Chapter 56: Hydrocephalus

• Hydrocephalus refers to the excess accumulation of cerebrospinal fluid (CSF). Most cases result from congenital or acquired obstructions to the flow of CSF from the brain to the spinal canal.

• Infants with hydrocephalus are often diagnosed on routine examination by finding head circumference disproportionately large for age or splitting of the cranial sutures.

• Older children with hydrocephalus will usually complain of headache, which is often progressive in nature, worse in the morning, awakens the patient from sleep, and is exacerbated by lying down or straining.

• It is imperative to begin treatment in the unstable patient before herniation occurs. Patients who are lethargic on presentation, those with a Glasgow Coma Scale <8, or those who deteriorate in the emergency department are intubated following rapid sequence induction procedures and ventilated to maintain Pco₂ at 35 torr. If there are signs of herniation such as unequal pupils, fixed and dilated pupils, or posturing, mild hyperventilation can be helpful on a short-term basis.

• Patients who do not respond with an improved mental status after intubation and controlled ventilation may benefit from diuretic therapy with mannitol or furosemide.

• After the patient is stabilized, a computed tomography scan or magnetic resonance image of the brain is performed to define the lesion and plan definitive treatment.

Hydrocephalus refers to the excess accumulation of CSF. This can occur because of obstruction of CSF flow, reduced absorption, or excess production. Most (70%) of CSF is produced by the choroid plexus and absorbed by the arachnoid villi and granulations. Flow direction is from the lateral ventricles to the third ventricle via the foramen of Monro. It then flows through the aqueduct of Sylvius to the fourth ventricles and exits via the foramina of Luschka and Magendie to the basal cisterns.^1,2 It then divides between the spinal subarachnoid space and the subarachnoid cisterns. CSF is absorbed through arachnoid villi covering the brain and leptomeninges, across the ependymal lining of the ventricles, and the spinal subarachnoid space.^1,2 Although there are several ways to categorize hydrocephalus based on the site of excess fluid collection, the primary concern in the emergency department is determining the etiology of the problem and instituting appropriate treatment.

Most cases of hydrocephalus result from congenital or acquired obstructions to the flow of CSF from the brain to the spinal canal. Congenital malformations include the Arnold–Chiari malformation, which is elongation and downward displacement of the brain stem into the fourth ventricle, and the Dandy–Walker malformation, which is a posterior fossa cyst that causes obstruction at the outlet of the fourth ventricle at the foramina of Luschka and Magendie.² Neural tube defects such as myelomeningocele (spina bifida) usually result in hydrocephalus due to a Chiari malformation, obstruction of the fourth ventricle, or stenosis of the aqueduct of Sylvius (aqueductal stenosis).² Intrauterine infections such as toxoplasmosis, rubella, cytomegalovirus, herpes, and syphilis can lead to hydrocephalus through inflammation of the ependymal lining of the ventricular system and lead to CSF flow obstruction. ^1,2 Intraventricular hemorrhage in preterm newborns can also lead to hydrocephalus. Beyond the neonatal period, the most common causes of acquired hydrocephalus are mass lesions, which include tumors, cysts, and abscesses. Other acquired causes of hydrocephalus are meningitis, encephalitis, vascular malformations, or intracranial hemorrhage.^1,2

The clinical presentation of hydrocephalus depends on the age of the patient and the rate at which it develops. Infants with hydrocephalus are often diagnosed on routine examination by finding head circumference disproportionately large for age or splitting of the cranial sutures. The unfused sutures of the infant allow the calvarium to expand and function as a pressure relief phenomenon. When the limitations of suture expansion are reached, intracranial pressure begins to rise precipitously, and the infant may experience irritability, poor feeding, or other behavioral changes. When intracranial pressure becomes severely elevated, the infant develops vomiting and lethargy, which can signal impending herniation. In addition to split sutures, the physical examination may reveal a bulging anterior fontanel and engorged scalp veins. Dysfunction of cranial nerve III may result in loss of upward gaze, or the “sundown or setting-sun” sign. Bobble-head doll movements may also occur, especially with aqueductal stenosis or a third ventricle cyst.¹

Older children with hydrocephalus will usually complain of headache, which is often progressive in nature, worse in the morning, awakens the patient from sleep, and is exacerbated by lying down or straining. The child may suffer visual symptoms that are difficult to specify, but may result in the patient being perceived as unusually clumsy. Gait disturbances can occur, especially ataxia, which is a characteristic of children with posterior fossa tumors. As with infants, older children develop vomiting as intracranial pressure begins to become severely elevated. Papilledema is a late finding in children and is rarely found in infants, but it implies a severe increase in intracranial pressure.

In the emergency department, the primary goal of management of the child with hydrocephalus is the assessment and control of elevated intracranial pressure. Patients may be quite stable or in imminent danger of herniation. Cushing's triad of hypertension, bradycardia, and abnormal respiratory patterns is a late sign of elevated intracranial pressure. Specific signs of herniation depend on the part of the brain involved. In uncal herniation, there is compression of the third cranial nerve with dilation of the ipsilateral pupil and contralateral hemiparesis. Herniation of the cerebellar tonsils through the foramen magnum is preceded by headache and stiff neck and characterized by fixed, dilated pupils. The loss of leg function on one side suggests herniation under the falx. Central herniation occurs when both cerebral hemispheres compress the midbrain and results in decreased level of consciousness, constricted pupils, and Cheyne–Stokes respirations.

It is imperative to begin treatment in the unstable patient before herniation occurs. Patients who are lethargic on presentation, those with a Glasgow Coma Scale <8, or those who deteriorate in the emergency department are intubated following rapid sequence induction procedures. Prior to intubation, ventilation with a bag-valve-mask device to attain a Pco₂ of 35 torr may provide sufficient cerebral vasoconstriction to reduce intracranial pressure enough to avert herniation. If there are signs of herniation such as unequal pupils, fixed and dilated pupils, or posturing, mild hyperventilation can be helpful on a short-term basis.^3,4 Ventilation is continued after intubation, keeping oxygenation and blood pressure within normal values. Patients who do not respond with an improved mental status to intubation and ventilation may benefit from diuretic therapy with mannitol (0.25–1 g/kg) or furosemide (1 mg/kg). It is appropriate to elevate the head of the bed to 30 degrees.⁴

After the patient is stabilized, a computed tomography scan or magnetic resonance image of the brain is performed to define the lesion and plan definitive treatment. For those children with hydrocephalus because of an obstruction in CSF flow, management includes insertion of a catheter from the ventricle to a distal site by a neurosurgeon. The most common site is the peritoneal cavity (VP), although the right atrium (VA) and pleura are also used (Figs. 56-1 and 56-2). If the cause of the increased intracranial pressure is due to trauma resulting in bleeding or cerebral edema, therapy usually includes placement of an intracranial pressure monitoring device by a neurosurgeon. In dire circumstances, a percutaneous ventricular tap may be performed.