Total Cranial Vault Remodeling

Armamentarium

  • #15 and #10 Scalpel blades

  • 2.5-cm Hypafix tape

  • 5-cm Crepe bandage

  • Appropriate sutures

  • Bone rongeurs, curved and straight

  • Bone wax

  • Burs: flat fissure/pineapple

  • Cat’s paw retractors

  • Dressing gauze

  • Electrocautery: needle, blade, bipolar

  • Gelfoam patties/surgical fibrillar

  • Hall Surgairtome

  • Hot water bath

  • Howarth elevator

  • Jelonet

  • Langenbeck retractors

  • Local anesthetic with vasoconstrictor

  • Mayo table

  • Medium Tegaderm

  • Midas electric drill craniotome

  • Modified Freer elevator

  • Penfield dural dissector

  • Preparation trolley: elastics/shaver

  • Resorbable plating kit (sonic weld)

  • Skin hooks

  • Stille-Listen bone cutter

  • Tessier elevators

History of the Procedure

Many techniques for remodeling the cranial vault have been proposed and range from simple suture removal to complete morphologic alteration of the cranium. Isolated sagittal synostosis, the most frequently occurring form of nonsyndromic single-suture synostosis, varies in severity but may have a profound effect on the entire cranial shape causing lengthening of the vault, biparietal narrowing, “bulleting” of the occiput, and frontal bossing (scaphocephaly). Craniosynostoses involving the coronal and metopic sutures may result in a brachycephalic/turricephalic deformity with a reverse pattern of calvarial distortion. The first surgical procedures for craniosynostoses were strip craniectomies of the fused sutures. These were undertaken in the 1890s to allow skull expansion, but surgical morbidity and refusion of involved sutures led to poor results. Barrier techniques were tried in order to cover the osteotomized bony margins and thereby prevent refusion, but again, with limited success. With increasing recognition that the whole vault was affected, extended strip craniectomies, and sometimes total vertex craniectomies, were then performed. During this same period, total removal of the cranial vault and helmet protection was being advocated in parts of Europe in an attempt to achieve a more normal skull morphology following reossification. However, bony regeneration proved to be incomplete and unpredictable. Strip craniectomies are still widely practiced today, but there is evidence that a more comprehensive approach to remodeling yields superior results. A more radical procedure was introduced by the neurosurgeon Jane, who reduced the fronto-occipital dimension of the head by first removing a transverse strip of bone posterior to the coronal suture connected to parasagittal resections bilaterally. Posteriorly the resected area extended laterally in front of the lambdoid sutures. Viewed from above, the resected bone resembled the shape of the Greek letter “pi,” after which Jane’s procedure was named. The calvarium was then squeezed together in the anteroposterior direction with lateral displacement of the parietal segments. The frontal and occipital deformities were not fully addressed, and the risk of raising intracranial pressure by brain compression caused concern, with some neurosurgeons recommending intraoperative pressure monitoring. A similar technique utilizing gradual cranial compression after a modified bone resection using reverse distraction has been reported. Others have recommended extensive posterior vault remodeling alone, allowing the frontal bossing to self-correct. A further technique developed by Renier with segment removal in an “H” pattern has been advocated for infants younger than 6 months where retrocoronal and prelambdoidal segments are removed together with central segments over the sagittal suture. Spring-mediated cranioplasties have also become popular for younger patients, but again, the anterior and posterior phenotypical features are not corrected and rely on helmeting. A large series of strip craniectomies using endoscopic techniques to treat scaphocephaly has been reviewed, and good results were reported for infants younger than 6 months, but extended helmet therapy following this surgery is essential. This technique is more suitable for mild to moderate cases that present early. Patients older than 7 to 8 months and those with more severe deformities are usually considered unsuitable for this approach. To correct the more severe deformities as well as cases presenting at a later age, a more radical approach was advocated. Dissatisfaction with multiple previous techniques led to the development of the “Melbourne technique” of total calvarial remodeling, devised by the senior author (ADH) and our team, which will be outlined in this chapter.

History of the Procedure

Many techniques for remodeling the cranial vault have been proposed and range from simple suture removal to complete morphologic alteration of the cranium. Isolated sagittal synostosis, the most frequently occurring form of nonsyndromic single-suture synostosis, varies in severity but may have a profound effect on the entire cranial shape causing lengthening of the vault, biparietal narrowing, “bulleting” of the occiput, and frontal bossing (scaphocephaly). Craniosynostoses involving the coronal and metopic sutures may result in a brachycephalic/turricephalic deformity with a reverse pattern of calvarial distortion. The first surgical procedures for craniosynostoses were strip craniectomies of the fused sutures. These were undertaken in the 1890s to allow skull expansion, but surgical morbidity and refusion of involved sutures led to poor results. Barrier techniques were tried in order to cover the osteotomized bony margins and thereby prevent refusion, but again, with limited success. With increasing recognition that the whole vault was affected, extended strip craniectomies, and sometimes total vertex craniectomies, were then performed. During this same period, total removal of the cranial vault and helmet protection was being advocated in parts of Europe in an attempt to achieve a more normal skull morphology following reossification. However, bony regeneration proved to be incomplete and unpredictable. Strip craniectomies are still widely practiced today, but there is evidence that a more comprehensive approach to remodeling yields superior results. A more radical procedure was introduced by the neurosurgeon Jane, who reduced the fronto-occipital dimension of the head by first removing a transverse strip of bone posterior to the coronal suture connected to parasagittal resections bilaterally. Posteriorly the resected area extended laterally in front of the lambdoid sutures. Viewed from above, the resected bone resembled the shape of the Greek letter “pi,” after which Jane’s procedure was named. The calvarium was then squeezed together in the anteroposterior direction with lateral displacement of the parietal segments. The frontal and occipital deformities were not fully addressed, and the risk of raising intracranial pressure by brain compression caused concern, with some neurosurgeons recommending intraoperative pressure monitoring. A similar technique utilizing gradual cranial compression after a modified bone resection using reverse distraction has been reported. Others have recommended extensive posterior vault remodeling alone, allowing the frontal bossing to self-correct. A further technique developed by Renier with segment removal in an “H” pattern has been advocated for infants younger than 6 months where retrocoronal and prelambdoidal segments are removed together with central segments over the sagittal suture. Spring-mediated cranioplasties have also become popular for younger patients, but again, the anterior and posterior phenotypical features are not corrected and rely on helmeting. A large series of strip craniectomies using endoscopic techniques to treat scaphocephaly has been reviewed, and good results were reported for infants younger than 6 months, but extended helmet therapy following this surgery is essential. This technique is more suitable for mild to moderate cases that present early. Patients older than 7 to 8 months and those with more severe deformities are usually considered unsuitable for this approach. To correct the more severe deformities as well as cases presenting at a later age, a more radical approach was advocated. Dissatisfaction with multiple previous techniques led to the development of the “Melbourne technique” of total calvarial remodeling, devised by the senior author (ADH) and our team, which will be outlined in this chapter.

Indications for the Use of the Procedure

The phenotypical deformities resulting from both the syndromic and nonsyndromic craniosynostoses have been better characterized with an ever-increasing understanding of the genetic basis of cranial suture fusion. There are differing views regarding the selection of procedures and the age at which they can be undertaken. In general, the extents of the calvarial distortions and constrictions are proportional to the site and number of sutures that are fused, as is the risk of raised intracranial pressure. To fully correct the more severe deformities, a more comprehensive alteration of the shape of the total cranial vault is often required. The most common condition suitable for total cranial vault reconstruction is moderate to severe scaphocephaly. Modifications of the Melbourne technique can be useful in other severe synostoses, in particular multisutural synostoses causing turricephaly, oxycephaly, and “cloverleaf” skull. A reverse type procedure can also be used to lengthen and lower the skull in severe brachycephaly resulting from coronal synostosis.

Scaphocephaly

In the scaphocephalic patient, the fusion of the sagittal suture causes narrowing of the bitemporal and biparietal dimensions with an elongated head and a higher vertex. The vertex is positioned anteriorly near the anterior fontanelle instead of posteriorly to the midline. There is an inferiorly sloping, posterior cranium constricting to a bullet-shaped occiput. The intracranial contents push anteriorly, causing compensatory frontal bossing. Partial fusion of the sagittal suture will lead to more localized adjacent transverse constrictions of the skull.

The diagnosis can be made clinically and confirmed with good plane film radiograph and three-dimensional computed tomography (CT). There is a low cranial index and usually an increased head circumference approximating the 90th percentile. Without treatment, the narrow head shape will persist and any frontal bossing often remains evident. Patients with moderate to severe deformities over the age of 9 months constitute the strongest indication for this procedure, as other therapies become less effective. The aim of the Melbourne procedure is to address all phenotypical features of the disorder and reconstruct the skull without any brain compression. In fact, the cranial volume is increased. By segmental repositioning, the sagittal suture is reshaped and placed in the normal adult position. The frontal bone is recessed and widened, along with the coronal suture. The occiput is elevated and widened to shorten the anteroposterior dimension and to position the vertex posteriorly. The biparietal diameter is markedly widened. The normal sutures are preserved as much as possible and repositioned, with the hope that this will allow the rest of the head to continue growing normally.

Brachycephaly (Turricephaly/Oxycephaly)

Patients with more vertical deformities secondary to multisuture synostoses such as Muenke syndrome exhibit a variable reverse pattern of deformity to scaphocephaly. The anteroposterior dimension of the skull is foreshortened with raised, flattened frontal and occipital regions and an increase in bitemporal width. The head height may be spectacularly increased in syndromic patients with synostoses of the coronal ring that includes the coronal, frontosphenoidal, and frontoethmoidal sutures. The pattern of segment repositioning required is the reverse of that described previously with lowering of the occiput by transferring a lower segment to increase the fronto-occipital dimension and narrow the head width.

Limitations and Contraindications

Early raised intracranial pressure with scaphocephaly is exceedingly rare but must be excluded preoperatively. Raised pressure may be found in other more severe forms of synostosis. Later clinical signs of raised pressure may occur in any child with synostoses, and these patients must be kept under review. Usually, cranial vault expansion is expedited if there are signs of pressure, and this is done prior to insertion of a neurosurgical shunt in order to allow the brain to expand and fill the increased volume created by the surgery. Often, expansion surgery may avert the need for shunting. In some forms of synostosis, especially those with an associated base of skull abnormalities (Apert and Pfeiffer syndromes, severe brachycephaly), the posterior fossa may be constricted and a Chiari malformation, and herniation of the cerebellar tonsils may be present. These patients may show prominent veins and venous markings, indicating compromise of venous sinus drainage and incipient raised pressure. It is prudent to consider early posterior fossa decompression, often by distraction, for these cases.

Total vault remodeling is a major procedure and requires an experienced craniofacial, neurosurgical, and anesthetic team. All children require an extensive medical workup including bleeding and clotting parameters, CT scan, neuropsychological assessment, and base-line 3D photography. Fortunately, contraindications to surgery are rare.

Technique: Total Calvarial Remodeling-Scaphocephaly

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Jun 3, 2016 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Total Cranial Vault Remodeling
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