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Study: CST Effective in Patients With Concurrent CRC, Voice Disorders


Analysis results highlight the efficacy of cough suppression therapy (CST) for those with chronic refractory cough and voice disorders.

Results of a retrospective analysis show cough suppression therapy (CST) represented a unifying approach for treatment in patients with chronic refractory cough (CRC) and comorbid voice disorders. Findings were published in The Laryngoscope.

Furthermore, the analysis found that when patients were treated for their primary complaint of chronic cough, CST offered crossover effects to their voices, meaning treatment of this primary complaint appears to improve function in systems that share a common pathway, the researchers explained.

Although nearly 10% of the world’s population suffers from chronic cough (cough lasting longer than 8 weeks), up to 20% of cases are unresponsive to medical interventions. “When cough persists longer than 8 weeks, despite treatment with medications, it is referred to as CRC,” the authors wrote. In addition, more than half of patients with chronic cough also have a concurrent voice disorder.

According to recent research, the most likely cause of CRC is sensory neuropathy of the larynx. “Motor and sensory neuropathy of the laryngeal nerve are thought to occur together and may explain the close link in the literature between cough and voice disorders,” the researchers said.

CST—a specific voice therapy for those with CRC—incorporates behavioral modifications and is provided by a speech language pathologist either alone or with medication. To determine whether treatment of CRC through cough suppression methods led to improvement in out-comes of severity of both cough and voice disorders, the investigators carried out a retrospective chart review of medical records obtained between September 2015 and May 2020.

All participants presented to the Loma Linda University otolaryngology clinic in California and completed the Voice Handicap Index-10 (VHI-10) and Cough Severity Index (CSI) surveys.

Patients “received between 1 and 13 CST treatment sessions before a follow-up examination with an otolaryngologist,” with a mean time between last treatment and posttreatment self- assessment of VHI-10 and CSI scores of 24.7 days.

Of the 43 individuals included in the analysis (40 females, 3 males), 27 were assigned to the cough (C) group and 16 to the cough and voice (CV) group.

Overall, the researchers found:

  • Posttest analysis showed significant improvement in cough severity for both groups and significant improvement in voice severity for the CV group
  • The VHI-10 scores for the C group did not change significantly
  • The median number of treatment sessions was 3, with a range of 1 to 13 sessions
  • Correlation between changes in severity and number of treatment sessions was not found to be significant at the tested level

“This is the first study to show that CST improves both cough and voice severity in patients with moderate to severe voice disorders refractory to traditional medical treatment for chronic cough,” the authors wrote.

The wide treatment windows observed in the study (mean 18 weeks in the C group vs mean 20.8 weeks in the CV group) was a result of barriers to treatment and follow-up, including factors like insurance approval and distance to the clinic.

The relatively small sample size and lack of control for types of voice disorders and types of medications used at baseline mark limitations to this study.

“The results indicate that patients who perceive their voice disorder as moderate to severe improved in their perception of cough and voice,” the authors concluded. “Although VHI-10 scores improved in the CV group, most patients still reported VHI-10 scores indicative of a voice disorder. The number of CST treatment sessions did not correlate with changes in the VHI-10 or CSI scores in either group.”


LaTour D, Crawley B, Krishna P, Hahn R, Murray T. Effects of cough suppression therapy on voice disorder severity. Laryngoscope. Published online June 24, 2021. doi:10.1002/lary.29705

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