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craniosynostosis
- (or craniostenosis):
- Premature fusion of cranial sutures resulting in deformity of cranial vault
- 1. Growth restriction perpendicular to fused suture
- 2. Compensatory skull overgrowth in unrestricted areas
- May also have Increased intracranial pressure (ICP), mental retardation, visual defects and cosmetic deformity are frequent causes of morbidity.
- EPIDERMIOLOGY
- 1/2000 (3.1~4.8 in 10,000 live births)
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Simple CS
involving only one suture
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Compound CS
two or more sutures are involved
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Primary CS
- (Idiopathic or Familial):
- usually manifests as a component of various craniofacial syndromes without clearly known causes or may result from genetic mutations
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Secondary CS:
results from a known underlying systemic or metabolic disorders such as hyperthyroidism, hypercalcemia, vitamin D deficiency, sickle cell disease and the conditions like microcephaly and encephalocele with diminished growth stretch at sutures
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Syndromic CS:
- about 10~20% of CS with extra-cranial anomalies (facial, limb, ear and/or heart malformations) diagnosed early in life
- more coronal CS
- seen in female and sagittal CS in male
- Non-syndromic CS
- (Isolated): constitutes 80~90% of CS cases without extra- cranial deformities and affects sagittal, coronal, metopic and lambdoid sutures (in descending order of frequency)
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Three types of articulations:
- 1. Sutures (Synarthrosis)– cranial vault
- 2. Synchondroses-- cranial base
- 3. Synovial joints-- TMJ with articular disk
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Cranial Cartilages
- Primary cartilage: Meckel’s
- Secondary cartilages: condylar,coronoid,symphyseal
- zygmotic
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Neurocranium
- (surrounds the brain)
- Cranial Embryology
- Skull vault->Dermatocranium—Membranous BF (CNC&PM)
- Skull base->Chondrocranium-- Endochondral BF
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Viscerocranium
- (forms the face)
- Cranial neural crest (CNC)
- Mandible
- Maxilla
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Sutures
- Major
- a. Metopic (frontal in utero)
- b. coronal
- c. sagittal
- d. lambdoi:
- 1. squamosal
- 2. synchondroses of the mid and posterior skull base
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Sagittal suture fusion:
- Results in restriction of biparietal growth (rare with neurologic deficits and elevated ICP)
- Dolichocephaly (Greek: dolikhos=long)
- Scaphocephaly (Greek: scaphe=boat): a subset of Dolichocephaly with obvious ridging fused sagittal sutures, the most common isolated CS in male
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Coronal suture fusion
- results in restriction of anterior-posterior calvarial growth
- (cause secondary facial abnormalities: midface hypoplasia and Harlequin Eye)
- Brachycephaly (Greek: brakhu=short): from bicoronal fusion
- Plagiocephaly (Greek: plagios=oblique): from unicoronal fusion
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Metopic suture fusion:
- usually occurs before 6 months (3-9 M) of age in utero fusion and 1/3 cases are syndromic with other midline anomalies (brain and palate)
- Trigonocephaly (Greek: trigonos= three angles): milder form “metopic ridge”
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Lambdoid suture fusion:
- Turrecephaly (Greek: turri=tower): bilateral lambdoid suture fusion (flattened occiput)
- Posterior plagiocephaly: unilateral lambdoid suture fusion
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Sagittal and Coronal sutures fusion:
- severe combinational synostoses may result in microcephaly (raised ICP and neurologic impairment)
- Oxycephaly (Greek: oxys=sharp)
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Sagittal, Coronal and Lambdoid sutures fusion
- generally have severe neurological impairment
- Kleeblattschadel (German: kleeblatt=cloverleaf; schadel=skull)
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Deformational or positional plagiocephaly
- Differential diagnosis:
- not a true synostosis due to no sutures are fused.
- It caused by compressional forces in utero and modulated by postnatal preferential head positioning in infants sleeping on their back.
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CS SYNDROMES (ACP constitutes 2/3)
- Craniofacial features (CF): skull deformity with raised ICP, hydrocephalus,optic atrophy and respiratory,speech and hearing problems, need surgucal intervention
- Noncraniofacial features (NCF): digital anomalies (H&F), cervical fusion, short humerus and femur and syndactyly.
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Apert’s syndrome:
- (1906 by Apert)
- CF: bilateral coronal synostosis at birth, small and malformed skull base, large
- fontanels and a gaping frontal midline defect; brain malformation and mental retardation
- NCF: cervical vertebral fusion(C5-6) (joint ankylosis), digital anomalies (H&F), acrocephalosyndactyly
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Crouzon’s syndrome:
- (1912 by Crouzon)
- CF: coronal suture and minor skull base suture closure (brachycephaly), midfacial
- hypopalsia, parrot-beak nose, hypertelorism and hydrocephalus. NCF: short humerus and femur, partial syndactyly (type II Crouzon), carpal fusion
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Pfeiffer’s syndrome:
- (1964 by Pfeiffer) (three types)
- Type I: most common, hearing loss with auditory stenosis and hypertelorism
- Type II: cloverleaf skull and severe proptosis
- Type III: features of Type I and II with mental retardation and hydrocephalus
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Gli3
- Greig syndrome
- first CS gene
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MSX-1&2
- Boston type CS
- second CS gene
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FGFR2
- Crouzon syndrome started journey of exploration of genes involved in syndromic CS (FGFR1,3, Twist— all in
- autosomal dominant inheritance pattern)
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Runx2
master in control of osteochondrogenesis
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Nell 1
a CS associated gene identified by Differential Display PCR
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strip craniectomy
- Surgical manegement:
- (usually most effective in the 1st year of life using “strip craniectomy” technique)
- a typical way for primary CS with obvious restriction of brain
- growth and raised ICP. ( or Endoscopic-assisted minimally invasive suturectomy plus cranial helmet). Multiple surgical corrections may be needed for syndromic patients than nonsyndromic ones due to facial suture anomaly.)
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