Tag: intracranial pressure

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Pulsatile Dynamics of the Optic Nerve Sheath and Intracranial Pressure

ONS and ICP

Neurosurgery 79:100–107, 2016

Raised intracranial pressure (ICP) may lead to increased stiffness of the optic nerve sheath (ONS).

OBJECTIVE: To develop a method for analyzing ONS dynamics from transorbital ultrasound and investigate a potential difference between patients with raised ICP vs normal ICP.

METHODS: We retrospectively analyzed data from 16 patients (#12 years old) for whom ultrasound image sequences of the ONS had been acquired from both eyes just before invasive measurement of ICP. Eight patients had an ICP $20 mm Hg. The transverse motion on each side of the ONS was estimated from ultrasound, and Fourier analysis was used to extract the magnitude of the displacement corresponding to the heart rate. By calculating the normalized absolute difference between the displacements on each side of the ONS, a measure of ONS deformation was obtained. This parameter was referred to as the deformability index. According to our hypothesis, because deformability is inversely related to stiffness, we expected this parameter to be lower for ICP $20 mm Hg compared with ICP ,20 mm Hg. The one-sided Mann-Whitney U test was used for statistical comparison.

RESULTS: The deformability index was significantly lower in the group with ICP $20 mm Hg (median value 0.11 vs 0.24; P = .002).

CONCLUSION: We present a method for assessment of ONS pulsatile dynamics using transorbital ultrasound imaging. A significant difference was noted between the patient groups, indicating that deformability of the ONS may be relevant as a noninvasive marker of raised ICP. The clinical implications are promising and should be investigated in future clinical studies.

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Terson syndrome in aneurysmal subarachnoid hemorrhage

Terson syndrome

Acta Neurochir (2016) 158:1027–1036

A large number of reports have not been able to clarify the pathophysiology of Terson syndrome (TS) in aneurysmal subarachnoid hemorrhage (aSAH).

Methods Prospective single-center study on aSAH patients. Fundoscopic and radiological signs of TS were assessed. The opening intracranial pressure (ICP) in patients who required a ventriculostomy was recorded with a manometer.

Results Six out of 36 included patients had TS (16.7 %), which was associated with unfavorable admission scores. Twenty-nine patients (80.5 %) required ventriculostomy; TS was associated with higher ICP (median, 40 vs. 15 cm cmH2O, p= .003); all patients with TS had pathological ICP values of >20 cmH2O. Patients with a ruptured aneurysm of the anterior cerebral artery complex were ten times as likely to suffer from TS (OR 10.0, 95 % CI 1.03–97.50). Detection of TS on CT had a sensitivity of 50 %, a specificity of 98.4 %, a positive predictive value of 83.3 %, and a negative predictive value of 92.4 %. Mortality was 45 times as high in patients with TS (OR 45.0, 95 % CI 3.86–524.7) and neurologic morbidity up until 3 months post-aSAH was significantly higher in patients with TS (mRS 4–6; 100 vs. 17 %; p = .001).

Conclusions Our findings demonstrate an association between raised ICP and the incidence of TS. TS should be ruled out in aSAH patients presenting comatose or with raised ICP to ensure upfront ophthalmological follow-up. In alert patients without visual complaints and a TS-negative CT scan, the likelihood for the presence of TS is very low.

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Perioperative monitoring of pulsatile and static intracranial pressure in patients with Chiari malformation type 1

Natural history of Chiari malformation Type I following decision for conservative treatment

Acta Neurochir (2016) 158:341–347

Patients with Chiari malformation type 1 (CMI) often present with elevated pulsatile and static intracranial pressure (ICP). The preferred treatment of CMI, foramen magnum decompression (FMD), is assumed to normalise ICP and craniospinal pressure dissociation. In order to further explore the mechanisms behind FMD, the present study investigated whether or not pulsatile and static ICP normalises immediately after FMD.

Method The study included CMI patients undergoing FMD with perioperative ICP monitoring as a part of clinical management. The pulsatile and static ICP scores were retrieved from the department’s ICP database, and the clinical and radiological data from the patient records.

Results Eleven patients were included in the study. During the first 3 days following FMD, mixed model analysis revealed no significant time-dependent differences of preoperatively elevated either pulsatile (mean wave amplitude,MWA; p=0.85) and/or static (mean ICP, p = 0.90) ICP. Percentage of mean ICP >15 mmHg increased during days 2 and 3 after FMD. Two patients from the present series had to receive ventriculoperitoneal shunt after FMD in the early postoperative period.

Conclusions The present observations suggest that anatomical restoration of cerebrospinal fluid pathways by FMD does not lead to immediate normalisation of preoperatively altered pulsatile and static ICP in patients withCMI. This finding may explain persistent symptoms during the early period after FMD.

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Effect of postural changes on ICP in healthy and ill subjects

ICP

Acta Neurochir (2015) 157:109–113

Reference values and physiological measurements of intracranial pressure (ICP) are primarily reported in the supine position, while reports of ICP in the vertical position are surprisingly rare considering that humans maintain the vertical position for the majority of the day. In order to distinguish normal human physiology from disease entities such as idiopathic intracranial hypertension and normal pressure hydrocephalus, we investigated ICP in different body postures in both normal and ill subjects.

Methods Thirty-one patients were included: four normal patients following complete removal of a solitary clearly demarcated small brain tumour and fitted with a telemetric ICP monitoring device for long-term ICP monitoring; 27 patients requiring invasive ICP monitoring as a part of their diagnostic work-up or monitoring of shunt treatment effect. ICP was recorded in the following body positions: upright standing, sitting in a chair, supine and right lateral lumbar puncture position.

Results Linear regression of median ICP based on patient posture, group, and purpose of monitoring presented a significant model (p<0.001), but could not distinguish between patient groups (p=0.88). Regression of differences in median ICP between body postures and supine ICP as the baseline, presented a highly significant model (p<0.001) and adjusted R2=0.86. Both body posture (p<0.001) and patient group (p<0.001) were highly significant factors.

Conclusions Differences in ICP between body postures enabled us to distinguish the normal group from patient groups. Normal patients appear able to more tightly regulate ICP when switching body postures.

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Assessment of intracranial dynamics in hydrocephalus: effects of viscoelasticity on the outcome of infusion tests

Assessment of intracranial dynamics in hydrocephalus- effects of viscoelasticity on the outcome of infusion tests

J Neurosurg 119:1511–1519, 2013

The treatment of hydrocephalus requires insight into the intracranial dynamics in the patient. Resistance to CSF outflow (R0) is a clinically obtainable parameter of intracranial fluid dynamics that quantifies the apparent resistance to CSF absorption. It is used as a criterion for the selection of shunt candidates and serves as an indicator of shunt performance. The R0 is obtained clinically by performing 1 of 3 infusion tests: constant flow, constant pressure, or bolus infusion. Among these, the bolus infusion method has the shortest examination times and provides the shortest time of exposure of patients to artificially increased intracranial pressure (ICP) levels. However, for unknown reasons, the bolus infusion method systematically underestimates the R0. Here, the authors have tested and verified the hypothesis that this underestimation is due to lack of accounting for viscoelasticity of the craniospinal space in the calculation of the R0.

Methods. The authors developed a phantom model of the human craniospinal space in order to reproduce in vivo pressure-volume (PV) relationships during infusion testing. The phantom model followed the Marmarou exponential PV equation and also included a viscoelastic response to volume changes. Parameters of intracranial fluid dynamics, such as the R0, could be controlled and set independently. In addition to the phantom model, the authors designed a computational framework for virtual infusion testing in which viscoelasticity can be turned on or off in a controlled manner. Constant flow, constant pressure, and bolus infusion tests were performed on the phantom model, as well as on the virtual computational platform, using standard clinical protocols. Values for the R0 were derived from each infusion test by using both a standard method based on the Marmarou PV equation and a novel method based on a system identification approach that takes into account viscoelastic behavior.

Results. Experiments with the phantom model confirmed clinical observations that both the constant flow and constant pressure infusion tests, but not the bolus infusion test, yield correct R0 values when they are determined with the standard method according to Marmarou. Equivalent results were obtained using the computational framework. When the novel system identification approach was used to determine the R0, all of the 3 infusion tests yielded correct values for the R0.

Conclusions. The authors’ investigations demonstrate that intracranial dynamics have a substantial viscoelastic component. When this viscoelastic component is taken into account in calculations, the R0, is no longer underestimated in the bolus infusion test.

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The intracranial volume pressure response in increased intracranial pressure patients

The intracranial volume pressure response in increased intracranial pressure patients- Part 1

Acta Neurochir (2012) 154:2271–2275

The intracranial pressure (ICP) is usually continuously monitored in the management of patients with increased ICP. The aim of this study was to discover a mathematic equation to express the intracranial pressure– volume (P–V) curve and a single indicator to reflect the status of the curve.

Methods Patients with severe brain damage who had bilateral external ventricular drainage (EVD) from December 2008 to February 2010 were included in this study. The EVD was used as drainage of CSF and ICP monitor. The successive volume pressure response values were obtained by successive drainage of CSF from ICP 20–25 to 10 mmHg. Parabolic, exponential, and linear regression models were designed to have a single parameter as the indicator to determine the P–V curves.

Results The mean of parameter “a” in the exponential equation is 1.473±0.054; in the parabolic equation, it is 0.332±0.061; and in the linear equation, it is 1.717±0.209. All regression equations of P–V curves had statistical significance (p<0.005). Parabolic and exponential equations are closer to the original ICP curve than linear equation (p< 0.005). There is no statistically significant difference between parabolic and exponential regressions.

Conclusions The P–V curve can be expressed with linear, parabolic, and exponential regression models in increased ICP patients. The parabolic and exponential equations are more accurate methods to represent the P–V curve. The single parameter in the three regression equations can be compared in different conditions of one patient in clinical practice.

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New Telemetric Intracranial Pressure-Monitoring System

Neurosurgery 70[ONS Suppl 1]:ons44–ons49, 2012 DOI: 10.1227/NEU.0b013e31822dda12 

The knowledge of intracranial pressure (ICP) is the basis of an appropriate neurosurgical treatment. Because clinical, fundoscopic, or radiological data alone are often elusive, a pre- or postoperative long-term monitoring of the ICP itself is desirable.

OBJECTIVE: We describe the first clinical experiences with a new telemetric ICPmonitoring device.

METHODS: The transducer of this telemetric intraparenchymal pressure probe is placed under the galea over the calvaria. ICP can be monitored via a special telemetric reader, placed over the intact skin, and the ICP values are stored in a small portable computer. The system does not require an intensive care environment and can be used in any ward or even at home. The system was successfully applied in 10 patients (age, 3- 56 years) in whom raised ICP due to hydrocephalus, shunt dysfunction, endoscopic third ventriculostomy failure, craniostenosis, or pseudotumor cerebri was suspected.

RESULTS: Continuous telemetric monitoring of ICP was performed for 2 to 24 weeks. In 7 patients, increased ICP values could be excluded, and further surgical maneuvers were avoided. In 3 patients, repeated plateaus or continuously raised ICP indicated surgery resulting in a normalization of ICP.

CONCLUSION: This new telemetric system was safe and effective for ICP measurement over a long period, including home monitoring. For the patients, it was easy to handle, and reliable data could be recorded over many weeks. Based on this preliminary experience, the authors consider the new system extremely advantageous in surgical decision making in particularly difficult cases of suspected abnormalities of ICP.

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A Randomized and Blinded Single-Center Trial Comparing the Effect of Intracranial Pressure and Intracranial Pressure Wave Amplitude-Guided Intensive Care Management on Early Clinical State and 12-Month Outcome in Patients With Aneurysmal Subarachnoid Hemorrhage

Neurosurgery 69:1105–1115, 2011 DOI: 10.1227/NEU.0b013e318227e0e1

In patients with aneurysmal subarachnoid hemorrhage (SAH), preliminary results indicate that the amplitude of the single intracranial pressure (ICP) wave is a better predictor of the early clinical state and 6-month outcome than the mean ICP.

OBJECTIVE: To perform a randomized and blinded single-center trial comparing the effect of mean ICP vs mean ICP wave amplitude (MWA)-guided intensive care management on early clinical state and outcome in patients with aneurysmal SAH.

METHODS: Patients were randomized to 2 different types of ICP management: maintenance of mean ICP less than 20 mm Hg and MWA less than 5mm Hg. Early clinical state was assessed daily using the Glasgow Coma Scale. The primary efficacy variable was 12-month outcome in terms of the Rankin Stroke Score.

RESULTS: Ninety-seven patients were included in the study. There were no significant differences in treatment between the 2 groups apart from a larger volume of cerebrospinal fluid drained during week 1 in the MWA group. There was a tendency toward higher Glasgow Coma Scale scores in the MWA group during weeks 1 (P = .08) and 2 (P = .07). Outcome in terms of Rankin Stroke Score at 12 months was significantly better in the MWA group (P < .05).

CONCLUSION: This randomized and blinded trial disclosed a significant better primary efficacy variable (Rankin Stroke Score after 12 months) in the MWA patient group. We suggest that proactive intensive care management with MWA-tailored cerebrospinal fluid drainage during the first week improves aneurysmal SAH outcome.

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Benign external hydrocephalus: a review, with emphasis on management

Neurosurg Rev. DOI 10.1007/s10143-011-0327-4

Benign external hydrocephalus in infants, characterized by macrocephaly and typical neuroimaging findings, is considered as a self-limiting condition and is therefore rarely treated. This review concerns all aspects of this condition: etiology, neuroimaging, symptoms and clinical findings, treatment, and outcome, with emphasis on management. The review is based on a systematic search in the Pubmed and Web of Science databases. The search covered various forms of hydrocephalus, extracerebral fluid, and macrocephaly. Studies reporting small children with idiopathic external hydrocephalus were included, mostly focusing on the studies reporting a long-term outcome.

A total of 147 studies are included, the majority however with a limited methodological quality. Several theories regarding pathophysiology and various symptoms, signs, and clinical findings underscore the heterogeneity of the condition. Neuroimaging is important in the differentiation between external hydrocephalus and similar conditions. A transient delay of psychomotor development is commonly seen during childhood. A long-term outcome is scarcely reported, and the results are varying.

Although most children with external hydrocephalus seem to do well both initially and in the long term, a substantial number of patients show temporary or permanent psychomotor delay. To verify that this truly is a benign condition, we suggest that future research on external hydrocephalus should focus on the long-term effects of surgical treatment as opposed to conservative management.

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Guidelines for the Management of Spontaneous Intracerebral Hemorrhage

Stroke. 2010;41:2108-2129. DOI: 10.1161/STR.0b013e3181ec611b

Purpose—The aim of this guideline is to present current and comprehensive recommendations for the diagnosis and treatment of acute spontaneous intracerebral hemorrhage.

Methods—A formal literature search of MEDLINE was performed. Data were synthesized with the use of evidence tables. Writing committee members met by teleconference to discuss data-derived recommendations. The American Heart Association Stroke Council’s Levels of Evidence grading algorithm was used to grade each recommendation. Prerelease review of the draft guideline was performed by 6 expert peer reviewers and by the members of the Stroke Council Scientific Statements Oversight Committee and Stroke Council Leadership Committee. It is intended that this guideline be fully updated in 3 years’ time.

Results—Evidence-based guidelines are presented for the care of patients presenting with intracerebral hemorrhage. The focus was subdivided into diagnosis, hemostasis, blood pressure management, inpatient and nursing management, preventing medical comorbidities, surgical treatment, outcome prediction, rehabilitation, prevention of recurrence, and future considerations.

Conclusions—Intracerebral hemorrhage is a serious medical condition for which outcome can be impacted by early, aggressive care. The guidelines offer a framework for goal-directed treatment of the patient with intracerebral hemorrhage.

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Transcranial Doppler Pulsatility Index: Not an Accurate Method to Assess Intracranial Pressure

Neurosurgery 66 (6):1050–1057.
DOI 10.1227/01.NEU.0000369519.35932.F2

Transcranial Doppler sonography (TCD) assessment of intracranial blood flow velocity has been suggested to accurately determine intracranial pressure (ICP).

OBJECTIVE: We attempted to validate this method in patients with communicating cerebrospinal fluid systems using predetermined pressure levels.

METHODS: Ten patients underwent a lumbar infusion test, applying 4 to 5 preset ICP levels. On each level, the pulsatility index (PI) in the middle cerebral artery was determined by measuring the blood flow velocity using TCD. ICP was simultaneously measured with an intraparenchymal sensor. ICP and PI were compared using correlation analysis. For further understanding of the ICP-PI relationship, a mathematical model of the intracranial dynamics was simulated using a computer.

RESULTS: The ICP-PI regression equation was based on data from 8 patients. For 2 patients, no audible Doppler signal was obtained. The equation was ICP = 23*PI + 14 (R2 = 0.22, P < .01, N = 35). The 95% confidence interval for a mean ICP of 20 mm Hg was −3.8 to 43.8 mm Hg. Individually, the regression coefficients varied from 42 to 90 and the offsets from −32 to +3. The mathematical simulations suggest that variations in vessel compliance, autoregulation, and arterial pressure have a serious effect on the ICP-PI relationship.

CONCLUSIONS: The in vivo results show that PI is not a reliable predictor of ICP. Mathematical simulations indicate that this is caused by variations in physiological parameters.

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Is ventriculomegaly in idiopathic normal pressure hydrocephalus associated with a transmantle gradient in pulsatile intracranial pressure?

Acta Neurochir (2010) 152:989–995. DOI 10.1007/s00701-010-0605-x

Purpose: In patients with idiopathic normal pressure hydrocephalus (iNPH) and ventriculomegaly, examine whether there is a gradient in pulsatile intracranial pressure (ICP) from within the cerebrospinal fluid (CSF) of cerebral ventricles (ICPIV) to the subdural (ICPSD) compartment. We hypothesized that pulsatile ICP is higher within the ventricular CSF.

Methods The material includes 10 consecutive iNPH patients undergoing diagnostic ICP monitoring as part of pre-operative work-up. Eight patients had simultaneous ICPIV and ICPSD signals, and two patients had simultaneous signals from the lateral ventricle (ICPIV) and the brain parenchyma (ICPPAR). Intracranial pulsatility was characterized by the wave amplitude, rise time, and rise time coefficient; static ICP was characterized by mean ICP.

Results None of the patients demonstrated gradients in pulsatile ICP, that is, we found no evidence of higher pulsatile ICP within the CSF of the cerebral ventricles (ICPIV), as compared to either the subdural (ICPSD) compartment or within the brain parenchyma (ICPPAR). During ventricular infusion testing in one patient, the ventricular ICP (ICPIV) was artificially increased, but this increase in ICPIV produced no gradient in pulsatile ICP from the ventricular CSF (ICPIV) to the parenchyma (ICPPAR).

Conclusions: In this cohort of iNPH patients, we found no evidence of transmantle gradient in pulsatile ICP. The data gave no support to the hypothesis that pulsatile ICP is higher within the CSF of the cerebral ventricles (ICPIV) than within the subdural (ICPSD) compartment or the brain parenchyma (ICPPAR) in iNPH patients.

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Cerebral Hemodynamic Changes in Severe Head Injury Patients Undergoing Decompressive Craniectomy

J Neurosurg Anesthesiol 2009;21:339–345

Objective: To assess the intracranial hemodynamic modifica- tions induced by a decompressive craniectomy (DC) after severe traumatic brain injury (TBI), using transcranial Doppler (TCD) ultrasonography and intracranial pressure (ICP) sensor. Mor- tality rate and neurological outcomes were also evaluated after this procedure.

Design: A prospective study was carried out on 26 TBI patients, measuring transcranial Doppler and ICP before, immediately after, and 48 hours after the DC, allowing for statistical analysis of hemodynamic changes. The mortality rate and the neuro- logical outcomes were assessed.

Measurements and Results: After DC, ICP decreased from 37±17 to 20±13mm Hg (P=0.0003). The global cerebral blood flow was modified with diastolic velocities rising from 23±15 to 31±13cm/s (P=0.0038) and a pulsatility index decreasing from 1.70±0.66 to 1.18±0.37 (P=0.0012). This normalization of the global cerebral hemodynamics after the DC was immediate, symmetric, and constant during the first 48 hours. Outcome was evaluated at 6 months: good recovery or moderate disability was observed in 11 patients (42%), persistent vegetative state in 7 patients (27%), and 8 patients died (31%).

Conclusions: The DC results in a significant, immediate, and durable improvement of ICP associated with a normalization of cerebral blood flow velocities in most TBI patients with refractory intracranial hypertension.


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Relationship between intracranial hemodynamics and microdialysis markers of energy metabolism and glutamate-glutamine turnover in patients with subarachnoid hemorrhage

J Neurosurg 111:910–915, 2009.DOI: 10.3171/2008.8.JNS0889

The aim of this study was to explore the relationship between hemodynamics (intracranial and systemic) and brain tissue energy metabolism, and between hemodynamics and glutamate (Glt)-glutamine (Gln) cycle activity.

Methods. Brain interstitial levels of lactate, pyruvate, Glt, and Gln were prospectively monitored in the neurointensive care unit for more than 3600 hours using intracerebral microdialysis in 33 patients with subarachnoid hemorrhage (SAH). Intracranial pressure (ICP), mean arterial blood pressure, and cerebral perfusion pressure (CPP) were recorded using a digitalized system.

Results. Interstitial Gln and pyruvate correlated with CPP (r = 0.25 and 0.24, respectively). Intracranial pressure negatively correlated with Gln (r = −0.29) and the Gln/Glt ratio (r = –0.40). Levels of Gln and pyruvate and the Gln/Glt ratio were higher and levels of Glt and lactate and the lactate/pyruvate ratio were lower during periods of decreased ICP (≤ 10 mm Hg) as compared with values in periods of elevated ICP (> 10 mm Hg). In 3 patients, a poor clinical condition was attributed to high ICP levels (range 15–25 mm Hg). When CSF drainage was increased and the ICP was lowered to 10 mm Hg, there was an instantaneous sharp increase in interstitial Glt and pyruvate in these 3 patients.

Conclusions. Increasing interstitial Gln and pyruvate levels appear to be favorable signs associated with improved CPP and low ICP. The authors suggest that this pattern indicates an energy metabolic situation allowing augmented astrocytic energy metabolism with accelerated Glt uptake and Gln synthesis. Moreover, their data raised the question of whether patients with SAH and moderately elevated ICP (15–20 mm Hg) would benefit from CSF drainage at lower pressure levels than what is usually indicated in current clinical protocols.

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Cerebral Hemodynamic Changes in Severe Head Injury Patients Undergoing Decompressive Craniectomy

J Neurosurg Anesthesiol 2009;21:339–345

A prospective study was carried out on 26 TBI patients, measuring transcranial Doppler and ICP before, immediately after, and 48 hours after the DC, allowing for statistical analysis of hemodynamic changes. The mortality rate and the neuro- logical outcomes were assessed.

Measurements and Results: After DC, ICP decreased from 37±17 to 20±13mm Hg (P=0.0003). The global cerebral blood flow was modified with diastolic velocities rising from 23±15 to 31±13cm/s (P=0.0038) and a pulsatility index decreasing from 1.70±0.66 to 1.18±0.37 (P=0.0012). This normalization of the global cerebral hemodynamics after the DC was immediate, symmetric, and constant during the first 48 hours. Outcome was evaluated at 6 months: good recovery or moderate disability was observed in 11 patients (42%), persistent vegetative state in 7 patients (27%), and 8 patients died (31%).

Conclusions: The DC results in a significant, immediate, and durable improvement of ICP associated with a normalization of cerebral blood flow velocities in most TBI patients with refractory intracranial hypertension.

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