Efficacy of Intramuscular Steroid Injection for Chronic Cough.

A significant subset of patients are found to have "unexplained chronic cough", which is a diagnosis of exclusion. For these patients, the etiology of the cough is often not isolated. However, the cause is thought to be related to hypersensitivity and inflammation of both the nerves involved in cough sensation and/or mucosa of the larynx. A similar theory described by Driessen et al. hypothesizes that neuroinflammation related to glial cells in central and peripheral neural pathways may contribute to chronic cough in a similar way to how chronic pain is mediated by this pathway. Glial cells in the central and peripheral nervous system may be an important target for steroid hormones and their metabolites, which may have impact on inflammation and excitatory action.

Superior laryngeal nerve injections have been well studied in literature and were recently studied here at the Medical University of South Carolina in a prospective placebo-controlled trial for use in neurogenic cough. This study showed that there was a significant improvement in cough compared to placebo. This study was completed using randomization of 17 patients into the control and steroid/lidocaine injection groups. In the treatment group, 80% of patients reported improvement in symptoms, while in the control group only 14% of patients reported improvement. The Leicester Cough Questionnaire (LCQ) and visual analog scoring were used to compare cough data from pre and post injection.

The hypothesis revolves around the idea that SLN blocks may actually work systemically, so the site of injection may not be the key in cough improvement. This combined with the theory on glial cell involvement and systemic steroid use to inhibit the neuroinflammatory pathway leads us to believe that intramuscular steroid injections could improve chronic cough. Therefore, this study focuses on the use of systemic intramuscular steroids in patients with chronic cough and we hypothesize that patients will have improvement in cough severity. By opening another treatment option that could be utilized by general (non-fellowship trained) otolaryngologists, access to care and treatment may be improved for patients with chronic cough.

Inclusion criteria

• History consistent with chronic unexplained or refractory cough
• Age ≥ 18

Exclusion criteria

• Current smokers
• Uncontrolled diabetes (A1c>7%)
• Patients on ACE inhibitors or Angiotensin II receptor blockers (ARBs)
• Abnormal pulmonary function testing (PFTs) since start of the cough
• Patients with uncontrolled obstructive sleep apnea
• Abnormal chest X-ray within past 6 months
• Uncontrolled reflux
• Prior superior laryngeal nerve injection
• Current neuromodulating medication use for chronic cough*