The problem can occur when the movements involved in swallowing are restricted due to a tumor, any type of blockage, or paralysis after a stroke.
Besides the motor problems, swallowing can be impaired due to sensory dysfunction, meaning when sensation (the ability to feel) is lost or reduced anywhere in the throat area.
The loss of sensation can be caused by a problem originating in the brain, such as what happens after certain types of stroke, or it can be a result of a nerve injury or swelling in the actual throat area.
"Mechanoreceptors and chemoreceptors in the laryngopharyngeal (LP) mucosa receive innervation from the internal branch of the superior laryngeal nerve (SLN), which serves as the afferent component of the LAR.
The motor neurons within the nucleus ambiguus then project to the recurrent laryngeal nerve (RLN), the efferent component.
In response to a unilateral stimulus, a discrete and rapid bilateral contraction of the thyroarytenoid (TA) muscles is produced"[8]
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 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 "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.
The strength of the air pulse given during sensory testing in acid-injured vocal cords due to acid reflux disease will necessarily be much greater in order to elicit an airway reflex than tissues that are not swollen.