Elevated Intracranial Pressure After Primary Surgical Correction of Sagittal Suture Craniosynostosis

Abstract

Study Design: A Case Report. Objective: Craniosynostosis is a craniofacial condition defined by premature fusion of at least one cranial suture. Resynostosis or secondary craniosynostosis of a previously patent adjacent suture following primary repair is a relatively common complication. While studies have assessed the rates of secondary craniosynostosis and subsequent reoperation, extremely limited data regarding reoperation techniques is available. Methods: We present a unique case of a pediatric patient with sagittal craniosynostosis who previously underwent a modified pi procedure and later developed resynostosis of the sagittal suture and secondary synostosis of the bicoronal sutures. We subsequently performed total cranial vault reconstruction with virtual surgical planning (VSP). Results: At his 31-month postoperative follow-up, he displayed normal head shape and denied any clinical signs of elevated intracranial pressures with a normal ophthalmological exam. Conclusions: The reoperation was successful with no significant postoperative complications noted. Performing geometric expansion with VSP to manage fusion of a previously open suture following primary treatment of sagittal synostosis should be considered within the armamentarium of operative options.

Introduction

Craniosynostosis involves premature fusion of at least one suture of the cranial vault affecting approximately one in 2000 to 2500 live births worldwide [1,2]. Sagittal synostosis is the most common form of craniosynostosis affecting up to 60% of those diagnosed with this craniofacial condition [3]. Craniosynostosis frequently results in abnormal head shape and may progress to intracranial hypertension (ICH) if operative management is delayed. Chronically elevated intracranial pressures can lead to permanent vision loss and cognitive deficits; thus, early intervention is desirable to prevent such adverse sequelae [4]. The armamentarium of surgical options available to correct craniosynostosis is vast, and the ultimate technique performed can largely be determined by the age at presentation, suture involvement, and severity of the condition.

Cranial vault remodeling is typically performed in patients older than 6 months of age to correct an abnormal head shape and prevent or treat ICH. However, primary repairs are not always successful with some patients demonstrating recurrent synostosis or premature fusion of initially patent sutures [2]. Secondary craniosynostosis (SCS) has particularly been defined as postoperative closure of previously normal, patent cranial sutures [5]. While studies have investigated the development of SCS, secondary revision of postoperative synostosis has not been adequately discussed in the literature [6]. We discuss our experience of a patient with sagittal craniosynostosis who presented with recurrent and delayed synostosis of adjacent sutures after initially undergoing open surgical repair. He subsequently underwent calvarial vault reconstruction with virtual surgical planning (VSP).

Patient Presentation

Our first patient was referred to our clinic by his pediatrician at six months of age due to abnormal head shape. 3D computed tomography (CT) imaging showed premature fusion of the sagittal suture. He originally underwent modified pi procedure at 7 months of age. Twenty months later, he developed progressive papilledema on ophthalmological exam with premature stenosis of the bicoronal sutures and restenosis of the sagittal suture as demonstrated by CT imaging (Figure 1A-1C). He denied headaches, nausea, vomiting, or vision changes. He subsequently underwent VSP with cranial vault remodeling at 28 months of age (Figure 2A-2F). At his 31-month postoperative followup, he displayed normal head shape and denied any clinical signs of elevated intracranial pressures (Figure 3A-3D). Ophthalmological exam was normal (Figure 4).

Operative Technique

The patient was placed in prone position with head on a horseshoe headrest. Access was obtained via a zigzag bicoronal incision. The previous bicoronal incision was used as the markings for current access. A frontal burr hole was created to preoperatively measure intracranial pressures. 3D virtual planning images were then referred to and the surgical guide was placed on the skull for proper marking. The marks to be cut from the surgical guide were examined and compared to the 3D virtual planning images to confirm that they were within the desired areas in the appropriate shapes along the skull. The markings created would then be used to create sagittal osteotomy segment and bifrontal/biparietal/bitemporal/ bioccipital jigsaw pieces on either side of the skull.

The osteotomy segments were then plated back together on the back table using intraoperative guides that were designed pre-surgically utilizing VSP. The final product was appropriately expanded and molded to account for prior fusion and reduce the risk of postoperative ICH. The bones were then secured into place utilizing resorbable KLS Martin plates and screws. After fixation, intracranial pressures were remeasured before closure. A subgaleal drain was placed and the galea and scalp skin were closed in layers. Operative blood loss in both cases was approximately 200 mL with no requirement for blood transfusion.

Discussion

Secondary craniosynostosis has been shown to be a rather common complication following initial corrective surgery [2,7,8,9]. Reoperation rates are also relatively high, though they appear to vary significantly in the literature [2,8,10,11]. A series by Fearon et al. [11] reported that only 1 of 89 patients (1.1%) underwent a revisional [11] operative procedure [11]. This is similar to the reoperation rate at our institution for isolated sagittal synostosis over the last 10 years, which is 1.3% (6 of 446 patients). However, in their retrospective review, Vaca et al. demonstrated a 6.1% reoperation rate for their craniosynostosis patients, and Layliev et al. found that 26.8% of their patients required reoperation [2,8]. The disparity in revision rates observed in the literature can likely be attributed to differences in study parameters. The patient population studied differed in follow-up time, the number and location of involved sutures, syndromic vs nonsyndromic status, surgical technique, and age at primary procedure. Additionally, the criterion used for reoperation were not well-defined in each study and likely varied from surgeon to surgeon. Reoperation rates are generally observed to be lower than rates of SCS largely because not every patient who presents with fusion of a suture postoperatively requires surgical intervention nor do all patients undergo CT imaging following primary surgical repair [2,12,13]. Typically, secondary surgery is reserved for patients who develop signs of ICH or who present with significant, progressive head shape deformities [2,14]. Thus, if a patient demonstrates reossification of a previously released suture or development of premature fusion of a secondary suture that is found incidentally on CT imaging, watchful waiting may be preferred to operative management. In our patient, he demonstrated signs of elevated intracranial pressures, which served as an indication for surgical intervention.

It should be noted that undergoing surgical intervention due to postoperative, premature fusion of cranial suture(s) can be misleading. While secondary craniosynostosis has been well-defined as postoperative fusion of previously patent sutures, studies assessing postoperative outcomes do not always distinguish between resynostosis and delayed synostosis of adjacent sutures [15]. This distinction is important and constructive given that the pathophysiology resulting in these two outcomes may not necessarily be the same. Vaca et al. [2] put it well by stating that ossification over a previously released pathologic suture illustrates bone formation overlying the suturectomy defect [2]. Though some authors report SCS and its associated reoperation rate as the primary postoperative outcome, future studies should continue to denote the specific outcomes of interest in order to provide proper conclusions.

Nevertheless, one should consider that numerous variables may influence the rate of secondary craniosynostosis and subsequent reoperation. Two of the frequently studied risk factors include timing of initial operation and syndromic status of the patient. From the literature, it is clear that syndromic patients develop higher rates of reoperation compared to nonsyndromic patients [7,13,16,17,18]. Williams et al. [7] reported that total reoperation rates following postoperative synostosis for syndromic and nonsyndromic patients was 27.3% and 5.9%, respectively [7]. Similarly, Foster et al. [16] found that 15.4% of syndromic patients and 5.7% of nonsyndromic patients developed recurrence of synostosis following primary wide craniotomy and craniofacial reconstruction [16].

Optimal timing for primary repair to mitigate the risk of secondary craniosynostosis formation is controversial in the literature. While some studies cite increased recurrence of suture stenosis when the primary craniosynostosis surgery was performed at an earlier age, others have found no difference in postoperative outcomes based on surgical timing. Cetas et al. [19] demonstrated that children who developed SCS were significantly younger (4.2 months) at initial operation compared to those who did not (9.5 months) [19]. Seruya et al., however, did not find any correlation with postoperative suture patency and surgical age for pediatric patients who underwent total vault reconstruction for sagittal synostosis [9]. More intriguing is that one study found that children older than 1 year of age were significantly more likely to develop resynostosis (P < .02) [16].

The initial operative technique performed has also been evaluated in terms of its potential impact on secondary craniosynostosis and subsequent reoperation. Similar to surgical age, optimal primary surgical technique has not clearly been elucidated. When comparing endoscopic and open operative approaches, Yarbrough et al. [15] found no significant difference in rates of postoperative synostosis for patients initially diagnosed with nonsyndromic craniosynostosis [15]. Still, lower rates of reoperation for patients who undergo less invasive procedures have also been observed. In one study, 12% of patients who underwent anterior twothirds cranial vault remodeling required reoperation compared to 1.5% of those who underwent sagittal strip craniotomy and barrel staving (P = .030) [19]. Seruya et al. [9] found that their rate of postoperative coronal synostosis following total calvarial reconstruction was four times greater than reported rates in the literature following extended strip craniectomies [9]. Our patient was nonsyndromic, as confirmed by genetic testing, and underwent initial surgery under the age of 1 year. Furthermore, he underwent an open procedure. While certain patient characteristics may foster a greater risk for SCS, our patient provides additional evidence that postoperative recurrence or delay of cranial suture fusion can manifest regardless of presentation.

Postoperative synostosis in syndromic and nonsyndromic craniosynostosis occurs due to distinctive etiologies. The etiology of SCS in syndromic craniosynostosis is attributed to the intrinsic pathophysiology of the cranial sutures caused by abnormal signaling from the calvarial base [2,5,19]. Consequently, when surgery is performed to correct the original calvarial deformity, postoperative fusion of other cranial sutures may still arise. These patients, therefore, typically require a greater degree of vigilance and frequency of postoperative clinic visits [14]. To better assess the fundamental reasonings for why postoperative synostosis develops without attributing the source to an intrinsic factor, nonsyndromic craniosynostosis patients have been exclusively studied in the setting of SCS to remove confounding variables [8,14,20]. The dura has been shown to notably maintain suture patency [3,21]. When undergoing cranial vault reconstruction, the underlying dura is separated from the skull, leading to inappropriate osteogenic signaling at the cellular level leading to subsequent SCS [5,9,14]. Kuang et al. [12] found that when manipulating the coronal sutures during sagittal synostosis repair, nearly 90% of patients developed postoperative coronal synostosis [12]. In another report comparing children who underwent surgical management of sagittal synostosis and those who did not, the rate of secondary coronal synostosis was significantly higher in the former [3]. It stands to reason then that the surgery itself may play a critical role in the development of SCS [2].

Though analysis of SCS following initial operation and its associated risk factors have been substantially assessed, a paucity of data exists for optimal surgical intervention to appropriately manage postoperative synostosis. In fact, only one case report by LoPresti et al. described the utility of VSP and 3D printed templates in a patient who required repeat cranial vault reconstruction following restenosis of the sagittal suture [6]. We reported one case of a pediatric patient who demonstrated resynostosis and SCS following initial surgery.

Since first described for the management of craniosynostosis 25 years ago, VSP has become increasingly popular as a modality for open craniosynostosis surgery [22,23]. While computer-aided design (CAD) planning originally resulted in the creation of 2D osteotomy templates, computer-aided manufacturing (CAM) initially addressed these shortcomings with the production of 3D constructs in the setting of metopic craniosynostosis diagnosed in a set of twins [22,24]. CAD/CAM allows the surgical team to preoperatively plan the procedure by constructing osteotomies and remodeling the calvarium to the desired shape [22,25]. Prefabricated surgical jigs as well as cutting and shaping guides are designed to address and correct the unique craniofacial presentation of each child prior to surgical intervention. Using age-appropriate normative cranial models, which was originally accomplished by Saber and colleagues, VSP can be performed to attain proper calvarial morphology from the patient’s distinct anatomical structure [25,26].

Several advantages associated with virtual surgical planning using CAD/CAM have been delineated for achieving intraoperative success. Chiefly, this operative modality obviates subjective interpretation and demonstrates reproducible and reliable post-surgical outcomes [25,27,28]. While VSP does not serve to replace surgeon operative skills, it minimizes user error and allows for optimal results tailored individually to each patient. Additionally, VSP leads to reduced surgical time and enhanced operative outcomes [29,30]. One study found that operative time for craniosynostosis patients undergoing VSP was significantly less than that for controls (non-VSP) at 265.61 minutes and 321.44 minutes, respectively (P = .01) [30]. Ganesh et al. [29] reported that children diagnosed with craniosynostosis who underwent VSP exhibited significantly less intraoperative blood loss compared to those who did not (218 mL and 250 mL, respectively; P = .014), which may be associated with reduced overall operative times [29]. The main drawback observed with VSP is its requirement for patients to undergo preoperative CT imaging under anesthesia, resulting in unnecessary radiation exposure [22,25,31]. Additionally, with this novel surgical technique comes a level of surgeon inexperience. Andrew et al. [30] reported that there was an apparent learning curve when surgeons initially utilized this operative modality [30]. Consequently, the surgical team should familiarize themselves with this technique in order to counteract any lack of experience they may initially have. Lastly, CAD/ CAM can be expensive. Accordingly, craniofacial surgeons should first evaluate the pricing of this technology to ensure that there are appropriate resources available for its utilization [22]. While the rates of SCS and subsequent revision for VSP vs traditional surgical planning have not been previously compared, one study concluded that it would not be unreasonable to imagine that the utility of VSP could possible reduce these rates [30]. However, in our review of the literature, there is no published data to support this claim. Future studies should aim to examine the impact VSP has on SCS and reoperation rates.

There is limited data in the literature regarding operative techniques utilized to increase intracranial volume and relieve intracranial hypertension for resynostosis or SCS. At our institution, we typically incorporate a geometric expansion in the posterior and middle cranial vaults, as seen in Figure 2. This pattern maintains a normocephalic shape while still achieving the increased intracranial volume required. Normal cranial expansion involves about a 10–15% increase in volume and is typically all that can be achieved given the limited elasticity of the overlying soft tissue envelope [32,33,34]. Any operation that tries to achieve more of an expansion in one setting risks wound healing issues with surgical dehiscence and wound breakdown [35,36]. Theoretically speaking, given that these patients are typically older than 2 years of age, the amount of brain and head growth that they will undergo until they are an adult is also no more than 10–20% [37,38]. It is practically impossible to estimate how much cranial expansion is absolutely required to correct elevated ICP in any given patient. If, however, the team believes more than 10–15% correction is required, distraction osteogenesis, as is used commonly in our syndromic patients, should be utilized. As our imaging and diagnostic technology advance, our correction methods may also improve.

We present a case of a patient with secondary fusion of a previously open cranial suture following primary treatment of sagittal suture craniosynostosis. He was secondarily managed for intracranial hypertension with a geometric expansion of the posterior and middle cranial vault. The patient went on to have improvement in papilledema and did not demonstrate any symptoms consistent with elevated ICP postoperatively.