Craniosynostosis Flashcards
Incidence of craniosynostosis
1:2500 live births
Normal cranial growth
Growth responds to increasing brain and CSF, brain triples by 1 year, quadruples by 2 years, 85% of adult growth by 3, near adult size ages 6-10
Two mechanisms of normal skull growth
Sutural - perpendicular to sutures
Appositional - bone resorption on the inner surface and deposition on the outer surface
Normal Suture Fusion
Metopic = 6-9 mo Sagittal = 22 yrs Coronal = 24 years Lambdoidal = 26 years Squamous = 35 years
Normal fontanelle closure
Posterior = 6-9 mo Anterior = 9-12 mo
Virchow’s Law
premature suture fusion results in cranial growth PARALLEL to sutures
Cranial base theory of suture closure
synostoses result from abnormal tension exerted by cranial base through the dura; theory does not account for isolated synostoses
Intrinsic suture biology theory of suture closure
Synostoses result from the osteoinductive properties of dura mater, which contains osteoblast-like cells
Extrinsic factor theory of suture closure
Synostoses result from extrinsic forces or systemic disease; in utero compression or ischemic event, hydrocephalus decompression, abnormal brain growth (microcephaly), systemic pathology (Rickets or hypothyroidism)
Genetics of crainiosynostosis
- 21% genetic (15% chromosomal abnormalities, 32% FGFR2, 25% FGFR3, 19% TWIST1, 7% EFNB1)
- 67% nonsyndromic
- 11.5% other syndromes
- Causative mutations found in 11% multisuture, 37.5% bilateral coronal, 17.5% unilateral coronal
Indications for treatment
- prevent or treat elevated ICP
- address skull deformity to aid in normal social interactions
Early suture closure may…
-decrease intracranial volume and restrict brain growth (cephalocranial disproportion) causing elevated ICPs (>15 mmHg)
Causes of elevated ICP in craniosynostosis
Cephalocranial disproportion
Intracranial venous congestion
Hydrocephalus
Upper airway obstruction
Intracranial volume in Apert Syndrome
Normal range at birth, but increases to greater than 3 standard deviations above normal at 3.5 mo of age, 83% incidence of elevated ICP
Difference in elevated ICP with # of involved sutures
Isolated synostosis = 13% incidence of increased ICP
Multiple synostoses = 42% incidence of increased ICP
Signs of elevated ICP
- morning headache, irritability, recurrent emesis, difficulty sleeping
- mental impairment/neuropsychiatric disorders
- change in developmental curve
- optic atrophy and vision loss
- documented elevated ICP
Chiari malformation
Downward displacement of cerebellar tonsils through foramen magnum; believed to be secondary to hindbrain growth in a small posterior fossa (in craniosynostosis)
70% of patients with Crouzon’s syndrome, 82% in Pfeiffer syndrome, 100% kleeblattschaedel; may cause noncommunicating hydrocephalus
Increased mental impairment associated with
Increased number of involved sutures; neurodevelopmental injury is gradual, irreversible, and difficult to detect
Physical examination signs of craniosynostosis
- no movement at sutures
- palpable ridges from thickening of closed sutures
- bulging fontanelles (Volcano sign)
ICP monitoring
- Direct intraparenchymal monitoring (benchmark but invasive)
- Radiography (AP, lateral, Townes, C spine); Harlequin sign seen on AP view, “thumbprinting” or “copper beating” from pressure gyri on inner table
- Fundus exam (papilledema)
- Transorbital ultrasound (measures optic sheath diameter)
- Visual evoke potentials (measures latency time -prolonged)
Sagittal Synostosis
- incidence 40-50%
- Scaphocephaly/dolichocephaly; “boat shaped”, increased AP diameter and decreased biparietal width, frontal bossing and occipital coning
- M:F 4:1
Metopic Synostosis
- 23-28%
- Trigonocephaly, “keel shaped, triangular”
- varied severity; bitemporal narrowing, hypotelorism, bilateral supraorbital retrusion, medial slanted lateral orbital rims, epicanthal folds
- intracranial findings: Omega sign, hard diagnosis by angle of pterygium to nasion
- anterior cranial base increased in AP diameter
- ICP elevation 4-10%
Unilateral Coronal Synostosis
- 13-20%
- leads to anterior plagiocephaly
Bicoronal synostosis
5-10%
leads to brachycephaly/turribrachycephaly
Lamdoid synostosis
<3%
Leads to posterior plagiocephaly with trapezoid configuration and mastoid bulge
Deformational plagiocephaly
- parallelogram configuration with ipsilateral occipital flattening and frontal bossing
- anterior displacement of ear
- 1:300 live births
- results from supine positioning, rotational forces (torticollis)
Crouzon Syndrome
- normal extremities
- AD, FGFR2
- 1: 25,000 (most common syndromic craniosynostosis)
- conductive hearing loss, exorbitism, anterior open bite
Apert Syndrome
- complex severe syndactyly
- 1: 100,000- 160,000
- 70% have decreased IQ
- 83% have elevated ICP and need VP shunt
- severe midface hypoplasia, high arch or cleft palate, class III malocclusion (may need trach)
Pfeiffer syndrome
- AD, FGFR2 in 95%, FGFR1 in 5%
- 1: 100,000
- broad thumbs/halluces, mild cutaneous syndactyly
- usually no mental impairment
- midface hypoplasia, strabismus, class III malocclusion and OSA (may need trach)
Saethre-Chotzen Syndrome
- AD, TWIST1 mutation
- 1:25,000-50,000
- low hairline and eyelid ptosis, facial asymmetry
- prominent crus helices
- short stature, partial syndactyly
Muenke Syndrome
- Common cause of unicoronal and bicoronal craniosynostosis with high reoperation rate
- Family history is common
- 1:10,000
- AD; pro250Arg mutation on FGFR3 on chromosome 4p
- thumb-like middle phalanges
- sensorineural hearing loss
Turricephaly
excessive skull height and vertical forehead from untreated brachycephaly
Oxycephaly
pointed head, forehead retroverted and tilted back; from pansynostosis
Kleeblattschaedel
Cloverleaf deformity; secondary to synostosis of all sutures except squamosal
Post-operative monitoring for open cranial vault procedures
Hematocrit (txf if <21) and sodium every 6 hrs x 24 hours
Q1h neuro checks
Observation in ICU for 24-48 hours
Complications of open cranial vault procedures
Bleeding from raw bone (most require transfusion)
Infection (postop fever is common)
Venous air embolism
CSF leak (check intraop with valsalva)
