The total volume of cerebrospinal fluid (CSF) in the adult ranges from 140 to 270 ml.
The volume of the ventricles is about 25 ml and 125 ml in subarachnoid spaces.
CSF is produced at a rate of 0.2 - 0.7 ml per minute or 600-700 ml per day.
Approximately 20 percent of the CSF is contained in the ventricles; the rest is contained in the subarachnoid space in the cranium and spinal cord.
Although the cerebrospinal fluid (CSF) is the pathway of anesthetic delivery and the diluent for neuraxially administered drugs, little is known about its volume, including variability among individuals, longitudinal distribution, or influence of body habitus. Models made to investigate subarachnoid anesthetic distribution lack valid dimensions.
Alterations in serum osmolarity change the CSF volume and concentrations of neurotransmitter metabolites because of the osmotic arrival of water from CNS blood capillaries in all CSF compartments 1).
Lebret et al first present an automatic method to estimate those volumes from a new three-dimensional whole body magnetic resonance imaging sequence. This enables us to statistically analyze the fluid volumes, and to show that the ratio of subarachnoid volume to ventricular one is a proportionality constant for healthy adults (=10.73), while in range [0.63, 4.61] for hydrocephalus patients. This indicates that a robust distinction between pathological and healthy cases can be achieved by using this ratio as an index 2) 3).
CSF volume was measured in volunteers, and the effect of obesity and abdominal compression on CSF volume was evaluated using magnetic resonance imaging. METHODS: Low thoracic and lumbosacral axial magnetic resonance images of 25 healthy volunteers were obtained at 8-mm intervals by fast spin-echo sequence, which highlights CSF. A repeat image series was performed in 15 subjects during external abdominal compression. In two subjects, images were obtained without compression for the entire vertebral column. Dural sac and spinal cord areas were determined in a blinded fashion for each image using video/digital analysis. Area of the sac minus area of the cord constituted area of CSF and roots (“CSF/root”); this area multiplied by 8 mm resulted in CSF/root volume per section.
There is great interindividual variability in CSF/root volume. From the T11-T12 disc to the sacral terminus of the dural sac, the mean volume for all subjects is 49.9 +/- 12.1 ml (mean +/- SD; range 28.0-81.1 ml). This volume was significantly less in relatively obese subjects (42.9 +/- 9.5 ml) than in nonobese subjects (53.5 +/- 12.9 ml). Abdominal compression decreased CSF/root volume by 3.6 +/- 3.2 ml. Sections through intervertebral foramina showed the biggest decrease with abdominal compression, with a lesser change in sections with veins and no change in the absence of these anatomic features. Total vertebral CSF/root volume in two subjects was 94.84 and 120.01 ml, respectively.
CSF volume is widely variable between individuals. The decreased CSF volume that results from increased abdominal pressure, such as with obesity or pregnancy, may produce more extensive neuraxial blockade through diminished dilution of anesthetic. The mechanism by which increased abdominal pressure decreases CSF volume is probably inward movement of soft tissue in the intervertebral foramen, which displaces CSF 4).
The amount of spinal cerebrospinal fluid (CSF) could be of importance for the understanding of CSF dynamics, CSF biomarker analyses as well as for the amount and effect of anaesthesia using intrathecally administered drugs. However, knowledge of spinal CSF volumes is scarce. The main purpose of this article is to present data on spinal CSF volumes. In total, 22 healthy individuals aged between 64 and 76 years underwent MR imaging with a 3D balanced turbo field echo pulse sequence, which provided high contrast between spinal cord, CSF and the extradural surroundings. The entire spinal CSF volume, the cervical, thoracic, and lumbosacral CSF volumes and the spinal cord volume were calculated. The total spinal CSF volume was 81 ± 13 ml (range 52-103 ml). The amount of CSF in the cervical region was 19 ± 4 ml, in the thoracic region 38 ± 8 and in the lumbosacral region 25 ± 7 ml. There was no difference between genders nor was there any correlation with height. The volume of the spinal cord was 20 ± 3 ml. The results present new magnetic resonance imaging-based data on the spinal CSF volume in healthy elderly individuals 5).
Assessment of CSF volume changes in mL CSF/scan can be conducted using CT. Counting voxels corresponding to the CSF eliminates mistakes due to inaccurate region demarcation. The obtained results (AC volume) show a high correlation with patient state 6).
The mean lumbosacral CSF volume and dural sac surface area in the nonpregnant state were 39.6 +/- 5.8 mL and 11.0 +/- 0.8 cm(2), respectively. Pregnancy was associated with compression of the dural sac, resulting in a significantly reduced mean CSF volume (33.2 +/- 6.2 mL) and dural sac surface area (9.9 +/- 1.0 cm(2)) in all subjects (P < 0.001). The mean change in CSF volume and dural sac surface area was 16.7% +/- 0.8% and 10.0% +/- 0.5%, respectively. Gestational week (between 31 and 39 wk) correlated significantly with the reduction in CSF volume (rho = 0.74, P < 0.001) and dural sac surface area (rho = 0.66, P < 0.01).
These findings indicate an association between gestational week (Weeks 31-39) and a reduction in both CSF volume and dural sac surface area. These reductions may, at least in part, explain the facilitation of the spread of intrathecal anesthesia in pregnant women 7).