IBSSD Development Disorders Student Notes PDF

L27: Development Disorders of the Head & Neck IBSSD 1525/1513 Dr. Samuel Gutherz  Outline Define common terms in clinical practice Examine a variety of disorders related to disrupted head & neck development Connect the disorders to the underly...

L27: Development Disorders of the Head & Neck IBSSD 1525/1513 Dr. Samuel Gutherz  Outline Define common terms in clinical practice Examine a variety of disorders related to disrupted head & neck development Connect the disorders to the underlying developmental processes Pathology Terms Etiology – cause of a disease Pathogenesis – the developmental process of a disease The response to the initial stimulus of a disease Pathology Terms A Sequence – a single anomaly has a B specific order of symptom development Robin sequence C Pathology Terms A Syndrome – collection of symptoms that X Y Z? frequently occur together due to a single cause Down syndrome Craniosyntosis Overview Premature closure of cranial sutures 1/2,500 births Isolated or part of a syndrome Results in Abnormal head shape High intracranial pressure that can impact neural development Sutures & Fontanelles Sutures – where 2 bones meet Fontanelles – where 3+ bones meet Allow movement of skull Fontanelle Location Closure Date bones during birth Anterior Frontals & Parietals 13–24 months Remain open for brain Posterior Parietals & Occipital 1–2 months growth Mastoid Parietal, Temporal, & Occipital 6–18 months Sphenoid Sphenoid, Parietal, Temporal, Frontal 6 months Pathology Etiology Genetic mutations Identifiable in 20–30% of patients Likely environmental factors play a role Mechanism NCC – mesoderm derived cell boundary disintegration Abnormal cell specification Premature loss of mesenchymal stem cells Treatment Surgical intervention High risk Postoperative helmet therapy Maintenance Treacher Collins Syndrome Overview Autosomal dominant genetic disorder TCOF1, POLR1D, POLR1B, POLR1C Often a new mutation 1/50,000 births Hypoplasia (underdevelopment) of orofacial region High degree of variation in presentation NCC Defect Reduction in # of NCC Neural crest cells Viscerocranium Cartilage, bone, dentin, tenson, dermis, sensory neurons, glandular connective tissue Presentation Hypoplasia of facial bones Mandible, maxilla, zygomatic Cleft palate External & internal ear defects Conductive hearing loss Eye Coloboma, palpebral fissure angle, eyelid droop, vision issues Tooth defects Respiratory issues – tongue obstruction Treatment Hearing aids Corrective surgery Urgent respiratory surgical needs Varying ages for palate, facial, ear, and tooth based on maturation 22q11.2 Deletion Syndromes Overview Deletion of long arm (q-arm) of chromosome 22 1/4,000 births Occurs during meiotic rearrangements Affects TBX1 gene Expressed in all germ layers of PA Communicate with NCCs Highly variable presentation Mechanism TBX1 Significant impact on 3rd & 4th pharyngeal pouches Hypoplasia or lack of thymus & parathyroid glands Remodeling of pharyngeal arteries Affects mesenchyme – epithelial interactions Significant impacts on cortical brain development Presentation Heart defects Palatal abnormalities Facial anomalies Immunodeficiency Learning & behavioral disabilities Speech and hearing deficiencies Frequent ear infections Increased risk of psychiatric disorders Treatment Surgical repair Aggressive infection treatment Calcium supplements Therapy and educational support Ankyloglossia “Tongue-Tied” Frenulum extends to apex of tongue Absence of normal cell degeneration Restricts tongue movement Typically stretches Therapy Surgical removal Thyroglossal Cyst Terms Cyst – thin-walled, fluid-filled sac Terms Fistula – a connection between a hollow organ and the external environment or between 2 hollow organs Thyroid Dev Remnants Remnant of thyroglossal duct Can occur anywhere along thyroid migration path Common near hyoid Always midline Infection Low risk of cancer Sistrunk procedure Low rate of recurrence Branchial Cleft Fistulas/Cysts Overview O Failure to close pharyngeal clefts Most common pharyngeal cleft 2 Overview Failure to close pharyngeal clefts Most common pharyngeal cleft 2 Fistula opens anterior to sternocleidomastoid Cyst – just below the angle of mandible Often enlarges during childhood  Internal Branchial Fistula Rupture of membrane between pharyngeal cleft & pouch Cervical sinus connected to pharynx Typically drains into tonsillar fossa Pierre Robin Sequence Overview Impacts 1st PA structures Genetic or environmental onset Idiopathic origin Isolated Robin Sequence associated with chromosomal mutations 1/8,500 births Often occurs with other syndromes/anomalies Mechanism Micrognathia → tongue displacement → obstructed closure of palatine shelves Theories Abnormal mandibular growth Tongue neuromuscular delay Mandibular compression Mechanism Micrognathia → tongue displacement → obstructed closure of palatine shelves Theories Abnormal mandibular growth Tongue neuromuscular delay Mandibular compression Symptoms Micrognathia Glossoptosis: tongue obstructing posterior pharynx and airway Cleft palate Treatment Prone positioning NPA – Nasopharyngeal airway tube Surgical intervention Craniofacial (Hemifacial) Microsomia  Overview Asymmetric malformation of 1st & 2nd PA Typically unilateral, can be bilateral Hypoplasia of face, ear, eye, teeth, cranial nerves Environmental factors, maternal intrinsic factors, genetic mutations 1/3,500 – 4,500 births Pathogenesis Abnormal vasculature or hemorrhaging Insufficient blood supply to face Stapedial artery Teratogen exposure Genetic component Disrupted mesenchymal communication Presentation Lack of defined criteria/high variability in phenotype Eliminating alternative diagnoses Minimum Ipsilateral mandibular and ear dysmorphia One from above + 2 additional unrelated anomalies Family history Additional symptoms Ocular deformities Extracranial defects: cardiac, neurological, skeletal Treatment Surgical intervention Functional first Reconstructive surgery mixed results Determined by extent of hypoplasia High rates of recurrence Supernumerary Teeth Overview Disruption of initiation stage Typically singular Typically posterior to the maxillary incisors Issues Crowding/displacement Failure to erupt Malocclusion Mechanisms Localized hyperactivity of dental lamina Genetic & environmental factors Family history increases risk Often related to additional syndromes Treatment: extraction Anodontia Overview Disruption of initiation stage Rarely complete Issues Malocclusion Speech impediment Aesthetics Downstream effects of treatments Mechanism Rarely isolated, typically part of a syndrome Defect of dental lamina Local, systemic, or genetic Strong familial inheritance Ectodermal dysplasia X Treatment: nothing or prosthetics Facial Clefts Cleft Palate/Cleft Lip Common craniofacial defects Difficulties with speech Genetic & nongenetic factors Cleft palate - incisive foramen Border between anterior & posterior clefts Can be combo Anterior Cleft Palates Incomplete fusion between intermaxillary segment and maxillary prominences Types Lateral cleft lip Cleft upper jaw Between primary and secondary palates Posterior Cleft Palates Non-fusion of palatine shelves of maxillary prominences Too small Failure of tongue to drop Failure to elevate Disrupted fusion process Types Cleft (secondary) palate Cleft uvula Cleft Lip 1/1000 births, most common in males Unilateral or bilateral Bilateral – separates intermaxillary segment from oral cavity Defective orbicularis oris, which closes mouth