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