A new study was published in the December 2010 edition of the journal Pediatrics addressing the risk of vocal cord paralysis after PDA ligation surgery for micropreemies (< 1000 g). The incidence is high: 54%.
What is vocal cord paralysis, why is this so common among preemies after PDA surgery, and why does it matter? To help answer these questions I enlisted the help of Dr. Russell Faust, a fantastic and very knowledgeable pediatric ENT (Ear, Nose, and Throat) specialist.
First of all, Dr. Faust was not surprised at the high incidence of vocal cord paralysis in this most recent study. While this study is small, the findings are in accordance with other research. One study from 2008 indicated an incidence of 67%. Basically, 1/2 to 2/3 of babies weighing less than 1,000 g will get a one sided vocal cord paralysis after PDA surgery.
What is a paralyzed vocal cord? There are two vocal cords and they meet in the middle of the trachea (windpipe). They move apart to let oxygen into the lungs and the flow of air across the cords creates our voice. The upside down slightly paler V shaped tissues in the photo above are the vocal cords, thanks Dr. Faust. When one is paralyzed it stays put in the middle (see the video below).
Why is this so common after PDA surgery (closing the patent ductus arteriosus)? The nerve that controls the left vocal cord (the recurrent laryngeal nerve) runs very close to the PDA. The surgeon is operating in a tiny area when a baby weighs less than 1,000 g, so injury is often not preventable. This is a recognized complication of the surgery and doesn’t mean than anything went wrong.
Why does the PDA need to be closed if the risk of vocal cord paralysis is so high? A PDA is an abnormal communication of blood between the left and right sides of the heart, causing the heart to work harder. For some preemies, this can affect oxygen levels or contribute to other problems. If a baby is doing well, then often the doctors can wait to see if the PDA will close by itself (it does sometimes). If a baby is too unstable for a “wait and see” approach, medication (indomethacin) can be used to close the PDA. If indomethacin doesn’t work or a baby can’t receive indomethacin (for example, they have necrotizing enterocolitis), the communication needs to be closed surgically.
What happens if the left vocal cord becomes paralyzed? According to Dr. Faust, there are several possible scenarios:
- Hoarse voice, as one side of the vocal cords can’t move, the flow of air is compromised, affecting the voice.
- Airway obstruction, which can be a cause of sleep apnea or even affect the ability to exercise by reducing the flow of oxygen to the lungs (the paralyzed vocal cord basically narrows the airway).
- Aspiration (stomach contents getting into the lungs). The vocal cords are the last line of defense protecting the lungs. If a baby refluxes and has vocal cord paralysis, aspiration is more likely to happen.
Should all babies who have PDA surgery see an ENT in follow up? Dr. Faust says only if there are problems, such as breathing issues (need to know if breathing problems due to vocal cord paralysis or to lung problems, such as bronchopulmonary dysplasia or asthma), possible sleep apnea, or suspected aspiration. Even if a baby just has a raspy voice, it is a good idea to have a pediatric ENT weigh in.
How is vocal cord paralysis diagnosed? The procedure is called a laryngoscopy, which involves passing a telescope through the mouth or nose into the airways to check if the vocal cords move back and forth. The video shows it nicely (one side stays put while the other moves…warning, an injection right into the vocal cords is performed in this video, and some might find it a little hard to stomach).
What can be done about a paralyzed vocal cord? Speech therapy can be helpful. Some children might need surgery to help open the paralyzed vocal cord. This doesn’t “fix” the nerve, but can open the airway if obstruction and breathing difficulties are an issue.
The bottom line? If your baby had PDA surgery (regardless of how much he weighed, but especially if he weighed less than 1,000 g) look out for any of the above problems. If you suspect an issue, ask for a referral to a pediatric ENT specialist.
Stay tuned for my next blog: tracheotomy and preemies (part two of my discussion with Dr. Faust).
Remember, this blog is not individual medical advice