Steroid and Local Anesthetic Injection Strategy for Sensory Neuropathic Cough

What Is the Source of This Idea?

The first peer-reviewed publication for steroid and local anesthetic injections we are aware of came from Simpson and colleagues in 2018¹.

As an aside: Our first use of superior laryngeal nerve (SLN) injection with local anesthetic was in 2005, in a patient whose severe case of sensory neuropathic cough (SNC) also led to the idea of using capsaicin for SNC².

Since Dr. Simpson’s original publication, several other reports have appeared and can be found with a simple online search.

What Medicines Are We Talking About Injecting?

• Steroid: We use triamcinolone, a suspension (particulate “depot” steroid) designed to act mainly at the injection site. Supplied at 40 mg/mL, we dilute it with an equal volume of local anesthetic to a total volume of 1 mL. The resulting dose is 20 mg per injection. The small volume requires careful, precise placement.
• Local anesthetic:  We use 2% lidocaine with epinephrine most often and have also used mepivacaine and bupivacaine. For reference:
  • Lidocaine 2% with epinephrine: 3–5 hours of effect (usually on the shorter end).
  • Mepivacaine 2–3% with epinephrine: also 3–5 hours.
  • Bupivacaine 0.5% with epinephrine: longest acting, 4–9 hours.

Without epinephrine, each of the local anesthetic injections last about half as long.

Which Patients Are “Best” Candidates?

At Bastian Voice Institute, we do not usually consider injection a first-line option. Instead, it follows lack of success with amitriptyline or desipramine, gabapentin or pregabalin, one or more SSRIs/SNRIs, and capsaicin.

The exception: patients who have traveled long distances. Because injections cannot be prescribed via telemedicine or phoned in to a pharmacy, we sometimes offer this procedure on a first visit to test its potential value in case subsequent, more standard options fail.

As always, we individualize care. Patients who describe touch sensitivity (e.g., gentle pressure on the trachea or thyrohyoid space triggering cough) may have a higher likelihood of benefit.

Where, Exactly, do You Inject?

This depends on the site of the patient’s “zing” (the sensation that initiates cough).

• Anatomy refresher:
  • The SLNs carry sensation from the supraglottis to the level of the vocal folds.
  • The subglottis and trachea receive sensory nerve supply mainly from recurrent laryngeal nerve branchlets.
  • Therefore, a “zing” in the trachea may not respond to SLN injection except, we wonder, possibly by systemic effect. *
• For the commonest “zing” location at the midline sternal notch. We inject close to the tracheal wall, aiming to cover rings 1–4 and the anterior half of the trachea. Occasionally, the needle tip briefly enters the trachea, provoking cough and a “bitter taste” comment. Ideally, we would target farther posteriorly (nearer the nerve branch origin), but that risks temporary vocal cord paralysis.
• Laryngeal or supraglottic “zing” (above the cricoid): We do bilateral SLN injections, dividing the 1 mL mixture between sides. Entry is between hyoid and thyroid cartilage, ~two-thirds back from the thyroid notch, angled straight medially, then medially and superiorly, and finally medially and anteriorly as if to reach the terminal sensory branches.
• Unilateral vs bilateral: Some suggest unilateral injection to avoid temporary swallowing disturbance. We do not find this necessary and “always” inject bilaterally unless the tickle is consistently and uniquely unilateral; prior research shows supraglottic anesthesia does not meaningfully impair swallowing mechanics³, and our experience confirms only possible transient “strange sensation” after bilateral injections.
• Other locations: Occasionally, patients have a focal “touch point” laterally in the neck. With extreme care, we may target that spot.

What Is Your Treatment Strategy and Frequency?

We distinguish between trial phase and ongoing management:

• Trial: If there is absolutely no response to the first injection, we usually do not repeat. If there is even modest benefit, we do two more injections, ~1 month apart.
• Ongoing: We then counsel patients on the potential risks of cumulative steroid exposure. We recommend at least 2 months between injections, ideally 3 months or longer.
  • Why 2 months and not longer? Because some patients’ severe, quality-of-life-diminishing cough returns by week 5–6.
  • At ~120 mg triamcinolone per year, risk of HPA (Hypothalamic–Pituitary–Adrenal) suppression is low in otherwise healthy adults not using other steroids.
  • Systemic absorption lasts ~3 weeks; HPA recovery may lag another 2–3 weeks. Thus, 8-week spacing is an acceptable minimum when compassion dictates.
  • Many patients wait longer; some obtain months of relief and return only 2–3 times per year.

How do Patients Tolerate Injections?

Remarkably well. These patients are often highly motivated, as their cough severely diminishes quality of life.

What Is the Expected Benefit?

Informally, perhaps 30–40% of this subgroup—those whose cough resisted multiple prior therapies—benefit. This rate is somewhat lower than published reports. Among our population, some enjoy dramatic, long-lasting relief; others experience only modest improvement lasting 4–6 weeks. As with all SNC treatments, results vary.

Have You Had Complications?

Minimal. Only one patient has reported a temporary bruise. We have had no cases of temporary vocal cord paralysis with pre-tracheal injections, nor swallowing or voice issues with SLN injections.

What Remains Uncertain?

Physicians should maintain a questioning posture and recognize unanswered questions:

1. Variation in reported response rates and duration suggests more study is needed regarding targeting and optimal dosing (our 20 mg vs the 40 mg used by others).
2. Our biggest question: Many patients improve transiently with systemic steroids (e.g., a methylprednisolone or prednisone taper), but relapse quickly after stopping. This raises the question: Are injections effective because of local action, systemic effect, or both?
   • Though it is true that depot triamcinolone delivers a much lower daily systemic exposure over a longer period, might some patients be exquisitely sensitive to even the equivalent of as little as ~5 mg/day?
   • What role does placebo play?
   • A triple-blind study comparing saline, triamcinolone into strap muscle, and triamcinolone into SNC target sites would help answer this.

Overall Impression

Steroid + local anesthetic injections for sensory neuropathic cough are a valuable but secondary option. They offer real relief for some patients, especially those who have exhausted oral medications, but the need for repeated injection in some is not ideal, and questions remain about mechanism and optimal injection sites and technique.

References