Table 2 This is a list of the parameters for simulations of a healthy subject
Parameter | Notation | Value | Units | Refs. |
|---|---|---|---|---|
Spinal venous pressure | \({p}_{vs}\) | 4.2 | mmHg | [53] |
Viscous pressure loss below the jugular veins | \({{p}_{vi}}_{s}\) | 2.2 | mmHg | [46] |
Viscous pressure loss above the jugular veins | \({{p}_{vi}}_{c}\) | 2 | mmHg | [46] |
Orbital pressure | \({p}_{orb}\) | 3 | mmHg | [52] |
Reference pressure CSF in supine | \({p}_{ref}\) | 9.1 | mmHg | [80] |
Exponential constant | \({p}_{1}\) | 2.1 | mmHg | As in Gehlen et al. [23]. \({p}_{ref}\) and (\({p}_{{c}_{sup}}\)) are required |
Offset pressure spinally | \({p}_{0s}\) | 4.9 | mmHg | Equation (14). \({p}_{vs}\) and \({p}_{ref}\) are needed |
Offset pressure cranially | \({p}_{0c}\) | 0.7 | mmHg | Equation (14). \({p}_{vs}\),\({{p}_{vi}}_{s}\), \({{p}_{vi}}_{c}\) and \({p}_{ref}\) are needed |
ONSAS pressure at baseline | \({p}_{{0}_{ONSAS}}\) | 7.35 | mmHg | Chosen so that ΔV_ONSAS = 0 in supine equilibrium |
CSF formation rate | \({Q}_{f}\) | 0.35 | ml/min | |
Craniospinal outflow resistance | \({R}_{out}\) | 8.6 | mmHg/(ml/min) | [33] |
Resistance of the ONS | \({R}_{ou{t}_{ONS}}\) | 3968 | mmHg/(ml/min) | Calc. from a “permeability” measure assessed by Raykin et al. [34] times \({\overline{A} }_{ONS}\) |
Resistance of cranial cervical junction | \({R}_{CS}\) | 0.001 | mmHg/(ml/min) | [35] |
Baseline LC resistance | \({R}_{LC}\) | 1.9e6 | mmHg/(ml/min) | See sensitivity analysis. Section “Specific flow resistances” |
Density of blood | \({\rho }_{b}\) | 1060 | kg/m3 | – |
Density of CSF | \({\rho }_{CSF}\) | 1000 | kg/m3 | – |
Viscosity of CSF | \(\mu\) | 0.9 | mPa s | – |
Gravitational acceleration | \(g\) | 9.81 | m/s2 | – |
Distance from jugular vein collapse to auditory meatus | \({l}_{ijv-c}\) | 0.1 | m | [53] |
Length from venous HIP to the jugular vein collapse | \({l}_{s-ijv}\) | 0.276 | m | [53] |
Length from venous HIP to the auditory meatus | \({l}_{s-am}\) | 0.376 | m | [53] |
Cranio-spinal elastance coefficient | \(E\) | 0.2 | 1/ml | [82] |
Constant reflecting spinal compliance contribution in supine | \({k}_{s}\) | 0.35 | – | |
Relative spinal outflow resistance | \({ROF}_{s}\) | 0.05 | – | Estimated as in Gehlen et al. [23] |
Distance from auditory meatus to posterior LC | \({l}_{AP}\) | 0.0519 | m | [51] |
Distance from cornea to anterior side of LC | \({l}_{SI}\) | 0.0379 | m | [51] |
Average ONS distensibility along the optic nerve* | \(D\) | 0.018 | mm/mmHg | \(D\) and \({D}_{i}\) are calculated as in Holmlund et al. [18] using ONS sizes from HUT and HDT MRI |
Intraocular pressure at the LC | \(IOP\) | 18.9 sup 15.1 upright | mmHg | [51] |