A delayed swallow reflex is a specific type of swallowing difficulty, or dysphagia, where the involuntary, protective actions of the throat are triggered too slowly. This reflex normally initiates immediately when food or liquid, known as a bolus, reaches a certain point in the throat. When this trigger is delayed, it compromises the safety of the swallow, allowing material to enter the unprotected airway. This condition affects a person’s ability to maintain adequate nutrition and hydration.
Understanding the Swallowing Mechanism
The act of swallowing is a complex neuro-muscular process divided into four distinct phases that move a bolus from the mouth to the stomach. The initial two phases, the Oral Preparatory and Oral Transit stages, are voluntary. During the Oral Preparatory phase, food is chewed and mixed with saliva to form a cohesive bolus.
The Oral Transit phase involves the tongue pushing the bolus backward toward the throat, or pharynx. When the bolus reaches the back of the mouth, sensory receptors stimulate the Pharyngeal phase. This third phase is entirely reflexive and involuntary, involving a rapid sequence of events that lasts less than a second.
The involuntary Pharyngeal phase includes the closing of the airway as the vocal cords adduct and the larynx elevates and moves forward. A delayed swallow reflex refers to the measurable lag time between the bolus entering the pharynx and the moment the pharyngeal phase is triggered. During this lag, the bolus can spill into the pharynx while the airway remains open, increasing the risk of material entering the lungs. The final, involuntary Esophageal phase transports the bolus down the esophagus to the stomach.
Recognizing the Signs of Delay
A delayed swallow reflex manifests through several observable signs indicating that the airway protection mechanism is not functioning in a timely manner. One common indicator is coughing or choking that occurs during or immediately after attempting to swallow food or liquids. This happens when the bolus enters the laryngeal vestibule before the airway can close effectively.
Another sign is a change in vocal quality, often described as a “wet” or “gurgly” sounding voice after swallowing. This acoustic change suggests that material is clinging to the vocal folds or structures just above them due to spillage caused by the delay. Individuals may also report the sensation of food sticking in their throat, prompting repeated swallowing or throat clearing.
In the pediatric population, consequences include poor weight gain or failure to thrive due to inefficient feeding. Infants might also exhibit repeated respiratory infections, which can indicate chronic, low-level aspiration.
Common Causes and Aspiration Risk
A delayed swallow reflex is a symptom of underlying neurological impairment, as the reflex arc involves sensory and motor pathways coordinated in the brainstem. Acute events like a stroke or traumatic brain injury (TBI) are common causes, as damage to the central nervous system disrupts the swallow trigger. Neurodegenerative conditions, such as Parkinson’s disease and Amyotrophic Lateral Sclerosis (ALS), also progressively impair reflexive responses, leading to a delay.
Age-related changes in muscle strength and sensory acuity, known as presbyphagia, also contribute to a slower reflexive response in older adults. The greatest danger associated with this delay is aspiration, which occurs when food or liquid enters the trachea and lungs. Aspiration is particularly likely with thin liquids because their low viscosity allows them to move quickly into the unprotected airway during the delay.
When foreign material is aspirated, it introduces bacteria into the lower respiratory tract, leading to aspiration pneumonia. The risk is compounded if the individual has a weakened cough reflex, which prevents them from forcefully clearing the material.
Diagnosis and Management Strategies
Diagnosis of a delayed swallow reflex is performed by a speech-language pathologist (SLP) using instrumental assessments that allow for direct visualization of the swallowing process. The Modified Barium Swallow Study (MBSS), or Video Fluoroscopic Swallowing Study (VFSS), is an X-ray procedure where the patient swallows barium-coated food and liquid. This allows clinicians to measure the time delay between the bolus entering the pharynx and the onset of the pharyngeal swallow.
Another assessment is the Fiberoptic Endoscopic Evaluation of Swallowing (FEES), which involves passing a flexible endoscope through the nose to view the pharynx and larynx directly. FEES is useful for observing residue that pools in the throat during the delay and for assessing the effectiveness of the patient’s protective cough. Management strategies focus on compensatory techniques and therapeutic exercises to improve function.
Compensatory techniques are strategies used during a meal to immediately improve swallow safety. Examples include the chin-tuck posture, which narrows the airway entrance to prevent premature spillage. Dietary modifications involve thickening liquids to slow their transit time, allowing the delayed reflex more time to trigger. Therapeutic exercises, such as the Mendelsohn maneuver, strengthen swallowing muscles and improve the duration of laryngeal elevation.