Research

Consider vocal cord dysfunction as a cause of chronic cough


Patients with chronic cough refractory to medical treatment may have an underlying vocal cord dysfunction (VCD) that is amenable to speech pathology.

According to a comparison of 51 patients with VCD and 39 patients with chronic cough from the John Hunter Hospital in Newcastle, the two conditions overlap.

The cross-sectional study found cough frequency was increased beyond the normal range in patients with VCD and their cough-related quality of life score was reduced.

Laryngoscopy findings were similar in the two groups with paradoxical vocal fold movement (PVFM) the defining criteria in all VCD patients and moderate-to-severe PVFM found in 69% of patients with chronic cough.

Abnormal vocal fold closure during phonation was also present in patients with chronic cough and similar between the VCD and chronic cough groups (78.4% v 64.1%; p=0.24).

“Although VCD is considered a disorder affecting respiration, this study shows that cough is a common and burdensome symptom in VCD, and that VCD should be considered as a potential diagnosis in patients with chronic cough. VCD could be a cause or a relevant comorbidity in chronic cough,” the study said.

Lead author and speech pathologist Dr Anne Vertigan told the limbic VCD was not always recognised in someone with chronic cough so people could be missing out on effective therapy.

“The primary treatment for VCD is speech pathology. We teach patients to breathe without constricting their larynx, so they get control over the vocal cords without spasming.”

She said many patients respond within three to four sessions.

“If you get patients who are refractory to that, there have been treatments e.g. botox to partially paralyse the spasming vocal cords,” she said.

Neuromodulators can also be effective in chronic cough but have been less studied in VCD.

Dr Vertigan said patients with chronic cough should have serious medical conditions such as lung cancer or cardiac problems ruled out.

“And the next step is to look at any underlying or treatable conditions that could be contributing to the cough. If asthma was the cause of the cough, you probably wouldn’t go down the speech pathology road, you would go more to addressing their asthma. Usually when the cough is considered to be refractory to that treatment, is when they get referred to speech pathology.”

“In terms of VCD, you can’t really diagnose it based on symptoms. There are symptoms that give you a hint of VCD but you really need laryngoscopy or hypertonic saline challenge or CT to diagnose it. You need some sort of imaging.”

She said there were a range of techniques for training patients to develop voluntary control over their vocal cords.

“Sometimes you can do that by breathing exercises, sometimes it might be more specific exercise for the vocal cords and what you find is different patients have different muscular patterns… we might experiment a bit with the patients to see what they can pick up the easiest. It’s not a cookbook approach.”

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