Pediatric Neurosurgery

Michael Edwards MD¹

Sam Cheshier MD¹

Michael I. Chen MD²

William W. Feaster MD²

¹SURGEONS

²ANESTHESIOLOGISTS

CRANIOFACIAL SURGERY

SURGICAL CONSIDERATIONS

Description: Craniofacial surgery is a broad term that refers to both cranial and/or facial reconstructive procedures for cranial dysostosis or craniofacial dysmorphism. Cranial dysostosis is the congenital maldevelopment of the cranial base and/or vault, 2° premature fusion of cranial sutures. More commonly referred to as craniosynostosis, the surgical correction of this disorder involves removal of the affected suture(s) and reconstruction of the cranial, orbital, or facial bones. The most common form of craniosynostosis—scaphocephaly—is caused by the fusion of the sagittal suture, which leads to a long and narrow calvarium. Other forms of craniosynostosis, in order of decreasing frequency, are coronal synostosis (brachycephaly), metopic synostosis (trigonocephaly), and lambdoidal synostosis (posterior plagiocephaly). Deformational occipital plagiocephaly refers to flattening of the occiput 2° preferential sleep position and the resultant deformation of the skull, ear, and face. This condition is not a form of craniosynostosis, and despite the potential for significant flattening of the head, reconstructive surgery is not indicated. Crouzon and Apert syndromes are inherited craniofacial disorders associated with craniosynostosis and facial/orbital dysmorphism. The facial deformities common to Crouzon and Apert are shallow and misplaced orbits, exophthalmos, and midface hypoplasia. In each form of craniosynostosis, sporadic or inherited, the abnormality is present at birth, but may not become recognizable until the rapid phase of brain growth, occurring in the 1st year of life, begins to accentuate the limitations on skull shape produced by the premature suture closure. In simple terms, the growth of the underlying brain drives the expansion of the skull, and closure of a suture produces reduced skull growth in the opposite direction.

Early recognition and correction of craniosynostosis results in the best cosmetic and neurologic outcome because, with release of the fused suture, the growing brain helps correct the abnormal cranial shape. Most procedures are scheduled during the 1st 6 mo of life; thus, the issue of blood volume and replacement becomes a critical factor for surgical and anesthetic consideration. The main principles of surgical treatment of craniosynostosis involve removal of the abnormal suture through a craniectomy or craniotomy, followed by reconstruction of the calvarium and/or orbit to overcome the cranial deformity and optimize the chance for normal cranial development. The surgery most often is done in conjunction with a pediatric neurosurgeon and a plastic surgeon. Patient positioning varies, depending on the approach to the craniectomy, and is generally prone for sagittal and lambdoidal synostosis and supine for coronal and metopic synostosis. Another surgical principle important for synostosis surgery is to minimize intraop blood loss. The surgical team should make every effort to reduce blood loss during the procedure by infiltrating the scalp with 1:400,000 epinephrine, using point electrocautery, preserving the pericranium, and fastidiously waxing the bone edges. The most common skin incision is a bicoronal opening that allows for access to the entire calvarium. The extent of the bone removal and reconstruction varies, depending on the type and number of sutures involved. Surgical correction of patients with Crouzon or Apert syndromes is often staged with correction of the cranial component, followed by a later procedure for the face, as described by Tessier and colleagues. Invariably, blood loss occurs from the scalp and bone, and the surgeon must remain mindful of the volume contained within the surgical field and readily communicate to the anesthesiologist when bleeding is felt to be either continuous or excessive. Injury to the underlying dural venous sinuses is rare, but the potential for catastrophic blood loss is great. Recent advances in endoscopy have led to the development of minimally invasive techniques for craniosynostosis in some centers, and reports suggest that use of the endoscope may reduce blood loss. Recombinant erythropoietin administered preop also has been studied in an attempt to reduce the need for intraop transfusion associated with repair of craniosynostosis. Rarely are subgaleal or epidural drains placed at the close of the procedure. The patient is monitored closely in the PICU for postop bleeding that may require additional transfusions in the 1st 24 h after surgery. In healthy infants, hematocrit values of 21-23 are tolerated, reducing the need for and amount of blood transfusion.

Usual preop diagnosis: Craniosynostosis (sagittal, coronal, metopic, lambdoidal); craniofacial dysmorphism; Apert syndrome; Crouzon syndrome; Pfeiffer syndrome; Saethre-Chotzen syndrome

▪ SUMMARY OF PROCEDURE

Position	Supine or prone (less common); or table 180°
Incision	Bicoronal, biparietal, Meisterschnitt, midsagittal
Special instrumentation	Midas Rex craniotome; absorbable plates and screws, Colorado needle
Unique considerations	↑ ICP and/or hydrocephalus may coexist. ↑ ICP is usually seen with multiple-suture synostosis; it rarely occurs in single-suture craniosynostosis (< 5-10%). Hydrocephalus typically is seen in monogenic conditions (e.g., Apert, Crouzon). Most neurosurgeons shunt the hydrocephalus and treat the ↑ ICP prior to craniosynostosis surgery.
Antibiotics	Vancomycin (15 mg/kg) or ceftriaxone (25-50 mg/kg; do not mix with Ca⁺⁺-containing solutions) for cranial surgery. Vancomycin or cefotaxime (50 mg/kg) for craniofacial surgery involving nasal sinuses (for 1 mo or 50 kg).
Closing considerations	Watch for ↑ blood loss from the scalp. To prevent excessive blood loss, reapproximate only one portion of the scalp at a time.
EBL	Highly variable; must be minimized. Amount depends on the preoperative condition, number of sutures involved, age of the patient, and magnitude of the repair. Operative injury to the venous sinuses may be catastrophic if hemostasis cannot be achieved or volume loss is excessive.
Postop care	PICU. Postop Hct/Hb levels required. If significant blood loss occurs during surgery, INR and coagulation parameters should be obtained. Blood transfusion is often necessary in infants (< 10 kg) or if Hct is between 21 and 23.
Mortality	< 1-2%
Morbidity	Meningitis Infection CSF rhinorrhea Pseudomeningocele formation due to unrecognized dural tear ↑ ICP (2° skull reshaping) Venous thrombosis or injury Neurological injury: Rare
Pain score	1-3

ANESTHETIC CONSIDERATIONS

PREOPERATIVE

Surgeons can repair the same craniosynostosis in several ways. It can range from a minor (endoscopic) to moderate (strip craniotomy) to major (cranial vault remodeling) surgery. If a surgeon chooses to perform less than a complete cranial vault remodeling, there is a higher possibility that a revision may be necessary in the future. The anesthetist must fully understand the surgeon’s plan to prepare for the issues that are more common with major surgery. The main issues are airway management and bleeding. Management of these issues is made more difficult because the repair is usually performed during the first 6 months of life.

Airway/Respiratory	Patients with craniosynostosis are often challenging intubations. Special considerations should be taken to ensure that their skull is well positioned prior to induction of anesthesia. Because Crouzon and Apert’s syndrome are associated with midface hypoplasia, the patient should be carefully evaluated for a difficult airway, and preparations should be made if one is anticipated. This may include FOI or Video laryngoscope.
Neurological	Presenting Sx in infants with craniosynostosis include progressive head deformation, progressively increasing irritability, crying, failure to eat, and failure to grow in head circumference. These Sx may be due in part to ↑ ICP. On physical examination, one or more of the cranial sutures are fused. Infants with other types of craniofacial deformity usually have no Sx related to their abnormalities.
Laboratory	Tests as indicated from H&P. Preop Hct, Hgb, platelets, INR
Premedication	Premedication is generally not necessary because the surgery is generally performed on infants. However, if necessary, midazolam 0.5 mg/kg can be used (see p. D-1), and sedatives may be contraindicated in the patient with ↑ ICP.

INTRAOPERATIVE

Anesthetic technique: GETA. The room and the bed should be kept warm prior to incision because the time from induction to draping may be extensive for line placement. Infants can unexpectedly cool rapidly during this period resulting in coagulopathies. There is no role for intraoperative cooling (neuroprotection) in craniosynostosis repair.

Induction	Standard pediatric induction (see p. D-1). Tape the tube firmly in place at one side of the mouth using benzoin adherent. Some surgeons like to suture the ETT in place. Verify ETT placement after the patient is in final position (see p. D-2). In prone patient, the anesthesia is usually placed in a horseshoe and not pinned for this procedure. For supine cases, the surgery usually involves reflection of the scalp down over the eyes and nose. Cornea shields or suturing the eyelids shut is preferred over eye tape.
Maintenance	Standard maintenance (see p. D-2). Muscle relaxation is useful during line placement and positioning. The surgeon may request mild hypotension during the removal of the bone flap to minimize bleeding. Hyperventilation to PCO₂ of 30 is often desired to lower the ICP at the beginning of the case.
Emergence	If the case is uncomplicated, the patient is extubated and goes to PICU for observation. In the rare situation that large amounts of blood products are transfused, extubation should be handled with care, as facial and airway swelling may result in airway compromise or loss of airway. Leave intubated if in doubt. If the ETT or eyes are sutured shut, the suture should be removed prior to extubation.
Blood and fluid requirements	Mod-to-large blood loss IV: 20-22 ga × 2-3 NS/LR @ 4 mL/kg/h 5% albumin Fluid warmer	Administer crystalloid and blood products as needed. Most of the bleeding is occult (lost in the drapes and sponges), and so it is not uncommon to begin transfusion pRBCs during incision to avoid getting behind. Correct any intraoperative coagulopathies. Aggressive transfusion must be tempered to prevent increased ICP. A tight dura may result in risk of dural sinus injury or get in the way of replacing the bone flaps. Tranexamic acid (TXA) 50 mg/kg followed by infusion of 5 mg/kg/hr has been shown to decrease blood loss.
Monitoring	Standard monitors (see p. D-1). ± Foley catheter ± Doppler ± Arterial line ± CVP line	Surgery is rarely done in sitting position so life-threatening venous embolism is rare. Due to the young age of these patients, a central line may be difficult. Some surgeons feel that an IJ central line may decrease venous drainage in infants. ↑ K⁺ and ↓ Ca⁺⁺ may occur with transfusions of blood products.
Positioning	OR table usually rotated 180°. [check mark] and pad pressure points [check mark] eyes	Prevent compression to the patient’s thorax by placing a Mayo stand over the chest area.
Complications	Major blood loss VAE	Treatment of venous air embolism—notify surgeon who will flood the field with saline, D/C N₂O, attempt to aspirate air from CVP, if present. Lower head of bed, compress jugular veins to decrease the rate of air entry. CPR as needed. PEEP is not recommended and may be deleterious. VAE more likely if dural sinus entered.

POSTOPERATIVE CONSIDERATIONS

Complications

Bleeding

Extubation

Hypovolemia

Significant bleeding may continue in the postop period.

Pain management

Parenteral opioids (see p. E-1). Avoid oversedation.

Fentanyl 1-2 mcg/kg q 60 min or morphine 0.05-0.1 mg/kg q 2 h.

Tests

Hct/Hb

Coagulation parameters

Hct/Hb levels are necessary to determine adequacy of blood replacement. Monitor closely for hypovolemia.

Suggested Readings

1. Bissonnette B, Brady KM, Wasley RB: Anesthesia for neurosurgical procedures. In: Gregory GA, Andropoulos DB eds. Pediatric Anesthesia, 5th edition. Wiley-Blackwell, Oxford: 2012, 540-569.

2. Dahmani S, et al: Perioperative blood salvage during surgical correction of craniosynostosis in infants. Br J Anesth 2000; 85(4): 550-5.

3. Fearon JA: Reducing allogenic blood transfusions during pediatric cranial vault surgical procedures: a prospective analysis of blood recycling. Plast Reconstr Surg 2004; 113(4):1126-30.

4. Fearon JA, Weinthal J: The use of recombinant erythropoietin in the reduction of blood transfusion rated in craniosynostosis repair in infants and children. Plast Reconstr Surg 2002; 109(7):2190-6.

5. Goobie SM, Meier PM, Pereira LM, et al: Effect of tranexamic acid in pediatric craniosynostosis surgery: a double-blind, placebo-controlled trial. Anesthesiology 2011; 144(4):862-71.

6. Hoffman HJ: Congenital malformations of the spine and skull. In: Goldsmith HS, ed. Practice of Surgery. Harper & Row, New York: 1980.

7. Jimenez DF, Barone CM, Cartwright CC, et al: Early management of craniosynostosis using endoscopic-assisted strip craniectomies and cranial orthotic molding therapy. Pediatrics 2002; 110:97-104.

8. Tessier P: Relationship of craniostenoses to craniofacial dysostoses and to faciostenoses: a study with therapeutic implications. Plast Reconstr Surg 1971; 48(3):224-37.

9. Vavilala MS, Soriano SG: Anesthesia for neurosurgery. In: Davis PJ, Cladis FP, Motoyama EK, eds. Smith’s Anesthesia for Infants and Children, 8th ed. Elsevier, Philadelphia: 2011, 713-45.

CLOSURE OF MYELOMENINGOCELE

SURGICAL CONSIDERATIONS

Description: Myelomeningocele is a neural tube defect characterized by failure of the spinal cord to fuse posteriorly during primary neurulation. This results in an open neural placode joined to the incomplete epithelial defect, usually located in the thoracolumbar spine, and rarely in the cervical spine. Associated CNS conditions are hydrocephalus and Chiari II hindbrain malformation, both of which usually contribute more to long-term morbidity than to the spinal cord defect itself. The presence of the myelomeningocele may be detected before birth by high-resolution ultrasound and/or elevated maternal serum alpha fetoprotein, as well as fetal MRI scans. The incidence of neural tube defects is declining in the United States, possibly due to maternal dietary folate supplementation and prenatal Dx and selective termination.

The fundamental goals of surgery are preservation of neural tissue, reconstitution of a normal intrathecal environment, and complete skin closure to prevent a spinal fluid leak and meningitis. Despite a very thin parchment of dystrophic epithelium attached to the placode, most myelomeningoceles leak spinal fluid from the time of birth.
Because of the risk of ventriculitis associated with the exposed subarachnoid space, closure of the myelomeningocele is recommended within 72 h after birth. Infants with neural tube defects have a higher incidence of other congenital anomalies, including neurogenic bladder and bowel, hydronephrosis, malrotation of the gut, VSD or ASD, and craniofacial disorders. The neonate should be screened for these potential abnormalities before undergoing surgery and, in general, this can be accomplished within 24 h after birth. During the procedure, the child is in the prone position. The defect is dissected so that the various anatomic layers can be separated. The edges of the placode (spinal cord) are mobilized from the adjacent epithelium and often imbricated to form a closed tube. The laterally displaced dura is dissected from the fascia and closed over the spinal cord, thus reconstituting the elements of the spine, except for the lamina defect that is not reconstructed. The paraspinous muscle and fascia are mobilized as a separate layer and the subcutaneous and skin layers comprise the final layer. In cases of large defects, local skin or myocutaneous flaps may be necessary to cover the spinal defect adequately. Progressive hydrocephalus usually presents within days to weeks after closure of the myelomeningocele, but ˜15% of patients will present at birth with significant hydrocephalus that requires early insertion of a VP shunt. Finally, in rare circumstances, prominent vertebral angulation, or kyphosis, at the defect could necessitate vertebrectomies to reestablish normal spinal alignment, usually at an older age.

Variant procedure or approaches: The efficacy of intrauterine myelomeningocele repair is currently being explored through a randomized multicenter trial, and the results may alter future approaches in favor of intrauterine closure if the incidence of hydrocephalus and neurologic deficit is reduced in these patients.

Usual preop diagnosis: Myelomeningocele; myeloschesis; meningocele; myelodysplasia; spina bifida aperta

▪ SUMMARY OF PROCEDURE

Position	Prone with rolls under chest and hips
Incision	Surrounding the defect, preserving skin that can be utilized in the closure. Use of plain lidocaine (0.25%) local anesthetic decreases blood loss.
Special instrumentation	Loupes or operating microscope
Unique considerations	Concomitant hydrocephalus, lower brain stem dysfunction. Need for blood replacement rare in straightforward cases. Latex precautions should be used in all cases (p. G-1).
Antibiotics	Ceftriaxone (50 mg/kg iv), do not infuse with Ca⁺⁺-containing solutions; vancomycin (15 mg/kg iv, infuse over 60 min)
Surgical time	1.5-3 h
Closing considerations	Skin closure may be complex and require rotation of flaps or aid of plastic surgeon.
EBL	Negligible-25 mL (in most cases)
Postop care	Neonatal nursery. Postop, child often nursed on stomach or side. Head size and head ultrasound are used to monitor for development of progressive hydrocephalus, which may require shunting.
Mortality	Approaching zero
Morbidity	Meningitis/ventriculitis Hind brain dysfunction Wound infection CSF leak Apnea, vocal cord paralysis
Pain score	3-5

▪ PATIENT POPULATION CHARACTERISTICS

Age range	Newborn (diagnosed at birth)
Male:Female	˜1:1
Incidence	1/1000 live births
Etiology	Congenital
Associated conditions	Hydrocephalus; lower extremity weakness; bowel and/or bladder dysfunction (neurogenic bladder) and/or hydronephrosis; scoliosis; Chiari II malformations; congenital cardiac anomalies **NB: Latex allergy is increased in this population. Latex precautions should be used beginning with the 1st operation. See Appendix G.

ANESTHETIC CONSIDERATIONS

PREOPERATIVE

Myelomeningoceles are congenital abnormalities of the spinal cord that result in a saccular protrusion near the base of the spine. The sac, containing neural elements and CSF, can vary in size from very small to a volume that occupies the whole lower spinal region. The Dx may be suspected from maternal alpha-fetoprotein screening, fetal ultrasound, or prenatal MRI and is confirmed at birth. It is generally believed that immediate repair of the sac and covering of the defect with skin is desirable to preserve neurological function and avoid infections. These newborns, therefore, usually are brought to surgery within 24-72 h after birth.

Cardiovascular	May have associated congenital anomalies. Test: ECHO
Neurological	Although difficult to assess at this age, newborns may have motor and/or sensory deficits in the lower extremities, neurogenic bladder, and lower cranial nerve dysfunction. Most have an Arnold-Chiari malformation, which requires a ventriculoperitoneal shunt after the myelomeningocele repair.
Renal	May have associated congenital anomalies. Tests: Renal ultrasound
Laboratory	Routine preop studies
Premedication	None necessary
Other NB:	Latex precautions for all patients (beginning from birth). See p. G-1.