Cerebrospinal fluid (CSF) plays a role in homeostatic hormonal signaling, chemical buffering, circulations of nutrients, and neurodevelopment. The two lateral ventricles drain into the third ventricle through the foramina of Monro. The third ventricle subsequently drains into the fourth ventricle through the narrowest portion of the ventricular system called the cerebral aqueduct. The roof of the fourth ventricle is bounded by the vermis of the cerebellum and the fastigium. CSF production is to a degree dependent on blood perfusion. In instances of increased intracranial pressure (ICP) with subsequent decreased cerebral perfusion, there will be a decrease in CSF production. CSF flows through net bulk flow from the lateral ventricles through the foramen of Monro into the third ventricle, then on into the fourth ventricle through the cerebral aqueduct. The pathways of CSF reabsorption include the ependymal layer of the ventricular system, and endothelial layer of the brain parenchyma.

This chapter discusses the diagnosis, evaluation and management of intracranial hemorrhage. It describes types of intracranial hemorrhage, including subarachnoid hemorrhage (SAH), subdural hemorrhage (SDH), epidural hemorrhage (EDH) and intracerebral hemorrhage (ICH). Emergent non-contrast head CT is the cornerstone for detection of ICH. MRI is equally effective in identifying ICH and better at detecting predisposing underlying parenchymal or vascular anomalies. Emergency department management focuses on protecting cerebral perfusion by balancing the forces of mean arterial pressure (MAP) and intracranial pressure (ICP). Patients should be positioned with the head of the bed elevated to 30 degrees to support cerebral venous drainage to reduce ICP. The main goal of emergency management is to temporize ICP changes, avoid secondary insults (e.g., hypoxia and hypotension) and protect cerebral perfusion pressure (CPP) while expediting neurosurgical evaluation for possible life-saving surgical intervention.