Chapter XVIII.9. Hydrocephalus
Lauren M. Muraoka
August 2022

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The editors and current author would like to thank and acknowledge the significant contribution of the previous authors of this chapter from the 2004 first edition, Dr. Andrťe M. Bouterie, and the 2014 second edition, Dr. Pippa R. Macdonald. This current third edition chapter is a revision and update of the original authorsí work.

A 12 week old female infant presents to the emergency department with progressive vomiting, lethargy, and difficulty feeding over the past two days. Her mother reports that she has been increasingly irritable in the last week and does not appear to be herself. She has been less interactive, and her cry has become more high-pitched and weak. She has not been breastfeeding well. Her mother is concerned because she thinks her infant's head has grown, and the fontanelle appears to be bulging. She thinks that the infant has felt warm, but she has not measured the temperature with a thermometer. She has had fewer wet diapers and no bowel movements today. She reports that the infant was born on time and that there were no prenatal or perinatal complications. The infant was released after a 48 hour stay in the regular newborn nursery, and had follow-up initially with her pediatrician about one week after discharge. She has had no further follow-up. From the previous medical records, it is confirmed that the infant was born at term. There was poor prenatal care, but the labor and delivery were unremarkable. Mother's prenatal labs were normal. The infant weighed 2900 grams at birth (25th percentile), measured 47.8 cm in length (10th to 25th percentile), and had a head circumference of 34 cm (25th percentile).

Exam: VS: T 36.5 C, P 165, R 45, BP 98/65. Weight 4.20 kg (5th percentile), length 57 cm (10th to 25th percentile), HC 42.6 cm (95th percentile). In general, this is a lethargic infant with a weak, high-pitched cry. Her head large and oddly shaped (like an inverted pear). Her scalp veins are prominent, and the anterior fontanelle is tense and bulging. Eyes show pupils which are equal and round, but are sluggishly reactive to light. Red reflex is present bilaterally. Extraocular movements (EOM) are clearly dysconjugate. She has a downward gaze. There is mild tachypnea with slight intercostal retractions. Lung fields are clear to auscultation bilaterally. Her heart examination reveals tachycardia with a regular rhythm without murmur. Capillary refill is 3 to 4 seconds. Her spine is straight without protrusions or apparent defects. Her upper extremities show good muscle tone and full range of motion with slightly brisk reflexes. Her lower extremities show increased muscle tone with brisk reflexes bilaterally. There is 4+ clonus bilaterally. Her suck reflex is poor. Her startle response is minimally present. Her grasp and glabellar reflexes are present. No parachute reflex can be elicited.

Imaging studies demonstrate hydrocephalus and aqueductal stenosis.

The patientís dehydration is treated and a ventriculoperitoneal shunt procedure is performed by a neurosurgeon. Following surgery, the patient's anterior fontanelle is concave and the head circumference shows a progressive decrease over time.

Hydrocephalus is defined as the abnormal accumulation of cerebrospinal fluid (CSF) within the central nervous system (CNS), due to CSF overproduction, obstruction of CSF flow, or blockage CSF absorption (1). This definition excludes such conditions as benign intracranial hypertension, in which there is no increase in CSF volume, as well as cerebral atrophy and focal destructive lesions, which lead to a passive accumulation of CSF secondary to an increase in available space (sometimes referred to as hydrocephalus ex vacuo) (2).

The body usually maintains a delicate balance between CSF production and absorption, with the total CSF volume being replaced 2 to 3 times per day. About 70% of CSF is produced by the choroid plexus located within the lateral, third, and fourth ventricles. About 25% of CSF is produced by extrachoroidal sources, including the capillary endothelium in the brain parenchyma. CSF flows through the ventricular system from the lateral ventricles to the third ventricle by way of the intraventricular foramen of Monro, then to the fourth ventricle through the aqueduct of Sylvius, and out the fourth ventricle through the foramina of Luschka and Magendie into the cisterna magna, where it then circulates throughout the subarachnoid space of the brain and spinal cord (3).

Two patterns of CSF absorption have been described as the major and minor pathways. In the major pathway, CSF is absorbed by the arachnoid villi via tight junctions of their endothelium due to the pressure gradient that exists between the venous channels and the ventricular system. In the minor pathway, CSF is also absorbed to a lower degree by nasal lymphatics (through the cribiform plate), along nerve root sleeves, and the choroid plexus itself. This minor pathway plays a significant role in neonates and infants in whom arachnoid granulations have not yet formed (3,4).

An increase in the total volume of CSF can be due to an excess CSF production, obstruction of flow, or reduced absorption. A choroid plexus papilloma is a tumor that contains functional choroid epithelium that causes overproduction of CSF so substantial that it may exceed absorptive capabilities. The rate of CSF absorption is capable of increasing linearly in response to an increase in CSF pressure over 7 mmHg, therefore, increased production of CSF will rarely result in hydrocephalus unless the production rate is very excessive, as in the case of a choroid plexus papilloma. However, it is more likely that such a tumor produces hydrocephalus by obstructing the flow of CSF at the foramen of Monro (5). Excluding this unusual exception of CSF over production, hydrocephalus can usually be classified as either communicating or non-communicating, depending on whether there is sustained CSF communication (and flow) between the ventricles to the subarachnoid space. Non-communicating hydrocephalus, also referred to as obstructive hydrocephalus, involves a disruption in flow of CSF from the ventricles to the subarachnoid space, whereas communicating hydrocephalus involves a disruption in absorption of CSF from the subarachnoid space to the venous circulation (1). Communicating therefore refers to whether the increase in CSF volume is spread throughout the CNS extra-axial space while non-communicating is confined to one or more of the cerebral ventricles (6).

The differential diagnosis of hydrocephalus is extensive. Hydrocephalus can be classified by etiology as either congenital or acquired. Congenital hydrocephalus is present at birth, while acquired hydrocephalus occurs after development of the brain and ventricles has occurred. Congenital hydrocephalus accounts for more than half of pediatric cases of hydrocephalus, and occurs in approximately 1/1000 births (6). Risk factors associated with congenital hydrocephalus include birth weight less than 1500 grams, prematurity, male sex, maternal diabetes, preeclampsia, lack of prenatal care, maternal obesity, and alcohol use during pregnancy (4).

Congenital hydrocephalus is often a result of structural abnormalities as seen in Dandy-Walker malformation, holoprosencephaly, myelomeningocele and Chiari malformations, congenital aqueductal stenosis, arachnoid cysts, vein of Galen malformation, congenital foramen of Monro atresia, or rarely congenital neoplasms. It is also more rarely caused by hemorrhage or infection during fetal growth and development (3,7). Congenital hydrocephalus can be further divided into syndromic or non-syndromic, with syndromic hydrocephalus referring to any hydrocephalus due to a genetic anomaly. The associated syndromes are numerous, and include X-linked hydrocephalus, chromosomal defects, Walker-Warburg syndrome, achondroplasia, and various lysosomal storage diseases (8). Acquired hydrocephalus etiologies include subarachnoid hemorrhage, intraventricular hemorrhage, CNS infection, brain tumors, choroid plexus papilloma, and extrinsic venous obstruction. A post-hemorrhagic etiology is the most common form of acquired hydrocephalus in infants, typically due to intraventricular hemorrhage in premature neonates. Other causes of acquired hydrocephalus include aqueductal stenosis related to intraventricular hemorrhage and intracranial neoplasms (4). The more common causes of hydrocephalus will be discussed below.

Dandy-Walker malformation (DWM) is a complex consisting of hypoplasia or agenesis of the cerebellar vermis, progressive cystic enlargement of the fourth ventricle, enlargement of the posterior fossa, and upward displacement of the tentorium, torcula (the point at which the dural venous sinuses connect to the posterior end of the superior sagittal sinus), and the transverse sinuses (9). DWM occurs in 1 in 35,000 births in the United States and is more common in females than males (10). Hydrocephalus is observed in 80% of cases of DWM and the incidence of DWM in congenital hydrocephalus is between 1% and 4% (11). Hydrocephalus may be present at birth or develop in infancy to childhood, and many display signs of increased intracranial pressure by 2 years of age. In addition to the usual findings of hydrocephalus, patients with DWM often have a prominent bulging occiput, ataxia, nystagmus, and cranial nerve deficits (9).

Chiari malformations involve inferior displacement of the cerebellum and brainstem. In the Chiari type I malformation, the cerebellar tonsils descend into the foramen magnum. In the Chiari type II malformation (also called the Arnold-Chiari malformation), a myelomeningocele causes the cerebellar vermis and tonsils, medulla, and pons to herniate through the foramen magnum into the spinal canal and compress the fourth ventricle (12). While both type I and type II malformations are associated with hydrocephalus, it is much more common in type II, occurring in up to 90% of patients with myelomeningocele (11). About 15% of infants with both hydrocephalus and Chiari II malformation will show signs of brainstem dysfunction (choking, vocal cord paralysis, apnea, pooled secretions) (3).

Aqueductal stenosis (aqueduct of Sylvius) is an important cause of hydrocephalus that can be either congenital or acquired, accounting for 5% of cases with congenital hydrocephalus (4) and up to 10% of all pediatric hydrocephalus cases. Aqueductal stenosis causes non-communicating hydrocephalus by obstructing the flow of CSF through the cerebral aqueduct with subsequent enlargement of the lateral and third ventricles, but a normal sized fourth ventricle (13). Congenital aqueductal stenosis encompasses not only narrowing of the cerebral aqueduct but also forking of the aqueduct, with formation of small aqueductal branches, and formation of an aqueductal septum (3). It is seen in X-linked hydrocephalus associated with stenosis of the aqueduct of Sylvius (HSAS) resulting from mutations in L1CAM that accounts for 10% of cases of hydrocephalus in males (6,14). HSAS is accompanied by different levels of intellectual impairment, seizure risk, and flexion-adduction abnormalities of the thumbs. Acquired aqueductal stenosis is most often due to germinal matrix hemorrhage, neoplasm, or infection with secondary gliosis (15).

Intraventricular hemorrhage (IVH) primarily occurs in preterm neonates and is due to a combination of associated factors including fragile immature germinal matrix vasculature, impaired autoregulation of cerebral blood flow, and cardiopulmonary instability (such as with a hemodynamically significant patent ductus arteriosus) (5,16). The germinal matrix develops deep to the ependymal lining of the ventricles with progenitor cells of the cerebral cortex and basal ganglia perfused by a fragile immature network of fine capillaries and veins. With fetal maturity, the germinal matrix gradually regresses. By 24 weeks gestation, the germinal matrix persists only over the caudate nucleus head and body, and by late preterm development around 36 weeks gestation, it is no longer present. IVH entails a rupture of the small vessels in the subependymal germinal matrix, and in newborns, IVH is graded from I to IV depending on the extent of hemorrhages into ventricles and into the parenchyma. IVH occurs with increased frequency and with higher grades with lower gestational age and lower birth weight. (15). IVH typically occurs shortly after birth, on the first day for 50% of affected newborns and before the fourth day of life in 90% (5, 13). When hydrocephalus occurs as a consequence of IVH, it is referred to as post-hemorrhagic hydrocephalus (PHH), and risk for developing PHH is associated with the degree of prematurity, birth weight, and the grade of IVH (17). PHH is thought to be due to impaired CSF absorption due to fibrosis and gliosis following hemorrhage, and dysfunction of ciliated ependymal cells. It may also be due to obstruction of the aqueduct from blood or blood products, and aberrant brain pulsations that can alter normal CSF flow dynamics leading to impaired CSF drainage (18). In approximately 25% to 30% of all preterm babies with IVH, progressive hydrocephalus may develop and is an important cause of mortality in preterm babies. It is important to have early identification of progressive PHH via serial ultrasonographic screening and expedient intervention. The definitive treatment of PHH is placement of a ventriculoperitoneal (VP) shunt which is needed in 25% of cases (16). Studies have shown that there are increased rates of shunt failure and infection if shunt procedures occur before the first 35 days of life, so temporary measures must be taken to halt progression. Repeat lumbar punctures up to once per day may be a temporizing intervention to drain CSF until the intrinsic flow or absorption adequately improves. For a more extended period of CSF drainage, a neurosurgically implanted ventricular access device (also called a ventricular reservoir) to facilitate CSF taps or CSF diversion through a vetriculosubgaleal shunt can be used. Other drugs that decrease CSF production such as acetazolamide, furosemide, and topiramate, and choroid plexus coagulation have also been explored with the overall goals to minimize neurologic injury and the need for VP shunt (5,16).

Infectious causes of hydrocephalus include meningitis, encephalitis, congenital syphilis, CMV (cytomegalovirus), toxoplasmosis, and mumps. Bacteria are the primary agents in neonatal infection, with E. coli and group B streptococcal infection involved in early-onset infection, and staphylococci implicated in later-onset infections. The formation of fibrotic adhesions in the ventricles, arachnoid villi, or basal cisterns are suspected to be the driving force behind post-infectious hydrocephalus (PIH). PIH is nearly always obstructive (19).

The clinical manifestations of hydrocephalus depend primarily on whether it is compensated or uncompensated (i.e., whether or not an increase in CSF volume has translated into an increase in intracranial pressure). Intracranial pressure (ICP) is the sum of pressures exerted by the brain parenchyma, the CSF, and the vascular system (brain perfusion). The Monro-Kellie doctrine states that due to the fixed volume of the cranium, an increase in volume of any one of these components will lead to an increase in ICP unless it is accompanied by an equivalent decrease in the volume of one of the other components (20). A gradual increase in CSF volume causes compression of brain parenchyma and vasculature to maintain a normal ICP, and patients will less likely present with characteristic signs and symptoms of acute increased ICP. Infants and young children with non-fused cranial bones also have the capability of spreading apart the cranial bones to achieve an increase in cranial volume (4,17) known as splaying of the cranial sutures, as opposed to normal close approximation or slight overlap of adjacent cranial sutures. The clinical features of hydrocephalus thus depend not only on the rate at which CSF volume increases but also upon the age of the child.

In children over 2 years of age, cranial sutures are generally closed and the clinical manifestations of hydrocephalus can vary depending on acute rapid progression vs. indolent gradual progression. With the acute onset of hydrocephalus, the child will likely present with signs and symptoms of increased ICP including nausea, vomiting, progressive or episodic headache especially in early morning, drowsiness, gait changes, papilledema with associated blurred vision, and impaired lateral or upward gaze (i.e., a downward gaze). Cushing's classic triad of hypertension with widened pulse pressure, bradycardia, and irregular respirations is a late finding of increased ICP in children, and when it occurs, it is associated with high rates of mortality due to poor brain perfusion and downward herniation of the contents of the cranium (20). More indolent but progressive hydrocephalus is subtle with symptoms varying from developmental delays or regression, decline in academic performance, behavioral changes, memory loss, papilledema, optic nerve atrophy, and a notable increased trajectory in head circumference growth for age (4). When hydrocephalus is long-standing, there may be signs of endocrine dysfunction such as short stature, menstrual irregularities, and diabetes insipidus (21).

Infants and young children less than 18 months of age are less likely to present with acute signs of increased ICP, since their cranial sutures are generally not yet fused allowing some enlargement of the skull (17). In severe hydrocephalus, the "setting sun" sign may be apparent, in which there is a forced downward deviation of both eyes leading to disappearance of a portion of the iris below the lower eyelid (9). More subtle signs of increased ICP are possible, particularly with a rapid accumulation of CSF, and may include drowsiness, irritability, poor feeding, and vomiting (17). Apneic spells, bradycardia, divergent strabismus, and/or upward gaze palsy (i.e., a downward gaze), may be evident if it is more severe whereas failure to thrive, delayed development, persistence of early infantile reflexes, and spasticity of the lower extremities may manifest if it is more gradual and chronic. (9).

A characteristic abnormality seen in infants is an abnormal rate of increase in head circumference or macrocephaly. Macrocephaly is defined as head circumference greater than 2 standard deviations above the mean based on body weight or length and may be present at birth or could develop gradually over time. Accompanying signs include distended scalp veins that become particularly dilated when the child cries, thin and shiny scalp skin, splaying of cranial sutures, and a large, tense, non-pulsatile anterior fontanel. Advanced hydrocephalus can lead to craniofacial disproportion where the face appears small relative to the cranium (inverted pear shape as in the case), accompanied by low-set ears and eyes (3).

The diagnosis of hydrocephalus requires identification of signs and symptoms of increased ICP as noted above, and confirmation of ventricular enlargement. Imaging techniques are usually required in the diagnosis of hydrocephalus, particularly in the fetal period. Ultrasonography (US) is used bedside as a screening tool for evaluation of ventriculomegaly and IVH prenatally and in neonates and infants with an open fontanelle. US is recommended as a cursory screening test since its imaging of the posterior fossa structures is limited and is highly operator-dependent (4). Computed tomography (CT) is a quick and widely available diagnostic study for acute situations, but there is concern of repeated use and ionizing radiation exposure. Thus, CT investigation should be used cautiously and sparingly to minimize radiation exposure. MRI is usually required and is the study of choice to assess ventricular size and morphology, and identify the cause of the ventricular enlargement (4,17). The differential diagnosis of macrocephaly includes chronic subdural hematoma, expanding porencephalic cyst, hydranencephaly (brainís cerebrum is replaced by fluid filled sacs), mass lesions, or megalencephaly (increase in the brain parenchyma itself) (22).

Treatment options depend on the childís age, symptomatology, and underlying cause of the hydrocephalus. Rapid onset of hydrocephalus with evidence of increased ICP is an emergency and requires urgent management. Post-hemorrhagic hydrocephalus can be treated with lumbar puncture in this situation. Percutaneous trans-fontanelle ventriculostomy may be used to decompress or acquire CSF for examination before definitive CSF diversion. Other measures include the insertion of a ventricular access device (VAD) or ventriculo-subgaleal shunt (VSGS). VAD placement involves insertion of a ventricular catheter and reservoir in the subgaleal space (reservoir in the scalp). VSGS entails the creation of a subgaleal pocket via blunt dissection and insertion of a ventricular catheter and outflow site that allows accumulation of CSF in the subgaleal space. While these temporary surgical measures can reduce the need for a permanent CSF diversion, many will still require definitive surgical management with a shunt (15).

Shunting procedures are the mainstay of treatment of hydrocephalus, allowing decompression of the ventricular system by diverting the CSF from the ventricular system into a distal cavity, most commonly, the peritoneum. VP shunts are the most common method in the surgical management of hydrocephalus (4). A VP shunt is placed between one of the lateral ventricles and the peritoneal cavity, which is preferential because the peritoneum can accommodate a greater catheter length and reduce the need for shunt replacement as the child grows (23). Alternative sites of drainage include the pleural cavity and the right atrium, the latter of which is known as a vascular shunt and is accomplished by way of the jugular vein and superior vena cava. Shunts allow unidirectional flow of CSF due to a valve system with a preset pressure requirement for flow (4).

Complications of VP shunting include infection, peritonitis, CSF ascites, inguinal hernia, intra-abdominal cysts, intracranial granulomas, gastrointestinal obstruction, migration of shunt within the peritoneal cavity, headache, and perforation of abdominal viscera (24). Infection occurs in 7% of patients with greater risk in those with higher numbers of past shunt revisions, prematurity, younger age, and a previous history of shunt infection. Infection risk is greatest in the 90 days following placement surgery (4). Headaches may occur due to shunt malfunction or could be due to "slit ventricle syndrome", a condition in which severe headaches and intracranial hypertension are accompanied by normally sized or small ventricles in a patient with a shunt (17). Craniosynostosis may also occur in infants in whom a shunt is placed, as decompression of the ventricles may interfere with cranial vault growth and lead to premature fusion of sutures in this population. Shunt-related craniosynostosis (SRC) typically affects those who were operated on during the first year of life (25). Rates of shunt failure are high, with up to 40% failing in the first year after placement. Clinical manifestations of shunt failure (also known as shunt obstruction) may include typical signs and symptoms of increased ICP such as bulging fontanelle, fluid collection along the shunt, depressed level of consciousness, irritability, abdominal pain, nausea and vomiting, accelerated head growth, and headache as well abnormal shunt pump refilling (17). Suspected shunt failure can be assessed with imaging studies such as a shunt series x-ray, CT, or MRI, and shunt patency imaging via nuclear medicine (11) . Common reasons for failure include obstruction, infection, mechanical failure, overdrainage, loculated ventricles, and abdominal complications (12). The preferred imaging modality of children with shunted hydrocephalus is quick-brain MRI (QB-MRI). The advantages of QB-MRI including avoiding the need for MRI sedation and avoiding the radiation associated with CT imaging with similar sensitivity to CT (17).

Endoscopic third ventriculostomy (ETV) is another treatment option for hydrocephalus if there is an obstruction of CSF flow distal to the third ventricle. For an ETV, an opening is created in the floor of the third ventricle to allow passage of CSF directly into the basal cisterns for subsequent absorption by arachnoid villi. Unlike VP shunt placement, which may be used to treat both communicating and non-communicating hydrocephalus, ETV is useful only in cases of non-communicating hydrocephalus. Additionally, given the poor development of arachnoid villi in young infants, failure rates are high in this population and therefore many experts do not recommend ETV in patients younger than 1 year of age. Because of this lower success rate in infants, choroid plexus cauterization (CPC) is often included in this operative setting for patients 12 to 24 months to increase success rates (15). The major advantages of ETV are avoidance of foreign body implantation, the establishment of a physiological CSF circulation, which can prevent many complications associated with VP shunt placement (24). Major complications of ETV include CSF leakage (1% to 6% of cases), meningitis (1% to 5%), cranial neuropathies (1% to 2%), seizures (1%), and endocrinologic complications (2% to 9%). In most studies, the risk of ETV failure ranges from 10% to 15% depending on the indications for ETV, etiology of hydrocephalus, and comorbid conditions. Other rare complications include hemiparesis, gaze palsy, memory disorders, and altered sensorium, intraoperative hemorrhage, permanent diabetes insipidus, weight gain, and precocious puberty (26).

Not all patients with hydrocephalus require surgical decompression of the ventricular system. In patients with hydrocephalus due to an accessible mass, resection of the mass may suffice to resolve the hydrocephalus and shunt placement or ventriculostomy may prove unnecessary (6). Mild and slowly progressive hydrocephalus may be initially treated with medical management (acetazolamide or furosemide) or observation alone. Observation is also reasonable in the rare case of chronic, non-progressive hydrocephalus with normal CSF pressure; however, these patients must be watched carefully for signs of neurologic impairment (2,16).

The prognosis and long-term outcomes of hydrocephalus vary greatly and are dependent upon the degree of ventricular enlargement, the presence of other structural abnormalities, the underlying etiology, and method of treatment. For example, cases of isolated congenital aqueductal stenosis carry a high risk of developmental delay at 68%, and epilepsy in up to 49% of cases, even with timely intervention. However, about 75% of those with myelomeningocele and shunted hydrocephalus may demonstrate normal intelligence quotients but may exhibit learning disabilities when attending school. Other studies show that those with higher spinal lesions and a greater number of shunt revisions were linked to poor motor independence and cognitive performance that may impact quality of life and employment. There are multiple complex factors that can affect the overall long-term outcomes in patients with hydrocephalus, and appropriate management requires early diagnosis, appropriate and timely intervention, and long-term management by a multidisciplinary team (15).

1. True/False: CSF overproduction is a common cause of hydrocephalus.
2. True/False: Hydrocephalus ex vacuo requires a VP shunt.
3. What are some signs and symptoms of increased ICP in a young child?
4. What is the difference between hydrocephalus, megalencephaly, and macrocephaly?
5. What would be the purpose of routine cranial ultrasound screening in very low birth weight infants?
6. True/False: The diagnosis of hydrocephalus in a neonate is made on the basis of increased ventricular size alone.
7. What is the "setting sun" sign?

1. Koleva M, De Jesus O. (2022) Hydrocephalus. StatPearls. Accessed July 19, 2022.
2. About-Hamden A, Drake J. Chapter 30. Hydrocephalus and Arachnoid Cysts. In: Swaiman KF, Ashwal S, Ferriero DM, Schor NF, et al (eds). Swaimanís Pediatric Neurology, 6th edition. 2017. Elsevier, Philadelphia. pp. 561-576.
3. Kinsman S, Johnston M. Chapter 609. Congenital Anomalies of the Central Nervous System. In: Kliegman RM, St. Geme JW, Blum NJ, et al (eds). Nelson Textbook of Pediatrics, 21st edition. 2020, Elsevier, Philadelphia, PA. pp. 3063-3082.
4. Patel S, Tari R, Mangano F. Pediatric Hydrocephalus and the Primary Care Provider. Pediatr Neurosurg Prim Care 2021;68(4):793-809.
5. Pina-Garza J, James K. Chapter 4. Increased Intracranial Pressure. Fenichelís Clinical Pediatric Neurology, 8th edition. 2019. Elsevier, Philadelphia. pp. 91-114.
6. Pina-Garza J, James K. Chapter 18. Disorders of Cranial Volume and Shape. Fenichelís Clinical Pediatric Neurology, 8th edition. 2019. Elsevier, Philadelphia. pp. 346-364.
7. Farb R, Rovira A. Chapter 2. Hydrocephalus and CSF Disorders. In: Hodler J. Kubik-Huch RA, von Schulthess GK (eds). Diseases of the Brain, Head and Neck, Spine 2020-2023: Diagnostic Imaging, 1st edition. 2020. Springer, Cham, Switzerland. pp. 11-24
8. Varagur K, Sanka SA, Strahle J. Syndromic Hydrocephalus. Neurosurg Clin North Am 2021;331(1):67-79.
9. Safier R, Cleves-Bayon C, Gaesser J. Chapter 16. Neurology. In: Zitelli BJ, McIntire MD, Nowalk AJ, Garrison MD (eds). Zitelli and Davisí Atlas of Pediatric Physical Diagnosis, 8th edition. 2023. Elsevier, Philadelphia. pp. 562-592.
10. Zamora EA, Ahmad T. (2022). Dandy Walker Malformation. StatPearls. Accessed July 20, 2022.
11. Lee R, Nagel S, Luciana M. Chapter 225. Cerebrospinal Fluid Disorders and Transitional Neurosurgery. In: Winn HR, Couldwell WT, Grady MS, Schaller K, et al. (eds). Youmans and Winn Neurological Surgery, 8th edition. 2021. Elsevier, Philadelphia. pp. 1711.
12. Gunny R, Saunders D, Argyropoulou M. Chapter 76. Pediatric neuroradiology. In: Adam A, Dixon AK, Gillard JH (eds). Grainger & Allisonís Diagnostic Radiology, 7th edition. Elsevier, Philadelphia. pp. 1984-2045.
13. Tomei K, Smith M. Chapter 57. Intracranial and Calvarial Disorders. In: Martin RJ, Fanaroff AA, Walsh MC (eds). Fanaroff and Martinís Neonatal-Perinatal Medicine, 11th edition. 2020. Elsevier, Philadelphia. pp. 1060-1072.
14. Guo D, Jian W, Fu Y, Guo Y, et al. A novel nonsense mutation in the L1CAM gene responsible for X-linked congenital hydrocephalus. J Gene Med 2020;22(7):e3180. Accessed July 21, 2022.
15. Pindrik J, Schulz L, Drapeau A. (2022). Diagnosis and Surgical Management of Neonatal Hydrocephalus. Sem Pediat Neurol 2022;42:100969. doi: 10.1016/j.spen.2022.100969
16. Ozek E, Kersin SG. Intraventricular hemorrhage in preterm babies. Turk Pediatri Ars 2020;55(3):215-221.
17. Ho W, Kestle J. Chapter 223. Hydrocephalus in Children: Etiology and Overall Management. In: Winn HR, Couldwell WT, Grady MS, Schaller K, et al. (eds). Youmans and Winn Neurological Surgery, 8th edition. 2021. Elsevier, Philadelphia. pp. 1696-1702.
18. Holste KG, Xia F, Ye F, Keep Rf, Xi G. Mechanisms of neuroinflammation in hydrocephalus after intraventiruclar hemorrhage: a review. Fluids Barriers CNS 2022;19(1):28.
19. Padayachy L, Ford L, Dlamini N, Mazwi A. Surgical treatment of post-infectious hydrocephalus in infants. Childs Nerv Syst 2021;37(11):3397-3406.
20. Pinto VL, Tadi P, Adeyinka A. (2022). Increased Intracranial Pressure. StatPearls. Accessed July 20, 2022.
21. Rosenberg GA. Chapter 88. Brain Edema and Disorders of Cerebrospinal Fluid Circulation. In: Jankovic JJ, Mazziotta JC, Pomeroy SL, Newman NJ (eds). Bradley and Daroffís Neurology in Clinical Practice, 8th edition. 2022. Elsevier, Philadelphia. pp. 1327-1344.
22. Jones S, Debopam S. (2022). Macrocephaly. StatPearls. Accessed July 21, 2022.
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24. Badhiwala J, Kulkarni A. Chapter 227. Ventricular Shunting Procedures. In: Winn HR, Couldwell WT, Grady MS, Schaller K, et al. (eds). Youmans and Winn Neurological Surgery, 8th edition. 2021. Elsevier, Philadelphia. pp.1714-1728.
25. Kim SA, Letyagin GV, Danilin VE, Sysoeva AA. Shunt-induced craniosynostosis: Topicality of the problem, choice of the approach, and features of surgical treatment. Zh Vopr Neirokhi Im N N Burdenko 2017;81(4):45-55. doi: 10.17116/neiro201781445-55
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Answers to questions
1. False. Choroid plexus papilloma is rare and is the only cause of hydrocephalus due to overproduction of CSF. In addition, even in the case of choroid plexus papilloma, most cases of hydrocephalus are actually due to obstruction of the fourth ventricle.
2. False. While this chapter did not discuss this much, hydrocephalus ex vacuo is not due to any of the hydrocephalus mechanisms that were discussed. It is a radiographic appearance due to brain atrophy (post-stroke or other serious brain injury). Since the brain is smaller (atrophied) within the skull, the ventricles appear larger and the fluid spaces over the brain are larger. The extra CSF resembles hydrocephalus in some ways but the extra CSF is merely occupying the extra space left by the smaller brain. This does not result in high pressure. Brain perfusion is maintained, and a VP shunt would not help this condition.
3. Nausea, vomiting, headache, drowsiness, gait changes, papilledema with associated blurred vision, and impaired lateral or upward gaze (i.e., a downward gaze).
4. Hydrocephalus is an increased volume of CSF within the CNS. Megalencephaly is an increase in the amount of brain parenchyma. Macrocephaly is an abnormally large head circumference (greater than 2 standard deviations above the mean) and may be a consequence of hydrocephalus, megalencephaly, or various other causes.
5. When present, intraventricular bleeding in the very low birth weight infant usually occurs within the first few days of life. Because up to 50% of these events will occur without immediate clinical symptomology, it is recommended that routine screening be performed between days 4 to 7 of life. For those with IVH, ultrasound screening can assess whether post hemorrhage hydrocephalus is developing.
6. False. The diagnosis of hydrocephalus in a neonate requires confirmation of increased rate of skull growth in addition to evidence of ventricular enlargement.
7. The setting-sun sign is a forced downward deviation of both eyes leading to disappearance of a portion of the iris below the lower eyelid. It is a sensitive (but usually late) sign of increased ICP, and is likely due to compression of periaqueductal structures. This sign appears in 40% of children with hydrocephalus and 13% of patients with VP shunt failure.

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