Head Development - Abnormalities

Introduction

File:Stage18-19 Cleft Primary Palate.jpg

Stage 18-19 Cleft Primary Palate

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.

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.

• Neural - 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),
• Skeletal - 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.

Fetal Alcohol Syndrome

Fetal Alcohol Syndrome

(FAS) Due to alcohol in early development (week 3+) leading to both facial and neurological abnormalities. This disorder was clinically described (USA) in humans about 30 years ago (1973), while historically alcohol's teratogenic effects were identified in the early 20th century in a mix with the prohibition cause of the period. Similar effects without the obvious alterations to appearance, but with nervous system effects, are sometimes identified as Fetal Alcohol Effects (FAE). Alcohol is able to cross the placenta from maternal circulation through the placenta into fetal circulation.

FAS Features:

• lowered ears, small face, mild+ retardation
• Microcephaly - leads to small head circumference
• Short Palpebral fissure - opening of eye
• Epicanthal folds - fold of skin at inside of corner of eye
• Flat midface
• Low nasal bridge
• Indistinct Philtrum - vertical grooves between nose and mouth
• Thin upper lip
• Micrognathia - small jaw

Exposure of embryos in vitro to ethanol simulates premature differentiation of prechondrogenic mesenchyme of the facial primordia (1999)

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Cite this page: Hill, M.A. (2024, May 7) Embryology Head Development - Abnormalities. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Head_Development_-_Abnormalities

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G