accurately and, in the majority of cases, there will inevitably be an underlying element of both stimuli involved in the reflex.
Gagging is considered to have a multifactorial aetiology. There are four factors which are believed to play a crucial role with regards to the aetiology of gagging, including:
Local and systemic factors
There is a vast array of underlying local and systemic factors which are responsible for lowering the threshold required for excitation of the vomiting centre.
Local factors
Local factors include nasal obstruction, catarrh, sinusitis, postnasal drip, nasal polyps, dry mouth and mucosal congestion of the upper respiratory tract.4
Systemic factors
Systemic factors include medications which predispose to nausea/vomiting as a side-effect, carcinoma of the stomach, chronic gastrointestinal disease, peptic ulceration, hiatus hernia and uncontrolled diabetes. Interestingly, patients with a habitual alcohol intake and those who smoke on a regular basis will be predisposed to a hypersensitive pharynx.5
The time of the day has also been closely linked with an increased gagging response. Individuals in the morning have an increased excitability of the vomiting centre as a result of associated metabolic disturbances, including carbohydrate starvation and dehydration with ketosis.6 This may be a useful consideration for the clinician when scheduling treatment sessions for patients with a hypersensitive gag reflex.
Anatomic factors
Gagging may occur in response to tactile stimulation of specific areas within the oral cavity. The ability of each patient to tolerate this varies widely and can normally only be accurately predicted via knowledge of the patient's past dental history. There are five intra-oral regions (Figures 3 and 4) which have been identified as ‘trigger zones’ for stimulating the gagging response:
These anatomical landmarks should be given special consideration during all stages of the dental examination and treatment. It cannot be stressed enough how important it is to apply this knowledge equally to all patients, including non-gaggers, as iatrogenic stimuli can induce maladaptive thought processes and exaggerated gagging issues could develop. In particular, clinicians can tactfully apply their knowledge of these high risk anatomical trigger sites to build patients' trust and confidence during the clinical appointment. Suggested approaches and considerations during the first examination and/or treatment appointment:
There have been numerous investigations undertaken to explore a potential association between anatomical abnormalities and oropharyngeal sensitivities with an increased gagging response.6,7 A controlled study, which investigated the radiographic anatomy of gaggers with non-gaggers, demonstrated no anatomical differences. Wright postulated that the afferent nerve distribution, particularly involving the vagus nerve, may be more extensive in gagging patients.8 Unfortunately, nerve innervation alone does not explain patients who have psychogenic triggers for gagging. Therefore, at the present time, there have been no clear links established in the literature between anatomical abnormalities and neural pathways with the gag reflex.
Psychological factors
There are two main mechanisms of learning, these are known as classical and operant conditioning.9 This is particularly relevant to severe forms of gagging, which are usually related to a learned behaviour.
Classical conditioning
Classical conditioning occurs when a previously neutral stimulus is paired with an unconditioned stimulus. For instance, if an overloaded impression tray is placed in the mouth which triggers the patient's gag response (Figure 5). As a consequence, the patient may learn to associate the stimulus with the unpleasant gagging sensation; therefore, a conditioned gag reflex has been established in relation to this procedure.
Operant conditioning
Operant conditioning occurs when an association is formed between the behaviour and the consequence of that behaviour. Therefore, depending on the outcome, the patient will be more or less likely to repeat the response again in the future. For example, if the patient learns that he/she can avoid having a restoration as a consequence of gagging, then he/she will be more inclined to repeat this behaviour in the future; this is termed negative reinforcement.
Interestingly, neural pathways from the medulla oblongata to the cerebral cortex allow the reflex to be modified by higher centres of the brain.9
The conditioned behaviour, which occurred as a result of fear and anxiety, links previously neutral stimuli to the gag reflex, including olfactory, gustatory, olfactory, visual and auditory stimuli. A clinician who has an appreciation for the underlying psychological components of gagging will have the foresight to create opportunities which will facilitate changes of the conditioned behaviours.
Iatrogenic factors
Tactile sensation of the oral tissues is an inevitable outcome when executing any form of dental treatment. If this is performed utilizing a poor clinical technique and with a lack of anatomical awareness, then the reflex may be elicited in patients who are naturally more resistant to gagging, and it will reinforce previously learned behaviours in patients who are already suffering from prominent gagging issues. For example, a distolingually over-extended lower denture which also encroaches upon the tongue space.
In situations where stimulation of the gag reflex is necessary for optimal treatment outcomes, such as a correctly extended complete upper denture, gagging information booklets and interventions should be instigated before starting the treatment and this should also factor into the consent process.
Assessment of gagging
A detailed patient history must be recorded at the initial appointment. The clinician should approach the patient with a caring and understanding attitude, which will build rapport, whilst developing trust. A useful guide to assess gagging patients has been outlined in Table 2. The ‘red flag’ warnings should become very apparent during the early stages of the consultation, when the right questions are asked.
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Identify the Initiating Event
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Triggers
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Clinical Features
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Dental History
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Relevant Patient Factors
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The clinical examination will vary greatly between different patients; for those with a more severe form of gagging, or extremely anxious patients, it may only be possible to perform a simple examination at the first visit in order to avoid pushing the patient beyond his/her limitations.
When the gagging is mainly somatogenic in nature, it is good practice to ‘map out’ the areas associated with gagging using the ball end of a burnisher instrument and document detailed findings in the patient's records.
At the second visit, the clinician should use the collated patient data to help facilitate treatment, taking into account any psychogenic factors that were previously mentioned. For example, ensure that the patient is taken promptly into the surgery if waiting enhances their anxiety, or mask any ‘trigger’ smells in the dental surgery. When performing treatment, it is advisable first to establish a good level of communication, such as hand signalling, and begin with only simple procedures in order to build-up the patient's confidence.
Grading the severity of the gag reflex
The Gagging Severity Index10 will help the clinician to identify the severity of the gagging condition and it will assist with the patient's treatment plan.
Grade I – Normal
Very occasional gag reflex which can be controlled by the patient. The patient has a normal gag reflex which is stimulated as a result of difficult treatment procedures.
Grade II – Mild gagging
Gagging occurs occasionally during routine dental procedures such as fillings and impressions. Importantly, the patient is able to maintain control over the gag reflex. No special treatment considerations are usually required. Behavioural interventions may be necessary during high risk procedures.
Grade III – Moderate gagging
Gagging occurs routinely during normal dental procedures, such as examination of high risk sites. The patient is unable to maintain control over the gag reflex once it has been stimulated and cessation of the treatment is necessary. This form of gagging may limit the potential treatment options and preventive gagging measures are normally employed successfully.
Grade IV – Severe gagging
Gagging occurs with all forms of dental treatment including simple examination. Therefore, treatment is not possible without utilizing interventions (see next paper in the series).
Grade V – Very severe gagging
This form of gagging does not require tactile sensation to trigger the reflex. As with grade IV, it demonstrates a conditioned behaviour and the ability of the cerebral cortex to influence the gagging centre. Treatment is not possible without utilizing interventions (see next paper in the series).
The grade IV and V severe forms of gagging will (rather obviously) have a substantial impact on affected patients' overall behaviour and their attendance of dental appointments. These types of patients are categorized under the psychogenic category, as there will be a strong underlying psychological element responsible for their exaggerated reflex.
Once this definitive diagnosis has been confirmed, it is important to consider whether the reflex could be successfully managed within the dental setting, or should the clinician consider enlisting the support of another medical colleague in order to avoid worsening the condition (discussed in the next paper in the series).
Conclusion
It is clear that, with an additional understanding of the gag reflex, the clinician can accurately assess and diagnose the patient, which should always take place prior to the clinical examination. Unfortunately, it is very easy for the clinician to reinforce negatively learned behaviours; this is particularly relevant to those who are severely affected by the condition. The clinician should therefore adopt a systematic approach for patients suffering from a severe gagging response. It is important for each clinician to be mindful of his/her own limitations. Where it is felt that the gagging severity is beyond the capability of general practice, then it is important to refer the patient for a specialist opinion at an early stage.