A stroke occurs when blood flow to a part of the brain is interrupted, causing brain cells to die. A frequent complication of this injury is dysphagia, the medical term for difficulty swallowing. This condition affects up to 78% of patients immediately after a stroke. The location and extent of the brain injury determine the type and severity of the resulting swallowing problem.
Understanding Dysphagia Following a Stroke
Normal swallowing is a complex, coordinated act involving dozens of muscles and several cranial nerves working in a precise sequence. The process has three main phases: the oral phase (voluntary preparation and movement of food), the pharyngeal phase (an involuntary reflex pushing food down the throat), and the esophageal phase (carrying food to the stomach). A stroke typically causes dysphagia by disrupting the motor and sensory control required for the oral and pharyngeal phases, resulting in muscle weakness or poor coordination.
The primary danger associated with uncoordinated swallowing is aspiration, where food, liquid, or saliva enters the airway below the vocal folds. The material can travel into the lungs, potentially leading to a serious lung infection known as aspiration pneumonia. Stroke-related dysphagia often involves a delayed swallowing reflex or inadequate airway protection, increasing the risk of this complication.
Specific Brain Regions Associated with Swallowing Problems
The type of stroke causing the most profound and persistent dysphagia is an infratentorial stroke, specifically one affecting the brainstem. The brainstem houses the “swallowing center,” including the nuclei for the glossopharyngeal (CN IX) and vagus (CN X) nerves. These nerves control the involuntary pharyngeal swallow reflex and motor control of the larynx. Damage to this area can lead to a failure of the swallowing reflex and poor airway closure, resulting in severe dysphagia with a high risk of aspiration.
Strokes in the cerebral hemispheres, known as supratentorial strokes, also cause swallowing difficulties, though they are often less severe than brainstem injury. These strokes affect the cortical areas responsible for planning and initiating the voluntary oral phase of swallowing. Lesions in the right cerebral hemisphere, particularly those involving the primary somatosensory and motor cortices (pre- and post-central gyri) and the insular cortex, are linked to dysphagia.
Swallowing function is represented bilaterally in the cerebral cortex, meaning damage to one side can often be compensated for by the undamaged side. This bilateral organization explains why a unilateral cortical stroke may cause milder or temporary dysphagia. However, strokes involving both sides of the brain (bilateral strokes) or those affecting the right hemisphere’s swallowing representation tend to produce lasting deficits. While brainstem damage impairs the automatic coordination of the swallow, cortical damage impairs sensory feedback and conscious initiation of the process.
Assessing the Severity of Swallowing Difficulty
The initial assessment of swallowing function is performed by a speech-language pathologist (SLP) using a clinical or bedside swallow evaluation. If a problem is suspected, instrumental assessments visualize the process and determine the nature and severity of the dysfunction. These objective measures detect “silent aspiration,” where material enters the airway without triggering a cough or other obvious signs.
Two primary instrumental tests are used for detailed analysis. The Fiberoptic Endoscopic Evaluation of Swallowing (FEES) involves passing a thin, flexible scope through the nose to view the pharynx and larynx during swallowing. This procedure can be performed at the patient’s bedside without radiation exposure, allowing the SLP to observe residue, penetration, and aspiration.
The other common test is the Videofluoroscopic Swallowing Study (VFSS), also known as a modified barium swallow. This involves the patient swallowing various food and liquid textures mixed with barium, a contrast material visible on a moving X-ray. The VFSS provides a comprehensive view of all swallowing phases, from oral preparation to entry into the esophagus, and is considered the gold standard for identifying the biomechanical cause of aspiration.
Therapeutic Approaches for Post-Stroke Dysphagia
Management of post-stroke dysphagia involves compensatory and rehabilitative strategies, along with dietary changes. Compensatory strategies provide immediate safety during the swallow without changing the underlying physiology. Examples include adjusting the patient’s posture, such as performing a chin-tuck to narrow the airway entrance, or using smaller, slower bites and sips.
Rehabilitative exercises strengthen the swallowing musculature and improve the timing of the swallow reflex. The Mendelsohn maneuver involves voluntarily holding the larynx at its highest point during the swallow to prolong the opening of the upper esophageal sphincter. Another exercise is the effortful swallow, where the patient is instructed to swallow as hard as possible to increase pressure and muscle force throughout the pharynx.
Dietary modifications ensure patient safety and adequate nutrition and hydration. This involves adjusting the consistency of foods and liquids to make them easier to control and less likely to be aspirated. Liquids may be thickened, and solid foods may be pureed or minced, based on the instrumental swallowing evaluation results. Maintaining proper nutrition and hydration is a primary goal of dysphagia management during rehabilitation.