Causes of Hypophonia
Neurologic Causes
- The American Academy of Otolaryngology-Head and Neck Surgery states that Parkinson's disease is the leading cause of hypophonia, characterized by reduced vocal intensity, monotone speech, and breathy phonation due to glottal insufficiency 1, 2
- Other extrapyramidal conditions, including spasmodic dysphonia, essential tremor, amyotrophic lateral sclerosis, and multiple sclerosis, can cause hypophonia 1, 3
- Peripheral nerve injury, such as vocal fold paralysis from recurrent laryngeal nerve damage, can cause breathy dysphonia and hypophonia 1, 4, 5
Structural Laryngeal Causes
- Glottal insufficiency, including vocal fold atrophy in elderly patients, can cause hypophonia, with a prevalence increasing to 2.5% in those over 70 years 1, 5
- Benign vocal fold lesions, such as vocal fold cysts, nodules, and polyps, can reduce vocal intensity when they prevent proper vocal fold approximation 6, 7, 4
Systemic and Medication-Related Causes
- The American Academy of Otolaryngology-Head and Neck Surgery recommends that patients with systemic diseases, such as rheumatologic/autoimmune conditions, gastroesophageal reflux disease, and pulmonary disease, be evaluated for hypophonia 1, 4
- Medications, including inhaled corticosteroids, antihistamines, diuretics, and anticholinergics, can cause mucosal drying and irritation, leading to hypophonia 5
Malignancy
- The American Academy of Otolaryngology-Head and Neck Surgery states that laryngeal cancer, lung cancer, and thyroid cancer can all present with hypophonia, and that smoking increases the odds of head and neck cancer 2-3 fold 1, 5
- Laryngoscopy should be performed within 4 weeks if dysphonia/hypophonia persists or immediately if a serious underlying cause is suspected 6, 7, 4
High-Risk Populations
- Professional voice users, smokers, and alcohol users require immediate evaluation for hypophonia due to their increased risk of serious underlying pathology 5, 7, 4