The larynx, commonly known as the voice box, is a critical part of the respiratory and digestive systems. It is located in the anterior neck at the level of the C3-C6 vertebrae and is responsible for several important functions including airway protection, respiration, swallowing, and phonation. There are a number of neurological conditions that can affect the larynx leading to problems with voice, swallowing, and breathing.
What is the larynx?
The larynx is a tubular organ made up of cartilage, muscles, ligaments, and membranes. It connects the pharynx (throat) to the trachea (windpipe) and allows air to pass from the nose and mouth into the lungs. The larynx houses the vocal folds which are two bands of smooth muscle that vibrate to produce sound for speech. Other key structures found in the larynx include:
- Epiglottis – A flap of elastic cartilage that closes over the larynx during swallowing to prevent aspiration.
- Vestibular folds – False vocal folds located above the true vocal folds.
- Arytenoid cartilages – A pair of small pyramid-shaped cartilages that help move and adjust tension on the vocal folds to change pitch.
- Cricoid cartilage – A ring of cartilage that forms the lower and back walls of the larynx.
- Thyroid cartilage – The largest cartilage in the larynx commonly known as the Adam’s apple.
In addition to producing voice for speech, key functions of the larynx include:
- Respiration – It allows air to pass into and out of the lungs for breathing.
- Swallowing – The larynx elevates during swallowing and the epiglottis closes to prevent food and liquids from entering the airway.
- Cough reflex – Irritation or blockage triggers an involuntary cough to clear the airway.
- Sphincter action – The vocal folds come together and the larynx constricts during certain activities to prevent the passage of materials through it.
What are the most common neurological conditions affecting the larynx?
There are several neurological disorders that can affect laryngeal function. The most common conditions include:
Vocal Fold Paralysis
Vocal fold (or cord) paralysis is the most common neurological cause of laryngeal dysfunction. It occurs when the nerve impulses to the laryngeal muscles are disrupted, leading to reduced mobility of the vocal folds. This affects voice production and airway protection.
Unilateral vocal fold paralysis (UVFP) is more common than bilateral paralysis. It occurs when just one vocal fold is impacted. Patients present with hoarseness, voice fatigue, aspiration, and sometimes shortness of breath. Bilateral paralysis causes more significant symptoms including breathing problems, stridor, and dysphonia.
Vocal fold paralysis has several potential causes:
- Iatrogenic damage during thyroid, cardiac, or anterior neck surgery
- Lung cancer infiltrating the recurrent laryngeal nerve
- Neurological disorders like stroke or multiple sclerosis
- Idiopathic (unknown cause)
Treatment focuses on injecting bulk agents into the fold to move it closer to midline, medializing the paralyzed fold surgically, or procedures on the mobile fold to improve voice.
Spasmodic Dysphonia
Spasmodic dysphonia is a neurological disorder characterized by involuntary spasms of the laryngeal muscles during speech. This causes breaks, choppiness, or tremulousness in the voice. Adductor spasmodic dysphonia is more common than the abductor type.
It is considered a focal dystonia since just the laryngeal muscles are impacted. The cause is unknown but may involve abnormalities in the basal ganglia.
Symptoms often begin gradually and worsen over time. Episodes may be triggered by stress. Diagnosis involves a neurological exam and detailed voice evaluation. BOTOX injections into the vocal folds is the primary treatment to temporarily paralyze the muscles.
Essential Tremor
Essential tremor is a progressive neurological disorder that causes involuntary, rhythmic shaking. The trembling most often impacts the hands but laryngeal tremor is also common. This leads to a tremulous, quivering voice.
Essential tremor typically begins gradually on one side of the body during adolescence or young adulthood. The voice may develop a vibrato-like quality. Alcohol and beta blockers may help reduce tremors.
Parkinson’s Disease
Parkinson’s disease is a progressive disorder of the nervous system. It arises due to loss of dopamine producing neurons. Early motor signs include tremor, rigidity, and slowness of movement.
Many patients also develop speech and voice disorders. Hypophonia refers to reduced voice volume. Monopitch, monoloudness, and breathy voice quality may also occur. Speech can become slow with imprecise consonants.
As Parkinson’s progresses, dysphonia and harsh, hoarse voice emerges. Medical, behavioral, and surgical approaches help manage symptoms.
Stroke
A stroke occurs when blood supply to part of the brain is disrupted. This starves brain cells of oxygen causing them to die. Strokes can be ischemic when a clot blocks an artery or hemorrhagic due to bleeding.
If stroke impacts the areas of the brain involved in speech and swallowing, dysarthria results. This is a motor speech disorder characterized by weakness, slowness, and lack of coordination of the speech muscles. Voice quality may sound strained, breathy, or hoarse after stroke.
Therapy helps strengthen muscles. Severe dysphagia may require feeding tubes until swallow function improves.
Multiple Sclerosis
Multiple sclerosis (MS) is an autoimmune disease attack that damages the myelin sheath coating nerve fibers. This disrupts nerve signaling leading to various neurological symptoms.
Laryngeal dysfunction occurs in an estimated 11-45% of those with MS. Breathy, hoarse voice quality, vocal fatigue, pitch breaks, and dysphagia are common complaints. Spastic dysarthria can also develop later in the disease.
Steroids help reduce inflammation during MS flares. Speech therapy aims to improve coordination and precision of speech.
What are the signs and symptoms of laryngeal disorders?
Depending on the underlying condition, there is wide variability in how neurological disorders of the larynx may present. However, some common signs and symptoms include:
- Hoarse, breathy voice
- Voice changes like tremor, roughness, or strained/strangled quality
- Vocal fatigue
- Reduced voice volume or projection
- Pitch breaks
- Wet, gurgly sounding voice
- Throat clearing
- Coughing or choking while eating or drinking
- Aspiration pneumonia
- Difficulty swallowing (dysphagia)
- Shortness of breath
- Stridor – high pitched, noisy breathing
Symptoms may begin gradually or have sudden onset after surgery or stroke. Often voice changes are the first sign of an underlying neurological disorder like Parkinson’s. Patients should be evaluated by a laryngologist and speech-language pathologist.
How are laryngeal conditions diagnosed?
A comprehensive workup is needed to diagnosis neurological laryngeal disorders. Typical diagnostic approaches include:
- Physical exam – Examining head and neck anatomy for lesions, swelling, nerve damage.
- Neurological exam – Assess nerve function, reflexes, coordination, and balance.
- Laryngoscopy – View vocal fold structure and mobility with mirrors or a flexible fiberoptic scope inserted through the nose.
- Voice evaluation – Perceptual analysis of voice quality, acoustical measurements, patient-reported impact scales.
- Swallow evaluation – Assess oral motor function and risk of dysphagia.
- Imaging – CT, MRI to identify lesions, nerve damage, or sources of compression.
- Laryngeal EMG – Measures muscle electrical activity to diagnose neuromuscular disorders.
These help determine the underlying etiology causing laryngeal signs and symptoms. Biopsies may be performed if cancer is suspected. The results guide appropriate treatment options.
How are laryngeal neurological disorders treated?
Treatment varies depending on the specific neurological condition causing laryngeal dysfunction. Some general management approaches include:
- Voice therapy – Exercises to strengthen vocal muscles and improve control. May teach compensatory strategies.
- Medications – Steroids to reduce inflammation, botox for spasmodic dysphonia, anticholinergics for tremor.
- Surgery – Injection laryngoplasty, laryngeal nerve decompression, medialization thyroplasty.
- Swallow therapy – Bolus modification, postural strategies, neurostimulation to improve dysphagia.
- Augmentative communication – Alphabet boards, speech generating devices for severe cases.
Supportive measures like humidification, hydration, and voice conservation may provide symptom relief. Close monitoring by a multidisciplinary team helps optimize outcomes.
What professions are involved in managing laryngeal disorders?
Several medical and allied health professions play important roles in assessing and treating laryngeal neurological disorders:
- Otolaryngologists – Ear, nose and throat physicians perform laryngoscopy, biopsies, and surgical interventions on the larynx.
- Neurologists – Diagnose and treat conditions impacting the nervous system.
- Speech-language pathologists – Specialists in communication and swallowing. Provide therapy for voice, speech, language, and dysphagia.
- Pulmonologists – Lung specialists who manage respiratory complications of laryngeal dysfunction.
- Gastroenterologists – Treat complications like reflux that can impact the larynx.
- Radiologists – Obtain and interpret CT, MRI, modified barium swallow studies.
Close collaboration between specialties ensures comprehensive management. Support staff like nurses, rehabilitation therapists, and social workers are also crucial.
Conclusion
In summary, there are a variety of neurological conditions that can dysfunction of the larynx. Vocal fold paralysis is the most common, resulting from damage to the recurrent laryngeal nerve. Other key disorders include spasmodic dysphonia, essential tremor, Parkinson’s disease, stroke, and multiple sclerosis.
Diagnosis involves a thorough workup to identify the underlying cause. Typical symptoms include hoarse, breathy voice, vocal fatigue, swallowing problems, and airway issues. An interprofessional team can provide medical and behavioral interventions to help optimize long-term outcomes.