Chapter 56: Hydrocephalus

High-Yield Facts

• 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 ...