Both the brain and the spinal cord are surrounded by cerebrospinal fluid, which circulates between the arachnoid mater and pia mater in the subarachnoid space. In a healthy person, cerebrospinal fluid is a clear, colorless fluid that serves, among other functions, to absorb shock for the central nervous system1. Cerebrospinal fluid is also attributed with immunological functions analogous to those of the lymphatic system, known as the glymphatic system2 3.
Production and volume4
Under physiological conditions, the central nervous system contains approximately 150ml of cerebrospinal fluid in an adult. Half of this is located in the subarachnoid space and the ventricular system of the skull, and half is located in the spinal canal.
| Population | CSF volume | CSF production |
|---|---|---|
| Newborn | 5 ml | 25 ml per day |
| Adult | 150 ml | 450–700 ml per day (0,3 to 0,35 ml per hour) |
Approximately 80 % of cerebrospinal fluid is produced by the choroid plexus of the two lateral ventricles, and the remaining 20 % originates from the choroid plexus of the fourth ventricle. Approximately 450 ml of cerebrospinal fluid is produced per 24 hours in an adult.
Absorption
Absorption occurs through the arachnoid granulations.
Composition of cerebrospinal fluid5
| Component | Unit | CSF | Plasma | CSF:Plasma Ratio |
|---|---|---|---|---|
| Osmolarity | mOsm/L | 295 | 295 | 1:1 |
| H2</sub>0 | 99% | 93% | ||
| Sodium | mmol/L | 138 | 138 | 1:1 |
| Potassium | mmol/L | 2,8 | 4,5 | 0,6 |
| Chloride | mmol/L | 119 | 102 | 1,2 |
| pC02</sub> | mm Hg | 47 | 41 (arterial) | 1,1 |
| pH | 7,33 | 7,41 | ||
| p02</sub> | mm Hg | 43 | 104 (arterial) | 0,4 |
| Glucose | mg/dl | 60 | 90 | 0,67 |
| Lactate | mmol/L | 1,6 | 1 | 1,6 |
| Pyruvate | mmol/L | 0,08 | 0,11 (arterial) | 0,73 |
| Total protein | mg/dl | 35 | 7000 | 0,005 |
| Albumin | mg/dl | 155 | 36600 | 0,004 |
| IgG | mg/dl | 12,3 | 9870 | 0,001 |
Collection of cerebrospinal fluid
Cerebrospinal fluid can be obtained for diagnostic examination using various procedures. Most commonly, cerebrospinal fluid is obtained via lumbar puncture. However, cerebrospinal fluid can also be obtained through an inserted external ventricular drain, shunt puncture, or intraoperative collection. The protein content is lower in ventricular cerebrospinal fluid than in lumbar cerebrospinal fluid.
Figure
References
CSF constituents. In: Greenberg M, ed. Handbook of Neurosurgery. 9th Edition. Thieme; 2019. ↩ ↩ ↩ ↩ ↩ ↩
Iliff JJ, Lee H, Yu M, et al. Brain-wide pathway for waste clearance captured by contrast-enhanced MRI. J Clin Invest. 2013;123:1299-1309. ↩ ↩
Iliff JJ, Goldman SA, Nedergaard M. Implications of the discovery of brain lymphatic pathways. Lancet Neurol. 2015;14:977-979. ↩ ↩