Introduction:
Laryngeal sensory neuropathy (LSN) is a relatively rare condition that affects the nerves in the throat. The exact cause of LSN is not fully understood, but it is assumed that it might be similar to other nerve disorders involving a combination of metabolic issues, nerve damage due to trauma or compression, or viral infections. LSN usually presents with general symptoms such as a chronic, dry cough, throat discomfort or unusual sensations, throat clearing, and voice changes. Some additional symptoms may include difficulty breathing, the sensation that something is stuck in the throat, and hoarseness of voice.
LSN often starts suddenly after a viral infection or surgery, but in some cases, patients may have had a chronic cough for a long time before being diagnosed. Patients with this condition typically have been dealing with it for a while and have seen multiple doctors. They might have received diagnoses such as postnasal drip, allergies, acid reflux, or asthma, but none of the medications have provided consistent relief. As a result, they feel frustrated, and the cough disrupts their social life, sleep, and work performance.
What Is the Cause of Laryngeal Neuropathy?
Laryngeal sensory neuropathy is a rare cause of persistent coughing. It happens when the larynx (voice box) gets injured and becomes overly sensitive, causing a persistent dry cough. Medications used for other nerve-related conditions, like painful diabetic neuropathy, can often help reduce the cough. While it is not completely understood what exactly causes laryngeal sensory neuropathy, it is believed that viral infections like the common cold can harm the nerves in the larynx. This damage leads to heightened sensitivity in the cough reflex.
There are several other causes, such as metabolic issues and nerve damage during medical procedures like intubation or airway endoscopy. When the nerves become excessively sensitive, certain things can trigger symptoms. Allergies, environmental factors like environmental irritants, changes in humidity, gastric reflux, viruses, and eating acidic or spicy foods are all potential triggers.
What Are the Symptoms of Laryngeal Sensory Neuropathy?
The main symptom of laryngeal sensory neuropathy is a persistent cough that is usually dry and does not bring up mucus. It often gets worse after being exposed to certain triggers. People with this condition may also feel a tickling, itching, or burning sensation in their throat, which may be more apparent at night or when the affected person is lying down. Other symptoms can include:
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Alteration or hoarsening of the voice.
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Always needing to clear the throat.
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Having trouble swallowing or having the sensation that something is stuck in the throat.
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Throat or neck pain or discomfort.
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Difficulty breathing or shortness of breath.
What Are the Risk Factors of Laryngeal Neuropathy?
The exact risk factors for laryngeal sensory neuropathy (LSN) are not fully understood. However, there are some known factors that may increase the risk of developing LSN. Individuals with type 2 diabetes mellitus are at higher risk, mainly due to the metabolic abnormalities associated with the condition. Those with goiter caused by thyroid disease are also more prone to LSN. The most common risk factors for LSN include prior viral infections and trauma, often related to surgeries or procedures involving the upper throat and digestive tract, such as endoscopy, intubation, or other surgeries.
How Is Laryngeal Sensory Neuropathy Diagnosed?
Patients with laryngeal sensory neuropathy (LSN) often undergo extensive evaluations by various specialists like pulmonologists, gastroenterologists, and ear, nose, and throat (otolaryngology) doctors before receiving a proper diagnosis. LSN is typically diagnosed by ruling out other possible causes based on the patient's medical history and clinical presentation.
Diagnosing laryngeal sensory neuropathy can be challenging for doctors, as the symptoms are similar to other conditions affecting the throat and airways. Healthcare professionals often begin by taking a thorough medical history to determine if the symptoms may be triggered by inappropriate stimuli or sensations in the throat.
Also, the larynx and throat are examined physically for redness, swelling, or other abnormalities. Blood tests and imaging tests could be helpful in order to rule out the possibility of other conditions. Blood tests can reveal whether an individual has infections or immune system disorders, while imaging tests can evaluate the chest and throat.
There is a possibility that a referral to a laryngologist, a specialist in the larynx and throat, will be necessary after their examination. A laryngologist may order various tests to support their diagnosis, including:
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Laryngoscopy: To perform a laryngoscopy, a thin, flexible tube equipped with a light and camera is inserted into the mouth and guided to the larynx. The doctor can look at how the vocal cords move and see if there are any signs of irritation or damage to the nerves in the larynx.
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Laryngeal Electromyography (EMG): This procedure determines the electrical activity of the laryngeal muscles.
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Provocative Testing: In this test, the larynx is exposed to various irritants or stimuli to see if the symptoms worsen.
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Acid Reflux Testing: Tests like pH impedance monitoring look at the pH levels of the larynx, which can be a sign of acid reflux.
How to Treat Laryngeal Sensory Neuropathy?
Although there is no cure for laryngeal sensory neuropathy, there are treatments available to help reduce and manage its symptoms. Similar to other sensory nerve disorders, patients with LSN may find symptom relief by using medications that affect nerve signaling, such as Gabapentin or low-dose tricyclic antidepressants like Amitriptyline (both collectively known as neuromodulators). One potential treatment option is therapeutic nerve blocks. Some experts believe that the internal branch of the superior laryngeal nerve could be responsible for neuropathy. If coughing is the main symptom, blocking this nerve branch might be considered to alleviate symptoms. A doctor can perform this treatment in their office if other treatments have not been effective.
One study published in 2010 looked at how to manage symptoms caused by the recurrent laryngeal nerve. The researchers studied a group of patients who had symptoms like voice problems, spasms in their vocal cords, and a persistent cough. These patients were treated with neuromodulators, and the researchers monitored their progress to see if their symptoms improved. The study suggests that patients with suspected problems with the recurrent laryngeal nerve often respond well to neuromodulator treatment. Additionally, taking precautions to prevent acid reflux and using medications to reduce stomach acid can help with chronic and recurring spasms in the throat. Patients who showed signs of nerve damage affecting movement tended to have better results with the neuromodulator treatment.
What Is the Link Between Laryngeal Sensory Neuropathy and COVID-19?
Laryngeal sensory neuropathy can occur as a complication of the COVID-19 infection. A recent study was done on patients who had experienced the COVID-19 infection and developed symptoms of LSN. The symptoms reported by the patients included vocal fatigue, hoarseness, dry throat, a foreign body sensation in the throat, and laryngeal tightening. The study results show that the patients exhibited functional abnormalities in the larynx and varying degrees of hoarseness. Therefore, this study strongly supports the idea that laryngeal sensory neuropathy can occur as a complication of COVID-19.
Conclusion:
In conclusion, it is crucial never to ignore seemingly minor symptoms, such as a small cough, as they could be indicative of a larger underlying issue like LSN. Early diagnosis and prevention are key to managing LSN effectively. Recognizing the potential signs and seeking medical attention promptly can help prevent further complications and ensure appropriate treatment. By being proactive in addressing even seemingly insignificant symptoms, we can safeguard our vocal health and overall well-being. Remember, taking action at the earliest signs can make a significant difference in managing LSN and preserving vocal function.
