Impaired Vocal Fold Motion in Neurodegenerative Disorders

Azulay Long^*
*Correspondence: Azulay Long, Department of Otolaryngology, University of Tokyo, Tokyo, Japan, Email:

Introduction

Neurodegenerative disorders encompass a group of conditions characterized by progressive degeneration of neurons, leading to functional impairments in various systems, including motor, cognitive, and autonomic functions. One common manifestation of neurodegenerative diseases is impaired vocal fold motion, which can significantly impact speech production, swallowing, and respiratory functions. This report explores the underlying mechanisms, clinical implications, diagnostic approaches, and management strategies for impaired vocal fold motion in the context of neurodegenerative disorders. The pathophysiology of impaired vocal fold motion in neurodegenerative disorders involves complex mechanisms that vary depending on the specific disease. In PD, impaired vocal fold motion is attributed to rigidity, bradykinesia, and hypokinesia affecting the laryngeal muscles. Reduced amplitude and variability of vocal fold vibration lead to monotone speech, reduced vocal loudness, and dysphonia.

Description

ALS results in progressive motor neuron degeneration, including those innervating the laryngeal muscles. Weakness and atrophy of these muscles lead to vocal fold paralysis or paresis, causing breathiness, hoarseness, and dysphonia. Vocal fold abnormalities in HD are linked to dystonia, involuntary movements, and dysphagia. Spasmodic and irregular vocal fold motion contribute to dysarthria and dysphonia in affected individuals. MSA is associated with autonomic dysfunction and parkinsonian features. Impaired vocal fold motion in MSA can result from both central nervous system involvement and autonomic dysfunction affecting laryngeal control. PSP leads to axial rigidity and bradykinesia, affecting vocal fold adduction and abduction. Stridor, dysphonia, and dysphagia are common manifestations of vocal fold dysfunction in PSP. The clinical manifestations of impaired vocal fold motion in neurodegenerative disorders are diverse and often overlap with other speech and swallowing difficulties [1].

Changes in vocal quality, including breathiness, hoarseness, strain, and monotony, are common in individuals with impaired vocal fold motion. These alterations affect speech intelligibility and communication effectiveness. In cases of severe vocal fold dysfunction, particularly in conditions like ALS or PSP, stridor may occur due to inadequate vocal fold adduction during inspiration, leading to noisy breathing and respiratory distress. Impaired vocal fold motion can contribute to swallowing difficulties, including aspiration risk, reduced laryngeal closure, and delayed swallow reflex. Dysphagia can result in choking, coughing, and compromised nutritional intake. Vocal fold dysfunction can impact respiratory functions, causing inefficient phonation, reduced vocal loudness, and increased vocal effort. Respiratory muscle weakness and coordination deficits further exacerbate these issues [2].

Accurate diagnosis of impaired vocal fold motion in neurodegenerative disorders requires a comprehensive evaluation. A thorough history and physical examination, focusing on speech, voice quality, swallowing function, and respiratory patterns, are essential for identifying vocal fold abnormalities. Direct or indirect laryngoscopy allows visualization of the vocal folds during phonation and respiration. Laryngeal imaging helps assess vocal fold mobility, symmetry, and mucosal integrity. EMG studies can evaluate the neuromuscular function of the laryngeal muscles, identifying patterns of denervation, weakness, or spasticity indicative of neurodegenerative involvement. VFSS assesses swallowing dynamics, including laryngeal closure, aspiration risk, and bolus transit, providing insights into the impact of vocal fold dysfunction on swallowing safety. Pulmonary function tests and respiratory muscle strength assessments help evaluate the impact of impaired vocal fold motion on respiratory functions, guiding interventions for respiratory support and management [3].

Management of impaired vocal fold motion in neurodegenerative disorders aims to improve speech clarity, swallowing safety, and overall quality of life. Individualized speech therapy programs focus on vocal exercises, breath support techniques, articulation exercises, and vocal hygiene practices to optimize vocal function and communication skills. Dysphagia therapy addresses swallowing difficulties through compensatory strategies, sensorymotor exercises, diet modifications, and positioning techniques to reduce aspiration risk and improve nutritional intake. AAC devices, such as speechgenerating devices and communication boards, assist individuals with severe vocal fold dysfunction in expressing their thoughts and needs effectively. Botulinum toxin injections may be used to temporarily improve vocal fold adduction in cases of spasmodic dysphonia or focal laryngeal dystonia. Surgical procedures, such as vocal fold medialization or arytenoid adduction, can restore vocal fold closure and improve voice quality in select cases [4].

Non-invasive ventilation or mechanical ventilation may be necessary for individuals with severe respiratory compromise due to vocal fold dysfunction, especially in advanced stages of neurodegenerative diseases. The future of managing impaired vocal fold motion in neurodegenerative disorders involves innovative approaches and research initiatives. Targeted therapies aimed at preserving motor neuron function and preventing neurodegeneration may offer potential benefits in delaying or mitigating vocal fold dysfunction in these conditions. High-resolution laryngeal imaging modalities, such as high-speed video endoscopy and optical coherence tomography, can provide detailed insights into vocal fold dynamics and structural changes, enhancing diagnostic accuracy and treatment planning.

Telemedicine platforms enable remote consultations, speech therapy sessions, and monitoring of vocal and swallowing functions, improving access to specialized care and enhancing continuity of treatment. Understanding the genetic factors contributing to vocal fold dysfunction in neurodegenerative disorders can inform personalized treatment approaches and targeted interventions based on genetic profiles. Advancements in regenerative medicine, including stem cell therapies and tissue engineering, hold promise for restoring damaged laryngeal tissues and promoting functional recovery in individuals with impaired vocal fold motion [5].

Conclusion

Impaired vocal fold motion represents a significant clinical challenge in the context of neurodegenerative disorders. The intricate interplay between motor neuron degeneration, muscle weakness, spasticity, and autonomic dysfunction contributes to a range of vocal fold abnormalities, impacting speech, swallowing, and respiratory functions. Understanding the complexities of this condition is paramount for optimizing patient care and improving quality of life. The pathophysiology of impaired vocal fold motion varies across neurodegenerative diseases. In Parkinson's disease (PD), laryngeal rigidity and bradykinesia lead to reduced vocal amplitude and variability, resulting in dysphonia and monotone speech.

Acknowledgement

None.

Conflict of Interest

None.

References

1. Checkoway, Harvey, Jessica I. Lundin and Samir N. Kelada. "Neurodegenerative diseases." IARC Sci Publ 163 (2011): 407-419.

   Google Scholar, Indexed at

2. Kovacs, Gabor G. "Concepts and classification of neurodegenerative diseases." Handb Clin Neurol 145 (2018): 301-307.

   Google Scholar, Crossref, Indexed at

3. Lamptey, Richard NL, Bivek Chaulagain, Riddhi Trivedi and Avinash Gothwal, et al. "A review of the common neurodegenerative disorders: Current therapeutic approaches and the potential role of nanotherapeutics." Int J Mol Sci 23 (2022): 1851.

   Google Scholar, Crossref, Indexed at

4. Gamboa, J., F. J. Jimenez-Jimenez, M. A. Mate and I. Cobeta. "Voice disorders caused by neurological diseases." Rev Neurol 33 (2001): 153-168.

   Google Scholar, Indexed at

5. Hecker, Pascal, Nico Steckhan, Florian Eyben and Björn W. Schuller, et al. "Voice analysis for neurological disorder recognition–a systematic review and perspective on emerging trends." Front Digit Health 4 (2022): 842301.

   Google Scholar, Crossref, Indexed at