Laryngeal Manifestations of Stroke - An Overview

Introduction

Stroke, a leading cause of long-term disability globally, affects various bodily functions, including speech and swallowing. However, one aspect often underestimated is its impact on the larynx. Laryngeal manifestations, ranging from mild voice changes to severe dysphagia and aspiration, significantly affect a stroke survivor's quality of life.

What Are the Causes of Laryngeal Manifestations of Stroke?

The causes are mentioned below:

• Ischemic or Hemorrhagic Stroke: Ischemic strokes, caused by a blockage in an artery supplying blood to the brain, or hemorrhagic strokes, resulting from bleeding into the brain tissue, can affect areas crucial for laryngeal function. Damage to specific brain regions, such as the brainstem, can disrupt the neural pathways responsible for controlling the larynx. The brainstem plays a pivotal role in coordinating the complex movements of swallowing and speech production. When compromised by stroke, it can lead to impairments in laryngeal function, including dysphonia and dysphagia.

• Brainstem Lesions: The brainstem contains nuclei and pathways involved in regulating various functions, including swallowing, cough reflex, and vocalization. Stroke-induced lesions in the brainstem can directly affect these nuclei and pathways, disrupting the neural circuits responsible for laryngeal control. This disruption can result in a range of laryngeal manifestations, from mild voice changes to severe swallowing difficulties.

• Cranial Nerve Involvement: Several cranial nerves innervate the larynx muscles and are integral to its proper function. For instance, the vagus nerve (cranial nerve X) provides motor innervation to the intrinsic muscles of the larynx. In contrast, the glossopharyngeal (cranial nerve IX) and hypoglossal (cranial nerve XII) contribute to sensory feedback and motor control during swallowing and speech. Damage to these cranial nerves due to stroke can lead to impaired laryngeal sensation, weakened muscle control, and compromised coordination, resulting in dysphonia and dysphagia.

• Corticobulbar Pathway Disruption: The corticobulbar pathway comprises neural connections between the cerebral cortex and the brainstem nuclei that control head and neck motor functions, including those involved in speech and swallowing. Stroke-related damage to this pathway can disrupt the descending motor commands necessary for precise laryngeal movements during speech and swallowing. Consequently, individuals may experience difficulties in vocalization and swallowing coordination.

• Reduced Sensation and Impaired Motor Control: Beyond direct damage to specific brain structures, stroke can also lead to more generalized impairments in sensation and motor control, affecting laryngeal function indirectly. Sensory deficits may reduce awareness of food or liquid in the pharynx, increasing the risk of aspiration. Likewise, motor deficits can lead to weakened laryngeal muscles and impaired coordination, further exacerbating dysphonia and dysphagia.

What Are the Symptoms of Laryngeal Manifestations of Stroke?

• Hoarseness (Dysphonia): Hoarseness refers to alterations in voice quality characterized by roughness, breathiness, or a strained vocal quality. It occurs due to disruptions in the laryngeal muscles' coordination, leading to irregular vibration of the vocal folds. Stroke-induced damage to the neural pathways controlling laryngeal function can result in hoarseness, impacting the clarity and intelligibility of speech.

• Weak Voice (Hypophonia): Hypophonia manifests as reduced vocal loudness or intensity, often resulting from weakened laryngeal muscles. Stroke-related motor control or muscle strength impairments can lead to decreased vocal projection, making it difficult for individuals to speak at a normal volume.

• Breathiness: Breathiness in the voice is characterized by an audible escape of air during a speech, resulting from incomplete closure of the vocal folds. Damage to the nerves or muscles in laryngeal closure can lead to breathy speech post-stroke, affecting vocal clarity and efficiency.

• Stridor: Stridor refers to a high-pitched, noisy breathing sound caused by turbulent airflow through partially obstructed airways. In stroke survivors with laryngeal dysfunction, stridor may occur during inspiration or expiration due to vocal fold paralysis or structural abnormalities, indicating compromised airway patency.

• Difficulty Initiating Speech (Apraxia of Speech): Apraxia of speech is a motor speech disorder characterized by difficulty initiating and executing volitional speech movements despite intact language comprehension and muscle strength. Stroke-induced damage to the cortical areas responsible for speech planning and programming can result in apraxia of speech, leading to hesitations, groping movements, and overall speech initiation difficulties.

• Coughing or Choking During Swallowing (Dysphagia): Dysphagia, or difficulty swallowing, is a common consequence of stroke-related laryngeal dysfunction. Impaired coordination of the swallowing muscles or sensory deficits in the pharynx can lead to coughing or choking episodes during eating or drinking. Dysphagia increases the risk of aspiration, where food or liquid enters the airway, potentially leading to pneumonia and respiratory complications.

• Recurrent Respiratory Infections: Laryngeal dysfunction post-stroke predisposes individuals to recurrent respiratory infections, such as pneumonia, due to aspiration of food, liquid, or saliva into the lungs. Aspiration pneumonia can exacerbate respiratory compromise and impede rehabilitation, necessitating vigilant monitoring and preventive measures.

How to Manage Laryngeal Manifestations of Stroke?

The treatment can be performed as follows:

• Speech Therapy: Speech-language pathologists (SLPs) play a pivotal role in rehabilitating laryngeal dysfunction post-stroke. Speech therapy interventions are tailored to address specific deficits in voice production, speech initiation, and swallowing function. Therapeutic exercises aim to strengthen laryngeal muscles, improve vocal fold closure, and enhance coordination of swallowing muscles. Techniques such as vocal exercises, breathing exercises, and sensory-motor retraining are utilized to optimize vocal quality and swallowing safety.

• Swallowing Therapy: Dysphagia management is a crucial component of stroke rehabilitation to minimize the risk of aspiration and associated complications. SLPs employ various swallowing therapy techniques, including swallow maneuvers, sensory stimulation, and dietary modifications. Swallowing exercises focus on improving oral motor control, bolus manipulation, and pharyngeal swallow coordination. SLPs also provide education on safe swallowing strategies and adaptive techniques to facilitate effective oral intake while reducing the risk of aspiration.

• Surgical Interventions: In severe cases of laryngeal dysfunction post-stroke, surgical interventions may be considered to improve vocal quality and swallowing function. Procedures such as vocal fold augmentation with injectable materials or implants enhance vocal fold closure and improve voice projection. Laryngeal reinnervation techniques, such as selective laryngeal adductor denervation-reinervation (SLAD-R), may restore laryngeal muscle function and coordination in select cases.

• Diet Modifications: Dietary adjustments are often necessary to accommodate swallowing difficulties and reduce the risk of aspiration. SLPs collaborate with dietitians to develop individualized diet plans based on the patient's swallowing abilities and nutritional needs. Texture modifications, such as thickened liquids or pureed foods, may be recommended to facilitate safe swallowing and prevent aspiration. Regular monitoring and reassessment of dietary tolerance are essential to ensure adequate nutrition and hydration.

• Postural Adjustments: Optimal positioning during eating and drinking can significantly impact swallowing safety and efficiency. SLPs guide proper postural techniques to facilitate effective bolus transport and minimize the risk of aspiration. Strategies such as chin tuck, head turn, or head tilt maneuvers may be employed to optimize airway protection and improve bolus clearance during swallowing.

• Respiratory Support: Individuals with laryngeal dysfunction post-stroke may benefit from respiratory support measures to manage associated respiratory complications. Respiratory therapists collaborate with the interdisciplinary team to assess respiratory function, provide pulmonary hygiene techniques, and implement ventilatory support as needed. Continuous monitoring of respiratory status is crucial to promptly detect and address any signs of respiratory compromise.

Conclusion

Laryngeal manifestations of stroke significantly impact a patient's functional outcomes and quality of life. Recognizing the underlying causes, promptly identifying symptoms, and implementing appropriate treatment interventions are essential to optimizing outcomes for stroke survivors. Multidisciplinary collaboration among healthcare professionals is paramount to comprehensive care addressing laryngeal dysfunction's neurological and functional aspects post-stroke.