Infant larynx


The infant larynx is different from the adult larynx, as
summarised below:
• Its size is approximately one-third of the adult larynx.
• The infant thyrohyoid membrane is much shorter,
and the thyroid notch is behind the hyoid bone.
• The thyroid cartilage is V-shaped in adults, but
more rounded in children.
• In a full-term newborn baby, the length of the glottis
is approximately 7 mm (range 6–8 mm), and the
width of the posterior glottis is 3–4 mm.
• Infant arytenoid cartilages are larger and longer,
comprising slightly more than 50% of the anteroposterior
glottis until 3 years of age. This ratio drops
to 20% in adults.
• The interarytenoid distance represents approximately
60% of the inner subglottic diameter in newborns,
and more than 70% of this diameter in adults.
• Cuneiform cartilages are proportionally larger in
infants than adults; they are not directly connected
with the arytenoid cartilages.
• The cephalad half of the infant cricoid is V-shaped and
becomes rounded at its lower level.
• The cartilages of the infant larynx are softer and
more pliable than in adults.
• The mucosae of the supraglottis and subglottis are
lax in infants and hence more prone to oedema
when inflamed or injured.

A thorough knowledge of the infant and child larynx
calls for the following medical and surgical decisions:
• When performing a full laryngofissure or a partial
cricotracheal resection (PCTR), the thyrohyoid
membrane must often be sectioned along the thyroid
cartilage’s upper rim to release the thyroid cartilage
from its cranial attachment and move it into the
operative field.
• Performance of a precise vertical midline thyrotomy
through the larynx’s anterior commissure can
be difficult in a round-shaped anterior thyroid cartilage.
This necessitates a vertical incision through
the epiglottis at the level of the thyroid notch, which
allows airway division under visual control without
damaging the anterior commissure; this is especially
relevant when the vocal cords are fused by a
laryngeal web or synechia.
• Owing to longer arytenoids, a shorter interarytenoid
distance and a V-shaped cephalad cricoid, endotracheal
intubation may damage the medial aspect of
the arytenoids and postero-lateral portion of the cricoid
ring.
• When performing a CO2-laser supraglottoplasty for
laryngomalacia, part of the cuneiform cartilages
must be vaporised to obtain a less bulky aryepiglottic
fold and induce submucosal fibrosis.
• The pliability of the thyroid cartilage allows the
surgeon to increase the subglottic lumen during
PCTR by performing an inferior midline thyrotomy;
this permits a better adaptation of the larger
tracheal ring used for the thyrotracheal anastomosis.
• A postoperative mucosal oedema of the glottis and
subglottis is more prominent in infants and children
than adults. Therefore, there is a greater need for
temporary postoperative intubation after singlestage
PCTR in the paediatric age group.
The infant and child trachea has the same overall configuration
as the normal adult trachea, except for its
size. From birth to late adolescence, the trachea
more than doubles in length, triples in diameter and
increases by sixfold in cross-sectional area, while
maintaining the same architecture of 16–20 horseshoeshaped
tracheal rings. The posterior membranous
trachea is flexible and consists of fibro-elastic and
muscular tissue layers.

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