Those with an HGR will often gag while eating thick or sticky foods that tend to get stuck in the mouth, such as bananas and mashed potatoes.įollowing intraoral stimulation, afferent fibers from the trigeminal (CN V), glossopharyngeal (CN IX), and vagus (CN X) nerves pass to the medulla oblongata. There will be no response when touching the damaged side.Ĭonversely, another study showed that 10-15% of individuals have a hypersensitive gag reflex. If both CN IX and CN X are damaged on one side, touching the intact side will result in a unilateral response with a deviation of the palate to that side. If the vagus (X) nerve is damaged and either side is touched, the soft palate will elevate and move toward the affected side. If the glossopharyngeal (IX) nerve is damaged on one side, there will be no response when touched. To test the gag reflex, you gently touch one and then the other palatal arch with a cotton swab or tongue blade, waiting each time for gagging. Testing the gag reflex can help assess CN IX and CN X damage. In certain instances, a lack of a gag reflex may be a symptom of a more severe medical condition, such as cranial nerve damage or brain death. This percentage may be higher in patients with a history of smoking or tobacco use. According to one study involving 140 people, 37% were found to have an absent gag reflex. It is not uncommon for an individual to lack a gag reflex. Here, sensory stimulation of the soft palate travels through the nucleus of the spinal tract of the trigeminal nerve.Īs previously stated, individuals may suffer from either a lack of a gag reflex or a hypersensitive gag reflex (HGR). Stimulation of the soft palate can also elicit the gag reflex in this case, the sensory limb is the trigeminal nerve (CN V). Efferent nerve fibers to the pharyngeal musculature traverse from the nucleus ambiguus through CN X, resulting in the bilateral contraction of the posterior pharyngeal muscles.Ĭontraction 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. In turn, these nuclei send fibers to the nucleus ambiguus, a motor nucleus in the rostral medulla. These sensations are carried by CN IX, 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. The stimulus is provided by sensation to the posterior pharyngeal wall, the tonsillar pillars, or the base of the tongue. The nerve roots of cranial nerves IX and X exit the medulla through the jugular foramen and descend on either side of the pharynx to innervate the posterior pharynx, posterior one-third of the tongue, soft palate, and the stylopharyngeus muscle. The gag reflex is controlled by both the glossopharyngeal (CN IX) and vagus (CN X) nerves, which serve as the afferent (sensory) and the efferent (motor) limbs for the reflex arc, respectively. In cases of psychogenic gag reflexes, even the thought of touching a sensitive trigger area, such as occurs when going to the dentist, can induce gagging. A psychogenic gag reflex presents following a mental trigger, typically without direct physical contact. A somatogenic gag reflex follows direct physical contact with a trigger area, which may include the base of the tongue, posterior pharyngeal wall, or tonsillar area. The gag reflex can be classified as either somatogenic or psychogenic.
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