Table 1 Measured parameters during LIT and presented other relevant methods of assessing intracranial dynamics
Parameter | Units | Measurement and Description |
|---|---|---|
Rout (resistance to outflow) | mmHg/ml/min | Measure of the resistance to CSF flow out of the craniospinal system. |
Po (opening pressure) | mmHg | Initial measurement of CSF pressure (CSFp) obtained during LIT, taken when the CSF is first accessed |
Pp (plateau pressure) | mmHg | The steady-state pressure reached during infusion once the infusion has been ongoing long enough for the pressure to stabilize. |
RAP | Correlation coefficient between mean ICP and AMP (i.e., the correlation coefficient [R] between AMP amplitude [A] and mean pressure [1]. Indicator of compensatory reserve, accurate measure of intracranial compliance. | |
SSp (sagittal sinus pressure) | mmHg | Venous pressure within the sagittal sinus. Reflects the pressure in the dural venous sinus system, role in the overall dynamics of CSF and ICP. |
PVI (pressure-volume index) | ml | Volume of a bolus injection required to achieve a tenfold increase in ICP. Indicator of CSF dynamics and intracranial elastance. |
Compliance | ml/mmHg | The change in volume (ΔV) per unit change in pressure (ΔP), exactly the inverse of elastance. Ability of the intracranial compartment to accommodate an increase in volume without a large increase in ICP |
Elasticity | mmHg/ml | Ability of an intracranial compartment to resume its normal shape after being compressed. Reflects the responsiveness of the craniospinal system to changes of ICP and CSF volume. It is the reciprocal value of compliance. |