what is acrania?
complete or partial absence of neurocranium
what is acrania associated with?
meroencephaly (causes acrania)
what is craniosynostosis?
prenatal fusion of cranial sutures that results in defects in the neurocranium
what is scaphocephaly?
premature closure of sagittal suture (long, narrow, wedge-shaped cranium)
what is brachycephaly?
premature closure of coronal suture (tower like cranium)
what is plagiocephaly?
premature closure of coronal suture on one side only (twisted and asymmetrical cranium)
what is trigonocephaly?
premature closure of frontal suture
what is microcephaly?
small calvaria
what causes microcephaly?
abnormal brain development in which the brain fails to grow
congenital anomalies of craniovertebral junction cause?
- basilar invagination
- assimilation of the atlas
- atlantoaxial dislocation
- arnold-chiari malformation
- separated dens from axis
how do external branchial sinuses form?
failure of second pharyngeal groove and cervical sinus to obliterate
where does an external branchial sinus emerge?
anterior border of SCM (discharge of mucus)
where do internal branchial sinuses open to?
tonsillar sinus or near palatopharyngeal arch (failure of 2nd pharyngeal pouch to disappear)
normal remnant of 2nd pharyngeal pouch?
tonsillar sinus
what is a branchial fistula?
abnormal canal that opens internally into tonsillar sinus and externally in the neck
a branchial fistula passes through what structures?
- platysma
- between internal and external carotid arteries
what is a piriform sinus fistula?
persistance of remnants of “ultimopharyngeal” body along its path to thyroid gland
what is a branchial cyst?
remnants of cervical sinus or 2nd pharyngeal groove
where are branchial cysts most often located?
lie free in neck inferior to angle of mandible & anterior border of SCM; parathyroid glands
what is a branchial vestige?
cartilagenous or bony remnants of pharyngeal arch cartilages under the skin on the side of the neck
where are branchial vestiges located?
anterior to inferior third of SCM
how does first arch syndrome occur?
insufficient migration of neural crest cells into first arch
infants with DiGeorge syndrome are born without what structures?
thymus and parathyroid glands
what is DiGeorge syndrome characterized by?
- congenital hypoparathyroidism
- lots of infections
- cardiac anomalies
why does DiGeorge syndrome occur?
third and forth pharyngeal pouches fail to differentiate into thymus and parathyroid glands
how does an accessory thymus occur?
tissue breaks free from developing thymus as it shifts caudally in the neck
where are ectopic sites for parathyroid glands?
inferiors can be near bifurcation of common carotid artery or in the thorax
accessory parathyroid glands occurs because?
extra division of primordia of original glands
absence of parathyroid glands occurs from?
failure of primordia to differentiate or from atrophy of a gland
what is the most common metabolic disorder in neonates?
congenital hypothyroidism
what can congenital hypothyroidism result in?
neurodevelopmental disorders and infertility if untreated
how do thyroglossal duct cysts occur?
remnant of thryoglossal duct persists in tongue or inferior to hyoid bone
how does a thryoglossal duct sinus occur?
infection of cyst leads to perforation of skin in median plane of neck
where is an ectopic thyroid gland located?
along thyroglossal duct (most common is lingual area)
why is it important to distinguish an ectopic thyroid gland from a thryoglossal duct cyst or accessory thyroid tissue?
to prevent accidental surgical removal of the thyroid
what is thyroid hemiagenesis?
unilateral failure of formation of thyroid lobe (usually left lobe)
what congenital tongue anomalies are associated with down’s syndrome?
fissuring of tongue and hypertrophy of lingual papillae
cysts in the tongue come from where?
thyroglossal duct
lingual cysts cause what?
pharyngeal discomfort and dysphagia
where do lingual fistulas open to?
from thyroglossal duct to foramen cecum into oral cavity
what is ankyloglossia?
short lingual frenulum that interferes with protrusion of tongue
is surgery required to fix ankyloglossia?
no. normal stretching usually does the trick
how does macroglossia occur?
generalized hypertrophy of developing tongue from lymphangioma (lymph tumor)
what syndrome is macroglossia usually found in?
downs syndrome
what is microglossia associated with?
micrognathia (underdeveloped mandible/recession of chin) and limb defects (Hanhart syndrome)
what is glossoschisis?
bifid or cleft tongue (incomplete fusion of tongue)
how does atresia of nasolacrimal duct occur?
failure of nasolacrimal duct to canalize
when are maxillary sinuses fully developed?
when all permanent teeth have erupted (early adulthood)
are frontal and sphenoid sinuses present at birth?
no
what forms the frontal sinus?
anterior ethmoidal cells grow into frontal bone —> frontal sinus
what forms the sphenoidal sinus?
posterior ethmoidal cells grow into sphenoid bone
the growth of the paranasal sinuses are important for?
altering size and shape of face and adding resonance to voice
how do anterior cleft anomalies occur?
deficiency of mesenchyme in maxillary prominences and median palantine process
how do posterior cleft anomalies occur?
defective development of secondary plate and growth problems of lateral palantine processes (no fusion)
what is a unilateral cleft lip?
failure of maxillary prominence on one side to unite with medial nasal prominence
what causes a persistant labial groove?
failure of mesenchymal masses to merge and proliferate
what is a simonart band?
bridge of tissue connecting incomplete unilateral cleft lip
what is a bilateral cleft lip?
failure of mesenchymal masses in both maxillary prominences to unite with medial nasal prominences
a bilateral cleft lip affects which muscle?
orbicularis oris
what is a median cleft lip?
failure of medial nasal prominences to merge and form median palatal process
median cleft of lower lip is caused by?
failure of mandibular prominences to merge
what does a cleft uvula look like?
fishtail appearance
what is a distinguishing landmark between anterior and posterior cleft anomalies?
incisive fossa
clefts of primary/anterior palate?
failure of lateral palatal processes to fuse with primary palate
clefts of secondary/posterior palate?
failure of lateral palatine processes to fuse with each other and nasal septum
clefts of primary and secondary palate?
failure of lateral palatine processes to fuse in primary plate, with each other, and with the nasal septum
cleft lip/palate are especially associated with which syndrome?
trisomy 13
what is congenital microstomia?
small mouth
why does congenital microstomia occur?
excess merging of mesenchymal masses in maxillary and mandibular prominences of first pharyngeal arch
why would a single nostril form?
if only one nasal placode forms
what’s a bifid nose?
medial nasal prominences don’t merge which causes nasal bridge to be bifid
oblique facial clefts cause what?
nasolacrimal ducts to be open grooves
bilateral facial clefts result in?
macrostomia