Other
developmental abnormalities in the face and jaws
Failure of fusion, or inclusions of epithelium
where various processes meet during development, can lead to cysts and fistulae
around the face, the jaws and the neck. Cysts may develop and then become
infected, leading to persistent sinuses. Examples are as follows.
• Pre-auricular cyst — fusion of the six tubercles around the external
auditory canal can lead to formation of one or more narrow, blind pits or,
perhaps, a cyst. Infection of the cyst may lead to a persistent discharging
sinus which would need to be excised.
• Periauricular dermoid cyst — these may develop from under the puma as a
fluctuant swelling, usually posteriorly. They occur in the position where the
two adjacent auricular tubicles should merge.
• Globulomaxillary cyst — cysts may develop in the alveolus in the position
where the globulomaxillary processes should fuse with the frontonasal process.
The cyst occurs lateral to a vital second upper incisor and canine. These have
to be differentiated from a radicular cyst developing on a nonvital lateral
incisor.
• Nasolabial cyst — these occur in a similar position to the
globulomaxillary cyst, but in the soft tissues of the upper lip. They are
extremely rare.
• Cysts of the incisive canal — the two palatal shelves fuse with the premaxilla
at the site of the exit from the palate of the nerve of the incisive canal. This
canal may form a cyst or be patent, leading to recurrent infections in this
area. Those that have a patent canal may enjoy the party -trick of producing a
high-pitched squeaking or whistling sound as they raise the pressure in the
mouth, discharging air into the nose.
• Oral dermoids — these are derived from embryonic epithelium and can occur anywhere
where the facial processes fail to fuse completely. They are rare, but the most
common site is the midline of the floor of the mouth. They should not be
confused with the ranula, which is a mucous extravasation cyst derived from the
lingual gland.
• Branchial cysts — these occur in the lateral aspect of the upper neck of young adults
as a slow-growing fluctuant swelling. It had been assumed that these occur as a
result of failure of fusion branchial arches. They are lined with lymphoid
tissue, and the current view is that they are derived from cystic transformation
of glandular epithelium included in lymphoid aggregates during embryogenesis.
The current nomenclature is lymphoepithelial cyst.
• Oral tori (Fig 37.19 and Fig
37.20) — it is uncertain as to whether these are true
developmental abnormalities. They occur at two major sites, the most common lies
on the medial side of the mandibular alveolus in the region of the premolar
teeth. Less frequently midline palatal tori occur, again in line with the
premolar teeth. These are dense,
• Cysts in the thyroglossal tract — the thyroid gland develops as an
evagination of the epithelium at the junction of the anterior two-thirds and the
posterior third of the tongue, the foramen caecum. A vestigial epithelial
remnant may remain and cysts may occur along the line of this duct. They may be
anywhere on a line from the surface of the tongue (Fig.
37.21), down to and
behind the hyoid bone or to the isthmus of the thyroid gland. Occasionally
thyroid tissue may develop and remain at the site of origin in the base of the
tongue.
Surgical
treatment
Cysts are, by definition, epithelial lined
cavities, and where swellings cause difficulty, embarrassment or recurrent