Nonsyndromic CraniosynostosisIntroduction of Craniosynostosis

The premature fusion of calvarial sutures

Occurs in approximately 1 in 2500 live births

The cause of craniosynostosis is still unknown.

Most commonly affected is the sagittal suture

Followed by the unilateral coronal, bilateral coronal, metopic, and lambdoid sutures

Classified as being either nonsyndromic or syndromic based on phenotypic descriptions

Cranial DevelopmentEarly theories of cranial maldevelopment in craniosynostosis

FIGURE 182-1 Early theories of cranial maldevelopment in craniosynostosis. Sommerring defined fusion of vault sutures with local growth restriction.

Virchow described fusion of vault sutures with local growth restriction and more distant cranial vault compression. Moss described a functional matrix theory whereby skull base and brain growth dictate form.  

ClassificationNonsyndromic Craniosynostosis

Syndromic Craniosynostosis

- approximately 85% of cases of craniosynostosis - certain genes are more likely to cause craniosynostosis of different sutures - Two most common types of “nonsyndromic” -Sagittal -Coronal

- much less common - more generalized disorder of mesenchymal development that may represent abnormalitiesin homeobox genes such as Runx2 or CBFA-δ autosomal dominant inheritance patterns are the general rule for the more common syndromes such as -Crouzon's syndrome -Apert's syndrome -Pfeiffer's syndrome -Carpenter's syndrome ; autosomal recessive

Sagittal craniosynostosis also known as scaphocephaly or dolichocephaly

the most common form of craniosynostosis

occurs at a rate of 1 in 5000 children

a male-to-female ratio of 3.5 : 1

Missense mutations(S188L and S201Y) in the TWIST box Usually, one of three varieties of sagittal synostosis predominates: Anterior compensation

Posterior compensation

“Golf tee” deformities.

The anterior type can be treated with the standard π (pi) procedure, with optional supplementary frontal craniotomy for reshaping and dura plication.

The posterior variety needs a posterior π procedure, but this often requires elevation of the parietal region as well.

This is a variety of the golf tee deformity, which may also involve frontal bossing and requires surgery in a modified prone position.

Coronal craniosynostosis the second most common form

occurs at a rate of 1 in 10,000 children

a male-to-female ratio of 1 : 2

syndromic craniosynostosis, especially Muenke's syndrome, may be associated with unicoronal synostosis

Unilateral coronal synostosisRidging of the prematurely fused half of the coronal suture

Flattening of the ipsilateral frontal and parietal bones

Bulging of the contralateral frontal and parietal bones

Bulging of the ipsilateral squamous portion of the temporal bone

Confirmatory radiographic findings “Harlequin” orbit deformity, characterized by elevation of the greater and lesser wings of the sphenoid ipsilateral to the fused coronal suture

CT of the cranial base demonstrates a shortened anterior cranial fossa and a narrowed sphenopetrosal angle ipsilateral to the fused coronal suture.

Bilateral coronal synostosisFlattening of the caudal portion of the frontal bones and supraorbital ridges, and bulging of the cephalad portion of the frontal bones.

The occiput is flattened

The squamous portion of the temporal bones is unusually prominent.

The vertex of the skull is more anteriorly situated than normal.

Radiographically, bilateral harlequin abnormalities are present in the orbits, and basal CT demonstrates shortened anterior cranial fossae and bilaterally narrowed sphenoid petrosal angles.

Metopic Synostosis Metopic synostosis is characterized by Bilateral flattening of the frontal bones

Anterior displacement of the coronal sutures

Lateral flaring of the posterior parietal regions

Hypotelorism

Flattening of the supraorbital ridges

Viewed from above, the skull has a characteristic triangular shape known as trigonocephaly.

Lambdoid Synostosis Flattening of the parietal and occipital regions ipsilateral to the fused portion of the suture.

If synostosis has occurred unilaterally, an asymmetric occiput is seen, characterized by flattening of the occiput ipsilateral to the fused suture and contralateral bulging evident in the parietal occiput region

If bilateral synostosis has occurred, symmetrical flattening of the occiput is seen.

If the synostosis is severe, skull deformities in the frontal region, which may include elevation of the vertex of the skull, are evident.

Posterior Synostosis Posterior deformities include Unilateral and bilateral lambdoid synostosis

With or without posterior sagittal synostosis or squamosal synostosis.

These are rare conditions, and the principal surgical difficulty lies in not being able to maintain the corrected posterior projection.

Jane has been using a single microplate attached just above the foramen magnum to correct this projection

The dead space obtained is so large that it is unlikely that significant inward migration could occur.

DiagnosisNon-syndromic craniosynostosis involving a single vault suture

observation of a typically deformed skull shape, with radiographs

the Virchow hypothesis of skull deformity , four tenets : (1) cranial vault bones directly adjacent to the prematurely fused vault suture act as a single bone plate, with reduced growth potential along all margins of that plate

(2) asymmetric bone deposition occurs at vault sutures along the perimeter of the bone plate, with increased bone deposition occurring at the suture margin located farther away from the plate

(3) the nonperimeter sutures in line with the fused suture deposit bone symmetrically at their sutural edges

(4) perimeter and sutures (in line) abutting the prematurely fused suture compensate to a greater degree than distant sutures

FIGURE 182-2 Observed characteristics of unilateral coronal synostosis. A, Fused left coronal suture (dashed line) joining the frontal and parietal bone, which acts as a single growth center (bone plate) with reduced growth potential. B, The margin of the abutting sutures peripheral to the “fused bone plate” deposits a greater amount of bone at the suture (plus signs) than at the margin of the suture adjacent to the fused bone plate (dots). C,Compensation for restricted skull growth occurs symmetrically at sutures that are “in line” with the fused suture. D,The greatest degree of compensation occurs in sutures closest to the fused suture (curved arrows), and the least degree occurs in sutures distant from the affected suture (straight arrow). 

The application of these principles to particular types of synostosis is as follows

Figure 182-2E represents sagittal synostosis, in which the coronal and lambdoid sutures show asymmetric growth, and the metopic suture shows symmetrical growth.

Figure 182-2F depicts coronal synostosis, with asymmetric growth at the metopic, lambdoid, and sagittal sutures and symmetrical growth at the unfused coronal suture. Figure 182-2G illustrates metopic synostosis, with symmetrical growth at the sagittal suture and asymmetric growth at the coronal sutures.

Figure 182-2H depicts lambdoid synostosis, with a fused lambdoid suture and bilateral growth at the lambdoid, unilateral at the sagittal, and unilateral at the squamosal sutures, displacing the ear downward rather than forward as in positional posterior These basic rules allow a cranial vault shape abnormality to be defined but do not determine its cause.

This precise definition is important because skull deformity associated with craniosynostosis must be distinguished from that related to uterine molding ; conditions such as

Plagiocephaly without craniosynostosis will improve with time and require no surgery,

whereas craniosynostosis deformities either persist or increase with time, indicating the need for surgery

TreatmentOperative Timing and Approaches Experimental evidence demonstrates that improved skull form is achieved with an operation before the human equivalent of 6 months of age

Objective of surgical treatment is to provide each patient with the best aesthetic outcome that can be achieved

The technique of surgical reconstruction must be tailored to the type of synostosis present and the age of the patient

Brain growth as it relates to the surgical fixation technique for individual elements of bone during skull reconstruction. Note that non rigid fixation methods are preferred during rapid phases of brain growth (i.e., in patients younger than 1 year). Patients older than 3 years are treated with more definitive fixation because a large percentage of adult brain volume has already been achieved. Patients between 1 and 3 years of age receive a combination of fixation techniques.Patients who are younger than 3 years have a substantial amount of brain growth remaining, but because those older than 3 years have already achieved approximately 85% to 90% of their ultimate brain mass

Metallic fixation devices are generally avoided in patients younger than 3 years owing to concerns related to the inward “migration” of the metal with further skull development. Resorbable plates, screws, and sutures are used instead of metallic devices

Operative complication : Cranioplasty Blood loss : Cancellous bone bleeding and Osteotomies Achieving good hemostasis intraoperatively and monitoring blood loss postoperatively because of low circulating blood volumes in very young patients Air embolus : Osteotomies(Regardless of patient position) Monitoring with Doppler examination and carbon dioxide and nitrogen detection techniques. Increase ICP : Reduction of skull height , High risk in Patients older than 1 year

Reductions in skull height greater than 1.5 cm

Had previous surgical procedures that rendered the dural scarred

Syndromic craniosynostosisFaciocraniosynostosis : important problems both functional : exorbitism, breathing difficulties

morphologic : facial retrusion, short nose, ocular malposition Treatment consideration all these parameters, and

close cooperation between the neurosurgeon and plastic craniofacial surgeon

Description and Classification of the Faciocraniosynsotoses Crouzon's Syndrome

Apert's Syndrome (Acrocephalosyndactyly)

Pfeiffer's Syndrome

Saethre-Chotzen Syndrome

Craniofrontonasal Dysplasia

Carpenter's Syndrome Common Syndromic Craniosynostosis

TYPE PHENOTYPIC FEATURES GENETIC MUTATION

Muenke's

Unicoronal or bicoronal craniosynostosis with brachydactyly, thimble-like middle phalanges, coned epiphyses, carpal and tarsal fusions, sensorineural hearing loss, and developmental delay

Autosomal dominant. Caused by a point mutation in Pro250Arg in the Ig II-III linker region of the FGFR3 gene on chromosome 4p16.3

Saethre-Chotzen

Coronal craniosynostosis with limb abnormalities (syndactyly of the second and third digits, bifid hallux) and facial abnormalities (facial asymmetry, low frontal hairline, ptosis, and small ears with prominent ear crura)

Autosomal dominant with complete penetrance and variable expressivity. Caused by loss-of-function mutations in TWIST(missense, nonsense, deletions, insertions, and duplications)

TYPE PHENOTYPIC FEATURES GENETIC MUTATION

Crouzon’s

Classic triad: coronal synostosis, midfacial hypoplasia, and exophthalmos; may also include involvement of other calvarial sutures, brachycephaly, hypertelorism, Chiari I malformation, hydrocephalus, and mental retardation

Autosomal dominant. Caused by numerous missense mutations in the Ig III domain of the FGFR2 gene (many involve the gain or loss of a cysteine residue)

Pfeiffer's

Type I: classic Pfeiffer's syndrome is a mild entityTypes II and III: more severe, with early deathFeatures include coronal synostosis with or without premature fusion of other calvarial sutures, broad fingers and toes, and partial syndactyly of the fingers and toes; may also include maxillary hypoplasia, small nose with a low nasal bridge, hypertelorism, shallow orbits, proptosis, strabismus, limb malformation, and radiohumeral synostosis

Type I: autosomal dominant inheritance. Caused by FGFR1mutations, including Pro252Arg in the Ig II-III linker region on chromosome 8p11.2-p11. Can also be caused by mutations in FGFR2and be associated with more severe phenotypic expressionTypes II and III: sporadic inheritance. Caused by FGFR2 mutations

Apert's

Coronal synostosis with severe syndactyly in the fingers and toes, symphalangism, radiohumeral fusion, and mental retardation

Autosomal dominant. Caused by a number of different mutations inFGFR2 on chromosome 10q26, including two missense mutations (Ser252Trp, Pro253Arg) and two Alu insertions

Jackson-Weiss

Craniosynostosis (ranging from brachycephaly to acrocephaly), with broad toes and a medially deviated great toe, second and third toe syndactyly, tarsal-metatarsal fusion, broad and short metatarsals and proximal phalanges, midfacial hypoplasia, hypertelorism, proptosis, and normal intelligence

Autosomal dominant. Caused by mutation A344G in the highly conserved Ig IIIc domain of FGFR2, as well as two nucleotide missense mutations that result in Cys342Ser and Cys342Arg

Craniofrontonasal Dysplasia (Carpenter's Syndrome)some have a bicoronal craniosynostosis and form a subgroup with a condition called craniofrontonasal dysplasia,

first described by Cohen in 1979

Brachycephaly, often marked, is associated with the facial anomalies of frontonasal dysplasia, which include

-hypertelorism

-a broad nasal bridge

-a bifid nose and

-Sometimes soft tissue syndactyly.

First described by Carpenter in 1901,this syndrome is characterized by craniosynostosis of varying sutures

variable polysyndactyly of the feet,

brachydactyly of the fingers

various soft tissue syndactyly.[5]

Additional abnormalities include

congenital cardiac defects,

short stature, obesity, and

neurocognitive deficiency. Inheritance is autosomal recessive.