Craniosynostosis

Question 1

Incidence of craniosynostosis

Answer 1

1:2500 live births

Question 2

Normal cranial growth

Answer 2

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

Question 3

Two mechanisms of normal skull growth

Answer 3

Sutural - perpendicular to sutures

Appositional - bone resorption on the inner surface and deposition on the outer surface

Question 4

Normal Suture Fusion

Answer 4

Metopic = 6-9 mo
Sagittal = 22 yrs
Coronal = 24 years
Lambdoidal = 26 years
Squamous = 35 years

Question 5

Normal fontanelle closure

Answer 5

Posterior = 6-9 mo
Anterior = 9-12 mo

Question 6

Virchow’s Law

Answer 6

premature suture fusion results in cranial growth PARALLEL to sutures

Question 7

Cranial base theory of suture closure

Answer 7

synostoses result from abnormal tension exerted by cranial base through the dura; theory does not account for isolated synostoses

Question 8

Intrinsic suture biology theory of suture closure

Answer 8

Synostoses result from the osteoinductive properties of dura mater, which contains osteoblast-like cells

Question 9

Extrinsic factor theory of suture closure

Answer 9

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)

Question 10

Genetics of crainiosynostosis

Answer 10

• 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

Question 11

Indications for treatment

Answer 11

• prevent or treat elevated ICP

- address skull deformity to aid in normal social interactions

Question 12

Early suture closure may…

Answer 12

-decrease intracranial volume and restrict brain growth (cephalocranial disproportion) causing elevated ICPs (>15 mmHg)

Question 13

Causes of elevated ICP in craniosynostosis

Answer 13

Cephalocranial disproportion
Intracranial venous congestion
Hydrocephalus
Upper airway obstruction

Question 14

Intracranial volume in Apert Syndrome

Answer 14

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

Question 15

Difference in elevated ICP with # of involved sutures

Answer 15

Isolated synostosis = 13% incidence of increased ICP

Multiple synostoses = 42% incidence of increased ICP

Question 16

Signs of elevated ICP

Answer 16

• morning headache, irritability, recurrent emesis, difficulty sleeping
• mental impairment/neuropsychiatric disorders
• change in developmental curve
• optic atrophy and vision loss
• documented elevated ICP

Question 17

Chiari malformation

Answer 17

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

Question 18

Increased mental impairment associated with

Answer 18

Increased number of involved sutures; neurodevelopmental injury is gradual, irreversible, and difficult to detect

Question 19

Physical examination signs of craniosynostosis

Answer 19

• no movement at sutures
• palpable ridges from thickening of closed sutures
• bulging fontanelles (Volcano sign)

Question 20

ICP monitoring

Answer 20

• 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)

Question 21

Sagittal Synostosis

Answer 21

• incidence 40-50%
• Scaphocephaly/dolichocephaly; “boat shaped”, increased AP diameter and decreased biparietal width, frontal bossing and occipital coning
• M:F 4:1

Question 22

Metopic Synostosis

Answer 22

• 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%

Question 23

Unilateral Coronal Synostosis

Answer 23

• 13-20%

- leads to anterior plagiocephaly

Question 24

Bicoronal synostosis

Answer 24

5-10%

leads to brachycephaly/turribrachycephaly

Question 25

Lamdoid synostosis

Answer 25

<3% | Leads to posterior plagiocephaly with trapezoid configuration and mastoid bulge

Question 26

Deformational plagiocephaly

Answer 26

- parallelogram configuration with ipsilateral occipital flattening and frontal bossing - anterior displacement of ear - 1:300 live births - results from supine positioning, rotational forces (torticollis)

Question 27

Crouzon Syndrome

Answer 27

- normal extremities - AD, FGFR2 - 1: 25,000 (most common syndromic craniosynostosis) - conductive hearing loss, exorbitism, anterior open bite

Question 28

Apert Syndrome

Answer 28

- 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)

Question 29

Pfeiffer syndrome

Answer 29

- 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)

Question 30

Saethre-Chotzen Syndrome

Answer 30

- AD, TWIST1 mutation - 1:25,000-50,000 - low hairline and eyelid ptosis, facial asymmetry - prominent crus helices - short stature, partial syndactyly

Question 31

Muenke Syndrome

Answer 31

- 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

Question 32

Turricephaly

Answer 32

excessive skull height and vertical forehead from untreated brachycephaly

Question 33

Oxycephaly

Answer 33

pointed head, forehead retroverted and tilted back; from pansynostosis

Question 34

Kleeblattschaedel

Answer 34

Cloverleaf deformity; secondary to synostosis of all sutures except squamosal

Question 35

Post-operative monitoring for open cranial vault procedures

Answer 35

Hematocrit (txf if <21) and sodium every 6 hrs x 24 hours Q1h neuro checks Observation in ICU for 24-48 hours

Question 36

Complications of open cranial vault procedures

Answer 36

Bleeding from raw bone (most require transfusion) Infection (postop fever is common) Venous air embolism CSF leak (check intraop with valsalva)