Intracranial Pressure Pulse Wave Research Articles

Intracranial pressure following surgery of an unruptured intracranial aneurysm—a model for normal intracranial pressure in humans

ObjectiveOptimizing the treatment of several neurosurgical and neurological disorders relies on knowledge of the intracranial pressure (ICP). However, exploration of normal ICP and intracranial pressure pulse wave amplitude (PWA) values in healthy individuals poses ethical challenges, and thus the current documentation remains scarce. This study explores ICP and PWA values for healthy adults without intracranial pathology expected to influence ICP.MethodsAdult patients (age > 18 years) undergoing surgery for an unruptured intracranial aneurysm without any other neurological co-morbidities were included. Patients had a telemetric ICP sensor inserted, and ICP was measured in four different positions: supine, lateral recumbent, standing upright, and 45-degree sitting, at day 1, 14, 30, and 90 following the surgery.ResultsICP in each position did not change with time after surgery. Median ICP was 6.7 mmHg and median PWA 2.1 mmHg in the supine position, while in the upright standing position median ICP was − 3.4 mmHg and median PWA was 1.9 mmHg. After standardization of the measurements from the transducer site to the external acoustic meatus, the median ICPmidbrain was 8.3 mmHg in the supine position and 1.2 mmHg in the upright standing position.ConclusionOur study provides insights into normal ICP dynamics in healthy adults following a uncomplicated surgery for an unruptured aneurysm. These results suggest a slightly wider normal reference range for invasive intracranial pressure than previously suggested, and present the first normal values for PWA in different positions. Further studies are, however, essential to enhance our understanding of normal ICP.Trial registration The study was preregistered at www.clinicaltrials.gov (NCT03594136) (11 July 2018)

Changes in intracranial pressure and pulse wave amplitude during postural shifts

Monitoring of intracranial pressure (ICP) and ICP pulse wave amplitude (PWA) is an integrated part of neurosurgery. An increase in ICP usually leads to an increase in PWA. These findings have yet to be replicated during the positional shift from supine to upright, where we only know that ICP decreases. Our main aim is to clarify whether the positional shift also results in a change in pulse wave amplitude. Our database was retrospectively reviewed for subjects having had a standardized investigation of positional ICP. In all subjects, mean ICP and PWA were determined with both an automatic and a manual method and compared using Student's t test. Finally, ICP and PWA were tested for correlation in both in supine and upright position. The study included 29 subjects. A significant change in ICP (Δ14.1mmHg, p < 0.01) and no significant change in PWA (Δ0.4mmHg, p = 0.06) were found. Furthermore, a linear correlation between ICP and PWA was found in both supine and upright positions (p < 0.01). We found that during the positional shift from supine to upright, ICP is reduced while PWA remains unaffected. This indicates that the pressure-volume curve is shifted downward according to a hydrostatic pressure offset, while the slope of the curve does not change. In addition, the correlation between ICP and PWA in both supine and upright position validates the previous research on the matter.

Continuous wavelet transform in the study of the time-scale properties of intracranial pressure in hydrocephalus.

Normal pressure hydrocephalus (NPH) encompasses a heterogeneous group of disorders generally characterized by clinical symptoms, ventriculomegaly and anomalous cerebrospinal fluid (CSF) dynamics. Lumbar infusion tests (ITs) are frequently performed in the preoperatory evaluation of patients who show NPH features. The analysis of intracranial pressure (ICP) signals recorded during ITs could be useful to better understand the pathophysiology underlying NPH and to assist treatment decisions. In this study, 131 ICP signals recorded during ITs were analysed using two continuous wavelet transform (CWT)-derived parameters: Jensen divergence (JD) and spectral flux (SF). These parameters were studied in two frequency bands, associated with different components of the signal: B1(0.15-0.3 Hz), related to respiratory blood pressure oscillations; and B2 (0.67-2.5 Hz), related to ICP pulse waves. Statistically significant differences (p < 1.70 × 10-3, Bonferroni-corrected Wilcoxon signed-rank tests) in pairwise comparisons between phases of ITs were found using the mean and standard deviation of JD and SF. These differences were mainly found in B2, where a lower irregularity and variability, together with less prominent time-frequency fluctuations, were found in the hypertension phase of ITs. Our results suggest that wavelet analysis could be useful for understanding CSF dynamics in NPH.This article is part of the theme issue 'Redundancy rules: the continuous wavelet transform comes of age'.

Associations of intracranial pressure with brain biopsy, radiological findings, and shunt surgery outcome in patients with suspected idiopathic normal pressure hydrocephalus.

It remains unclear how intracranial pressure (ICP) measures are associated with brain biopsies and radiological markers. Here, we aim to investigate associations between ICP and radiological findings, brain biopsies, and shunt surgery outcome in patients with suspected idiopathic normal pressure hydrocephalus (iNPH). In this study, we retrospectively analyzed data from 73 patients admitted with suspected iNPH to Kuopio University Hospital. Of these patients, 71% underwent shunt surgery. The NPH registry included data on clinical and radiological examinations, 24-h intraventricular pressure monitoring, and frontal cortical biopsy. The mean ICP and mean ICP pulse wave amplitude were not associated with the shunt response. Aggregations of Alzheimer's disease (AD)-related proteins (amyloid-β, hyperphosphorylated tau) in frontal cortical biopsies were associated with a poor shunt response (P = 0.014). High mean ICP was associated with Evans' index (EI; P = 0.025), disproportional sylvian and suprasylvian subarachnoid spaces (P = 0.014), and focally dilated sulci (P = 0.047). Interestingly, a high pulse wave amplitude was associated with AD-related biopsy findings (P = 0.032), but the mean ICP was not associated with the brain biopsy. The ICP was not associated with medial temporal lobe atrophy, temporal horn widths, or white matter changes. ICP B waves were associated with less atrophy of the medial temporal lobe (P = 0.018) and more severe disproportionality between the sylvian and suprasylvian subarachnoid spaces (P = 0.001). The EI and disproportional sylvian and suprasylvian subarachnoid spaces were associated with mean ICP. Disproportionality was also associated with ICP B waves. These associations, although rather weak, with elevated ICP in 24-h measurements, support their value in iNPH diagnostics and suggest that these radiological markers are potentially related to the pathogenesis of iNPH. Interestingly, our results suggested that elevated pulse wave amplitude might be associated with brain amyloid accumulation.

Relationship between intracranial pressure and phase contrast cine MRI derived measures of intracranial pulsations in idiopathic normal pressure hydrocephalus

Phase contrast cine MRI with determination of pulsatile aqueductal cerebrospinal fluid (CSF) stroke volume and flow velocity has been suggested to assess intracranial pulsations in idiopathic normal pressure hydrocephalus (iNPH). We aimed to compare this non-invasive measure of pulsations to intracranial pressure (ICP) pulse wave amplitude from continuous ICP monitoring. We hypothesised that a significant correlation between these two markers of intracranial pulsations exists. Fifteen patients with suspected iNPH had continuous computerised ICP monitoring with calculation of mean ICP pulse wave amplitude (MWA) from time-domain analysis. MRI measured CSF aqueductal stroke volume and peak flow velocity. Mean MWA was 5.4mmHg (range 2.3–12.4mmHg). Mean CSF stroke volume and peak flow velocity were 65μl (range 3–195μl) and 9.31cm/s (range 1.68–15.0cm/s), respectively. No significant correlation between the invasive and non-invasive measures of pulsations existed (Spearman r=−0.30 and r=−0.27, respectively; p>0.05). We observed marked intra-individual fluctuation of MWA during continuous ICP monitoring of an average of 6.0mmHg (range 2.8–12.2mmHg). The results suggest a complex interplay between measures of pulsations derived from snapshot MRI measurements and continuous computerised ICP measurements, as no significant relationship existed in our data. Further study is needed to better understand the temporal profile of CSF MRI flow studies, as substantial variation in MWA over the course of several hours of ICP monitoring is common, suggesting that these physiologic fluctuations might obscure MRI snapshot measures of intracranial pulsations.

Effect of infusion tests on the dynamical properties of intracranial pressure in hydrocephalus

Background and objectiveHydrocephalus comprises a number of conditions characterised by clinical symptoms, dilated ventricles and anomalous cerebrospinal fluid (CSF) dynamics. Infusion tests (ITs) are usually performed to study CSF circulation and in the preoperatory evaluation of patients with hydrocephalus. The study of intracranial pressure (ICP) signals recorded during ITs could be useful to gain insight into the underlying pathophysiology of this condition and to further support treatment decisions. In this study, two wavelet parameters, wavelet turbulence (WT) and wavelet entropy (WE), were analysed in order to characterise the variability, irregularity and similarity in spectral content of ICP signals in hydrocephalus. MethodsOne hundred and twelve ICP signals were analysed using WT and WE. These parameters were calculated in two frequency bands: B1 (0.15–0.3 Hz) and B2 (0.67–2.5 Hz). Each signal was divided into four artefact-free epochs corresponding to the basal, early infusion, plateau and recovery phases of the IT. We calculated the mean and standard deviation of WT and WE and analysed whether these parameters revealed differences between epochs of the IT. ResultsStatistically significant differences (p < 1.70⋅10−3, Bonferroni-corrected Wilcoxon signed-rank tests) in pairwise comparisons between phases of ITs were found using the mean and standard deviation of WT and WE. These differences were mainly found in B2. ConclusionsWavelet parameters like WT and WE revealed changes in the signal time-scale representation during ITs. Statistically significant differences were mainly found in B2, associated with ICP pulse waves, and included a higher degree of similarity in the spectral content, together with a lower irregularity and variability in the plateau phase with respect to the basal phase.

Pulsatile Intracranial Pressure and Cerebral Autoregulation After Traumatic Brain Injury

Strong correlation between mean intracranial pressure (ICP) and its pulse wave amplitude (AMP) has been demonstrated in different clinical scenarios. We investigated the relationship between invasive mean arterial blood pressure (ABP) and AMP to explore its potential role as a descriptor of cerebrovascular pressure reactivity after traumatic brain injury (TBI). We retrospectively analyzed data of patients suffering from TBI with brain monitoring. Transcranial Doppler blood flow velocity, ABP, ICP were recorded digitally. Cerebral perfusion pressure (CPP) and AMP were derived. A new index-pressure-amplitude index (PAx)-was calculated as the Pearson correlation between (averaged over 10s intervals) ABP and AMP with a 5min long moving average window. The previously introduced transcranial Doppler-based autoregulation index Mx was evaluated in a similar way, as the moving correlation between blood flow velocity and CPP. The clinical outcome was assessed after 6months using the Glasgow outcome score. 293 patients were studied. The mean PAx was -0.09 (standard deviation 0.21). This negative value indicates that, on average, an increase in ABP causes a decrease in AMP and vice versa. PAx correlated strong with Mx (R (2)=0.46, P<0.0002). PAx also correlated with age (R (2)=0.18, P<0.05). PAx was found to have as good predictive outcome value (area under curve 0.71, P<0.001) as Mx (area under curve 0.69, P<0.001). We demonstrated significant correlation between the known cerebral autoregulation index Mx and PAx. This new index of cerebrovascular pressure reactivity using ICP pulse wave information showed to have a strong association with outcome in TBI patients.

O.057 Correlation between ventriculo-aqueductal and ventriculo-cisternal perfusion for determination of cerebrospinal formation in cats

Phase contrast cine MRI with determination of pulsatile aqueductal cerebrospinal fluid (CSF) stroke volume and flow velocity has been suggested to assess intracranial pulsations in idiopathic normal pressure hydrocephalus (iNPH). We aimed to compare this non-invasive measure of pulsations to intracranial pressure (ICP) pulse wave amplitude from continuous ICP monitoring. We hypothesised that a significant correlation between these two markers of intracranial pulsations exists. Fifteen patients with suspected iNPH had continuous computerised ICP monitoring with calculation of mean ICP pulse wave amplitude (MWA) from time-domain analysis. MRI measured CSF aqueductal stroke volume and peak flow velocity. Mean MWA was 5.4 mmHg (range 2.3–12.4 mmHg). Mean CSF stroke volume and peak flow velocity were 65 μl (range 3–195 μl) and 9.31 cm/s (range 1.68–15.0 cm/s), respectively. No significant correlation between the invasive and non-invasive measures of pulsations existed (Spearman r = −0.30 and r = −0.27, respectively; p > 0.05). We observed marked intra-individual fluctuation of MWA during continuous ICP monitoring of an average of 6.0 mmHg (range 2.8–12.2 mmHg). The results suggest a complex interplay between measures of pulsations derived from snapshot MRI measurements and continuous computerised ICP measurements, as no significant relationship existed in our data. Further study is needed to better understand the temporal profile of CSF MRI flow studies, as substantial variation in MWA over the course of several hours of ICP monitoring is common, suggesting that these physiologic fluctuations might obscure MRI snapshot measures of intracranial pulsations.

Intracranial Pressure Monitoring and Assessing Intracranial Compliance in Brain Injury

Caring for the patient with a brain injury is a dynamic process with the goal of providing therapy to prevent secondary injury. Until practitioners have a better understanding of the pathophysiology of ischemia and the response of therapies for treating increased ICP, they must use the tools that exist. ICP monitoring gives a rough index of the relationships and the response of the intracranial contents to changes in volume that may produce increases in pressure and further damage. Understanding the information supplied by ICP monitoring is imperative to successful management of increased ICP.

頭蓋内圧脈波の振動解析に関する研究 線形振動モデルによるシミュレーション

頭蓋内圧脈波の振動解析に関する研究 線形振動モデルによるシミュレーション

Monitoring of cerebrospinal dynamics using continuous analysis of intracranial pressure and cerebral perfusion pressure in head injury.

Cerebrospinal dynamics has been investigated by statistical analysis of results of computerised monitoring of 80 head injured patients admitted to the Intensive Care Unit at Pinderfields General Hospital. One minute average values of intracranial pressure (ICP), systemic arterial pressure (ABP), cerebral perfusion pressure (CPP), amplitude of the fundamental component of the intracranial pressure pulse wave and the short-term moving correlation coefficient between that amplitude and mean ICP (RAP) were recorded. It was found that reduction of CPP down to 40 mmHg was more often caused by decrease in ABP than increase in ICP. Further falls in CPP below 40 mmHg were caused by substantial increases in ICP above 25 mmHg. The relationship between the ICP pulse wave amplitude and CPP showed a significant gradual increase in amplitude with CPP decreasing from 75 to 30 mmHg. For CPP below 30 mmHg there is a sharp decrease in amplitude followed by a change in the coefficient RAP from positive to negative values. This was interpreted as a sign of critical disturbance in cerebral circulation.

Analysis of intracranial pressure pulse wave in experimental hydrocephalus

Much has been written about the relationship between the pulse pressure (PP) of the intracranial pressure pulse wave (ICPPW) and ventricle dilatation. Some data suggest that high PP is the cause of ventricle dilatation, and other authors have reported that high PP results from decreased intracranial compliance. In order to clarify these points, the amplitude of PP and pressure-volume response (PVR: an indicator of intracranial compliance) were measured in bilateral ventricles using Hochwald's hydrocephalic model (right-left difference in ventricle size is clear due to hemicraniectomy). Hydrocephalus was induced by means of intracisternal injection of a kaolin powder solution to dogs. The mean ICP, amplitude of the PP, PVR and ventricle size (estimated by MR imaging) were evaluated in pathologic conditions induced by the following procedures. Group A, control: kaolin-induced hydrocephalus without craniectomy; group B: kaolin-induced hydrocephalus with right-sided craniectomy; group C: kaolin-induced hydrocephalus with right-sided craniectomy and dural resection; group D: kaolin-induced hydrocephalus with right-sided craniectomy, dura resection and temporal muscle resection. Using MR imaging, the same degree of symmetrical ventricle dilatation was identified in all groups except group D. Group D alone demonstrated a difference in ventricular size (craniectomy side > non-craniectomy side). There was no appreciable difference in mean ICP between any two groups. However, the amplitude of PP and the PVR decreased stepwise from group A to group D. The difference in the amplitude of the PP and PVR between the right and left ventricles was not significant in any group.(ABSTRACT TRUNCATED AT 250 WORDS)

Origin of lumbar cerebrospinal fluid pulse wave.

System analysis was performed on 16 adult mongrel dogs to determine the origin of the lumbar cerebrospinal fluid pulse wave. The descending thoracic aorta was occluded to evaluate the effects of the spinal arterial pulsations, and the thoracic aorta and inferior vena cava were simultaneously occluded to evaluate the effects of the spinal venous pulsations. It was concluded that, in the first harmonic wave, the components of the lumbar cerebrospinal fluid pulse wave are as follows: spinal arterial pulsations, 39.4%; spinal vascular (arteries and veins) pulsations, 77%; venous pulsations in the spinal canal, 37.6%; and the intracranial pressure pulse wave transmitted through the spinal canal from the intracranial space to the lumbar level, 23%.

Interpretation of ICP pulse waves to determine intracerebral compliance.

Recently, several authors have identified the need for monitoring cerebral compliance in addition to intracranial pressure (ICP) when managing patients with neurologic dysfunction. Analysis of the ICP pulse wave is one method for determining compliance. The ICP pulse wave, observed on a continuous real time pressure monitor display corresponding to each heart beat has three components analogous to the components of the arterial pulse wave. Analysis allows determination of intracerebral compliance. Implications for nursing care and suggestions for research based on ICP pulse wave analysis will also be discussed.

A mathematical study of human intracranial hydrodynamics. Part 1--The cerebrospinal fluid pulse pressure.

An original mathematical model of human intracranial hydrodynamics is proposed. Equations able to mimic the behavior of the intracranial arterial vascular bed, intracranial venous vascular bed, cerebrospinal fluid absorption and production processes, and the constancy of overall intracranial volume are separately presented and discussed. The model parameters were given normal values computed using physiological considerations and recent anatomical data. In this paper the model is used to simulate the genesis and morphology of the intracranial pressure pulse wave. In particular, dependence of the intracranial pressure pulse amplitude on mean intracranial pressure, obtained from the model, shows excellent agreement with recent experimental findings. The model explains the intracranial pressure pulse wave as the result of the pulsating changes in cerebral blood volume (related to cerebrovascular compliance) which occur within a rigid space (i.e., the craniospinal compartment). At low and medium values of intracranial pressure, the intracranial pressure pulse amplitude mainly reflects the cerebral pressure-volume relationship. However, during severe intracranial hypertension, an abrupt increase in the cerebrovascular compliance becomes evident, which is reflected in an abrupt increase in the intracranial pressure pulse wave.

Non-invasive measurement in intracranial pressure and analysis of the pulse waveform.

Non-invasive measurement of the intracranial pressure (ICP) via the anterior fontanelle by using an applanation transducer has been performed. Recently, a new fontanometer using an applanation transducer has been developed in our department by improving the conventional Statham transducer, P-50 which is currently accepted for its high reliability. In this study, by analysing patterns of the ICP pulse waves obtained from this new fontanometer, its clinical evaluation has been made in 27 neonates and infants in intracranial pathologies. Analysing the ICP waveforms, the first peak (P1) was divided by the following second peak (P2) and the changes in P1/P2 were examined. A differential amplifier, a dP/dt detector, was also used to make it easier to identify the turning point on the pulse waves. The results obtained demonstrated that the waveforms of ICP in neonates as well as infants are influenced by not only the intracranial constituents but compliance of the container such as the scalp, cranium and the meninges.

Changes in intracranial pressure (ICP) pulse wave following hydrocephalus.

The pulse pressure (PP) of the intracranial pressure pulse wave (ICPPW) was measured in experimental and clinical hydrocephalus: namely, obstructive and kaolin-induced hydrocephalus as an experimental study, and noncommunicating and communicating hydrocephalus as a clinical study. At approximately the same ICP level, the PP was much higher in the obstructive hydrocephalus group and slightly higher in the kaolin-induced hydrocephalus group than in the controls. Also the PP level in noncommunicating hydrocephalus patients [3.19 mm Hg (SD: 1.04)] was significantly (P less than 0.05) higher than that in the communicating hydrocephalus patients [1.88 mm Hg (SD: 0.60)]. The results of our research suggest that the stronger the disturbance of the communication of the CSF between cranial cavity and spinal cavity the higher the PP of ICPPW. This results from the distensibility of the spinal dural sac and exerts a great influence on the elasticity and the PP of the cranial system. It is reasonable, therefore, to suggest that a marked increase in the ratio of the PP to the ICP in the normal or slightly high ICP hydrocephalus may indicate disturbance of the CSF flow, especially loss of CSF communication between the cranial and spinal compartments.

Influence of Intracranial Components on Intracranial Pressure Pulse Wave

The following studies were made in order to clarify whether the intracranial pressure pulse wave (ICPPW) varies according to the pathological changes at the same level of intracranial pressure (ICP). The mean ICP and the ICPPW [particularly the pulse pressure (PP), and the tangent (rising slope)] were examined in four groups of anesthetized dogs under artificial respiration; 1) cisternal saline injections (control), 2) hypercapnia induced, 3) acute hydrocephalus, 4) chronic hydrocephalus. The following results were obtained: (1) In the control group, the PP and the tangent rose linearly with ICP; (2) At the same ICP level, hypercapnia increased the PP to a level higher than that of the control group. This is due to the fact that hypercapnia produced a significant increase in dv (pulsatile change in cerebral blood volume); (3) At an ICP level, acute hydrocephalus increased the PP and the tangent to levels higher than those of the control group. This may have been caused by an increase in the intracranial liquor and the isolation from the spinal sac, which acts to modulate pressure. (4) At an ICP level, chronic hydrocephalus increased the PP to a level higher than that of the control group. This may have been caused by an increase of intracranial liquor. It is concluded that ICPPW is influenced not only by ICP but by intracranial pathological changes.