From the Guidelines
Cerebrospinal fluid (CSF) is primarily produced by the choroid plexus in the brain's ventricles through a process of filtration and active secretion, where arterial blood is filtered to form CSF. The choroid plexus epithelial cells filter blood plasma and actively transport ions, creating an osmotic gradient that draws water into the ventricles to form CSF 1. Approximately 500 mL of CSF is produced daily, with about 150 mL circulating at any given time. After production, CSF flows through the ventricular system, into the subarachnoid space surrounding the brain and spinal cord, and is eventually reabsorbed into the bloodstream via arachnoid granulations. When CSF production or flow is disrupted, management depends on the specific issue, such as:
- Hydrocephalus (excess CSF) which is typically treated with surgical placement of a shunt system to divert fluid from the ventricles to another body area for absorption, commonly the peritoneal cavity (ventriculoperitoneal shunt) 1.
- Endoscopic third ventriculostomy which creates a new pathway for CSF flow.
- For reduced CSF production, as in some cases of intracranial hypotension, treatment may include hydration, caffeine (500-1000 mg daily), or an epidural blood patch where autologous blood is injected into the epidural space to seal CSF leaks 1. Medications like acetazolamide (250-1000 mg daily) can reduce CSF production when needed by inhibiting carbonic anhydrase, which is involved in the ion transport mechanisms of CSF formation 1. It's worth noting that the management of CSF production and flow disruption should prioritize the patient's morbidity, mortality, and quality of life, and the treatment approach may vary depending on the underlying cause and severity of the condition 1.
From the Research
Process of CSF Production
- Arterial blood becomes cerebrospinal fluid (CSF) through a process of secretion, primarily via the choroid plexus 2.
- Various transport mechanisms facilitate CSF secretion, including the role of aquaporins, which is a recent discovery and an area of ongoing research 2.
- The choroid plexus is a specialized vascularized tissue located within the cerebral ventricles, responsible for regulating CSF, immune response, endocrine metabolism, and other physiological functions 3.
Management of CSF Disruption
- Hydrocephalus is a condition characterized by abnormal excessive accumulation of CSF in the ventricular system, often due to an imbalance of CSF circulation and homeostasis 3, 4, 5.
- The choroid plexus plays a critical role in hydrocephalus, and strategies that reduce choroid plexus CSF secretion have been shown to be effective in treatment 3.
- CSF diversion via ventriculoperitoneal shunts is a common treatment for hydrocephalus, but it is limited by complications such as infection, obstruction, and valve malfunction 5.
- Alternative treatments, such as endoscopic third ventriculostomy and choroid plexus coagulation, may be effective in select patients with hydrocephalus due to choroid plexus hyperplasia 4.
CSF Circulation and Removal
- The glymphatic pathway is a dedicated peri-vascular network that facilitates metabolic waste clearance from the central nervous system via CSF transport 6.
- The glymphatic pathway is functionally coupled by interstitial bulk flow supported by astrocytic aquaporin 4 water channels, and plays a critical role in removing metabolic waste products from the central nervous system during sleep 6.
- The glymphatic system has greatly improved our understanding of key factors that control removal of metabolic waste products from the central nervous system in health and disease, and identifies an additional purpose for sleep 6.