Laryngomalacia (floppy larynx)
What is laryngomalacia?
The larynx (voice box) is a funnel-shaped framework of cartilage, muscle and soft tissue, which lies at the top of the trachea (windpipe). This has some very important functions. The vocal cords, bands of soft tissue, come together and vibrate to make voice sounds when we speak. During swallowing, the larynx acts like a sphincter valve for the airway, so stop food and liquid passing into the windpipe and lungs. But at the same time, the larynx needs to open up when we breathe. This depends on the cartilages being stiff enough to keep the airway open, and the muscles coordinating to move the vocal cords apart and brace open the larynx each time with take a breath in.
Early in life, the larynx can be quite soft, and the muscles are not always well-coordinated. Therefore, when breathing in, the larynx can partially close up, just like a drinking straw collapses if a thick milkshake is drunk too quickly. The cartilage funnel is not stiff enough and the muscles aren't coordinated enough to hold the airway open when breathing in. As a result, some babies will have breathing noise (also called stridor), which is a result of air turbulence, and they may also have to work harder to breathe.
What are the symptoms and signs of laryngomalacia?
Babies with laryngomalacia will make noise when they breathe in. Noisy breathing arising from air turbulence at the level of the larynx or upper windpipe is also known as stridor. This can result from various causes, but laryngomalacia is the commonest cause in young babies.
The noise can occur from the time of birth, but often parents will notice it for the first time after a week or two of life. The stridor noise can vary between babies. Sometimes it sounds like a tuneful squeak, but in other babies it may be harsher and more rough. Mucus and saliva in the airway, especially during feeding, can make additional gurgling noise. When babies breathe harder, the noise will tend to be louder, for instance during feeding, crying or excitement. When sleeping, the breathing is usually more gentle, with less airflow, so the noise will tend to be less.
The position of the baby will also make a difference. When lying down on the back, the cartilage which lies over the top of the larynx like a lid (the epiglottis) can flop down, reducing air flow and causing more noise and work of breathing. On the front, or side, this is less of a problem, so babies may find it easier to breathe if nursed in these positions.
Greater work of breathing
The breathing muscles in the chest will draw air into the airway every time a breath is taken. The airways of the nose and throat are beautifully designed to allow air to flow smoothly, with minimal resistance, which uses the least effort. When the airway is narrowed, as in laryngomalacia, the air flow becomes more turbulent and rough, meaning that it is harder to breathe in and out. This requires more effort. Babies will breathe faster and more deeply, often with some strain in their chest muscles and rib cage. The breast bone (sternum) may suck in, and there may be a tug of the windpipe seen in the neck. The nostrils can also flare open. If the breathing is very laboured, babies can become anxious and distressed. They may also become pale, with blueness around the lips and tongues. While this is unusual in laryngomalacia, it does sometimes occur in severe cases, or where there is some other abnormality in the airways or lungs, for instance.
Reflux of stomach contents (possetting) up into the throat is often seen as well in babies with laryngomalacia. It is not known whether babies with laryngomalacia are more likely to have reflux because of swallowing air during feeds, or whether the laryngomalacia itself occurs because of irritation by stomach acids and enzymes after reflux. It may be a combination of these factors. Medical treatment for reflux may be appropriate if the symptoms are significant.
Babies will often find that breathing and feeding at the same time is challenging. They breathe almost entirely through their noses, and have to swallow milk at the same time, which takes significant effort and coordination. If the breathing is laboured, as in laryngomalacia, feeding can become inefficient and slow. Babies can also become tired and they lose interest in feeding, so they are hungry and unsettled. This can also be made worse if there is reflux at the same time.
Poor weight gain and failure to thrive
Babies are born at different weights. They then should grow and gain weight steadily and consistently. This can be recorded on their growth charts, found in each baby's Red Book. Anything which reduces the efficiency of feeding can result in lower amounts of milk in each feed and therefore fewer calories consumed per day. If reflux is significant, then milk may also be brought up, with less being digested.
Additionally, breathing also uses energy. When breathing normally, babies use about one fifth to one sixth of all their energy to power their breathing muscles. If the work of breathing is increased, then extra calories are needed, and these are diverted away from growth and weight gain.
So, laryngomalacia, like other breathing-related conditions, can lead to poor weight gain and failure to thrive, because of reduced intake of milk (feeding difficulties and reflux) and increased energy requirements.
What other problems can produce similar symptoms?
Laryngomalacia is the commonest reason for babies to have noisy breathing (stridor). But, in fact, anything which partially blocks the airway at the level of the larynx or windpipe can result in similar noisy breathing- it's just that these other problems are less common.
Other problems which can give rise to stridor in babies include mucus cysts around the larynx, narrowing below the vocal cords, paralysis of one or both of the vocal cords or a blood vessel birth mark (a haemangioma) in the airway. Stridor may also occur because of narrowing or floppiness of the windpipe (trachea).
Telling the difference between these possible causes of noisy breathing is sometimes difficult. But the features of laryngomalacia can help to make this distinction.
- Usually presents a short time after birth, rather than at birth, but this is not always the case
- Generally does not result in severe respiratory distress and blue spells requiring emergency medical treatment
- Occurs in children who have no history of resuscitation at birth, requiring a breathing tube, for instance
- Tends to be less obvious at night, when breathing gently during sleep
- Tends to gradually improve, rather than getting worse
Other conditions can be present at the same time as laryngomalacia, so this possibility should be considered if the history is not typical, or breathing difficulties are significant.
What investigations are needed?
The information obtained from parents is very important, and will answer some of the issues discussed above. Babies may be seen first by a midwife or health visitor, their GP, or paediatrician, rather than an ENT doctor. The first priorities are to ask the right questions, helping to reach a diagnosis, and to exclude other issues. It is very important to ask about feeding and weight gain, and also to measure and record this in the Red Book.