Endoscopically Assisted Approaches for Craniosynostosis
Timothy W. Vogel
Brian S. Pan
DEFINITION
Craniosynostosis is a condition caused by the premature fusion of calvarial sutures.
The fused suture restricts the growth of the developing brain, leading to compensatory morphologic changes of the calvarium.
Endoscopically assisted approaches for the treatment of craniosynostosis entail removal of the affected suture through small scalp incisions. The technique is passive, dependent on the natural growth of the underlying brain to facilitate correction once the site of growth restriction is released.
The use of postoperative molding helmets is commonly coupled with this technique to actively direct the vectors of brain growth.1
Although variations in the timing of surgery exist between craniofacial centers, this technique is generally reserved for patients less than 6 months of age.
Decreased operative times, blood loss, cost, and length of hospital stays have all been reported as advantages to this minimal access approach.2
ANATOMY
The normal calvarium is composed of five major bones and sutures (FIG 1A).
The bones include two frontal bones, two parietal bones, and a single occipital bone.
The major sutures consist of three paired sutures (the coronal, lambdoidal, and squamosal) and two single sutures (the sagittal and metopic)
There are six fontanelles, soft membranous gaps that represent the confluence of the bones and the sutures of the skull. These include the anterior and posterior fontanelles and the paired sphenoid and mastoid fontanelles (FIG 1B).
Partial or complete fusion of the affected suture can occur.
FIG 1 • Sutures and fontanelles of the skull. A. Met, metopic suture; L cor, left coronal suture; Sag, sagittal suture; L lamb, left lambdoid suture; A font, anterior fontanelle; P font, posterior fontanelle. B. S font, sphenoid fontanelle; M font, mastoid fontanelle.
Identification via palpation of the anterior and posterior fontanelles, or the confluence of the affected sutures if the fontanelles have closed, is critical for incision placement.
This allows adequate exposure of the targeted suture and avoids injury to the underlying dura if the fontanelles are open.
PATIENT HISTORY AND PHYSICAL FINDINGS
Patients are usually diagnosed within the first few months of life, but the diagnosis may not be readily apparent due to temporary deformation of the head following birth.
A thorough clinical history should be obtained including length of gestation, weight, and complications during gestation and following birth.
Sleeping position, overall health, and a family history regarding abnormal head shape should also be obtained.
The neck should be assessed for torticollis, and hands and feet should be inspected for abnormalities associated with syndromic craniosynostosis.
Although CT scans are routinely obtained for confirmation purposes, physical examination alone has been shown to be 98% reliable for diagnosis in a level 1, prospective multicenter study.3
Growth inhibition occurring perpendicular to the fused suture is the classic teaching for determining the suture responsible for the morphological changes of the calvarium in affected patients.
Growth inhibition is in actuality multidimensional, however, with the remaining open sutures compensating for the area of restriction.4
Sagittal synostosis
In addition to an elongated head (dolichocephaly), there is a decrease in the posterior skull width and height, often with narrowing of the occipital bulb.
Compensatory growth occurs anteriorly involving the coronal and metopic sutures, which results in frontal bossing.
Clinocephaly, presenting as a saddle-shaped deformity dorsal to the open coronal sutures, is often present as well.
Metopic synostosis
The classic physical examination findings include a triangular head shape (trigonocephaly) with reduced bifrontal width, supraorbital pinching, and increased posterior width of the calvarium.
The open sagittal and lambdoid sutures facilitate this compensatory growth pattern.
Hypotelorism may also be appreciated.
Coronal synostosis
The growth restriction caused by closure of the coronal suture results in ipsilateral flattening of the forehead, elevation of the orbit, and anterior positioning of the auricle.
The dorsal aspect of the calvarium is often flattened.
The open coronal suture compensates leading to contralateral frontal bossing and a more dorsally positioned auricle.
The nose is often deviated toward the fused suture.
Bicoronal synostosis
Symmetrical flattening of the forehead with widening of the bilateral temporal regions and elevated height of the calvarium (turribrachycephaly) is the result of fusion of the bilateral coronal sutures.
Concomitant elevation of the supraorbital aspect of the frontal bones may lead to a proptotic appearance.
Lambdoid synostosis
The hallmark of lambdoid craniosynostosis is a mastoid bulge on the affected side.
There is flatness and decreased height of the posterior skull on the affected side as well.
The unaffected lambdoid and sagittal sutures compensate for the growth restriction leading to a contralateral posterior bossing.
This presentation can be easily confused with deformational plagiocephaly.
IMAGING
A three-dimensional (3D) computed tomographic (CT) scan is the ideal study for the diagnosis of craniosynostosis and preoperative planning and to facilitate discussion with patient families.
The patency of sutures and fontanelles can be assessed, the skeletal deformity visualized, and underlying brain abnormalities (eg, Chiari malformation) may be ruled out.
SURGICAL MANAGEMENT
The authors offer a minimal access approach for infants between 6 and 12 weeks of age. In children with mild deformation, this approach may be considered until 16 weeks of age.
In general, posterior vault distraction is recommended for children with bicoronal, bilateral lambdoid, and synostosis.
The main objective of the endoscopic-assisted operation is to completely remove the fused suture using a small incision that will be concealed with hair growth and to avoid injury to the underlying dura.
The main steps of the procedure:
Strategically make incisions that exposes the fused suture or sutures.
Create an optical tunnel to see the fused suture and for removal of the bone.
Make a small craniotomy and enlarge it enough to place the endoscope and to facilitate epidural dissection.
Perform craniectomy of the affected suture either en bloc or in multiple pieces.
Achieve hemostasis that is confirmed with endoscopic visualization and close the skin.Related posts:
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