Introduction
Sagittal suture craniosynostosis is the most common type of sutural stenosis and affects males more than females at a rate of 3.5:1. , It is a genetic condition with which a number of genes have been associated, and they include: ALX₄ ; BBS9 ; BPM2 ; ERF ; FGR1 ; FGFR2 ; nonetheless, most patients presenting with isolated single suture synostosis are completely normal otherwise and do not present in association with syndromes. IGF1R ; MSX2 ; PTHZR ; S1X2 ; SMAD6 ; and TWIST1. The classic clinical presentation is commonly described as scaphocephaly or dolichocephaly. Due to bone growth restriction in a vector perpendicular to the suture, continued normal compensatory brain growth leads to bifrontal bossing and forehead prominence. Additionally, there is marked occipital protrusion and skull elongation in the anterior-posterior axis. The parietal eminences are constricted and there is slanting and downward angulation of the parietal bones. Depending on what part of the suture is closed, the overall head shape will vary and a number of different phenotypic presentations may occur ( Fig. 8.1 ). As previously stated, numerous procedures have been developed to treat this condition. Simple and complex strip craniectomies have been done since the 1890s. A number of calvarial vault remodeling surgeries are currently being performed worldwide by a large number of craniofacial centers. Due to the nature of the condition, a simple linear cut of the stenosed suture will lead to very rapid restenosis. A small strip craniectomy will have the same fate a few weeks later. Because we operate on young infants, our approach has been to make wider craniectomies. Thus, the craniectomy size and width is inversely proportional to the patient’s age.
Patient Positioning
The patient’s position of choice is the modified prone or “sphynx” position. Adequate and secure positioning can be achieved with a number of different frameworks, including headrest such as the pediatric Doro cranial stabilization system (Pro Med Instruments GmbH, Freiburg, Germany). Our method of choice has been the use of a suction stabilized beanbag ( Fig. 8.2 ), which has a great level of flexibility for contouring. A thin viscoelastic pad is placed on top of the beanbag, followed by a clean bed sheet. A Bair Hugger pediatric heating blanket is placed on the patient for temperature control (3M, St. Paul, MN). After endotracheal intubation, a coordinated patient move is done in conjunction with the anesthesia team to place the patient prone on the beanbag at the end of the surgical table (placed at 180 degrees from anesthesia end; Fig. 8.3 ). The patient’s neck is extended so that the top of the head is parallel to the floor. Cast padding is carefully placed on all potential pressure points, such as the shoulders, elbows, knees, and ankles. Once the patient is placed in the sphynx position, the anesthesia team must listen for breath sounds and make absolutely sure that they are equally bilateral. The endotracheal (ET) tube needs to be introduced deeper than normal so that it moves to the appropriate location after neck hyperextension. If proper ET tube positioning is not procured, ventilator problems will occur after the incision is made, which can lead to emergent break down of the sterile surgical field and even the need for reintubation of the patient. Every effort is made to secure the ET tube and ventilator circuit to the beanbag and table in order to prevent inadvertent extubation. A throat pack is routinely inserted to improve tube stability and minimize air leaks.
Because of the patient’s location in relation to the heart (higher), the risk of venous air embolism (VAE) occurring is relatively high. It may occur directly into the sagittal sinus, a detached bridging vein, a contrical vein, or a large osseous channel. If large enough, a VAE can have a significant negative impact and may even be fatal. As such, it is imperative that monitoring for VAE during the entire procedure be instituted. The simplest and best way to monitor for such an event is to use a precordial doppler ( Fig. 8.4A ). The sensor is placed on the left side of the chest in front of the heart and maximal signal pick-up is aided with a lubricant ( Fig. 8.4B ). Once a stable signal is obtained, a 4- × 4-inch gauze is placed on top of the sensor and the entire unit is secured in place with foam tape ( Fig. 8.4C ). To document that the system is properly functioning, the anesthesia team rapidly flushes a milliliter of saline through an IV line and the subsequent echo signal is heard, which indicates a functioning system.
The surgical setup and draping are shown on Fig. 8.5 . After draping with towels, a 1016 self-adhesive collecting pouch is placed around the patient’s head and a split drape is positioned under the pouch. Cottonoids and different sizes of Gelfoam pieces are placed behind the patient’s head for quick and easy surgeon access. Self-adhering instrument pouches are placed on either side of the head. The right pouch holds the suction cautery, Bovie hand piece, bipolar, and suction. The left pouch holds another suction (large diameter) and a second Bovie hand piece. To minimize cable entanglement, a towel is stapled to the drapes over all of the running lines and cables.
Incisions
In order to completely release the stenosed sagittal suture, the exposed surgical field should extend from the anterior fontanelle to the lambda. Even though the exposure can be done with a single incision midway between these points, we have found that it is much safer to do so via two separate incisions. At the beginning of our series, we placed the anterior incision directly over the anterior fontanelle, but later modified it to be approximately 2 to 3 cm behind the fontanelle ( Fig. 8.6 ). This configuration has several advantages. It decreases the distance between the incisions and makes endoscopic manipulation easier. It places the incision away from the coronal suture, thereby minimizing the risk of dural tears when doing the wedge osteotomies. In case of the occasional durotomy, the two incisions give greater access to the dura for primary repair and closure. The incisions are made with the Bovie needle tip coagulation set on the cut mode at 15 watts. When done properly, the dermis is cleanly incised and there is no burning or damage to this skin layer ( Fig. 8.7 ). Deeper dissection is done with the needle tip on the coagulation mode set at 20 watts. Because of the scalp’s mobility, the incisions need not be long and usually suffice at about 3 cm ± 1 cm. At the end of the procedure, the scalp incisions are infiltrated with bupivacaine 0.25% with epinephrine 1:250,000 at 1 cc/kg. The incision is closed with 4-0 monocryl interrupted galeal sutures and the dermis sealed with Mastisol and Steri-strips. The patient’s head is not shaved or hair clipped except for a very small strip at the site of the incision. Large amounts of hair can be covered and stapled out of the way ( Fig. 8.8 ). The posterior incision is placed immediately in front of the lambda with its epicenter over the sagittal suture ( Fig. 8.9 ).
Procedure
Subgaleal Dissection
The scalp is separated from the underlying cranium/pericranium by developing a bloodless plane of dissection using the monopolar needle tip coagulator ( Fig. 8.10 ). The rhinoplasty lighted retractor is used to elevate the scalp and expose the loose areolar tissue plane. If two surgeons are operating, they can simultaneously open both incisions and develop the subgaleal plane as needed with the help of an assistant ( Fig. 8.11 ), which will, of course, decrease surgical operative time. Typically, a number of small perforating vessels are seen and sequentially coagulated ( Fig. 8.12 ). These vessels are more prominent and engorged when there is an increase in intracranial pressure. If properly done, complete dissection of this plane is developed in a bloodless fashion, extending from anterior fontanelle to lambda and 3 cm on either side of the midline.
Osteotomies
Development of the anterior transverse osteotomy is begun with a paramedian burr hole done with a pediatric craniotome (7 mm) perforator. The burr hole is placed to the left of the stenosed suture 2 or 3 cm from the midline, depending on the patient’s age. Bony hemostasis is obtained with bone wax and/or Surgiflo. A #1 Penfield dissector (cupped end) is inserted under the bone and gently passed towards the midline, developing an epidural plane. A 4- or 5-mm Kerrison rongeur is sequentially used to create the anterior osteotomy across the midline and sagittal sinus ( Fig. 8.13 ). Bony hemostasis is attained with a combination of suction electrocautery (60 watts) of the osteotomized bone, Gelfoam, and pressure with cottonoids. The #1 Penfield is placed under the bone and advanced anteriorly to reach the anterior fontanelle. Direct palpation of the scalp corroborates the placement of the #1 Penfield to the dura at the fontanelle ( Fig. 8.14A ). A triangular section of bone is removed by carefully placing the Mayo scissors and cutting the bone from the anterior osteotomy to the fontanelle extending from the lateral aspect of the osteotomy on each side ( Fig. 8.14B ). Removal of this piece of triangular bone ( Fig. 8.14C ) allows for placement and insertion of the endoscope under the bone posteriorly ( Fig. 8.14D ). A second transverse osteotomy is done immediately in front of the lambda. In a similar fashion, a burr hole is placed on the left side of the posterior incision and a Kerrison rongeur is used to remove the bone in a piecemeal fashion towards the midline. Extreme care is taken when crossing the stenosed suture in the midline. The stenosed sagittal suture at this level commonly has a deep bony keel that indents the sagittal sinus ( Fig. 8.15 ). Tearing the sinus at this point of the procedure could have dire consequences given the limited exposure of the sinus. If a prominent bony keel is encountered, it is safest to make a second burr hole on the contralateral side and remove bone from that direction. This maneuver leaves the keel exposed on both sides and makes it easier and safer to pass a #1 Penfield under it to fully free the sinus. Once fully dissected, the bone is completely removed, thereby completing the osteotomy.
