Goals of Treatment Hydrocephalus can present in an acute or subacute fashion Most children with hydrocephalus will need surgical treatment CLINICAL PEARLS AND PITFALLS Hydrocephalus has been categorized as obstructive (noncommunicating) or nonobstructive (communicating) Most cases of pediatric hydrocephalus, even congenital, have a delayed diagnosis Hydrocephalus is rarely a stand-alone diagnosis and is often secondary to additional pathology Hydrocephalus is the excess accumulation of cerebrospinal fluid (CSF), usually as the result of obstruction in CSF absorption, resulting in raised ICP CSF is produced by the choroid plexus which is located within all four ventricles in the brain Under normal conditions, the CSF exits the fourth ventricle to circulate in the subarachnoid space to be absorbed back into the venous system largely through arachnoid villi located at the superior sagittal sinus Obstructive (or noncommunicating) hydrocephalus does not allow for the CSF to leave the ventricular system, and nonobstructive (or communicating) hydrocephalus occurs when the obstruction to CSF absorption lies outside the ventricular system in the subarachnoid space or at the arachnoid villi Common causes of obstructive hydrocephalus include stenosis of the cerebral aqueduct (from congenital causes, midbrain tumors, following hemorrhage or infection) and posterior fossa tumors Common causes of nonobstructive hydrocephalus include scarring of the subarachnoid space and arachnoid villi following intraventricular hemorrhage (IVH) in premature infants or meningitis In congenital conditions such myelomeningocele, the cause of hydrocephalus is likely multifactorial and may involve both obstructive and nonobstructive elements Genetic causes are a less likely cause, including X-linked aqueductal stenosis and primary ciliopathies Current Evidence Infections are a common cause of hydrocephalus in infants and children An estimated 1% of pediatric patients who survive bacterial meningitis, including gram-negative organisms (particularly Escherichia coli ) which occur most frequently in the neonatal age group, Haemophilus influenzae, Streptococcus pneumoniae, and group B streptococci, develop progressive hydrocephalus Other less common infectious causes of hydrocephalus in children include tuberculosis meningitis whose worldwide prevalence is rising, toxoplasmosis (or other members of the TORCH group) usually diagnosed in the perinatal period, and viral meningitis and encephalitis Head trauma has been recognized as a common cause of hydrocephalus About 4% of patients develop posttraumatic hydrocephalus requiring surgical CSF diversion True congenital hydrocephalus, meaning hydrocephalus present at birth, has an estimated incidence of 0.2 to 0.8/1,000 live births in the United States The incidence of congenital hydrocephalus associated with conditions, such as Dandy–Walker malformation (approximately 85% to 95%), myelomeningocele (approximately 80% to 90%), and IVH of prematurity (approximately 35%), is better established Midline arachnoid cysts and tumors related to the ventricular system can cause hydrocephalus by obstruction of the CSF pathways Tumors may also cause hydrocephalus by spilling blood or protein into the CSF, making the CSF more viscous, overloading the absorptive capacity of the arachnoid villi, and resulting in a communicating hydrocephalus Clinical Considerations Clinical Recognition Infants presenting symptoms include macrocephaly, bulging fontanelle, excessive irritability, lethargy, or vomiting Sunsetting of the eyes may be present This usually occurs later in the clinical course and consists of a spectrum of findings, including components of Parinaud syndrome (downward eye deviation, lid retraction, and convergenceretraction nystagmus) As raised ICP progresses, infants may develop bradycardia and/or apneic episodes In older children, the more common presenting symptoms include headache, nausea, or vomiting These symptoms tend to be more common in the mornings, when ICP is higher after having been recumbent overnight Other symptoms may include visual field deficits or double vision This could be the result of severe papilledema or the because of the underlying cause of hydrocephalus, for example, a large suprasellar tumor causing obstructive hydrocephalus and compressing the optic chiasm Double vision might be described, usually from a unilateral or bilateral abducens nerve palsy, a classic false-localizing sign in raised ICP Focal neurologic deficits attributable to the underlying cause of the hydrocephalus, such as ataxia from a posterior fossa tumor or bitemporal hemianopia from a suprasellar tumor, may also be present Clinical Pitfall Benign macrocephaly is the most common diagnosis for an increasing head circumference The typical infant, more commonly male, will be one whose head circumference has risen to or above the 98th percentile; but without a bulging fontanelle nor overt clinical signs of increased ICP Brain imaging (by ultrasound, CT, or MRI) will show enlarged subarachnoid spaces over both frontal lobes This has sometimes been termed “extraventricular obstructive hydrocephalus,” although it is not truly hydrocephalus Diagnostic Imaging Hydrocephalus is ultimately diagnosed with cranial imaging A CT scan provides very good detail to make the diagnosis, is readily available, and can be done very quickly It does, however, expose the child to radiation Axial CT imaging will show enlarged ventricles The pattern of enlarged ventricles, both lateral ventricles and third ventricle (or “triventricular”) or all four ventricles, will vary depending on the etiology of the hydrocephalus ( Fig 122.4 ) MRI provides greater anatomical detail of the brain and ventricles, but it can be less readily available and may require use of a general anesthetic Depending on the results of a CT, an MRI may be necessary, particularly if a tumor is suspected or if CT is unable to clearly elucidate the etiology A fast-spin, limited sequence MRI may also be considered to evaluate ventricular anatomy with radiation exposure or need for sedation Ultrasound may be the most appropriate imaging modality for infants with suspected benign macrocephaly and a patent anterior fontanelle This may confirm diagnosis and no further imaging may be necessary Management When assessing a child with hydrocephalus, the acuity of the situation needs to be thoroughly assessed If the child is in extremis, for example, an obtunded child or a lethargic infant with bradycardia, the situation is emergent After ensuring the basics of airway and cardiorespiratory maintenance, emergent cranial imaging and assessment by a neurosurgeon are essential Definitive treatment will require some form of surgery In some cases, there may be discreet tumor mass causing obstructive hydrocephalus and the goal of surgery will be tumor resection, which may relieve the hydrocephalus In other situations, treatment will require diversion of the CSF itself, in the form of either a CSF shunt or an endoscopic third ventriculostomy (ETV) FIGURE 122.4 An approximately 4.7 × 3.3 × 3.5 cm T1 hypointense, minimally heterogeneous, circumscribed mass fills the fourth ventricle, which is effaced toward the right, and displaces the pons and medulla anteriorly There is resultant mild– moderate dilatation of the lateral ventricles, third ventricle, and cerebral aqueduct ... Evidence Infections are a common cause of hydrocephalus in infants and children An estimated 1% of pediatric patients who survive bacterial meningitis, including gram-negative organisms (particularly