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O.030 The relationship between aqueductal pulsatility and ventriculomegaly in experimental extraventricular hydrocephalus
S8
Abstracts of the Hydrocephalus 2008 Congress / Clinical Neurology and Neurosurgery 110S (2008), S1–S41
CSF pulse waveform may provide a reliable prognostic evaluation in NPH patients before shunting.
O.027 Comparison of intraparenchymal and CSF pulse waves N. Lenfeldt 1 , A. Behrens 1 , L.-O. Koskinen 1 , J. Malm 1 , A. Eklund 2 Neuroscience, 2 Biomedical Engineering and Informatics, Umeå University, Umeå, Sweden
1 Clinical
Background: The ICP pulse wave is getting more and more attention in research on traumatic brain injury and hydrocephalus. This study aims to investigate the measurability of the ICP pulse wave via lumbar space. Methods: Ten patients with confirmed communicating CSF-systems were included in the study. ICP was measured in the parenchyma above the frontal right ventricle, and CSF pressure (LP) was measured via the lumbar space. Pressure was manipulated by CSF infusion from baseline (mean = 19 mm Hg) to a maximum excess pressure (mean = 45 mm Hg). The amplitude of the ICP wave was analysed using Matlab and SPSS. Results: The mean difference between the intracranial and lumbar amplitude was 0.55 mm Hg (SD=1.48) [range: -2.3 to +3.6] (p<0.05). Analyse of each pressure level showed that the amplitude difference was only significant at baseline (0.91 mm Hg (SD= 1.68)[range: -0.35 to +2.90], pressure range 10 to 23 mm Hg). A general linear model revealed that amplitude difference was significantly affected by factors related to the individual patients. Conclusion:. At baseline pressures there was a systematic difference between the ICP and LP amplitude which could be relevant if INPH patients are selected for surgery based on pulse amplitude. At higher pressure levels the pressure pattern tended to be more equalised in the craniospinal system. Furthermore, there seems to be a patient specific difference in amplitude as well which could be due to differences between sensors or have physiological reasons.
O.029 Are intracranial volume variations dependent on cerebrospinal fluid pressure? I.R. Manchester 1 , K.S. Andersson 2 , J. Malm 3 , A. Eklund 4 1 Department of Applied Physics and Electronics, 2 Department of Radiation Sciences, 3 Department of Clinical Neuroscience, 4 Department of Biomedical Engineering and Informatics, Umeå University Hospital, Umeå, Sweden Introduction and Motivation: The CSF pressure is known to be affected by intracranial volume variations. We consider the converse question, how are intracranial volume variations affected by CSF pressure? To this end we present a new method of analysis of infusion test data which can shed light on the mechanism of CSF pressure variations from known sources, such as breathing and unknown sources resulting in B-waves and other phenomena. Method: One performs constant-pressure infusion test, in which CSF pressure is regulated to an increasing sequence of levels between 2.5 and 4.5 kPa. For each pressure level, an estimation of volume variations is derived using an inverse of the dynamical model of Marmarou. These volume variations are band-pass filtered to extract B-wave and breathing patterns, and the magnitudes are compared. Results: Preliminary results from a case study of 5 patients indicate that the variations associated with B-waves (12.5’–100 second cycles) do not have a consistent dependence on CSF pressure. However, volume variations due to breathing (2–5 second cycles) decreased at higher CSF pressures in all patients: standard deviations of volume variations at 4.5 kPa fell to 0.67±0.12 of their values at 2.5 kPa (min 0.5, max 0.81). Discussion: The different relationships between pressure and volume seen in the frequency ranges associated with breathing and B-waves indicate that these variations may be driven by different sources. Studies are planned to examine whether the observed trends are statistically significant over larger groups of patients and healthy subjects.
O.030 The relationship between aqueductal pulsatility and O.028 The effect of body position on cerebrospinal fluid (CSF)
ventriculomegaly in experimental extraventricular hydrocephalus
movement and pressure M. Klarica 1 , M. Rados 1 , G. Erceg 1 , D. Oreskovic 2 , M. Bulat 1 1 Croatian Institute for Brain Research and Department of Pharmacology, University of Zagreb School of Medicine, Zagreb, Croatia; 2 Rudjer Boskovic Institute, Zagreb, Croatia
M.E. Wagshul 1 , S. Rashid 1 , J. Li 2 , M. Yu 1 , J.P. McAllister 2 Brook University and Brookhaven National Lab, Stony Brook, NY, USA; 2 Primary Children’s Hospital and the University of Utah, Salt Lake City, UT, USA
Change of body position, from horizontal to vertical, is followed by transient fall of intracranial pressure presumably due to CSF and blood shift from cranium to lower parts of body. We hypothesized that these effects are not related to the cranial fluid volume changes, but depend on laws of fluid mecahnics and cervico-lumbar redistribution of fluids To test this, we compared changes in anaesthetized cats (n=5) and in the new artificial model of the CSF system with dimensions similar to the CSF system in cats, consisting of non-distensible cranial and distensible spinal part. The measuring cannulae were introduced into lateral ventricle (4 cm from foramen magnum) and lumbar subarahnoid space (L3; 31 cm from formen magnum). In horizontal position the pressures were similar in cranial and lumbar regions in both animal and artificial model (about +16 cm H2 O). In vertical position the CSF pressure in cranium (-3.80±1.39 cm H2 O) and lumbar region (+31.00±3.12 cm H2 O) of cats was almost the same as in “cranial” (-4.06±0.11 cm H2 O) and “lumbar” (+30.92±0.16 cm H2 O) region of model. Changes in pressure on the model were not followed by the changes of fluid volume in the non-distensible cranial part of model. Thus, similarity of results between cat and the model implicates that CSF pressure in cranium in upright position is determined by laws of fluid mechanics but not by changes of CSF and blood in cranium. In each body position the cranial volume of CSF and blood remains constant, which enables a good blood brain perfusion.
Because many observations about communicating (CH) hydrocephalus have not been explained, we explored aqueductal CSF pulsatility in a novel model of basal cistern obstruction. CH was induced in adult rats (n=16) by injecting kaolin into the basal cisterns; saline-injected animals served as controls. Animals were imaged on a 9.4T microMRI and CSF pulsatility was assessed by measuring aqueductal stroke volume (SV) and comparing it to ventricular volume (VV). Based on the extent of ventriculomegaly and CSF pulsatility, two distinct groups were identified. Group 1 (n=6) was characterized by severe ventriculomegaly and highly increased CSF pulsations that persisted for 100 days. Group 2 animals (n=3) unexpectedly exhibited an initial rapid increase in SV and VV that returned to near control values after day 8 while VV remained elevated. These groups might represent two different forms of CH, and the abrupt drop in SV in a subset of the animals following the acute stage (Group 2) may explain some of the variability found in clinical studies of hyperdynamic aqueductal pulsations in NPH. The strong correlation between SV and VV suggests a causal relationship in severe CH cases and may also explain the excellent prediction of shunt success in cases of extreme hyperdynamic pulsatility. The “correction” of elevated SV in the chronic stage may indicate an active compensatory mechanism. Finally, the CSF distributions indicate that the CSF access to the ventral SAS may be the most important factor in the development of hydrocephalus in this model.
1 Stony
Abstracts of the Hydrocephalus 2008 Congress / Clinical Neurology and Neurosurgery 110S (2008), S1–S41
CSF pulse waveform may provide a reliable prognostic evaluation in NPH patients before shunting.
O.027 Comparison of intraparenchymal and CSF pulse waves N. Lenfeldt 1 , A. Behrens 1 , L.-O. Koskinen 1 , J. Malm 1 , A. Eklund 2 Neuroscience, 2 Biomedical Engineering and Informatics, Umeå University, Umeå, Sweden
1 Clinical
Background: The ICP pulse wave is getting more and more attention in research on traumatic brain injury and hydrocephalus. This study aims to investigate the measurability of the ICP pulse wave via lumbar space. Methods: Ten patients with confirmed communicating CSF-systems were included in the study. ICP was measured in the parenchyma above the frontal right ventricle, and CSF pressure (LP) was measured via the lumbar space. Pressure was manipulated by CSF infusion from baseline (mean = 19 mm Hg) to a maximum excess pressure (mean = 45 mm Hg). The amplitude of the ICP wave was analysed using Matlab and SPSS. Results: The mean difference between the intracranial and lumbar amplitude was 0.55 mm Hg (SD=1.48) [range: -2.3 to +3.6] (p<0.05). Analyse of each pressure level showed that the amplitude difference was only significant at baseline (0.91 mm Hg (SD= 1.68)[range: -0.35 to +2.90], pressure range 10 to 23 mm Hg). A general linear model revealed that amplitude difference was significantly affected by factors related to the individual patients. Conclusion:. At baseline pressures there was a systematic difference between the ICP and LP amplitude which could be relevant if INPH patients are selected for surgery based on pulse amplitude. At higher pressure levels the pressure pattern tended to be more equalised in the craniospinal system. Furthermore, there seems to be a patient specific difference in amplitude as well which could be due to differences between sensors or have physiological reasons.
O.029 Are intracranial volume variations dependent on cerebrospinal fluid pressure? I.R. Manchester 1 , K.S. Andersson 2 , J. Malm 3 , A. Eklund 4 1 Department of Applied Physics and Electronics, 2 Department of Radiation Sciences, 3 Department of Clinical Neuroscience, 4 Department of Biomedical Engineering and Informatics, Umeå University Hospital, Umeå, Sweden Introduction and Motivation: The CSF pressure is known to be affected by intracranial volume variations. We consider the converse question, how are intracranial volume variations affected by CSF pressure? To this end we present a new method of analysis of infusion test data which can shed light on the mechanism of CSF pressure variations from known sources, such as breathing and unknown sources resulting in B-waves and other phenomena. Method: One performs constant-pressure infusion test, in which CSF pressure is regulated to an increasing sequence of levels between 2.5 and 4.5 kPa. For each pressure level, an estimation of volume variations is derived using an inverse of the dynamical model of Marmarou. These volume variations are band-pass filtered to extract B-wave and breathing patterns, and the magnitudes are compared. Results: Preliminary results from a case study of 5 patients indicate that the variations associated with B-waves (12.5’–100 second cycles) do not have a consistent dependence on CSF pressure. However, volume variations due to breathing (2–5 second cycles) decreased at higher CSF pressures in all patients: standard deviations of volume variations at 4.5 kPa fell to 0.67±0.12 of their values at 2.5 kPa (min 0.5, max 0.81). Discussion: The different relationships between pressure and volume seen in the frequency ranges associated with breathing and B-waves indicate that these variations may be driven by different sources. Studies are planned to examine whether the observed trends are statistically significant over larger groups of patients and healthy subjects.
O.030 The relationship between aqueductal pulsatility and O.028 The effect of body position on cerebrospinal fluid (CSF)
ventriculomegaly in experimental extraventricular hydrocephalus
movement and pressure M. Klarica 1 , M. Rados 1 , G. Erceg 1 , D. Oreskovic 2 , M. Bulat 1 1 Croatian Institute for Brain Research and Department of Pharmacology, University of Zagreb School of Medicine, Zagreb, Croatia; 2 Rudjer Boskovic Institute, Zagreb, Croatia
M.E. Wagshul 1 , S. Rashid 1 , J. Li 2 , M. Yu 1 , J.P. McAllister 2 Brook University and Brookhaven National Lab, Stony Brook, NY, USA; 2 Primary Children’s Hospital and the University of Utah, Salt Lake City, UT, USA
Change of body position, from horizontal to vertical, is followed by transient fall of intracranial pressure presumably due to CSF and blood shift from cranium to lower parts of body. We hypothesized that these effects are not related to the cranial fluid volume changes, but depend on laws of fluid mecahnics and cervico-lumbar redistribution of fluids To test this, we compared changes in anaesthetized cats (n=5) and in the new artificial model of the CSF system with dimensions similar to the CSF system in cats, consisting of non-distensible cranial and distensible spinal part. The measuring cannulae were introduced into lateral ventricle (4 cm from foramen magnum) and lumbar subarahnoid space (L3; 31 cm from formen magnum). In horizontal position the pressures were similar in cranial and lumbar regions in both animal and artificial model (about +16 cm H2 O). In vertical position the CSF pressure in cranium (-3.80±1.39 cm H2 O) and lumbar region (+31.00±3.12 cm H2 O) of cats was almost the same as in “cranial” (-4.06±0.11 cm H2 O) and “lumbar” (+30.92±0.16 cm H2 O) region of model. Changes in pressure on the model were not followed by the changes of fluid volume in the non-distensible cranial part of model. Thus, similarity of results between cat and the model implicates that CSF pressure in cranium in upright position is determined by laws of fluid mechanics but not by changes of CSF and blood in cranium. In each body position the cranial volume of CSF and blood remains constant, which enables a good blood brain perfusion.
Because many observations about communicating (CH) hydrocephalus have not been explained, we explored aqueductal CSF pulsatility in a novel model of basal cistern obstruction. CH was induced in adult rats (n=16) by injecting kaolin into the basal cisterns; saline-injected animals served as controls. Animals were imaged on a 9.4T microMRI and CSF pulsatility was assessed by measuring aqueductal stroke volume (SV) and comparing it to ventricular volume (VV). Based on the extent of ventriculomegaly and CSF pulsatility, two distinct groups were identified. Group 1 (n=6) was characterized by severe ventriculomegaly and highly increased CSF pulsations that persisted for 100 days. Group 2 animals (n=3) unexpectedly exhibited an initial rapid increase in SV and VV that returned to near control values after day 8 while VV remained elevated. These groups might represent two different forms of CH, and the abrupt drop in SV in a subset of the animals following the acute stage (Group 2) may explain some of the variability found in clinical studies of hyperdynamic aqueductal pulsations in NPH. The strong correlation between SV and VV suggests a causal relationship in severe CH cases and may also explain the excellent prediction of shunt success in cases of extreme hyperdynamic pulsatility. The “correction” of elevated SV in the chronic stage may indicate an active compensatory mechanism. Finally, the CSF distributions indicate that the CSF access to the ventral SAS may be the most important factor in the development of hydrocephalus in this model.
1 Stony