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Questions and Answers
What is the primary cause of thyroglossal cysts?
Which statement about facial clefts is true?
What is the most common location for thyroglossal cysts to be found?
What is a branchial cleft cyst typically a result of?
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Which of the following is NOT an effect associated with facial clefts?
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Which type of cleft disorder is characterized by a cleft palate but doesn't typically affect other structures?
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What might happen if an intact frenulum does not stretch with use?
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Which of the following statements regarding anterior cleft disorders is accurate?
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What type of genetic disorder is Treacher Collins Syndrome classified as?
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Which feature is commonly associated with Treacher Collins Syndrome?
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What is the main effect of the 22q11.2 deletion syndromes?
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Which symptom is NOT typically associated with 22q11.2 deletion syndromes?
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What is the primary mutation involved in Treacher Collins Syndrome?
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What developmental issue does ankyloglossia typically involve?
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Which of the following best explains the concept of a syndrome?
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Which symptom is characteristic of the developmental deficits seen in 22q11.2 deletion syndromes?
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What is the most common location for cysts or fistulas associated with underdevelopment of the mandible?
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Which syndrome is characterized by underdevelopment of the mandible and posterior tongue placement?
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What is a common cause of supernumerary teeth?
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Which of the following is NOT commonly associated with anodontia?
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Hemifacial microsomia primarily affects which anatomical structures?
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Which of the following can result from hyperdontia?
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Anodontia can be partially caused by which of the following?
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Which chromosome is NOT mentioned as related to mutations causing Pierre Robin sequence?
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Study Notes
Developmental Disorders of the Head & Neck
- Disease: Etiology and pathogenesis are understood.
- Syndrome: Etiology is understood, but pathogenesis is unknown.
- Sequence: Etiology is unknown, but pathogenesis is understood.
Treacher Collins Syndrome (TCS)
- Rare genetic disorder affecting development of the 1st and 2nd pharyngeal arches.
- Autosomal dominant disorder with a mutation in the TCOF1 gene on chromosome 5.
- Leads to hypoplasia (underdevelopment) of the maxilla, mandible, zygomatic arches, and palate.
- Usually bilateral, but cosmetic changes can be asymmetrical.
Common Presentations of Treacher Collins Syndrome
- Downward slanting of the palpebral fissures.
- Increased distance between the eyes.
- Palatal clefts.
- Defective development of the ear ossicles causing conductive hearing loss.
- Impaired vision.
- Retrusion of mandible and/or maxilla.
22q11.2 Deletion Syndromes (e.g. DiGeorge Syndrome)
- De novo mutation where a portion of the long arm of chromosome 22 is deleted.
- Disrupts neural crest cell function, impacting development of multiple pharyngeal arches.
- Highly variable presentation, but may include:
- Heart and aortic arch defects.
- Underdeveloped or absent thymus resulting in immunodeficiency.
- Mild cosmetic facial deformities.
- Learning difficulties.
- Increased risk of mental illness.
Ankyloglossia (Tongue-tie)
- Frenulum remains fully intact, attaching to the tip of the tongue, restricting lingual movement.
- Frenulum may stretch with use, restoring normal function.
- Therapy or surgical removal of part of the frenulum may be necessary.
Thyroglossal Cyst
- Forms anywhere along the path of the thyroid gland's descent due to a thyroglossal duct remnant.
- Most commonly found at or just below the body of the hyoid.
- Always located in the midline.
- Can connect to the external environment, forming a thyroglossal fistula.
Facial Clefts
- Various defects due to failed midline palatal structure development.
- Result in cosmetic abnormalities, speech and feeding difficulties, ear infections, hearing loss, and dental malocclusion.
- Causes include genetic factors, teratogenic compounds, and nutritional deficits.
- Incisive foramen differentiates anterior and posterior cleft disorders.
Anterior Cleft Disorders
- Lateral cleft lip (unilateral or bilateral).
- Cleft upper jaw.
- Cleft between primary and secondary palates.
Posterior Cleft Disorders
- Cleft secondary palate (unilateral or bilateral).
- Cleft uvula (usually the least complicated but can affect speech).
Branchial Cleft Cyst
- Occurs when the 2nd pharyngeal arch fails to develop caudally, leaving pharyngeal clefts 2, 3, and/or 4 intact.
- These clefts can form cysts, sinuses, or fistulas.
- Most commonly found directly beneath the angle of the mandible, anterior to the sternocleidomastoid.
- Usually become visible in adolescence.
- Fistulas commonly connect to the external surface, rarely to the pharynx.
Pierre Robin Sequence
- Can occur with other syndromes or independently due to mutations on chromosomes 2, 3, 11, or 17.
- Cause is unknown.
- Begins with underdevelopment of the mandible, followed by posterior placement of the tongue (glossoptosis), and potentially cleft palate and airway disruption.
Hemifacial Microsomia
- Second most common craniofacial developmental disorder after facial clefts.
- Results from underdevelopment or malformation of the 1st and 2nd pharyngeal arches, affecting maxilla, temporal, and zygomatic bones, as well as external ear development.
- Usually asymmetrical.
- Cause is unknown.
Supernumerary Teeth (Hyperdontia)
- Presence of excessive teeth.
- More common in permanent teeth and the maxilla than the mandible.
- Most common around the maxillary incisors, followed by the teeth distal to the maxillary 3rd molar or the premolar region of either jaw.
- Causes are uncertain but may involve genetic components, persistent dental placodes, or hyperactivity of dental lamina.
- Can delay eruption of adjacent teeth, cause malocclusion, dental crowding, or tooth displacement.
Anodontia
- Partial (one to several teeth) or complete absence of teeth.
- Most commonly affects the permanent 3rd molar, maxillary lateral incisor, and mandibular 2nd premolar.
- Often linked to ectodermal dysplasias.
- Can result from congenital factors, endocrine dysfunction, or excessive radiation exposure.
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Description
Explore the various developmental disorders affecting the head and neck, with a focus on specific syndromes like Treacher Collins Syndrome and 22q11.2 deletion syndromes. Understand their etiology, pathogenesis, and common clinical presentations. This quiz will test your knowledge on these rare genetic disorders.
