Sensory neurological disorders of the larynx include laryngeal hyperesthesia, laryngeal paraesthesia, laryngeal hypesthesia, and laryngeal anaesthesia. These sensory issues often appear alongside motor disorders, while isolated sensory neurological disorders are relatively rare.
Laryngeal Hyperesthesia and Laryngeal Paraesthesia
Laryngeal hyperesthesia refers to an increased sensitivity of the laryngeal mucosa to ordinary stimuli, such as food or saliva coming into contact with the larynx, which can frequently trigger coughing and laryngospasm. Laryngeal paraesthesia is characterized by abnormal sensations within the larynx, including itching, burning, pain, dryness, or a foreign body sensation. These conditions are commonly caused by acute or chronic laryngeal inflammation, excessive smoking or alcohol use, or diseases of adjacent organs that trigger reflexes via the vagus nerve. They are also frequently observed in patients with neurasthenia, hysteria, anemia, menopause, or those with heavy voice usage, such as singers, teachers, and sales professionals.
Clinical Manifestations
Patients often experience discomfort in the larynx, such as itching, burning pain, or a sensation of a foreign body. These sensations often result in attempts to clear secretions through coughing, spitting, or swallowing. Reflex coughing is also common.
Examination
Laryngoscopic examination typically reveals no obvious abnormalities. Attention should be given to the presence of saliva pooling in the piriform fossa or lesions in the posterior cricoid region to rule out tumors in the postcricoid or hypopharyngeal area.
Treatment
A careful examination is needed to rule out organic lesions. Detailed explanations can help alleviate the patient’s concerns. The underlying cause should be identified and treated accordingly. Local sensory electrotherapy can be considered as suggestive treatment, with the aim of diverting the patient’s focus.
Laryngeal Hypesthesia and Laryngeal Anaesthesia
Both conditions involve lesions of the superior laryngeal nerve and are often accompanied by laryngeal muscle paralysis. These disorders can be classified as central or peripheral:
Central Nervous System Disorders
Examples include cerebral hemorrhage, posterior inferior cerebellar artery thrombosis, brain tumors, and multiple sclerosis.
Peripheral Nerve Disorders
Causes may include lead poisoning, tumor compression or invasion of the neck, thorax, or cranial base, as well as neuritis caused by viral or bacterial infections. Trauma or iatrogenic damage to the internal branch of the superior laryngeal nerve could also lead to these conditions.
Clinical Manifestations
Unilateral hypesthesia may be asymptomatic or cause occasional coughing. In cases of bilateral involvement, laryngeal mucosal sensory impairment can lead to reflexive glottic closure dysfunction, increasing the risk of aspiration. Severe cases may result in complications such as aspiration pneumonia.
Examination
Laryngoscopic findings are generally unremarkable. When the laryngeal mucosa is touched with a laryngoscope or probe, a decrease or absence of laryngeal mucosal reflexes can be noted. Attention should also be given to areas such as the postcricoid region and piriform fossa, and imaging of the head and neck may be necessary to rule out tumors or other pathologies causing sensory abnormalities in the larynx.
Treatment
Treatment should target the underlying cause if identified. In unilateral or mild cases, no specific treatment may be required, though swallow rehabilitation exercises can be helpful. A diet consisting primarily of thick puréed foods, with minimal intake of liquid foods, is suggested. Severe cases may require nasal feeding to prevent aspiration. Sensory electrotherapy of the larynx can be trialed to promote sensory recovery.