8 Dynamics of Cerebrospinal Fluid: From Theoretical Models to Clinical Applications
189
volume-pressure curve retrieval, the least-mean-square model fitting, and an examination of the relationship between the pulse amplitude and the mean CSF pressure
(Fig. 8.3d).
8.5 Long-Term ICP Monitoring
Monitoring of ICP over a longer period can be performed safely using intraparenchymal probes [45, 46]; less frequently, this is performed by lumbar puncture
or a needle inserted in a preimplanted reservoir. Continuous, real-time analysis of
the data, using a pressure monitor connected to a computerised system, is very
helpful. We have found that the most reliable results require overnight monitoring
[46]; however, when this is impossible, a minimum half an hour monitoring
is necessary. New devices allowing telemetric intracranial pressure monitoring
over long periods could be helpful for ICP-guided valve adjustments in complex
situations [47, 48]. In contrast, it is well established that a single manometric lumbar
CSF pressure measurement may be misleading [49].
8.6 Compensatory Parameters Derived from the Infusion
Test and ICP Monitoring
8.6.1 RCSF and Pb
Infusion study (constant rate [50] or any other variation of controlled but variable
rate [36, 38, 51]) allows variables describing the state of CSF compensatory
reserve to be estimated. Traditionally, the two most important parameters are
resistance to CSF outflow (R CSF ) and baseline CSF pressure (p b ). Elevated R CSF
(>13 mmHg/(mL/min) [35, 42] or >18 mmHg/(mL/min) [34]) signifies disturbed
CSF circulation. Elevated baseline pressure (p b > 18 mmHg) may signify an
uncompensated cerebrospinal volume-expanding process.
8.6.2 Pulsatility and Pulse Amplitude
Analysis of ICP pulse pressure amplitude could be valuable in managing iNPH
patients: elevated mean pulse amplitudes during long-term ICP monitoring [52] and
potential reduction pulse pressure [53] could be associated with significant clinical
response to shunt surgery. Moreover, the presence of a ‘lower breakpoint point’ of
the pulse pressure amplitude during infusion tests [54] could be associated with
significant clinical response to shunt surgery.
189
volume-pressure curve retrieval, the least-mean-square model fitting, and an examination of the relationship between the pulse amplitude and the mean CSF pressure
(Fig. 8.3d).
8.5 Long-Term ICP Monitoring
Monitoring of ICP over a longer period can be performed safely using intraparenchymal probes [45, 46]; less frequently, this is performed by lumbar puncture
or a needle inserted in a preimplanted reservoir. Continuous, real-time analysis of
the data, using a pressure monitor connected to a computerised system, is very
helpful. We have found that the most reliable results require overnight monitoring
[46]; however, when this is impossible, a minimum half an hour monitoring
is necessary. New devices allowing telemetric intracranial pressure monitoring
over long periods could be helpful for ICP-guided valve adjustments in complex
situations [47, 48]. In contrast, it is well established that a single manometric lumbar
CSF pressure measurement may be misleading [49].
8.6 Compensatory Parameters Derived from the Infusion
Test and ICP Monitoring
8.6.1 RCSF and Pb
Infusion study (constant rate [50] or any other variation of controlled but variable
rate [36, 38, 51]) allows variables describing the state of CSF compensatory
reserve to be estimated. Traditionally, the two most important parameters are
resistance to CSF outflow (R CSF ) and baseline CSF pressure (p b ). Elevated R CSF
(>13 mmHg/(mL/min) [35, 42] or >18 mmHg/(mL/min) [34]) signifies disturbed
CSF circulation. Elevated baseline pressure (p b > 18 mmHg) may signify an
uncompensated cerebrospinal volume-expanding process.
8.6.2 Pulsatility and Pulse Amplitude
Analysis of ICP pulse pressure amplitude could be valuable in managing iNPH
patients: elevated mean pulse amplitudes during long-term ICP monitoring [52] and
potential reduction pulse pressure [53] could be associated with significant clinical
response to shunt surgery. Moreover, the presence of a ‘lower breakpoint point’ of
the pulse pressure amplitude during infusion tests [54] could be associated with
significant clinical response to shunt surgery.