Head and Neck Development Abnormalities
© Dr Mark Hill (2011)
Many head and neck structures are derived from pharyngeal arches 1 and 2 which undergo extensive remodelling during head development. Within the head are embedded many other complex developing structures, it is therefore not uncommon for this body region to have many associated abnormalities. Note that for neural and other head organs, look at the relevant section of notes which have their own abnormalities page.
Cleft lip and palate are covered in detail in Face Abnormalities notes. Because the head contains many different structures also review notes on Face Abnormalities, Neural - cephalic,
Musculoskeletal - skull, Special Senses - eye, ear, nose), Respiratation - pharynx,
Integumentary (Teeth), Endocrine (thyroid, pituitary).
Page Links: Introduction | Head and Neck Abnormalities | Pharyngeal Abnormalities | Cephalic Disorders |
Cleft Lip and Palate | First Arch Syndrome | Australian Statistics 1981-1992 | Self
Assessment Questions | OMIM Database | PubMed Database | Virtual Childrens Hospital cases | Terms
Related Pages: Face Abnormalities | Skull - Synostosis Abnormalities | Thyroid Abnormalities
Teeth Abnormalities | Eye Abnormalities |
Head and Neck Abnormalities
- Congenital Auricular Sinuses and Cysts
- Pharyngeal Abnormalities
- Piriform Sinus Fistula
- First Arch Syndrome
- Treacher Collins syndrome
- Pierre Robin syndrome
- DiGeorge syndrome
- Accessory thymic tissue
- Ectopic parathyroid glands
- Thyroid Gland Anomalies
The four different types of pharyngeal abnormalities are relatively rare.
- Sinuses - a pharyngeal groove defect, when a portion of the groove persists and opens to the skin surface, located laterally on the neck.
- Fistula - a pharyngeal membrane defect, a tract extends from pharynx (tonsillar fossa) beween the carotid arteries (internal and external)
to open on side of neck.
- Cysts - a cervical sinus defect, remants of the cervical sinus remains as a fluid-filled cyst lined by an epithelium.
- Vestiges - cartilaginous or bony developmental remnants lies under the skin on side of neck.
Cephalic (Greek, kephale = head) are a group of abnormalities that relate to a wide range of skeletal (skull) and neural (brain) associated defects including:
Anencephaly, Hydrocephalus, Encephalocele, Colpocephaly (occipital horn enlargement),
Lissencephaly (smooth brain), Porencephaly (cyst or cavity in cerebral hemisphere), Acephaly (absence of head),
Exencephaly (brain outside skull), Macrocephaly (large head), Micrencephaly (small brain), Otocephaly (absence of lower jaw), Brachycephaly (premature fusion of coronal suture), Oxycephaly (premature fusion of coronal suture + other), Plagiocephaly (premature unilateral fusion of coronal or lambdoid sutures), Scaphocephaly (premature fusion of sagittal suture), Trigonocephaly.
Links: Neural Abnormalities - Cephalic | NINDS - Cephalic Disorders
The way in which the upper jaw forms from fusion of the smaller upper prominence of the first pharyngeal arch leads to a common congenital defect in this region called "clefting", which may involve either the upper lip, the palate or both structures.
(More? Primary Palate | Face Abnormalities).
- International Classification of Diseases code 749.1 for isolated cleft lip and 749.2 for cleft lip with cleft palate.
- Australian national rate (1982-1992) 8.1 - 9.9 /10,000 births.
- Of 2,465 infants 6.2% were stillborn and 7.8% liveborn died during neonatal period.
- rate similar in singleton and twin births.
- International Classification of Diseases code 749.0
- Australian national rate (1982-1992) 4.8 - 6 /10,000 births.
- Of 1,530 infants 5.5% were stillborn and 11.5% liveborn died during neonatal period.
- slightly more common in twin births than singleton.
(Data: Congenital Malformations Australia 1981-1992 P. Lancaster and E. Pedisich ISSN 1321-8352)
OMIM: OMIM Database Entry- Cleft Lip List |
Orofacial Cleft with or without cleft palate
Search Pubmed Now: cleft+lip |
First Arch Syndrome
There are 2 major types of first arch sydndrome, Treacher Collins and Pierre Robin, both result in extensive facial abnormalites. (More? Face Abnormalities).
Search Pubmed Now: facial+cleft
Medline Plus - Pierre Robin Syndrome |
Medline Plus - Treacher Collins Syndrome
Data shown as a % of all Major Abnormalities
based upon published statistics using the same
groupings as CMA 81-92.
You can also see: all the
statistical data as graphs
List of all Minor Abnormalities
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- anlage- (Ger. )
primordium, structure or cells which will form a
- brain- general term for the central
nervous system formed from 3 primary
membrane- (=oral membrane) at cranial
(mouth) end of gastrointestinal tract (GIT)
where surface ectoderm and GIT endoderm meet.
(see also cloacal
membrane- at caudal (anal) end of
gastrointestinal tract (GIT) where surface
ectoderm and GIT endoderm meet forms the
openings for GIT, urinary, reproductive tracts.
(see also buccopharyngeal
- connective tissue-
- dermomyotome- dorsolateral half of each
somite that forms the dermis and muscle.
- dorsal root ganglia-
(=spinal ganglia) sensory ganglia derived from
the neural crest lying laterally paired and
dorsally to the spinal cord (in the embryo found
ventral to the spinal cord). Connects centrally
with the dorsal horn of the spinal cord.
- dura mater-
- ectoderm- the
layer (of the 3 germ cell layers) which form the
nervous system from the neural tube and neural
crest and also generates the epithelia covering
- endoderm- the
layer (of the 3 germ cell layers) which form the
epithelial lining of the gastrointestinal tract
(GIT) and accessory organs of GIT in the
- epiblast- the
layer (of the bilaminar embryo) that generates
endoderm and mesoderm by migration of cells
through the primitive streak. The remaing cells
factor- usually a protein or peptide that
will bind a cell membrane receptor and then
activates an intracellular signaling pathway.
The function of the pathway will be to alter the
cell directly or indirectly by changing gene
expression. (eg shh)
(=homeobox) family of
transcription factors that bind DNA and activate
gene expression. Expression of different Hox
genes along neural tube defines rostral-caudal
axis and segmental levels.
- mesoderm- the
middle layer of the 3 germ cell layers of the
embryo. Mesoderm outside the embryo and covering
the amnion, yolk and chorion sacs is
- muscle- 3 main
types of muscle (smooth, cardiac and skeletal)
all derived from mesoderm but different
crest- cell region at edge of neural plate,
then atop the neural folds, that remains outside
and initially dorsal to the neural tube when it
forms. These paired dorsal lateral streaks of
cells migrate throughout the embryo and can
differentiate into many different cell
types(=pluripotential). Those that remain on the
dorsal neural tube form the sensory spinal
ganglia (DRG). Neural crest cells migrate into
tube- neural plate region of ectoderm
pinched off to form hollow ectodermal tube above
notochord in mesoderm.
opening at either end of neural tube:
cranial=rostral=anterior, caudal=posterior. The
cranial neuropore closes (day 25) approx. 2 days
(human) before caudal.
- notochord- rod
of cells lying in mesoderm layer ventral to the
neural tube, induces neural tube and secretes
sonic hedgehog which "ventralizes" the neural
tube and may influence somite development.
- otocyst- (=otic
vesicle) sensory placode
which sinks into mesoderm to form spherical
vesicle (stage 13/14 embryo) that will form
components of the inner ear.
- pharyngeal arches- (=branchial
arches, Gk. gill) form structures of the head.
Six arches form but only 4 form any structures.
Each arch has a pouch, membrane and cleft.
uppermost end of GIT, beginning at the
buccopharyngeal membrane and at the level of the
cord- caudal end of neural tube that does
not contribute to brain. Note: the process of
secondary neuralation contributes the caudal end
of the spinal cord.
- sonic hedgehog-
(=shh) secreted growth factor that binds patched
(ptc) receptor on cell membrane. SHH function is
different for different tissues in the embryo.
In the nervous system, it is secreted by the
notochord, ventralizes the neural tube, inducing
the floor plate and motor neurons.
factor- a factor (protein or protein with
steroid) that binds to DNA to alter gene
expression, usually to activate. (eg steroid
hormone+receptor, Retinoic acid+Receptor, Hox,
Pax, Lim, Nkx-2.2)
Glossary of Terms
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