UNSW Embryology

Head and Neck Development Abnormalities

© Dr Mark Hill (2011)

Acknowledgements

Introduction

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
  • Sinuses
  • Fistula
  • Cysts
  • Vestiges
• Piriform Sinus Fistula
• First Arch Syndrome
• Treacher Collins syndrome
• Pierre Robin syndrome
• DiGeorge syndrome
• Accessory thymic tissue
• Ectopic parathyroid glands
• Thyroid Gland Anomalies

Pharyngeal Abnormalities

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 Disorders

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

Clefting

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).
Cleft Lip 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.
Cleft Palate 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 | cleft+palate

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

Links: Medline Plus - Pierre Robin Syndrome | Medline Plus - Treacher Collins Syndrome

Self Assessment Questions

Australian Statistics 1981-1992

About Data

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

PubMed Database

Online Medline Database PubMed- Medline

National Library of Medicine (US) search service to access the 9 million citations in MEDLINE and Pre-MEDLINE (with links to participating on-line journals), and other related databases.

Internet Search this database or use the form below with the keyword or related topics. You can also restrict to reviews or by date published.

Development Terms

• anlage- (Ger. ) primordium, structure or cells which will form a future structure.
• brain- general term for the central nervous system formed from 3 primary vesicles.
• buccopharyngeal membrane- (=oral membrane) at cranial (mouth) end of gastrointestinal tract (GIT) where surface ectoderm and GIT endoderm meet. (see also cloacal membrane)
• 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 membrane)
• 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 the embryo.
• 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 embryo.
• epiblast- the layer (of the bilaminar embryo) that generates endoderm and mesoderm by migration of cells through the primitive streak. The remaing cells form ectoderm.
• growth 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)
• hox- (=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 extraembryonic mesoderm.
• muscle- 3 main types of muscle (smooth, cardiac and skeletal) all derived from mesoderm but different regions.
• myotome-
• myoblast-
• neural 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 the somites.
• neural tube- neural plate region of ectoderm pinched off to form hollow ectodermal tube above notochord in mesoderm.
• neuropore- 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.
• pharynx- uppermost end of GIT, beginning at the buccopharyngeal membrane and at the level of the pharyngeal arches.
• segmentation-
• spinal 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.
• transcription 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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Quick Links

Head and Neck Pages:

| References | | OMIM | Questions | Medline | Pig Stage 13/14 | Human (Stage22) | Human (stage 22) | Selected Human (stage 22) | Text only page | WWW Links

Development Notes ----------------- Menstrual Cycle Week 1 Week 2 Week 3 Week 4 Placenta Serial Images Molecular Dev Abnormal Dev Postnatal Dev Notes Index

System Notes ----------------- All Systems Heart/Cardiovascular Respiratory Coelomic cavity Gastrointestinal Tract Head and Neck Neural Neural Crest Eye Ear Nose Endocrine Renal Genital Musculoskeletal Integumentary

Movies ----------------- Movies Quicktime Flash Audio Week 1 Week 2 Week 3 Stage 13 Stage 22 Neural Heart Gastrointestinal Renal Genital Other Embryos

Other Embryos ----------------- All Animals Chicken Fly Frog Mouse Rabbit Rat Worm Zebrafish Guinea Pig

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