Cerebrospinal Fluid Disorders and Transitional Neurosurgery

Improved treatments for hydrocephalus have increased survival into adulthood. As neurosurgeons treat more patients with “transitional hydrocephalus,” understanding the cerebrospinal fluid (CSF) system becomes more relevant. The ventricles, cisterns, subarachnoid space, periarterial and foraminal passages, interstitial fluid (ISF) space, and lymphatic vessels constitute a complex anatomic and physiologic unit called the cerebral fluid system (CFS). This encompasses the dynamics not only of CSF but also of ISF, lymphatic fluid, and intravascular fluid. Like other physiologic systems that fail or function poorly as a result of an acquired or congenital disease, treatment of CFS disorders requires a deeper understanding of these intertwined mechanisms. Cushing first conceived the CSF system as a single interconnected fluid space conducting flow from the choroid plexus to the arachnoid villi. Though this is a useful concept, the idea of a simple bulk flow circuit is contradicted by many clinical and experimental findings, at least partially explaining why the surgical treatment of CSF disorders remains fragmented and often ineffective. New research insights are allowing for treatments that better approximate the intrinsic physiology. Although hydrocephalus has been considered the primary disease of the CFS, other disorders of this system include intracranial hypertension and hypotension, trapped ventricles, cysts, and Chiari malformation with syrinx. Hydrocephalus itself is heterogeneous, with different etiologies and pathophysiologic characteristics. This chapter briefly discusses new concepts in CFS anatomy and physiology and the interaction among the related systems. Challenges in treating chronic CFS disorders during the transition from childhood onset to the chronic adult stage are emphasized. This chapter discusses CFS disorders without separate dedicated chapters, such as slit ventricle syndrome and intracranial hypotension. Idiopathic intracranial hypertension (IIH), intracranial cysts, Chiari malformation, and syringomyelia as they relate to CFS dysfunction are also examined.