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12. PEDIA TRIC NEUROSURGERY Jodi L. Smith ommon pediatric neurosurgical problems trea ted by neurosurgeons will be included on the American Board of Neurological Surgery (ABNS) Oral Board Examination. Therefore, one should be familiar with the neurosurgical management of such problems, which include disorders of cerebrospinal fluid (CSF) dynamics, congenital cranial and spinal malforma tions, tumors, vascular congenital and acquired disorders, intracranial and spinal infections, and intractable epilepsy. Neurological disorders that mimic pediatric neurosurgical conditions may also be on the examination. In this chapter, clinical vignettes comprising common pediatric neurosur gical conditions will be presented, including hydroceph alus, myelomeningocele, intraventricular hemorrhage (IVH) of prematurity, craniosynostosis, and posterior fossa tumors. Actual clinical encounters seen in the pediatric emer gency department, clinic, or hospital are simulated on the examination. The board candidate (i.e., examinee) will be given the history, physical examination, pertinent imaging studies, and test results and will then be expected to provide a rational differential diagnosis and plan of management, outline the risks of surgery and describe the operation if proposed, and handle intraoperative and postoperative complications that occur. The examinee should also understand and be able to discuss the natural history of the problem that is being tested. Many conditions in pediatric neurosurgery can be approached in different ways. T reatment modalities are influenced by neurosurgical training and experience, geo graphical location, and available resources. Oral Board examiners realize this and are interested in responses that reflect the best evidence, the most extensive experience, and the safest approach. References at the end of this chapter provide information regarding the various management strategies available for common pediatric neurosurgical diseases. CASE 1 HISTORY AND PHYSICAL EXAMINA TION Y ou are covering for your pediatric neurosurgery partner, who is on a well- deserved 2- week vacation, when you are called by the neonatal intensive care unit (NICU) to eval uate and treat a 1- hour- old male infant with spina bifida (SB) born by cesarean delivery at 37 + 6 weeks estimated gestational age with a birth weight of 4.95 kg. At birth, he received stimulation and brief blow- by oxygen for cyanosis. At the time of your examination, he is awake, alert, and in no acute distress. He is on room air. He has severe macro cephaly, frontal bossing, scalp vein distention, and cranial suture diastasis. His anterior fontanelle (AF) is convex and tense. His head circumference (occipital frontal circumference [OFC] is 50 cm. He moves his extremities and with draws to tickle in all four extremities. He flexes and extends his hips and knees bilaterally but has weak ankle dorsiflex ion and no plantar flexion bilaterally. His back reveals an open neural tube or myelomeningocele defect (Figures 12.1 and 12.2). IMAGING STUDIES Imaging studies reveal extreme hydrocephalus with severe dilation of the lateral ventricles and complete effacement of the sulci. The cerebral cortex is extremely thinned and is compressed against the inner table of the calvarium (Figure 12.3). ANALYSIS OF CASE AND SURGICAL PLAN Myelomeningocele defects result from incomplete devel opment of the primary neural tube.

h severe dilation of the lateral ventricles and complete effacement of the sulci. The cerebral cortex is extremely thinned and is compressed against the inner table of the calvarium (Figure 12.3). ANALYSIS OF CASE AND SURGICAL PLAN Myelomeningocele defects result from incomplete devel opment of the primary neural tube. This, in turn, results in protrusion of malformed neural tissue and meninges through an opening in the vertebral arches, muscle, fascia,

h severe dilation of the lateral ventricles and complete effacement of the sulci. The cerebral cortex is extremely thinned and is compressed against the inner table of the calvarium (Figure 12.3). ANALYSIS OF CASE AND SURGICAL PLAN Myelomeningocele defects result from incomplete devel opment of the primary neural tube. This, in turn, results in protrusion of malformed neural tissue and meninges through an opening in the vertebral arches, muscle, fascia, 136 • G OODMAN ’S N EUROSURGERY O RAL B OARD R E v IEW and skin with associated loss of motor and sensory function below the level of the defect. In addition, most neonates have associated malformations, including hydrocephalus, Chiari II malformation, orthopedic deformities of their lower extremities, and urogenital anomalies from involve ment of sacral nerve roots. Preoperative Evaluation Neonates with SB present with a sac- like protrusion con taining a neural placode and CSF ventral to the placode. Examination should include measurement of the OFC as well as assessment of general vigor (especially cry and suck); upper and lower extremity motor and sensory function; anal sphincter function; site, level, and size of the myelomeningocele defect; and orthopedic deformities, such as club feet and kyphosis and scoliosis. One should also look for signs and symptoms of hydrocephalus and Chiari II mal formation. The neonate in this case has at least two major problems that must be treated:  myelomeningocele defect and extreme hydrocephalus. Myelomeningocele closure in a newborn is relatively straightforward. Key aims of this procedure include the preservation of neurological function, detection of asso ciated anomalies, and prevention of postoperative com plications, with early closure representing an important component of initial management. Closure may be delayed up to 72 hours without an increase in complications. Preoperatively, the patient should be maintained in a prone position to prevent rupture of the myelomeningocele sac and trauma to the neural placode. The defect should be covered with a sterile, saline- soaked gauze to prevent desiccation of the exposed neural tissue. T o prevent rapid evaporation of the saline, the dressing is covered with a plastic wrap, and sterile saline is trickled onto the gauze at a rate of 3 mL/ hr. Intravenous fluids are started, and systemic anti biotics (e.g., ampicillin and gentamicin) are given. A head ultrasound is obtained to evaluate for hydrocephalus. The goal of surgery is anatomic reconstruction of the defect, closing the neural placode into a neural tube to establish a microenvironment conducive to neuronal function. The exposed neural tissue is functional and should be preserved. This requires preservation of the vascular supply to the placode, which passes through the laterally reflected dura to supply the myelomeningocele.

osing the neural placode into a neural tube to establish a microenvironment conducive to neuronal function. The exposed neural tissue is functional and should be preserved. This requires preservation of the vascular supply to the placode, which passes through the laterally reflected dura to supply the myelomeningocele. Procedure: Myelomeningocele Closure Closure of the myelomeningocele defect involves the fol lowing steps: (1) separation of the neural placode from the skin by first making an incision at the junction of the normal and abnormal thin skin around the entire circumference of the myelomeningocele; (2) separation of the placode from the abnormal thin skin to prevent formation; (3)  pial- topial closure of the placode into a tube using interrupted 7- 0 nylon sutures (Figure 12.4); (4) disconnection of the dura at its most lateral extent where it is attached to the underside of the skin lateral to the open skin edge, leaving a small rim of dura attached to the skin edge, which will strengthen the skin edge and aid in skin closure; (5) watertight closure of the dura around the newly created neural tube, without constricting the underlying neural tissue or interfering with its vascular supply, using a running 6- 0 silk suture (Figure 12.5); (6) mobilization and midline approximation of lateral paraspinous muscles and fascia if possible; (7) surgical correction of any significant kyphotic deformity if present; (8) mobi lization of the skin, including the subcutaneous layer; and (9)  tension- free closure of the skin in the midline with interrupted or running 5- 0 nylon sutures (Figure 12.6). The timing of CSF diversion is controversial and depends on the severity of the hydrocephalus. More than Figure 12.1 One- hour- old male infant born at 37 + 6 weeks with a lumbosacral myelomeningocele defect and severe hydrocephalus with associated macrocephaly. Figure 12.2 Lumbosacral myelomeningocele defect in a 1- hour- old male infant born at 37 + 6 weeks.

al and depends on the severity of the hydrocephalus. More than Figure 12.1 One- hour- old male infant born at 37 + 6 weeks with a lumbosacral myelomeningocele defect and severe hydrocephalus with associated macrocephaly. Figure 12.2 Lumbosacral myelomeningocele defect in a 1- hour- old male infant born at 37 + 6 weeks. PEDIA TRIC NEUROSURGERY • 137 85% of infants with SB develop hydrocephalus. Identifying impending hydrocephalus can help achieve optimal neurological function. The goal is to maintain appropriate ven tricular system pressure and CSF volume. The patient in this case has obvious severe hydrocephalus (see Figures 12.1 and 12.3) and would benefit from shunt placement at the time of myelomeningocele repair to reduce the risks for CSF drainage and wound breakdown postoperatively. Procedure: Shunt Placement After informed consent is obtained and a time- out per formed, intravenous access is achieved, cardiopulmonary monitoring is established, the patient is intubated, and general anesthesia is induced. In an infant with extreme hydrocephalus requiring shunt placement, one could use a fixed medium or high pressure or a programmable type of shunt valve and either a frontal or occipital approach. If a right occipital approach is chosen, the infant is positioned supine with the head turned to the left, a gel donut placed under the head, and a gel roll placed under the shoulders bilaterally posteriorly. All pressure points are carefully padded. T wo linear incision sites are marked— one in the right occipital region 3 cm lateral to the midline and 1 cm supe rior to the lambdoid suture and the other one in the abdominal midline 2 fingerbreadths inferior to the xiphoid process. The entire area between and including the two incision sites is prepared and draped in a sterile fashion. Before opening Figure 12.3 Axial head computed tomographic scans (A and B) showing extreme hydrocephalus with severe dilation of the lateral ventricles and a thin rim of cortical mantle in a 1- hour- old male infant born at 37 + 6 weeks with a myelomeningocele defect. Figure 12.4 Anatomic reconstruction of the placode into a tube using interrupted 7- 0 nylon sutures. Figure 12.5 Closure of the dura around the newly created neural tube using a running 6- 0 silk suture.

and a thin rim of cortical mantle in a 1- hour- old male infant born at 37 + 6 weeks with a myelomeningocele defect. Figure 12.4 Anatomic reconstruction of the placode into a tube using interrupted 7- 0 nylon sutures. Figure 12.5 Closure of the dura around the newly created neural tube using a running 6- 0 silk suture. 138 • G OODMAN ’S N EUROSURGERY O RAL B OARD R E v IEW the incisions, a prophylactic antibiotic is administered (e.g., cefazolin [Kefzol], 25 mg/ kg). The incisions are infiltrated with 0.25% bupivacaine (Marcaine) with 1:200,000 U of epinephrine and then opened with a No. 15 scalpel blade. The midline abdominal incision is made and the fascia is opened in the midline to expose the preperitoneal space. The peritoneum is identified, grasped with forceps or a hemostat, and opened with scissors. Entrance into the peritoneal cavity is confirmed with a No. 4 Penfield, and the peritoneum is retracted with microhemostats. The dura is cauterized and opened, and an antibioticimpregnated ventricular catheter is passed into the occipital horn of the right lateral ventricle. The length of the cath eter is determined before placing the catheter by measuring the patient’s head from the entry site in the right occipital region to just past the right coronal suture. This will place the tip of the ventricular catheter within the frontal horn of the lateral ventricle. CSF is sent for routine studies, including cell count, differential, culture and sensitivity, Gram stain, glucose, and protein. The ventricular catheter is secured to the shunt reservoir with a 3- 0 silk tie. The distal shunt tubing is examined for CSF flow, and the tubing is passed into the peritoneal cavity. Of note, more recently, fetal surgery has been advo cated as a means of improving neurologic outcome based on the results of the Management of Myelomeningocele Study (MOMS) trial. This study compared the outcomes of in utero myelomeningocele repair with standard postnatal repair. In this trial, prenatal surgery for myelomeningocele reduced the need for shunting and improved motor out comes at 30 months. However, this procedure was associ ated with both maternal and fetal risks (e.g., increased risk for preterm delivery and uterine dehiscence at delivery). Moreover, the risk for recurrent tethered spinal cord in children who have undergone this method of myelomeningocele closure is currently unknown. Infants with SB may also present with a symptomatic Chiari type II malformation. Chiari II malformations can cause deterioration of respiration, swallowing, and overall neurological functioning. This can be an important cause of death for patients with SB. Chiari II malformations consist of a spectrum of abnormalities, including lacunar skull (i.e., thinning and scalloping of the calvarium producing a “copper- beaten” appearance), small posterior fossa, lowlying transverse sinus and torcular Herophili, fenestrated falx, heart- shaped tentorial incisura with upward hernia tion of the cerebellum, medullary kinking, beaking of the tectal plate, prominence of the massa intermedia, enlarge ment of the suprapineal recess, elongation of the fourth ventricle, syringohydromyelia, and downward displacement of the cerebellar vermis, fourth ventricle, medulla, and pons through the foramen magnum (Figure 12.7). Neonates with symptomatic Chiari II malformation present with inspira tory stridor, apnea, dysphagia or nasal regurgitation, aspiration, weak or absent cry, weakness or spasticity in the upper or lower extremities, and opisthotonic posturing. Older children and adolescents have a more insidious presenta tion with syncopal episodes, nystagmus, oscillopsia, lower cranial nerve palsies, hyperreflexia, and spastic quadripa resis.

regurgitation, aspiration, weak or absent cry, weakness or spasticity in the upper or lower extremities, and opisthotonic posturing. Older children and adolescents have a more insidious presenta tion with syncopal episodes, nystagmus, oscillopsia, lower cranial nerve palsies, hyperreflexia, and spastic quadripa resis. T reatment consists of surgically decompressing the posterior fossa and upper cervical spinal canal (typically a bony decompression only because of the low- lying torcular Figure 12.6 T ension- free closure of the skin in the midline with interrupted or running 5- 0 nylon sutures. Figure 12.7 Sagittal brain magnetic resonance image in a child with spina bifida showing findings of a Chiari II malformation.

pinal canal (typically a bony decompression only because of the low- lying torcular Figure 12.6 T ension- free closure of the skin in the midline with interrupted or running 5- 0 nylon sutures. Figure 12.7 Sagittal brain magnetic resonance image in a child with spina bifida showing findings of a Chiari II malformation. PEDIA TRIC NEUROSURGERY • 139 region) after making certain that the patient’s shunt is functioning appropriately. Symptomatic Chiari II malforma tions need prompt neurosurgical intervention. COMPLICA TIONS T wo relatively common potential complications of myelomeningocele repair are CSF drainage and postoperative wound breakdown. CSF drainage most often results from untreated hydrocephalus and requires CSF diversion by means of ventricular shunt placement. W ound breakdown frequently results from a tight skin closure leading to com promise of the vascular supply. W ound dehiscence is managed most effectively with wet- to- dry dressing changes, which facilitate wound healing by secondary intention. Several complications can occur with shunting, and these are discussed in Case 5. CASE 2 HISTORY AND PHYSICAL EXAMINA TION After finishing with the myelomeningocele repair and shunt placement in the baby with spina bifida discussed, you were called back to the NICU to see another baby. Specifically, the NICU attending called you for a consul tation on an adorable 950- g, 28- day- old former 24- week preterm male infant with increasing ventriculomegaly and OFC in the face of a grade III IVH of prematurity. He required high- flow oscillatory ventilation for about 4 days after birth followed by conventional ventilatory support for about 2 weeks. He was on continuous positive airway pressure (CPAP) when the consultation was requested. In addition to the increase in OFC, he has been having frequent episodes of apnea and bradycardia, and his AF has become more convex. On examination, his cranial sutures are split more than 1 cm, his OFC is 28 cm (up from 27 cm 2 days ago), and he has frontal bossing, scalp vein distention, and a bulging and convex AF . He is on CPAP. He is moving all extremities well with good strength and withdraws his extremities to noxious stimulation. He has mildly increased tone throughout his extremities bilaterally. IMAGING STUDIES The patient’s initial head ultrasound (HUS) shortly after birth revealed a small cystic structure near the caudotha lamic groove of unknown etiology but concerning for pos sible hemorrhage. His ventricles and cisterns were normal for age at that time. However, follow- up head computed tomography (CT) 1 week later revealed grade III IVH bilaterally and mild ventriculomegaly. Another HUS the following week revealed stable grade III bilateral IVH without evidence of blood in the brain parenchyma. The lateral ventricles remained dilated but were stable in size and shape. One more HUS was obtained 1 week later (i.e., on the day the consultation was requested) because of increasing OFC. This showed hydrocephalus with a marked increase in the size of the lateral, third, and fourth ventricles (Figures 12.8). The scan also showed retraction of the clot within the lateral ventricles and no evidence of parenchymal hemorrhage. ANALYSIS OF CASE AND SURGICAL PLAN IVH or hemorrhage into the germinal matrix (GM) tis sues of the developing brain with possible rupture into the ventricular system and brain parenchyma occurs primarily Figure 12.8 Axial head ultrasound views of a former 24- week preterm male infant with a grade 3 intraventricular hemorrhage (IVH) of prematurity at 17 days of age (A) and at 28 days of age  (B).

(GM) tis sues of the developing brain with possible rupture into the ventricular system and brain parenchyma occurs primarily Figure 12.8 Axial head ultrasound views of a former 24- week preterm male infant with a grade 3 intraventricular hemorrhage (IVH) of prematurity at 17 days of age (A) and at 28 days of age  (B). 140 • G OODMAN ’S N EUROSURGERY O RAL B OARD R E v IEW in premature infants. The GM is a highly vascular tissue layer in the developing brain that gives rise to future neu rons and glial cells. It is located beneath the ependymal lining of the lateral ventricles. The GM, which receives a disproportionate amount of the total cerebral blood flow (CBF) through immature and fragile periventricular capil laries with impaired autoregulation, undergoes involution until 36 weeks’ estimated gestational age. It is susceptible to hypotension and hypoperfusion, which can lead to infarction and then disruption. Increased cerebral perfu sion pressure (CPP) in conjunction with increased CBF and hypoxia is the common denominator for most of the risk factors for IVH of prematurity, which include rapid volume expansion, seizures, pneumothorax, cyanotic heart disease (e.g., patent ductus arteriosus), anemia, hypoglyce mia, blood pressure fluctuations, and infants on mechani cal ventilatory support. Other risk factors include younger gestational age, low birth weight, acidosis, hypercapnia, increased venous pressure, and coagulopathy. There is a direct correlation between younger gestational age and the severity of periventricular- intraventricular hemorrhage in premature infants. Optimal neonatal care with an empha sis on measures that minimize CBF variations is crucial to reducing the incidence of these hemorrhages in premature infants. The grading system that is most commonly used to describe periventricular- intraventricular hemorrhage in premature infants is that reported by Papile and colleagues. This grading system consists of four grades of hemor rhage: I, subependymal; II, IVH without ventricular dila tion; III, IVH with ventricular dilation; and IV , IVH with parenchymal hemorrhage. Procedure The infant in this case has symptomatic hydrocephalus related to a grade III IVH. He required an emergent ven tricular tap because of frequent apneic and bradycardic events along with increased fullness of the AF . In a premature infant, a ventricular tap is done with a 22- or 25- gauge 1.5- inch spinal needle in the frontal region on the side with the largest frontal horn using sterile technique after a timeout has been performed. Care is taken when aspirating CSF to hold the needle still and prevent it from injuring the brain. The amount of CSF aspirated depends on the full ness of the AF . If the CSF is bloody or the infant is too small to accommodate a shunt (i.e., <1.5– 2 kg), a ventricular tap ping reservoir should be placed. Because of symptomatic hydrocephalus in the face of bloody CSF and small body size, the patient in this case subsequently underwent placement of a right frontal ven tricular right- angled 3- cm reservoir and catheter for serial tapping of cerebrospinal fluid. Placement of a ventricular tapping reservoir is typically done in the operating room (OR) under general anesthesia through a linear right frontal incision and bur hole made 3  cm lateral to the midline and just anterior to the coronal suture. Standard external anatomic landmarks are used to pass the catheter into the right frontal horn. A subgaleal pocket is created posterior to the bur hole to accommodate the tapping res ervoir, and the reservoir is secured to pericranium using suture. Daily 10- to 20- mL CSF taps are performed until the CSF clears and the patient is big enough to undergo successful shunt placement.

heter into the right frontal horn. A subgaleal pocket is created posterior to the bur hole to accommodate the tapping res ervoir, and the reservoir is secured to pericranium using suture. Daily 10- to 20- mL CSF taps are performed until the CSF clears and the patient is big enough to undergo successful shunt placement. Alternatively, a ventriculo subgaleal shunt can be created by leaving the reservoir open and allowing CSF to drain into a subgaleal pocket created posterior to the reservoir at the time of shunt placement. About a month later, the patient was taken back to the OR for placement of a right occipital medium pressure ventriculoperitoneal shunt (VPS) system, as described in Case 1. He weighed 1.8 kg at the time of shunt placement and had no history of necrotizing enterocolitis or intraabdominal problems, making him a good candidate for a VPS. COMPLICA TIONS Several complications can occur with shunting, and these are discussed in Case 5. One of the most common com plications observed in preterm infants requiring reservoir placement is breakdown of the skin overlying the reservoir. When this happens, the reservoir must be removed and the wound closed. If subsequent CSF cultures show evidence of infection, intravenous antibiotics are given. Moreover, serial ventricular taps must be performed to treat elevated intracranial pressure until the infection clears and a shunt can be placed. CASE 3 HISTORY AND PHYSICAL EXAMINA TION A 4- month- old male infant has a large abnormally shaped head noticed at birth. The infant was born at 40 weeks’ estimated gestational age by vaginal delivery, weighing 7 lb, 4 oz. There were no problems with pregnancy, labor, or delivery. He has been meeting developmental milestones appropriately. On examination, he has an abnormally elongated head, protuberance of the occiput, frontal bossing, biparietal narrowing, and palpable ridging along the entire

by vaginal delivery, weighing 7 lb, 4 oz. There were no problems with pregnancy, labor, or delivery. He has been meeting developmental milestones appropriately. On examination, he has an abnormally elongated head, protuberance of the occiput, frontal bossing, biparietal narrowing, and palpable ridging along the entire PEDIA TRIC NEUROSURGERY • 141 sagittal suture, and his AF has already closed (Figure 12.9). His neurological examination is normal for his age. IMAGING STUDIES The patient has sagittal craniosynostosis resulting in scaphocephaly (also called dolichocephaly). The diagnosis is made clinically (see Figure 12.9). Although unnecessary and relatively undesirable owing to potential harmful effects of radiation exposure, the diagnosis can also be established radiographically with a plain film of the skull or head CT with or without three- dimensional reconstructions. ANALYSIS OF CASE AND SURGICAL PLAN The cranium consists of several plates of bone separated by sutures— fibrous joints that function by depositing bone at their margins in response to brain expansion. The skull grows to accommodate brain growth, especially during first 2 years of life when brain volume can increase up to three times its size at birth. The cranial sutures must remain open for the skull to grow and achieve its characteristic normo cephalic shape. When one or more cranial sutures close too early, the skull ceases to grow in the direction perpendicular to the closed suture but continues to grow parallel to the closed suture. Craniosynostosis is the term used to describe this condition, and the shape of the skull is altered in a predictable way with recognizable patterns that depend on which suture is fused. The correct treatment of any craniosynostosis requires that a correct diagnosis be made. There are two primary goals of treatment of craniosyn ostosis: (1) to release the fused sutures to allow the brain to grow and expand normally and prevent problems associated with increased intracranial pressure; and (2) to establish the normal contour of the skull and thereby minimize psycho social problems. Premature closure of the sagittal suture as seen in the child presented in this case results in scaphocephaly/ dolichocephaly. Morphologic findings in sagittal synostosis are due to restricted growth of the parietal bones in the plane perpendicular to the fused sagittal suture and compensa tory skull growth parallel to the fused suture at the unfused coronal and lambdoid sutures. This leads to an abnormally long, narrow head with varying degrees of frontal and occipital bossing and a keel- like ridge along the sagittal suture. The type of surgical treatment is based on the patient’s age and the severity and location of the cranial deformity at time of presentation. In the very young infant, irrespec tive of the degree of skull deformity resulting from sagit tal craniosynostosis, surgical techniques that prevent early recurrence of fusion of the parietal bones at the vertex fol lowing bony removal will produce an excellent cosmetic result owing to forces generated by the rapidly growing brain and the ability in early infancy to form new bone (to close the gaps). If the diagnosis is made early (i.e., within first 2– 4 months of life), optimal treatment consists of wide resec tion of the sagittal suture (5  cm), bilateral coronal and lambdoid synostectomies, and biparietal barrel stave oste otomies with bending of the parietal tines of bone outward. Special equipment used in the surgical correction of sagittal synostosis includes at least two large- bore peripheral intravenous catheters, an arterial line, a Foley catheter, a pre cordial Doppler and end- tidal CO 2 monitor to detect air embolism, and a high- speed drill system.

f the parietal tines of bone outward. Special equipment used in the surgical correction of sagittal synostosis includes at least two large- bore peripheral intravenous catheters, an arterial line, a Foley catheter, a pre cordial Doppler and end- tidal CO 2 monitor to detect air embolism, and a high- speed drill system. In addition, the Figure 12.9 Anteroposterior (A) and lateral (B) views of a 4- month- old male infant with scaphocephaly due to premature fusion of the sagittal suture.

f the parietal tines of bone outward. Special equipment used in the surgical correction of sagittal synostosis includes at least two large- bore peripheral intravenous catheters, an arterial line, a Foley catheter, a pre cordial Doppler and end- tidal CO 2 monitor to detect air embolism, and a high- speed drill system. In addition, the Figure 12.9 Anteroposterior (A) and lateral (B) views of a 4- month- old male infant with scaphocephaly due to premature fusion of the sagittal suture. 142 • G OODMAN ’S N EUROSURGERY O RAL B OARD R E v IEW infant should be typed and cross- matched for at least 1 U of packed red blood cells. Procedure Surgical correction of sagittal craniosynostosis can be per formed open or endoscopically. A basic description of the open technique follows. The patient is then turned to a prone position overlying two well- padded gel chest rolls. The head is positioned prone on a well- padded horseshoe head holder, taking care to prevent pressure on the globes. A 2- 0 silk suture is pressed against the scalp just posterior to the coronal suture to create a line extending from ear to ear. This is used as a reference line to mark a scallop- patterned bicoronal incision, taking care to stay well behind the hair line (Figure 12.10). The anterior and posterior scalp flaps are elevated in the subgaleal/ supraperiosteal plane to expose the lambdoid sutures and coronal sutures. Next, the bone cuts are marked by incising the pericra nium with Bovie electrocautery, including a sagittal strip of bone extending 2.5  cm lateral to the midline on both sides, 3 cm posterior to the lambdoid sutures, and 2 to 3 cm anterior to the coronal sutures; the coronal and lambdoid synostectomies; and multiple biparietal barrel stave oste otomies (Figures 12.11). A  high- speed drill is then used to make multiple cuts (Figure  12.12A), beginning with removal of the sagittal strip and followed by removal of the bilateral lambdoid and coronal sutures and adjacent bone in strips measuring roughly 1.5 cm wide × 4 cm long. Next, several barrel stave osteotomy cuts are made within the parietal and extending into the temporal bones bilat erally (Figures 12.12B and C). The tines of bone are then bent outward to expand the patient’s head in the parietal regions bilaterally. This technique permits bitemporal and biparietal cranial growth to resume and leads to an excellent cosmetic result (Figure 12.13). COMPLICA TIONS Serious complications can occur during surgical correction of sagittal synostosis. Detection of possible air emboli war rants immediate flooding of the field with irrigation, lowering the head of the bed, and waxing of all bone edges. It is essential to know the amount of blood that is lost during the procedure and to monitor the coagulation status and platelet count. Give blood products when indicated and promptly replace fluid losses to maintain hemodynamic stability. When possible, dissect in a supraperiosteal plane to minimize blood loss from the bone, and wax all bone edges when cut. Dural lacerations must also be monitored for and repaired to prevent persistent CSF leak. Additional risks include increased blood loss and the need for blood trans fusion intraoperatively, postoperative wound infection with the potential for operative management, injury to the brain, and persistent asymmetry requiring further surgery. CASE 4 HISTORY AND PHYSICAL EXAMINA TION A 16- year- old young man presents to your emergency department with progressively worsening headaches for 10 days and vomiting for 2 days. He has a history of sinus itis, treated with oral antibiotics. On examination, he is neurologically intact except for very mild bilateral upper Figure 12.10 V ertex (A) and lateral (B) views of a scaphocephalic infant positioned prone on a horseshoe head holder for surgery and showing a scalloped- patterned bicoronal incision.

history of sinus itis, treated with oral antibiotics. On examination, he is neurologically intact except for very mild bilateral upper Figure 12.10 V ertex (A) and lateral (B) views of a scaphocephalic infant positioned prone on a horseshoe head holder for surgery and showing a scalloped- patterned bicoronal incision. PEDIA TRIC NEUROSURGERY • 143 extremity dysmetria on finger- nose- finger testing. Imaging studies are presented. IMAGING STUDIES The imaging studies (Figures 12.14) demonstrate a 4.3- × 3.4- × 3.9- cm mass likely arising from the posterior and inferior aspect of the fourth ventricle or cerebellar tonsils. The differential diagnosis includes ependymoma, medulloblas toma, and pilocytic astrocytoma. There is moderate hydrocephalus and compression of the brainstem at the level of the foramen magnum secondary to the mass. ANALYSIS OF CASE AND SURGICAL PLAN Posterior fossa tumors are common in children. Some of the more common posterior fossa tumors include (1) cystic cerebellar astrocytoma (juvenile pilocytic astrocytoma— JPA), typically located medially in the vermis or laterally in the cerebellar hemisphere or peduncle; (2)  medulloblastoma (cerebellar primitive neuroectodermal tumor— PNET), typically arising from the superior medullary velum and growing to fill the fourth ventricle; (3)  ependymoma, typically arising from the floor of the fourth ventricle and extending out the foramina of Luschka into the cerebello pontine angle; and (4)  hemangioblastoma— cystic tumor with mural nodule found most commonly in children with von Hippel- Lindau syndrome (Figure 12.15A). PREOPERA TIVE MANAGEMENT When a child presents with a posterior fossa tumor, it is crucial to obtain brain and full spine magnetic resonance imaging (MRI) (Figures  12.15B and C) with and with out contrast and typically under general anesthesia. These studies enable the neurosurgeon to determine whether the Figure 12.11 V ertex (A) and lateral (B) views of a scaphocephalic infant showing bone cuts marked by incising the pericranium, including a sagittal strip of bone extending 2.5 cm lateral to the midline on both sides, 3 cm posterior to the lambdoid sutures, and 2 to 3 cm anterior to the coronal sutures; coronal and lambdoid synostectomies; and multiple biparietal barrel stave osteotomies. AB C Figure 12.12 Views of a scaphocephalic infant after sagittal strip craniectomy (A), bilateral coronal and lambdoid synostectomies (B), and biparietal barrel stave osteotomies  (C).

and 2 to 3 cm anterior to the coronal sutures; coronal and lambdoid synostectomies; and multiple biparietal barrel stave osteotomies. AB C Figure 12.12 Views of a scaphocephalic infant after sagittal strip craniectomy (A), bilateral coronal and lambdoid synostectomies (B), and biparietal barrel stave osteotomies  (C). 144 • G OODMAN ’S N EUROSURGERY O RAL B OARD R E v IEW tumor arises from the cerebellar hemispheres, vermis, or fourth ventricle and whether the tentorial notch, brainstem, or lateral recesses of the fourth ventricle are involved— information that is key to understanding potential for harm to surrounding tissues and to making appropriate judg ments regarding the extent of tumor removal at the time of surgery. These studies also reveal whether the patient has hydrocephalus and whether there are drop metastases present. In the face of symptomatic obstructive hydrocephalus, the patient often requires emergent CSF diversion, which is accomplished by placement of a frontal external ventricular drain (EVD) according to external anatomic landmarks and sterile technique and tunneled to and secured at a dis tant exit site. In the past, placement of a VPS was advocated as a means of treating symptomatic hydrocephalus in these patients; however, shunts have fallen out of favor recently because they take away the patient’s chance to be shunt independent and expose the patient to potential perils of upward herniation and shunt dependency. If the patient is only mildly symptomatic and surgery is imminent, acet azolamide (Diamox) may be used (25 mg/ kg/ day divided three times daily). In addition, the patient is started on dexamethasone (Decadron; up to 4 mg every 6 hours) along with a histamine- 2 blocker. The patient is typed and crossmatched for 1 to 2 U of packed red blood cells. The parents will ask about prognosis. Prognosis with medulloblastoma depends on age at time of diagnosis (<2  years old with worse prognosis), amount of resection (best prognosis if able to resection all but 1.5  cm 2), and Figure 12.13 Lateral views of a scaphocephalic infant before (A) and 1- month after (B) the sagittal strip craniectomy, bilateral coronal and lambdoid synostectomies, and biparietal barrel stave osteotomies. Figure 12.14 A 16- year- old boy with a 4.3- × 3.4- × 3.9- cm contrast- enhancing posterior fossa mass and associated obstructive hydrocephalus— sagittal (A) and axial (B) views.

nd 1- month after (B) the sagittal strip craniectomy, bilateral coronal and lambdoid synostectomies, and biparietal barrel stave osteotomies. Figure 12.14 A 16- year- old boy with a 4.3- × 3.4- × 3.9- cm contrast- enhancing posterior fossa mass and associated obstructive hydrocephalus— sagittal (A) and axial (B) views. PEDIA TRIC NEUROSURGERY • 145 presence of drop metastases. All patients require adjuvant chemotherapy (and craniospinal radiotherapy if >3– 4 years of age). Recent genomic studies have identified four dis tinct, nonoverlapping molecular variants of medulloblas toma:  WNT, SHH, group C, and group D, each with distinct demographics, clinical presentation, transcrip tional profiles, genetic abnormalities, and clinical outcome. Prognosis with ependymoma depends on the extent of resection; radiotherapy is typically used to treat residual tumor in children older than 3 to 4 years. With cerebellar astrocytoma, gross total removal of the tumor is typically curative, and no adjuvant therapy is required. The timing of surgery depends on the patient’s presenting signs and symptoms. T ypically, the operation is per formed the next operating day after imaging studies have been performed. The operation can be performed either in the prone or sitting position. The prone position minimizes the risk for air embolus. If the sitting position is used, a central venous line should be placed, and a precordial Doppler and end- tidal CO 2 monitor should be used to detect air embolism during the operation. With pediatric patients, the type of head fixation device depends on age and skull thickness. T ypically, a 3- pin skull clamp is used with pediatric pins if the patient is 3 to 7 years of age or adult pins if older than 7 years (Figure 12.16). A  well- padded horseshoe head holder is used for patients who are younger than 3  years, and special care is taken to prevent pressure on the globes. When positioning the patient prone, the neck may be gently flexed to provide better access to the posterior fossa, but one should leave roughly 2 fingerbreadths between the chin and the sternal notch or neck to prevent compromise of venous return. Cranial nerve monitoring may be helpful, especially if the tumor extends out the cerebellopontine angle. An intra venous antibiotic (usually a cephalosporin if the patient is not allergic) is given just before the time of EVD insertion if placed intraoperatively or within 1 hour of making the incision. If an EVD is not inserted preoperatively or in the OR before positioning, it is important to prepare for an occipital bur hole (i.e., 6– 7 cm superior to the inion and 3 cm lat eral to midline) and make sure there is an EVD catheter on the operating field. A midline suboccipital skin incision is made from the external occipital. A craniotomy bone flap is turned, using a high- speed drill with footplate attach ment and extending from below the transverse sinus supe riorly to the foramen magnum inferiorly, after placing bur holes along superior aspect of flap. The lateral extent of the AB C Figure 12.15 Magnetic resonance images of hemangioblastoma in child with von Hippel- Lindau syndrome— brain, axial (A); spine, sagittal (B); spine, transverse  (C). Figure 12.16 A 16- year- old boy with a posterior fossa tumor positioned prone in three- point skull fixation with electrodes in place for intraoperative monitoring of cranial nerves VII to XII on the right.

astoma in child with von Hippel- Lindau syndrome— brain, axial (A); spine, sagittal (B); spine, transverse  (C). Figure 12.16 A 16- year- old boy with a posterior fossa tumor positioned prone in three- point skull fixation with electrodes in place for intraoperative monitoring of cranial nerves VII to XII on the right. 146 • G OODMAN ’S N EUROSURGERY O RAL B OARD R E v IEW craniotomy depends on the size and location of the tumor. Posterior cervical laminectomies are also performed based on the caudal extent of the tumor. The dura is opened in a Y- shaped fashion and tacked up to the adjacent muscle or fascia, and the arachnoid is also opened and tacked up to the dura (Figure 12.17). Opening the arachnoid over the cisterna magna enables CSF to drain and provides relaxation of cerebellum. The tumor is removed, taking care to avoid injuring the floor of the fourth ventricle, the deep cerebellar nuclei, and the middle cerebellar peduncles but with the goal of achieving a com plete resection if safely possible. T o get to midline tumors, one can open the vermis vertically in the midline, open it transversely, or use a tela chorioidea approach, wherein the cerebellar hemispheres are retracted laterally and the vermis is elevated to expose the tela chorioidea (i.e., the arachnoid and blood vessels going to choroid plexus). The dura is closed in a watertight fashion with a patch graft consisting of harvested pericranium or a dural sub stitute, and the bone flap is replaced with titanium micro plates and screws. The incision is closed in multiple layers. Complete excision is the goal for nearly all focal lowgrade astrocytomas or noninfiltrating posterior fossa tumors (Figure 12.18). The initial objective in most cases is brainstem decompression and reduction of tumor bulk. Attachments of tumor to brainstem, cerebellar peduncles, or cranial nerves are usually taken down last using the Figure 12.17 View of a posterior fossa hemangioblastoma after opening the dura. AB C DE F Figure 12.18 Magnetic resonance images from an 8- year- old boy before (A– C) and after (D– F) complete excision of a midline posterior fossa juvenile pilocytic astrocytoma.

or cranial nerves are usually taken down last using the Figure 12.17 View of a posterior fossa hemangioblastoma after opening the dura. AB C DE F Figure 12.18 Magnetic resonance images from an 8- year- old boy before (A– C) and after (D– F) complete excision of a midline posterior fossa juvenile pilocytic astrocytoma. PEDIA TRIC NEUROSURGERY • 147 operating microscope. Care must be taken to avoid injury to the deep cerebellar nuclei, cerebellar peduncles, and floor of the 4th ventricle. All radiographically enhancing tissue should be removed completely— including the cyst wall if it enhances. COMPLICA TIONS There are several complications that can occur with poste rior fossa tumor resections. During the opening of the dura, the surgeon must be ready for possible torrential bleeding from intradural venous lakes or the circular sinus. Such bleeding is typically controlled with cotton patties containing Gelfoam powder soaked in thrombin, hemostatic clips, or oversewing of the dural edge to stop the bleeding. It is essential to know the amount of blood that is lost during the procedure and to monitor the coagulation status and platelet count. Give blood products when indicated and promptly replace fluid losses to maintain hemodynamic stability. Another possible complication that the surgeon must be ready for at all times is venous air embolism. A precor dial Doppler and end- tidal CO 2 monitor help to detect air embolism during the operation. If suspected and a central venous line is present, the anesthesiologist can try to aspirate air through the central venous line. At the same time, the surgeon inspects the field to determine the source of the venous air embolus. Common sites include the diploic space of bone, veins located laterally along the craniocervical junction and between C1 and C2, and the cut edge of muscle. Detection of possible air emboli warrants immediate flooding of the field with irrigation, lowering the head of the bed, and waxing of all bone edges. Jugular venous compression can be performed to decrease venous return and facilitate identification of an air leak by causing bleeding from the site that is the source of entry of air into the systemic circulation. If the end- expired CO2 continues to decrease, the end- expired nitrogen con tinues to increase, or the mean arterial pressure begins to decrease, the wound should be closed rapidly and the patient transported intubated to the intensive care unit for further management. Cerebellar mutism or posterior fossa syndrome is a rare complication of removal of midline cerebellar tumors. The exact mechanism of this syndrome is poorly understood. It involves an array of signs and symptoms, including decreased or absent speech, dysphagia, cranial nerve palsies, decreased motor movement with inability to coordinate voluntary movements, ataxia, and emotional lability. Patients are usually very whiny, irritable, and unable to speak for a period of time after surgery. It can occur immediately or appear in a delayed fashion. It is not uncommon for a child to speak a few words after surgery and then be mute the following day. Cerebellar mutism may be present for up to 3 to 6 months but is usually more short- lived. There are no reported cases in which a child with cerebellar mutism did not get return of functional speech. CASE 5 HISTORY AND PHYSICAL EXAMINA TION A 7- year- old boy presents to your emergency department with persistent headaches and vomiting after sustaining a concussion. He reportedly collided with another child on the playground 5 days before his arrival in the emergency department. On examination, he is awake, alert, and ori ented but has mental slowness. He has bilateral papilledema but no evidence of Parinaud’s syndrome.

sistent headaches and vomiting after sustaining a concussion. He reportedly collided with another child on the playground 5 days before his arrival in the emergency department. On examination, he is awake, alert, and ori ented but has mental slowness. He has bilateral papilledema but no evidence of Parinaud’s syndrome. He has right upper extremity dysmetria on finger- nose- finger testing and is hypersensitive to noise and light. Otherwise, he is neuro logically intact. His imaging studies are presented. IMAGING STUDIES A head CT scan was obtained. The scout revealed splay ing of the coronal suture and multiple craniolacunias (Figure 12.19). The axial cuts on the CT scan showed massive enlargement of his lateral and third ventricles, tran sependymal CSF absorption, and a small aqueduct with calcification in the tectum consistent with a tectal plate glioma (Figure 12.20). A brain MRI scan was subsequently obtained that revealed hydrocephalus secondary to obstruction of the aqueduct resulting from a small tectal plate gli oma (Figure 12.21). Like the head CT, the brain MRI also revealed severe transependymal CSF absorption. ANALYSIS OF CASE AND SURGICAL PLAN The patient has hydrocephalus diagnosed 5 days after sus taining a concussion. With bilateral papilledema, his symptoms are most likely the result of hydrocephalus and not postconcussive. In the case of a child presenting with acute hydrocephalus later like this child, always consider the possibility of tumor or occult infection as the cause. T reatment of hydrocephalus from obstruction of the aqueduct in an older child (2  years or older) can include placement of a shunt or performing an endoscopic third ventriculostomy (ETV). ETV involves the use of a rigid endo scope to create an opening in the floor of the third ventricle

occult infection as the cause. T reatment of hydrocephalus from obstruction of the aqueduct in an older child (2  years or older) can include placement of a shunt or performing an endoscopic third ventriculostomy (ETV). ETV involves the use of a rigid endo scope to create an opening in the floor of the third ventricle 148 • G OODMAN ’S N EUROSURGERY O RAL B OARD R E v IEW just in front of mammillary bodies. This is done through a frontal bur hole. The opening in the floor of the third ventricle is widened with a Fogarty balloon catheter. CSF can flow through this opening into the basilar cisterns and bypass the area of aqueductal stenosis. ETV eliminates the need for a shunt but has failure rates comparable to a shunt. Risks and benefits for each procedure should be explained to the patient’s parents and a decision made as to which surgical procedure is the right procedure for the patient. The child in this case underwent placement of a right parietooccipital programmable shunt with a siphon guard (Figure 12.22). His opening pressure at the time of catheter placement in the OR was more than 56 cm H 2O. The shunt was initially set at 130 mm Hg, and the setting was confirmed with a lateral skull film. The tectal plate glioma was managed conservatively. The patient did very well initially with good ventricu lar decompression and resolution of his preoperative symptoms. However, about 6  months later, he presents with recurrence of his headaches, vomiting, and lethargy. The emergency department calls you to see this child after a head CT showed an interval increase in ventricular size (Figure 12.23). Children with shunt- dependent hydrocephalus require lifelong follow- up to make sure that the shunt is function ing adequately. T wo key points to remember when taking care of children with shunted hydrocephalus are that (1) it is always the shunt, and (2)  the parents are always right. In a child with shunted hydrocephalus who presents with signs and symptoms of hydrocephalus, a shunt malfunc tion must be considered. A  head CT or fast- spin MRI is obtained and must be compared with a similar study from a time when the patient was doing well in order to evalu ate for ventricular enlargement (see Figure 12.23). A shunt series is also obtained to look for kinking or discontinuity of the shunt system (Figure 12.24), catheter malposition, inadequate length of the distal shunt tubing, or a CSF pseudocyst. Remember— if you order a study, look at it— do not Figure 12.19 Head computed tomographic scout film revealing splaying of the coronal suture and multiple craniolacunias in a 7- year- old boy with newly diagnosed, symptomatic, obstructive hydrocephalus. AB C Figure 12.20 Axial head computed tomographic scans from a 7- year- old boy with newly diagnosed, symptomatic, obstructive hydrocephalus showing massive enlargement of his A and B: lateral and C: third ventricles, transependymal cerebrospinal fluid absorption, and a small aqueduct with calcification in the tectum consistent with a tectal plate glioma.

tomographic scans from a 7- year- old boy with newly diagnosed, symptomatic, obstructive hydrocephalus showing massive enlargement of his A and B: lateral and C: third ventricles, transependymal cerebrospinal fluid absorption, and a small aqueduct with calcification in the tectum consistent with a tectal plate glioma. PEDIA TRIC NEUROSURGERY • 149 depend on the radiologist’s interpretation. In the face of ventricular enlargement and symptoms of elevated intra cranial pressure, a shunt malfunction is presumed, and the patient is taken to the OR for shunt exploration and revi sion as indicated. A proximal shunt malfunction is typically associated with precipitous development of elevated ICP so that the shunt should be revised shortly after patient arrives at the hospital. In contrast, most distal shunt malfunctions not associated with a short catheter are due to infection, which can be determined by tapping the shunt and looking for a CSF pseudocyst on the shunt series or abdominal ultra sound or CT (Figure 12.25). Hence, in the face of a distal shunt malfunction, one should look carefully at the CSF before performing a shunt revision to make sure an infec tion is not present. A child with an abdominal pseudocyst will present with worsening incontinence, abdominal distention, and head aches. The head CT typically shows ventricular enlargement consistent with a shunt malfunction related to decreased abdominal CSF absorption. If a CSF pseudocyst is found, consider the shunt infected until proved otherwise. In 70% of patients with a shunt malfunction, there are overt signs of elevated intracranial pressure such as head aches, vomiting, and lethargy, which will progress to stu por, coma, and death if the shunt is not promptly revised. In the other 30%, there are subtle signs of deterioration as the ventricles enlarge over time, which include changes in behavior, chronic daily headaches, and a decline in school performance. Electively lengthen a shunt if the child is known to be shunt dependent from prior shunt malfunctions or if the head CT scan shows slit ventricles (Figure 12.26) or a thick calvarium because both of these features have been shown to be associated with shunt dependency. Never place a connector at the abdominal end of the incision because this will limit the ability of the distal shunt tubing to elongate with Figure 12.21 Brain axial (A) and sagittal (B) magnetic resonance images showing obstruction of the aqueduct resulting from a small tectal plate glioma. Figure 12.22 Axial head computed tomographic scan after placement of a right parietooccipital programmable shunt with a siphon guard.

stal shunt tubing to elongate with Figure 12.21 Brain axial (A) and sagittal (B) magnetic resonance images showing obstruction of the aqueduct resulting from a small tectal plate glioma. Figure 12.22 Axial head computed tomographic scan after placement of a right parietooccipital programmable shunt with a siphon guard. 150 • G OODMAN ’S N EUROSURGERY O RAL B OARD R E v IEW continued growth of the child and will frequently result in separation of the shunt tubing at the site of the connector. If a child has not had any shunt problems previously and is completely asymptomatic with a short shunt, continued observation is recommended, and the shunt is not length ened electively. However, close follow- up is crucial because the child may develop subtle signs of decompensated hydrocephalus. COMPLICA TIONS Several complications can occur with shunting. Shunt tubing is made of silicone elastomers and, as such, can calcify and break over time, especially in the neck above clavicle where there is increased motion (see Figure 12.24). Distal shunt tubing can also erode into abdominal viscera and be seen protruding from the anus. Intraventricular hemor rhage can occur at the time of a proximal shunt revision as the obstructed catheter is removed. Often, choroid plexus is stuck to the fenestrated end of the ventricular catheter and can cause bleeding as the catheter is removed (see Figure 12.26). In this situation, the shunt operation may need to be aborted and an EVD placed until the blood clears from the CSF . Overshunting or overdrainage can lead to the formation of subdural hematomas, craniosynostosis with craniocere bral disproportion, or slit ventricle syndrome. A child suf fering from slit ventricle syndrome (Figure 12.27) typically complains of headaches, nausea, and dizziness, especially when upright and most often later in the day. Shunt infection is another possible complication of shunting. Shunt infection increases the mortality rate and risk for seizures and results in decreased intelligence quo tient (IQ). There is a 2% to 8% incidence of infection with each shunt operation, and 5% to 15% of shunts become infected over the life of the shunt. Shunt infections typi cally occur within the first 6 months after a shunt is placed. Specifically, 70% of shunt infections are diagnosed within the first month after surgery, and 90% within 6 months after Figure 12.23 A, B: Axial head computed tomography scans showing an interval increase in ventricular size concerning for shunt malfunction. Figure 12.24 Lateral skull view of shunt series showing discontinuity of the shunt system.

fections are diagnosed within the first month after surgery, and 90% within 6 months after Figure 12.23 A, B: Axial head computed tomography scans showing an interval increase in ventricular size concerning for shunt malfunction. Figure 12.24 Lateral skull view of shunt series showing discontinuity of the shunt system. Figure 12.25 Head (A, B) and abdominal (C) computed tomographic scans showing a distal shunt malfunction due to a large cerebrospinal pseudocyst. AB C Figure 12.26 A– C: Axial head computed tomographic scans in a patient with shunt-dependent hydrocephalus showing slit ventricles.

fections are diagnosed within the first month after surgery, and 90% within 6 months after Figure 12.23 A, B: Axial head computed tomography scans showing an interval increase in ventricular size concerning for shunt malfunction. Figure 12.24 Lateral skull view of shunt series showing discontinuity of the shunt system. Figure 12.25 Head (A, B) and abdominal (C) computed tomographic scans showing a distal shunt malfunction due to a large cerebrospinal pseudocyst. AB C Figure 12.26 A– C: Axial head computed tomographic scans in a patient with shunt-dependent hydrocephalus showing slit ventricles. 152 • G OODMAN ’S N EUROSURGERY O RAL B OARD R E v IEW surgery. Shunt infection is rare after 6 months. Risk factors for shunt infection include young age, poor skin condition, length of the operation, CSF leak from the incision, num ber of shunt revisions, and concomitant infection, A child with a shunt infection typically presents with increasing irritability, persistent low- grade fever, decreased appetite, and abdominal pain within 2 weeks after shunt placement or revision. The ventricles may be stable on head CT, whereas a CSF pseudocyst may be seen on the shunt series. Fever in the early postoperative period (i.e., <6  months) is concerning for a shunt infection and should be considered as such until proved otherwise. If a shunt infection is suspected, a shunt tap is performed with a 25- gauge butterfly needle using sterile technique, and CSF is sent for routine studies including protein, glucose, cell count and differential, Gram stain, and culture and sensitivities. A CBC, erythrocyte sedimentation rate, and C- reactive protein are also ordered. After CSF has been obtained, broad- spectrum intravenous antibiotics (e.g., vancomycin and cefotaxime) are started. The most com mon organism causing shunt infection is Staphylococcus species. If the white blood cell count is elevated in the CSF or CSF cultures and Gram stain are positive, the child is taken to the OR for complete shunt removal and placement of an EVD and a temporary central venous line. The antibiotics are tapered based on the results of the culture and sensitiv ity studies. CSF is sent until cultures are negative. The child remains externalized on intravenous antibiotics for up to 14 days after the first negative CSF culture. After the infection has been adequately treated, the EVD is removed, and a new shunt is placed. BIBLIOGRAPHY Adzick NS, Thom EA, Spong CY, et  al. A randomized trial of prena tal versus postnatal repair of myelomeningocele. N Engl J Med . 2011;364(11):993– 1004. Albright AL, Pollack IF, Adelson PD. Operative T echniques in Pediatric Neurosurgery. New Y ork, NY: Thieme; 2001. Cheek WR, ed. Atlas of Pediatric Neurosurgery . Philadelphia, PA:  W. B. Saunders Company; 1996. Goodrich JT. Pediatric Neurosurgery (Neurosurgical Operative Atlas) . 2nd ed. New Y ork, NY: Thieme; 2008. Northcott PA, Korshunov A, Witt H, et  al. Medulloblastoma comprises four distinct molecular variants. J Clin Oncol . 2011;29(11):1408– 1414. Papile LA, Burstein J, Burstein R, Koffler H. Incidence and evo lution of subependymal and intraventricular hemorrhage:  a study of infants with birth weights less than 1,500 gm. J Pediatr. 1978;92(4):529– 534. Figure 12.27 A, B: Axial head computed tomographic scans showing intraventricular hemorrhage (IVH) in a patient who presented with a proximal shunt malfunction due to ventricular catheter obstruction. Choroid plexus was struck to the fenestrated end of the catheter, and removal of the catheter resulted in significant IVH requiring external ventricular drain placement.