As the complexity of hospitalized children continues to increase, hospitalists routinely encounter children with neurosurgical issues. Pediatric hospitalists must be familiar with the clinical presentation, diagnostic evaluation, and management of common pediatric neurosurgical problems. This chapter focuses on hydrocephalus and head trauma. While an increase in intracranial pressure (ICP) is a feature of both, increased ICP is primarily covered in the hydrocephalus section. Other important neurosurgical topics covered elsewhere include: Abusive Head Trauma (Chapter 40), Central Nervous System Infections (Chapter 98), and Cerebrospinal Fluid Shunt Assessment and Puncture (Chapter 188).
Hydrocephalus is the abnormal increase in cerebrospinal fluid (CSF) volume in the cranial cavity caused by a disturbance in CSF flow. Hydrocephalus is derived from the Greek term hydrokephalos, or “water on the brain.” Hydrocephalus can be acute, subacute, or chronic. Historically, hydrocephalus has been classified as obstructive (non-communicating) or communicating. In obstructive hydrocephalus, the flow is obstructed within the ventricular system or its connections to the subarachnoid space. In communicating hydrocephalus, the CSF reabsorption is impaired but flow is not obstructed. More recently, hydrocephalus has been defined as an active distension of the ventricular system of the brain related to inadequate passage of CSF from its point of production within the ventricular system to its point of absorption into the systemic circulation.1
CSF is produced primarily by modified ependymal cells in the choroid plexus in each cerebral ventricle. CSF circulates from the pair of lateral ventricles, through the foramen of Monro to the third ventricle, then through the aqueduct of Sylvius to the fourth ventricle, and then through the paired lateral foramina of Luschka and the foramen of Magendie to the subarachnoid space, to the arachnoid granulations, and finally to the dural sinuses and into the venous drainage system for absorption (Figure 159-1). Under normal conditions, daily production should approximately equal absorption to maintain a fairly constant volume of CSF.
Illustration of cerebrospinal fluid circulation.
Mechanisms of hydrocephalus include obstructed CSF circulation, compromised absorption of CSF, or rarely, overproduction of CSF. Obstruction of CSF circulation (or non-communicating hydrocephalus) is the most common mechanism, with dilatation of the ventricular system seen proximal to the obstruction. Impaired absorption of CSF (or communicating hydrocephalus) results in dilatation of the entire ventricular system. An increased amount of CSF typically results in increased ventricular size and increased ICP.
Increased Intracranial Pressure
According to the Monro-Kellie doctrine, the brain is a closed compartment, and its internal pressure is determined by the volume of the three intracranial components: blood, CSF, and brain tissue. The pressure within the calvarium, or ICP, is typically between 8 and 12 mmHg in ...