Superior Laryngeal Nerve Blocks Effective for Neurogenic Cough

A new study added to the body of evidence that superior laryngeal nerve (SLN) blocks are an effective treatment for neurogenic cough.

Writing in The Laryngoscope, researchers examined the charts of patients between 2018 and 2020 who were treated with SLN block. At short-term follow-up, all 13 patients with short-term follow-up data had statistically significant decreases in scores on the Cough Severity Index (CSI), with a mean baseline CSI of 24.3 decreasing to 16.15 (mean improvement 8.15; 95% CI, 2.75-13.5; P = .006).

Cough is one of the most common reasons patients visit their physician. Over 30 million visits and $600 million spent on over-the-counter medication can be attributed to patients whose chief complaint is cough, the authors noted. Chronic cough is defined as symptoms lasting more than 8 weeks. The estimated worldwide prevalence is 9.7% and is associated with significant morbidity, including urinary incontinence, depression, insomnia, and anxiety.

Cough is usually caused by asthma, gastroesophageal reflux disease, and upper airway cough syndrome. Neurogenic cough describes cases that do not fit under those categories. Although the cause is under debate, one hypothesis is insult to the superior laryngeal nerve, such as from viral infections or environmental hazards. SLN blocks—following the established treatment of the combination of corticosteroid and local anesthetic injections used in neuropathies—represent a cost-effective, low-risk supplement or alternative to the primary modes of treatment: respiratory retraining therapy and neuromodulating medications.

Patients with evidence of Vocal Fold Motion/Vibratory Abnormalities (VFA) (n = 8) experienced a greater therapeutic effect, the study showed. They showed improvement in short-term CSI scores, with a mean baseline of 24.13 decreasing to 14.5 (mean improvement 9.63; 95% CI, 4.46-14.8; P = .004), while the remaining 5 patients did not show statistically significant improvement. Short-term follow-up was an average of 24 days.

Patients with evidence of VFA also showed long-term improvement that approached statistical significance, with a mean baseline CSI of 22.56 decreasing to 14.56 (mean improvement 8.00; 95% CI, –0.86 to –16.86; P = .057), while patients without VFA did not. In the aggregate, however, the 13 patients had no statistically significant decrease. Long-term follow-up was an average of 269 days.

Clinically speaking, 10 of 12 patients with improved scores reported feeling better after the SLN block. Even 3 of 4 who did not have improved CSI scores reported subjective improvement.

“The consistency of our results with the prior studies lends credence to SLN blocks potential efficacy,” the authors wrote. “However, the effect size of our cohort is more modest than other studies.”

The response aligns with the current understanding of chronic cough as a sensory neuropathy, the authors said. Respiratory retraining therapy, neuromodulating medications, botulinum toxin A injections, and vocal cord injection augmentation are believed to work by altering the neuromuscular sensory input leads to chronic cough. VFAs may represent evidence of laryngeal hypersensitivity that is more conducive to SLN block. The authors recommended larger studies to further evaluate the correlation.

Reference

Duffy JR, Litts JK, Fink DS. Superior laryngeal nerve block for treatment of neurogenic cough. Laryngoscope. Published online April 24, 2021. doi:10.1002/lary.29585