Surgery for Nonsyndromic Single-Suture Craniosynostosis Treatment & Management

No medical treatment exists for craniosynostosis, and helmet therapy alone does not correct the head shape. Because of the progressive nature of the cranial deformity, most children with craniosynostosis are recommended for surgery. However, children with mild deformities or those who present late without signs of increased intracranial pressure (ICP) are occasionally treated without surgery.

The literature is mixed with respect to the ability of surgery to affect cognitive outcomes. ^[13]  Nevertheless, there has been some evidence to suggest that earlier more comprehensive cranial vault reconstructions are associated with improved cognitive outcomes as compared with less comprehensive procedures or comprehensive procedures performed later. ^{[14, 15]}  Even with early comprehensive surgery, studies suggest that subtle learning disabilities persist. ^[16]

Surgical options

Although there are several options for the treatment of single-suture craniosynostosis (SSC), each is designed to return the skull shape toward a more normal contour and allow for unrestricted cranial expansion. The two basic types of techniques are as follows:

• Cranial vault reconstruction (CVR)
• Suturectomy (strip craniectomy), which is most often followed by the use of a molding helmet

CVR has the advantage of immediately correcting the cranial shape but the disadvantage of being a more extensive operation associated with larger incisions, higher rates of transfusion, and longer hospital stays.

A national longitudinal comparison of strip craniectomy (n = 251) with CVR (n = 1811) for craniosynostosis management identified socioeconomic disparities between strip craniectomy patients and CVR patients. ^[17] CVR was found to be more commonly performed in underrepresented minorities and patients with Medicaid, whereas strip craniectomy was common in the White population and patients with private insurance. Although CVR was associated with higher hospital charges and complication rates than strip craniectomy, the differences were less than expected.

Alternatives to these procedures have also been described, including spring-mediated ^[18] and external distraction devices. ^[19] Spring-assisted surgery has gained popularity. It originated in 1997 with Lauritzen in Sweden. ^[20]  Lauritzen’s group in Gothenburg has preferentially used spring cranioplasty in children up to age 6 months and the modified pi-plasty in older children. ^[21]  Initial use of this approach focused on SSC, particularly sagittal synostosis.

Valetopoulou et al performed a systematic review (22 studies; N = 1094) comparing endoscopic strip craniectomy followed by postoperative molding helmet therapy (ESC-H; n = 605) with spring-assisted cranioplasty (SAC; n = 489) for correction of nonsyndromic sagittal SSC. ^[22]  They found outcomes to be broadly similar and concluded that the available evidence was insufficient to establish either ESC-H or SAC as superior in this setting. Much of the literature consisted of single-center retrospective studies of low methodologic quality; international multicenter randomized controlled trials comparing ESC-H with SAC would be required in order to yield definitive and generalizable data.

Distraction osteogenesis for unicoronal craniosynostosis has been described. ^[23]

Timing of surgical intervention

Although there is not a standard of care regarding the exact timing of surgery for craniosynostosis, surgery is generally recommended during the first year of life. The age at which surgery is performed is somewhat technique-dependent. Endoscopic-assisted suturectomies followed by molding helmet therapy are generally performed prior to 4 months, ^[24] before the compensatory deformities become more of an issue and while the skull is more malleable. Suturectomy relies on early brain growth to passively change the shape of the skull. More comprehensive CVRs are generally performed in the second half of the first year of life and actively change the shape of the skull.

Although earlier surgery may be associated with improved cognitive outcomes, the risk of surgical morbidity and mortality must also be considered. In addition, there is evidence to suggest that earlier surgery is associated with a higher incidence of recurrence and a more frequent requirement for repeat procedures. ^[25]  The true impact of timing of surgery on neurodevelopmental outcomes has not been defined with certainty. ^[26]  

Preparation for surgery

CVR procedures to correct craniosynostosis are known to result in extensive blood loss. Bleeding is the main cause of mortality after surgery to correct craniosynostosis. Meticulous hemostasis and early transfusion can mitigate the results of blood loss. ^{[27, 28]}

Tranexamic acid (TXA) has been described in the literature as an adjuvant for reducing blood loss and transfusion requirements. A double-blind, placebo-controlled trial was performed with TXA during correction of craniosynostosis. ^[29] Patients were loaded with 50 mg/kg of TXA after induction of anesthesia, before incision, which was followed by infusion of 5 mg/kg/hr during surgery. These patients were compared with those receiving placebo and found to have lower perioperative mean blood loss (65 mL/kg vs 119 mL/kg) and lower perioperative mean blood transfusion (33 mL/kg vs 56 mL/kg).

Another group, in a randomized double-blind study, pretreated patients with erythropoietin (600 U/kg) once a week for 3 weeks leading up to surgery. ^[30] The volume of packed erythrocytes transfused was reduced by 85% intraoperatively and by 57% throughout the study period. Other studies in children undergoing cardiac surgery or spinal surgery for scoliosis have found similar benefits.

The mechanism by which TXA works is not well understood; moreover, the studies have been criticized for the heterogenous populations and attenuated power of the studies. ^[31] Research has continued in this area, in particular with regard to TXA dosing. Overall, many centers have adopted the use of TXA to lower transfusion rates given the current data available. 

Controlled hypotension to reduce blood loss during fronto-orbital advancement was studied by Seruya et al. ^[32] Mean arterial pressure (MAP) and calculated blood loss were evaluated. An inverse relation between MAP and calculated blood loss was discovered; however, on further evaluation, it was found that blood loss was the cause of changes in MAP.

In sagittal synostosis, the skull is long and narrow. Correction requires reconstruction of the skull so that it is rendered wider as compared with its anterior-posterior length. One factor that must be taken into account during preoperative planning and repair is compensatory growth, which can be anterior, posterior, or both. 

Surgical goals are to shorten the skull and to widen it with correction of severe compensatory growth. Additionally, a bifrontal craniotomy is required to correct the frontal bossing. In similar fashion, if the compensatory growth involves the occipital bone, an occipital craniotomy may be beneficial. If compensation involves both frontal and occipital bones, then surgery often must be performed with the patient in a modified prone position and must include both a bifrontal and an occipital craniotomy. However, some surgeons do not advocate frontal craniotomy, on the grounds that this compensation has been shown often to improve over time with surgical correction during infancy. ^[33]

Permanent marker is used to delineate the planned incision line with the patient in the prone position for this case example. The incision line is planned in a curved manner to allow a more cosmetically pleasing result as the child ages. (See the image below.) The focus of this correction will be on the parietal bones and occipital narrowing.

Preoperative view of sagittal craniosynostosis with bicoronal incision marked. Prone position. Note biparietal narrowing and occipital narrowing.

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The bicoronal incision is made, and Raney clips are placed on both sides of the wound to maintain meticulous hemostasis. One of the more significant risks to an infant undergoing CVR is blood loss. The surgical team and the anesthesiology team must work together to reduce risks and treat blood loss quickly so as to avoid complications. The image below depicts full exposure of the skull with scalp flaps retracted in prone position. The margins of the planned cuts to remove the sutures with the craniotome are also drawn with a marker. The central line marks the fused sagittal suture, with lines on each side of it marking a central segment for removal.

Intraoperative view of sagittal craniosynostosis after scalp flap reflection. Note Raney clips on skin edges. Markings designate sites of craniotomy with exception of central marking, which identifies fused sagittal suture at midline. Central segment of bone including suture will be removed. Prone position.

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The anterior fontanelle must be teased away from the surrounding skull before the craniotome can be used to create the cuts that will remove the sutures of interest. Care must be taken not to disturb the superior sagittal sinus. The cuts to remove the suture are made with the craniotome. The central segment including the sagittal suture is then easily removed and placed aside to use as part of the final construct if needed. Bilateral closed wedge-shaped osteotomies are performed near the patent lambdoid sutures to allow shortening of the anterior-posterior length.

In the final configuration (see the image below), the parietal bones have been widened at their lateral bases, and the occipital bone has been flattened and brought closer to the parietal bones to shorten anterior-posterior length. In young infants, the vertex segment of bone may be discarded or used as bone graft between the parietal bones. In older children, this segment is used for bone graft; filling cranial defects from surgery is less reliable in this population.

Intraoperative view of sagittal craniosynostosis after removal of bone. Parietal bones on each side have been divided into segments and widened. Occiput has been flattened, as demonstrated by surgeon's finger. Prone position.

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After closure (see the image below), the improvement in width and occipital flattening is apparent.

Sagittal craniosynostosis after repair with scalp closed. Prone position.

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The unilateral coronal craniosynostosis produces a forehead that is typically bossed on one side and recessed on the other. In this case, a bifrontal craniotomy is required, with reconstruction of the frontal bone. In particular, the bossed area must be recessed and reduced. An orbital rim advancement is also required.

In patients with right unilateral coronal craniosynostosis, the bossed left forehead and the recessed right forehead are readily apparent (see the image below).

Preoperative top-down view of patient with unilateral (right) coronal craniosynostosis. Note flattened right forehead with elevated orbit and contralateral left side prominence (bossing) of forehead.

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Preoperative top-down CT view of same patient with unilateral (right) coronal craniosynostosis. Note flattened right forehead with elevated orbit and contralateral left side prominence (bossing) of forehead.

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Upon reflection of the scalp, one can appreciate the recessed right forehead and a bossed left forehead with much more clarity (see the image below). The goal of correction is to bring the right forehead forward and the left forehead back slightly, in relation to each other, so that as the child grows, the forehead will be even when viewed from above. Some centers advocate “overcorrecting” the recessed/synostotic side to prevent recrudescence. 

Intraoperative view of same patient with unilateral (right) coronal craniosynostosis, looking directly down onto forehead. Top of head is at bottom of picture. Two sides of forehead were exchanged, placing prominent left side on right and flattened right side on left after contouring. Right side is overcorrected in position as compared with left.

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The superior orbital rim will be advanced on the right as well, with the use of some autologous bone from the suturectomies. The frontal bones are removed with the craniotome. The superior orbital rim is removed with a combination of a high-speed saw and osteotomes. The periorbita is protected with a malleable retractor. Once the superior orbital rim is removed, it is remodeled.

In this case, the superior orbital rim is remodeled by extending the right side with autologous bone and absorbable plates. Once the superior orbital rim has been remodeled to correct the recessed right side and bossed left side, it is ready to be reattached with absorbable plates to the surrounding bones, including the frontal bones, which have already been reshaped. The corrected frontal bones and superior orbital rim are reattached with absorbable plates. The right frontal region is no longer recessed, and the left frontal region is no longer bossed.

With the closure complete (see the image below), the symmetry of the frontal bones is more obvious. The advancement of the right side and the partial recession of the left frontal region can be appreciated.

Intraoperative top-down view of same patient with unilateral (right) coronal craniosynostosis at completion of repair. Right side is overcorrected in position as compared with left at orbital rim (upper right portion of image).

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The bilateral coronal synostosis produces a skull that is excessively tall and short. The surgery to correct this should produce a skull that is longer in the anterior-posterior dimension and shorter in the superior-inferior dimension. As with the unilateral coronal synostosis, an orbital rim advancement is required. Decreasing the vertical height of the skull can be challenging but can be accomplished using a variety of techniques, each with their particular advantages and limitations.

In the example illustrated (see the images below), surgical treatment was performed in two stages. First, a biparieto-occipital osteotomy was performed, with external detractors designed to lengthen the skull but also to decrease the vertical height. After the bone consolidated, a standard fronto-orbital approach was performed to correct the recessed forehead and orbital rims.

Bilateral coronal craniosynostosis repair. 3D rendering of standard CT performed on postoperative day 1 after consolidation and then months later. Note lengthening of skull, as well as decrease in vertical height.

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Bilateral coronal craniosynostosis repair. 3D rendering of standard CT performed on postoperative day 1 after subsequent fronto-orbital advancement.

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Metopic synostosis is characterized by trigonocephaly. The forehead appears ridged, and the patient has hypotelorism and proptosis (see the images below).

Preoperative view of patient with metopic craniosynostosis (supine position). Note bifrontal narrowing and posterior parietal widening giving triangular shape (trigonocephaly) to skull on top-down view.

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Preoperative CT of patient with metopic craniosynostosis. Note bifrontal narrowing and posterior parietal widening giving triangular shape (trigonocephaly) to skull on top-down view. Note fused (absent) metopic suture anteriorly at midline with other sutures patent (visible).

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This condition is repaired by advancing the orbital rims, which are noted to be recessed, in addition to removing the fused metopic suture. The forehead requires careful reconstruction. Some institutions perform an endoscopic strip suturectomy through a small incision and then helmet the child to reshape the head as the child grows. ^[34]  In this example, a fronto-orbital reconstruction is performed, much as for the unilateral coronal patient but with a focus on correction of the bilateral flattening. After forehead scalp reflection, the bony deformity is exposed (see the image below).

Intraoperative view of metopic craniosynostosis skeletal deformity after scalp flap reflection.

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A bifrontal craniotomy is performed removing the forehead, and this is followed by  removal of the supraorbital bandeau (bar). This supraorbital bar is deformed, with bilateral narrowing and a triangular shape (see the image below). 

Intraoperative view of released fronto-orbital bandeau (top-down) prior to remodeling. Note triangular shape with flattening laterally.

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The flattening is contoured to a projected, more arched configuration, and it is stabilized to the parietal bones on each side with resorbable plates. The frontal bones are contoured to match the supraorbital bar and attached. The scalp is closed. (See the image below.)

Completion of repair for metopic craniosynostosis with scalp closed.

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Lambdoid synostosis is characterized by unilateral flattening of the ipsilateral parietal bone and, particularly, the ipsilateral occiput. Compensatory changes include overgrowth of the ipsilateral mastoid bone with inferior deflection of the ipsilateral ear, as well as overgrowth of the contralateral parietal bone. This creates a skull that is parallelogram-shaped when viewed from behind.

The goals of surgery are to create a rounder ipsilateral parieto-occipital region, to remove and elevate the ipsilateral overgrown mastoid, and to reduce the contralateral overgrown parietal bone. (See the image below.) Care should be taken to protect the major venous sinuses during this approach; preoperative computed tomography (CT) venography can be helpful. Multiple options are available to accomplish the reshaping and are less standardized than the options for other craniosynostoses.

Lambdoid craniosynostosis repair. 3D rendering of standard CT performed on postoperative day 1 following reconstruction. Bilateral parietal craniotomies were performed, leaving sagittal suture in place. Bioccipital craniotomy was accomplished, and overgrown mastoid bone was removed and then elevated with bone grafts from craniotomies. Bone from contraleral parietal bone was used for occipital reconstruction. Ipsilateral partietal bone was placed contralaterally, and bone from bioccipital craniotomy was used to reconstruct ipsilateral parietal bone.

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After cranial vault remodeling procedures, patients are monitored in the pediatric intensive care unit (ICU). Serial hemoglobin and coagulation parameters are evaluated until stabilization is achieved. Patients receive transfusions as needed according to set cutoffs. Postoperative imaging may be performed to assess for early postoperative complications and to demonstrate the new arrangement of the bony architecture of the cranial vault. 

Complications are rare after craniofacial surgery. Hypovolemic shock can occur if significant intraoperative blood loss has not been replaced in a timely manner. Blood loss during surgery has been shown to increase with longer operating times, particularly when such times exceed 5 hours. Additionally, recognized craniofacial syndromes and pansynostosis have also been associated with increased blood loss during surgery. ^[35]

Intraoperative dural tears that remain unrecognized can cause postoperative cerebrospinal fluid (CSF) leaks and resultant infection or subgaleal fluid collections. Epidural or subdural hematoma can occur.

Almost all patients develop facial swelling postoperatively, more prominently around the eyes, which rarely causes problems; however, parents and caregivers should be counseled appropriately. Wound infections are generally rare. The frequency of these complications is less than 10%.

Restenosis, though rare, can occur. Long-term follow-up is warranted. Patients are also assessed at regular intervals to monitor for the ossification of cranial defects left during the reconstruction. Serial head circumference measurements are obtained to confirm proper growth of the skull. Although ophthalmologic evaluations do not effectively rule out intracranial hypertension, they can be a useful adjunct in monitoring for its occurrence.