Sensory Neuropathic Cough (SNC)

Q: What causes SNC?

Nobody knows for certain what causes SNC. We have a number of patients whose SNC began soon after a shingles outbreak in the throat. Others began to cough not long after thyroidectomy or other neck surgery. A very large number describe the beginning soon after an upper respiratory infection—usually a memorable one.Suppose we could prove that SNC/ laryngospasm was caused by a viral injury. In that case, it would not be seen as a continuing infection, but instead as a chronic neural injury. Think, for example, of the post-herpetic neuralgia that can be permanent after a shingles (herpes zoster) outbreak. Treating with antivirals, say a few months after the infection and after the neural injury had occurred would not be expected to heal the damaged nerve endings. Or an extreme example just to send the point home: If a person lost an arm due to the “flesh-eating” streptococcus, treating for streptococcus a month after the loss of the arm (and resolution of the infection) would not restore the arm.Viruses often seem to have a kind of “tropism.” Ever notice how some upper respiratory infections spread through a family, and seem to have highly similar effects? Everyone starts with scratchy throat, then the nose runs, then the cough starts. Etc. One solution could be a “virus” shared by three family members that had similar effects on all of them.If sensory neuropathic cough were in fact a virus-induced neural injury, then it would be possible that more than one member of a family could develop SNC. It is interesting that I have many patients whose mother, or sister, etc. also have SNC. Did they share a virus? Or is it a genetic “susceptibility” in families?

When coughing doesn’t stop.

Sensory Neuropathic Cough (SNC) is a chronic cough disorder that is thought to have a neurogenic cause. SNC¹ is also sometimes referred to as a cough caused by “laryngeal sensory neuropathy,” or is sometimes grouped within the more general category of “refractory chronic cough.”

Symptoms of Sensory Neuropathic Cough

A person with SNC may cough dozens to hundreds of times per day, often also waking up at night to cough. A few of these daily coughing attacks may become violent and last 30 seconds to several minutes. The person’s eyes may tear up and the nose may run; the person may gag or throw up; the person may leak urine, or worse; a few of our patients have even broken one or more ribs during a violent coughing attack.

A key characteristic of SNC is that a coughing attack is typically, though not always, preceded by an abrupt sensation in the throat; this sensation may be described as a “tickle,” a “sudden dry patch,” “like inhaling a powdered doughnut,” “dripping mucus,” or something else.

Possible Explanation for SNC

SNC is thought to be a relative to neuralgia, like post-herpetic neuralgia (persistent pain long after an outbreak of shingles has resolved), or even diabetic neuropathy (“I feel bees stinging my feet”), except that the sensations felt by SNC patients are not painful. With SNC, it may be that the nerve endings in a person’s throat have become damaged, so that they “misfire” and cause this cough-provoking tickling or similar sensations.

Treatment for SNC

Many individuals with SNC have found relief through use of a neuralgia medication, such as amitriptyline ², desipramine ³, gabapentin ⁴, pregabalin, oxcarbazepine, and others. These kinds of medications may help to reduce or abolish a person’s coughing by diminishing the nerve-ending “misfires” caused by SNC.

In our experience, patients sometimes need to work through more than one of these neuralgia medication options, at varying dosage levels, before they arrive at a satisfactory degree of relief. Another treatment option that can be tried is capsaicin⁵. For more about treatment, see our second video (SNC: Medications) below.

What causes SNC?

Nobody knows for certain what causes SNC. We have a number of patients whose SNC began soon after a shingles outbreak in the throat. Others began to cough not long after thyroidectomy or other neck surgery. A very large number describe the beginning soon after an upper respiratory infection—usually a memorable one.

Suppose we could prove that SNC/ laryngospasm was caused by a viral injury. In that case, it would not be seen as a continuing infection, but instead as a chronic neural injury. Think, for example, of the post-herpetic neuralgia that can be permanent after a shingles (herpes zoster) outbreak. Treating with antivirals, say a few months after the infection and after the neural injury had occurred would not be expected to heal the damaged nerve endings. Or an extreme example just to send the point home: If a person lost an arm due to the “flesh-eating” streptococcus, treating for streptococcus a month after the loss of the arm (and resolution of the infection) would not restore the arm.

Viruses often seem to have a kind of “tropism.” Ever notice how some upper respiratory infections spread through a family, and seem to have highly similar effects? Everyone starts with scratchy throat, then the nose runs, then the cough starts. Etc. One solution could be a “virus” shared by three family members that had similar effects on all of them.

If sensory neuropathic cough were in fact a virus-induced neural injury, then it would be possible that more than one member of a family could develop SNC. It is interesting that I have many patients whose mother, or sister, etc. also have SNC. Did they share a virus? Or is it a genetic “susceptibility” in families?

How do I find a doctor for SNC?

Call the otolaryngology (ENT) department of a nearby university or other large medical center. Ask to speak to the triage nurse. Ask that nurse if there are one or more doctors there who have a special interest in neurological coughing. You may need to make a few different phone calls to find a doctor in your area known to have this particular interest.

If you can’t find any such doctors, you might also try calling the pulmonary departments of nearby universities or large medical centers. Or, alternatively, you might simply share the information you found about sensory neuropathic cough with your primary care physician and ask, “Could I please try low-dose amitriptyline?”

As a last resort, you would of course also be welcome to come to our office in the Chicago area. After that first visit, Dr. Bastian would (if your diagnosis is indeed sensory neuropathic cough) be able to manage your treatment from a distance. But of course, for most people it’s not possible to travel so far.

Audio Examples of SNC

Interview with a SNC patient

Second interview with a different SNC patient

SNC and throat clearing of 36 Years’ duration

Fourth interview with a different SNC patient

SNC cough phenomenology: different than that of pneumonia, asthma, or acid reflux!

SNC Medications

Note: Some aspects of these patients’ experiences are atypical; not all patients have the same experience with SNC.

Photos of SNC

A collection of photo essays demonstrating SNC in various patients:

Bruising from Sensory Neuropathic Cough

Bruise caused by violent coughing (1 of 2)

Closer view of bruise, with small collection of white mucus in the middle.

Bruise caused by violent coughing — Closer view of bruise (2 of 2)

A person with violent sensory neuropathic coughing may injure the vocal cords, as illustrated by this bruise, right vocal cord (left of photo).

Example 2

Bruise from coughing (1 of 3)

This man had an episode of aggressive coughing a week earlier. Note the bruising over the vocal processes, which receive the major collisional force during coughing.

Pre-phonatory instant (2 of 3)

The vocal processes are approaching the point of touching (contact would occur gently with onset of talking and more aggressively with coughing).

Phonation (3 of 3)

Vocal cords are now in full contact. Note the unrelated moderately-severe vocal cord bowing.

Example 3

Bruising from SNC (1 of 1)

This individual occasionally coughs to the point of hoarseness. Particularly noteworthy is the subglottic bruise (arrow, dotted line) caused by profound Valsalva-retching kind of coughing. The rest of the right cord (left of photo) is also bruised.

Hemoptysis

SNC patient (1 of 6)

A very worried patient with sensory neuropathic cough has scheduled a return appointment. On arrival she states that she cannot rest due to a trace of hemoptysis a week earlier. What begins as a simple upper aerodigestive tract examination represented by this view of her normal nasopharynx is easily expanded…

Panoramic view (2 of 6)

Detailed inspection of base of tongue, hypopharynx, and laryngeal vestibule, represented by this panoramic view, also show no abnormality. And the examination can continue…

Lidocaine (3 of 6)

Simple instillation of lidocaine into the trachea allows this view into the upper trachea.

Carina (4 of 6)

And this view, with the carina in clear view.

Right mainstem bronchus (5 of 6)

Deep inside right mainstem bronchus and…

Left mainstem bronchus (6 of 6)

…into left mainstem bronchus also reveal no lesions and no “trail of blood.” Simple watchful waiting for more hemoptysis is acceptable to the patient. CXR is optional in the near-term.

Videos about SNC

SNC Medications + Treatments

This is a newer discussion of sensory neuropathic cough, based in a caseload of (surely) well over a thousand patients. The attempt is to touch upon the major points:

Explanation of “damaged nerve endings” as the cause;
The futility of allergy, acid reflux, and asthma treatments;
The unfrutiful “chasing of mucus;”
The use of medications that calm down damaged, jittery nerve endings;
And a brief description of the many current treatment options.

SNC, Part I: Coughing That Won’t Go Away

Sensory neuropathic cough is a chronic cough condition that does not respond to the usual treatments. Many individuals who have been coughing for years find relief from treatment with “neuralgia” medications.

SNC Part II: Medications

Dr. Bastian continues from SNC, Part I and introduces potential medications to treat sensory neuropathic cough.

Still Coughing After COVID?

In this video, Dr. Robert W. Bastian explains three explanations for coughing in the context of Covid-19 infection, with emphasis on the potential for sensory neuropathic cough (Phase 3).