The complications and the position of the Codman MicroSensor™ ICP device: an analysis of 549 patients and 650 Sensors

Acute intracranial hemorrhage during the installation of the LICOX microdialysis system: A case report

Neuro-monitoring is widely employed for the evaluation of intubated patients in the intensive care unit with stroke, severe head trauma, subarachnoid hemorrhage and/or hepatic encephalopathy. The present study reports the case of a patient with acute intracranial hemorrhage following the insertion of neuromonitoring catheters, which required surgical management. The patient was a 14-year-old male who sustained a severe traumatic brain injury and underwent a right-sided hemicraniectomy. During the installation of the neuromonitoring catheters, an acute hemorrhage was noted with a rapidly elevating intracranial pressure. A craniotomy was performed to identify and coagulate the injured cortical vessel. As demonstrated herein, the thorough evaluation of the clotting profile of the patient, a meticulous surgical technique and obtaining a post-insertion computed tomography scan may minimize the risk of any neuromonitoring-associated hemorrhagic complications.

Intrasellar Pressure is Related to Endocrine Disturbances in Patients with Pituitary Tumors

OBJECTIVE

The aim of this study was to investigate the association between intraoperative intrasellar pressure (ISP) and pre- and postoperative endocrine disturbances with focus on hyperprolactinemia and hypopituitarism in patients with pituitary tumors.

METHODS

The study is a consecutive, retrospective study with ISP collected prospectively. One hundred patients operated with transsphenoidal surgery due to a pituitary tumor, who had their ISP measured intraoperatively, were included. Data on patient endocrine status preoperatively and from 3-month postoperative follow-up were collected from medical records.

RESULTS

The risk of preoperative hyperprolactinemia in patients with nonprolactinoma pituitary tumors increased with ISP (unit odds ratio 1.067, n = 70) (P = 0.041). Preoperative hyperprolactinemia was normalized at 3 months after surgery. Mean ISP was higher in patients with preoperative thyroid-stimulating hormone (TSH) deficiency (25.3 ± 9.2 mmHg, n = 37) than in patients with intact thyroid axis (21.6 ± 7.2 mmHg, n = 50) (P = 0.041). No significant difference in ISP was found between patients with and without adrenocorticotropic hormone(ACTH) deficiency. No association was found between ISP and postoperative hypopituitarism at 3 months after surgery.

CONCLUSIONS

In patients with pituitary tumors, preoperative hypothyroidism and hyperprolactinemia may be associated with higher ISP. This is in line with the theory of pituitary stalk compression, suggested to be mediated by an elevated ISP. ISP does not predict the risk of postoperative hypopituitarism 3 months after surgical treatment.

Accuracy of Intracranial Pressure Monitoring-Single Centre Observational Study and Literature Review

Intracranial hypertension and adequacy of brain blood flow are primary concerns following traumatic brain injury. Intracranial pressure (ICP) monitoring is a critical diagnostic tool in neurocritical care. However, all ICP sensors, irrespective of design, are subject to systematic and random measurement inaccuracies that can affect patient care if overlooked or disregarded. The wide choice of sensors available to surgeons raises questions about performance and suitability for treatment. This observational study offers a critical review of the clinical and experimental assessment of ICP sensor accuracy and comments on the relationship between actual clinical performance, bench testing, and manufacturer specifications. Critically, on this basis, the study offers guidelines for the selection of ICP monitoring technologies, an important clinical decision. To complement this, a literature review on important ICP monitoring considerations was included. This study utilises illustrative clinical and laboratory material from 1200 TBI patients (collected from 1992 to 2019) to present several important points regarding the accuracy of in vivo implementation of contemporary ICP transducers. In addition, a thorough literature search was performed, with sources dating from 1960 to 2021. Sources considered to be relevant matched the keywords: "intraparenchymal ICP sensors", "fiberoptic ICP sensors", "piezoelectric strain gauge sensors", "external ventricular drains", "CSF reference pressure", "ICP zero drift", and "ICP measurement accuracy". Based on single centre observations and the 76 sources reviewed in this paper, this material reports an overall anticipated measurement accuracy for intraparenchymal transducers of around ± 6.0 mm Hg with an average zero drift of <2.0 mm Hg. Precise ICP monitoring is a key tenet of neurocritical care, and accounting for zero drift is vital. Intraparenchymal piezoelectric strain gauge sensors are commonly implanted to monitor ICP. Laboratory bench testing results can differ from in vivo observations, revealing the shortcomings of current ICP sensors.

Intrasellar pressure in patients with pituitary adenoma - relation to tumour size and growth pattern

BACKGROUND

Only a few earlier publications on intrasellar pressure (ISP) have not been able to fully clarify any association between ISP and pituitary adenoma size and growth pattern. The aim of the study was to determine if intrasellar pressure (ISP) is elevated in patients with pituitary adenoma, and if the pressure is associated with tumour size and growth pattern.

METHODS

The study included 100 patients operated for suspected pituitary adenoma, who have had their ISP measured intraoperatively. All adenomas were classified on the basis of Knosp and SIPAP, from which further classification of invasiveness was performed. MRT examinations were used to calculate the tumour volume and diameter in three axes.

RESULTS

After exclusions, 93 cases were analysed. The mean ISP was 23.0 ± 8.4 mmHg. There were positive correlations between ISP and tumour volume and tumour diameters along all three axes. Coronal tumour diameter showed the strongest correlation with ISP elevation in a multivariate effect test. Adenomas classified as parasellar invasive (Knosp grade 3-4) showed higher mean ISP than adenomas considered as non-invasive (Knosp 0-2).

CONCLUSIONS

ISP is affected by tumour anatomy and correlates positively with tumour volume. Tumour width, i.e. diameter in the coronal plane, appears to be the measure that most strongly affects the ISP. This is confirmed by the association between ISP elevation and parasellar growth.

Intracranial Pressure Monitoring in the Intensive Care Unit for Patients with Severe Traumatic Brain Injury: Analysis of the CENTER-TBI China Registry

BACKGROUND

Although the current guidelines recommend the use of intracranial pressure (ICP) monitoring in patients with severe traumatic brain injury (sTBI), the evidence indicating benefit is limited. The present study aims to evaluate the impact of ICP monitoring on patients with sTBI in the intensive care unit (ICU).

METHODS

The patient data were obtained from the Collaborative European Neurotrauma Effectiveness Research in Traumatic Brain Injury China Registry, a prospective, multicenter, longitudinal, observational, cohort study. Patients with sTBI who were admitted to 52 ICUs across China, managed with ICP monitoring or without, were analyzed in this study. Patients with missing information on discharge survival status, Glasgow Coma Scale score on admission to hospital, and record of ICP monitoring application were excluded from the analysis. Data on demographic characteristics, injury, clinical features, treatments, survival at discharge, discharge destination, and length of stay were collected and assessed. The primary end point was survival state at discharge, and death from any cause was considered the event of interest.

RESULTS

A total of 2029 patients with sTBI were admitted to the ICU; 737 patients (36.32%) underwent ICP monitoring, and 1292 (63.68%) were managed without ICP monitoring. There was a difference between management with and without ICP monitoring on in-hospital mortality in the unmatched cohort (18.86% vs. 26.63%, p < 0.001) and the propensity-score-matched cohort (19.82% vs. 26.83%, p = 0.003). Multivariate logistic regressions also indicated that increasing age, higher injury severity score, lower Glasgow Coma Scale score, unilateral and bilateral pupillary abnormalities, systemic hypotension (SBP ≤ 90 mm Hg), hypoxia (SpO2 < 95%) on arrival at the hospital, and management without ICP monitoring were associated with higher in-hospital mortality. However, the patients without ICP monitoring had a lower length of stay in the ICU (11.79 vs. 7.95 days, p < 0.001) and hospital (25.96 vs. 21.71 days, p < 0.001), and a higher proportion of survivors were discharged to the home with better recovery in self-care.

CONCLUSIONS

Although ICP monitoring was not widely used by all of the centers participating in this study, patients with sTBI managed with ICP monitoring show a better outcome in overall survival. Nevertheless, the use of ICP monitoring makes the management of sTBI more complex and increases the costs of medical care by prolonging the patient's stay in the ICU or hospital.

Noninvasive Estimation of Pulsatile and Static Intracranial Pressure by Optical Coherence Tomography

Purpose

To explore the ability of optical coherence tomography (OCT) to noninvasively estimate pulsatile and static intracranial pressure (ICP).

Methods

An OCT examination was performed in patients who underwent continuous overnight monitoring of the pulsatile and static ICP for diagnostic purpose. We included two patient groups, patients with idiopathic intracranial hypertension (IIH; n = 20) and patients with no verified cerebrospinal fluid disturbances (reference; n = 12). Several OCT parameters were acquired using spectral-domain OCT (RS-3000 Advance; NIDEK, Singapore). The ICP measurements were obtained using a parenchymal sensor (Codman ICP MicroSensor; Johnson & Johnson, Raynham, MA, USA). The pulsatile ICP was determined as the mean ICP wave amplitude (MWA), and the static ICP was determined as the mean ICP.

Results

The peripapillary Bruch's membrane angle (pBA) and the optic nerve head height (ONHH) differed between the IIH and reference groups and correlated with both MWA and mean ICP. Both OCT parameters predicted elevated MWA. Area under the curve and cutoffs were 0.82 (95% confidence interval [CI], 0.66–0.98) and -0.65° (sensitivity/specificity; 0.75/0.92) for pBA and 0.84 (95% CI, 0.70–0.99) and 405 µm (0.88/0.67) for ONHH. Adjusting for age and body mass index resulted in nonsignificant predictive values for mean ICP, whereas the predictive value for MWA remained significant.

Conclusions

This study provides evidence that the OCT parameters pBA and ONHH noninvasively can predict elevated pulsatile ICP, represented by the MWA.

Translational Relevance

OCT shows promise as a method for noninvasive estimation of ICP.

Escalation therapy in severe traumatic brain injury: how long is intracranial pressure monitoring necessary?

Traumatic brain injury frequently causes an elevation of intracranial pressure (ICP) that could lead to reduction of cerebral perfusion pressure and cause brain ischemia. Invasive ICP monitoring is recommended by international guidelines, in order to reduce the incidence of secondary brain injury; although rare, the complications related to ICP probes could be dependent on the duration of monitoring. The aim of this manuscript is to clarify the appropriate timing for removal and management of invasive ICP monitoring, in order to reduce the risk of related complications and guarantee adequate cerebral autoregulatory control. There is no universal consensus concerning the duration of invasive ICP monitoring and its related complications, although the pertinent literature seems to show that the longer is the monitoring maintenance, the higher is the risk of technical issues. Besides, upon 72 h of normal ICP values or less than 72 h if the first computed tomography scan is normal (none or minimal signs of injury) and the neurological exam is available (allowing to observe variations and possible occurrence of new-onset pathological response), the removal of invasive ICP monitoring can be justified. The availability of non-invasive monitoring systems should be considered to follow up patients' clinical course after invasive ICP probe removal or for substituting the invasive monitoring in case of contraindication to its placement. Recently, optic nerve sheath diameter and straight sinus systolic flow velocity evaluation through ultrasound methods showed a good correlation with ICP values, demonstrating their potential role in place of invasive monitoring or in the early weaning phase from the invasive ICP monitoring.

The Sensor Reservoir-does it change management?

BACKGROUND

The Miethke Sensor Reservoir sits within a ventriculoperitoneal shunt system to give a reading of the pressure within the shunt. This information can guide the management of hydrocephalus patients who present frequently with headaches.

METHODS

We reviewed a cohort of 12 patients who underwent implantation of a Sensor Reservoir to assess how the management of their symptoms changed over a 4-year period.

RESULTS

When comparing the group before the Sensor Reservoir and after the Sensor Reservoir insertion, there was a 75% reduction in number of CT head scans (P<0.05), 100% reduction in episodes of ICP monitoring (P<0.05), 55% reduction in number of X-ray shunt series, and a 50% reduction in acute presentation to hospital with shunt-related symptoms. The number of clinic attendances increased by 44%. In addition, cost analysis showed a saving of £6952 per patients over the 2-year period following Sensor Reservoir insertion as a result of reduced admissions and investigations. Complications were seen in 3 patients-two patients developed shunt-related infections, and 1 patient underwent shunt revision due to a proximal shunt obstruction. Seventy-five percent of patients showed an improvement in their symptoms at the end of the 4-year period.

CONCLUSION

Implantation of a Sensor Reservoir in shunt patients with chronic headaches can reduce the number of investigations and hospital admissions and guide management resulting in a clinical improvement.

Using Optical Coherence Tomography as a Surrogate of Measurements of Intracranial Pressure in Idiopathic Intracranial Hypertension

Importance

There is an unmet need for noninvasive biomarkers of intracranial pressure (ICP), which manifests as papilledema that can be quantified by optical coherence tomography (OCT) imaging.

Objective

To determine whether OCT of the optic nerve head in papilledema could act as a surrogate measure of ICP.

Design, Setting, and Participants

This longitudinal cohort study used data collected from 3 randomized clinical trials that were conducted between April 1, 2014, and August 1, 2019. Participants who were female and had active idiopathic intracranial hypertension were enrolled from 5 National Health Service hospitals in the UK. Automated perimetry and OCT imaging were followed immediately by ICP measurement on the same day. Cohort 1 used continuous sitting telemetric ICP monitoring (Raumedic Neurovent P-tel device) on 1 visit. Cohort 2 was evaluated at baseline and after 3, 12, and 24 months and underwent lumbar puncture assessment of ICP.

Main Outcomes and Measures

Optical coherence tomography measures of the optic nerve head and macula were correlated with ICP levels, Frisén grading, and perimetric mean deviation. The OCT protocol included peripapillary retinal nerve fiber layer, optic nerve head, and macular volume scans (Spectralis [Heidelberg Engineering]). All scans were validated for quality and resegmented manually when required.

Results

A total of 104 women were recruited. Among cohort 1 (n = 15; mean [SD] age, 28.2 [9.4] years), the range of OCT protocols was evaluated, and optic nerve head central thickness was found to be most closely associated with ICP (right eye: r = 0.60; P = .02; left eye: r = 0.73; P = .002). Subsequently, findings from cohort 2 (n = 89; mean [SD] age, 31.8 [7.5] years) confirmed the correlation between central thickness and ICP longitudinally (12 and 24 months). Finally, bootstrap surrogacy analysis noted a positive association between central thickness and change in ICP at all points (eg, at 12 months, a decrease in central thickness of 50 μm was associated with a decrease in ICP of 5 cm H2O).

Conclusions and Relevance

In this study, optic nerve head volume measures on OCT (particularly central thickness) reproducibly correlated with ICP and surrogacy analysis demonstrated its ability to inform ICP changes. These data suggest that OCT has the utility to not only monitor papilledema but also noninvasively prognosticate ICP levels in idiopathic intracranial hypertension.

Correlation Between Invasive and Noninvasive Technique of Intracranial Pressure Measurement in Children With Traumatic Brain Injury: An Observational Study

BACKGROUND

Direct measurement of intracranial pressure (ICP) is an invasive technique with potential complications, which has prompted the development of alternative, noninvasive, methods of ICP assessment. The aim of this study was to determine the relationship between noninvasive ultrasound-based measurement of optic nerve sheath diameter (ONSD), transcranial Doppler-derived pulsatility index (PI), and invasive ICP measurements in children with traumatic brain injury (TBI).

METHODS

Children aged 1 to 18 years undergoing invasive ICP monitoring following TBI were included in the study. Noninvasive ONSD and PI measurements were compared with simultaneous invasive ICP.

RESULTS

In all, 406 measurements of ONSD and PI were obtained in 18 patients. ONSD and PI correlated with ICP (r=0.76 and 0.79, respectively), combining ONSD and PI resulted in an even stronger correlation with ICP (r=0.99). Formulas were derived from mixed-effect models that best fitted the data for noninvasive ICP estimation. A combination of ONSD and PI had the highest ability to detect ICP >20 mm Hg (area under the receiver operating characteristic curve=0.99, 95% confidence interval: 0.99-1.00). Optimal cutoff values for the prediction of intracranial hypertension were 5.95 mm for ONSD (sensitivity, 92%; specificity, 76%) and 1.065 for PI (sensitivity, 92%; specificity, 87%).

CONCLUSIONS

In children with TBI, a combination of ONSD and PI strongly correlates with invasive ICP and has potential to screen for intracranial hypertension noninvasively. ONSD and PI may be useful tools for assessing ICP where invasive monitoring is unavailable or contraindicated.

Complications of elective intracranial pressure monitoring in adult hydrocephalus

Continuous invasive monitoring of intracranial pressure (ICP) can be used in the diagnosis and management of various types of chronic cerebrospinal fluid (CSF) circulation disorders, such as hydrocephalus, shunt dysfunction and idiopathic intracranial hypertension. The risk profile and incidence of adverse events of this surgical procedure in this patient population is not well established. We aimed to investigate and describe the risks of ICP monitoring in adult patients with chronic CSF circulation disorders. We analysed 152 patients undergoing continuous ICP monitoring between 2010 and 2019, mainly for idiopathic normal pressure hydrocephalus. The average duration of ICP monitoring was 17 h 51 min. We observed no major adverse events, such as symptomatic intracranial haemorrhage, intracranial infection, or persistent neurological deficit. Minor complications were seen in 7% of patients and included accidental removal of the ICP probe in 4 patients, inability to remove the probe requiring surgical removal in 2 patients and single generalised seizures in 2 patients. In summary, the risk of serious adverse events and complications from invasive ICP monitoring in chronic CSF circulation disorders in adult patients appears to be low.

Intracranial Pressure and Intracranial Elastance Monitoring in Neurocritical Care

Patients with acute brain injuries tend to be physiologically unstable and at risk of rapid and potentially life-threatening decompensation due to shifts in intracranial compartment volumes and consequent intracranial hypertension. Invasive intracranial pressure (ICP) monitoring therefore remains a cornerstone of modern neurocritical care, despite the attendant risks of infection and damage to brain tissue arising from the surgical placement of a catheter or pressure transducer into the cerebrospinal fluid or brain tissue compartments. In addition to ICP monitoring, tracking of the intracranial capacity to buffer shifts in compartment volumes would help in the assessment of patient state, inform clinical decision making, and guide therapeutic interventions. We review the anatomy, physiology, and current technology relevant to clinical management of patients with acute brain injury and outline unmet clinical needs to advance patient monitoring in neurocritical care.

Prostacyclin Affects the Relation Between Brain Interstitial Glycerol and Cerebrovascular Pressure Reactivity in Severe Traumatic Brain Injury

Background

Cerebral injury may alter the autoregulation of cerebral blood flow. One index for describing cerebrovascular state is the pressure reactivity (PR). Little is known of whether PR is associated with measures of brain metabolism and indicators of ischemia and cell damage. The aim of this investigation was to explore whether increased interstitial levels of glycerol, a marker of cell membrane damage, are associated with PR, and if prostacyclin, a membrane stabilizer and regulator of the microcirculation, may affect this association in a beneficial way.

Materials and Methods

Patients suffering severe traumatic brain injury (sTBI) were treated according to an intracranial pressure (ICP)-targeted therapy based on the Lund concept and randomized to an add-on treatment with prostacyclin or placebo. Inclusion criteria were verified blunt head trauma, Glasgow Coma Score ≤ 8, age 15–70 years, and a first measured cerebral perfusion pressure of ≥ 10 mmHg. Multimodal monitoring was applied. A brain microdialysis catheter was placed on the worst affected side, close to the penumbra zone. Mean (glycerol_mean) and maximal glycerol (glycerol_max) during the 96-h sampling period were calculated. The mean PR was calculated as the ICP/mean arterial pressure (MAP) regression coefficient based on hourly mean ICP and MAP during the first 96 h.

Results

Of the 48 included patients, 45 had valid glycerol and PR measurements available. PR was higher in the placebo group as compared to the prostacyclin group (p = 0.0164). There was a positive correlation between PR and the glycerol_mean (ρ = 0.503, p = 0.01) and glycerol_max (ρ = 0.490, p = 0.015) levels in the placebo group only.

Conclusions

PR is correlated to the glycerol level in patients suffering from sTBI, a relationship that is not seen in the group treated with prostacyclin. Glycerol has been associated with membrane degradation and may support glycerol as a biomarker for vascular endothelial breakdown. Such a breakdown may impair the regulation of cerebrovascular PR.

Monitoring and Measurement of Intracranial Pressure in Pediatric Head Trauma

Purpose of Review: Monitoring of intracranial pressure (ICP) is an important and integrated part of the treatment algorithm for children with severe traumatic brain injury (TBI). Guidelines often recommend ICP monitoring with a treatment threshold of 20 mmHg. This focused review discusses; (1) different ICP technologies and how ICP should be monitored in pediatric patients with severe TBI, (2) existing evidence behind guideline recommendations, and (3) how we could move forward to increase knowledge about normal ICP in children to support treatment decisions.

Summary: Current reference values for normal ICP in adults lie between 7 and 15 mmHg. Recent studies conducted in “pseudonormal” adults, however, suggest a normal range below this level where ICP is highly dependent on body posture and decreases to negative values in sitting and standing position. Despite obvious physiological differences between children and adults, no age or body size related reference values exist for normal ICP in children. Recent guidelines for treatment of severe TBI in pediatric patients recommend ICP monitoring to guide treatment of intracranial hypertension. Decision on ICP monitoring modalities are based on local standards, the individual case, and the clinician's choice. The recommended treatment threshold is 20 mmHg for a duration of 5 min. Both prospective and retrospective observational studies applying different thresholds and treatment strategies for intracranial hypertension were included to support this recommendation. While some studies suggest improved outcome related to ICP monitoring (lower rate of mortality and severe disability), most studies identify high ICP as a marker of worse outcome. Only one study applied age-differentiated thresholds, but this study did not evaluate the effect of these different thresholds on outcome. The quality of evidence behind ICP monitoring and treatment thresholds in severe pediatric TBI is low and treatment can potentially be improved by knowledge about normal ICP from observational studies in healthy children and cohorts of pediatric “pseudonormal” patients expected to have normal ICP. Acceptable levels of ICP − and thus also treatment thresholds—probably vary with age, disease and whether the patient has intact cerebral autoregulation. Future treatment algorithms should reflect these differences and be more personalized and dynamic.

Relationship between intracranial pressure and phase-contrast cine MRI-derived measures of cerebrospinal fluid parameters in communicating hydrocephalus

Background

To explore the correlation between intracranial pressure (ICP) and cerebrospinal fluid (CSF) parameters assessed by phase-contrast cine MRI (PC-MRI).

Methods

Fifteen normal people and 80 subjects with communicating hydrocephalus who underwent PC-MRI examinations from a single center were included in this cross-sectional study. In addition to recording patient's age, heart rate, blood pressure and body mass index (BMI), ICP and CSF hemodynamic parameters, such as flow velocity and aqueduct diameter, were measured for correlation analysis.

Results

The mean ICP and CSF aqueduct diameter in hydrocephalus patients were 151.05 mmH₂O and 2.877 mm, respectively, and the maximum (6.938 cm/s) and mean (0.845 cm/s) CSF flow velocities were significantly higher in these patients compared with the controls (P<0.05). After adjusting for age, heart rate, blood pressure, and BMI, there was no significant relationship between peak velocity and ICP (P>0.05). Furthermore, a nonlinear relationship was observed between the ICP and the average velocity of CSF, and the ICP and aqueduct diameter. The ICP increased with the average velocity above 1.628 cm/s (P≤0.01), and the aqueduct diameter increased more than 3.6 mm (P<0.001).

Conclusions

This study found significant correlations between ICP and average velocity and aqueduct diameter. These findings can be useful in assisting clinicians in predicting ICP more effectively, thus improving patient management.

Complications of invasive intracranial pressure monitoring devices in neurocritical care

Intracranial pressure monitoring devices have become the standard of care for the management of patients with pathologies associated with intracranial hypertension. Given the importance of invasive intracranial monitoring devices in the modern neurointensive care setting, gaining a thorough understanding of the potential complications related to device placement-and misplacement-is crucial. The increased prevalence of intracranial pressure monitoring as a management tool for neurosurgical patients has led to the publication of a plethora of papers regarding their indications and complications. The authors aim to provide a concise review of key contemporary articles in the literature concerning important complications with the hope of elucidating practices that improve outcomes for neurocritically ill patients.

Proteomic differences between focal and diffuse traumatic brain injury in human brain tissue

The early molecular response to severe traumatic brain injury (TBI) was evaluated using biopsies of structurally normal-appearing cortex, obtained at location for intracranial pressure (ICP) monitoring, from 16 severe TBI patients. Mass spectrometry (MS; label free and stable isotope dimethyl labeling) quantitation proteomics showed a strikingly different molecular pattern in TBI in comparison to cortical biopsies from 11 idiopathic normal pressure hydrocephalus patients. Diffuse TBI showed increased expression of peptides related to neurodegeneration (Tau and Fascin, p < 0.05), reduced expression related to antioxidant defense (Glutathione S-transferase Mu 3, Peroxiredoxin-6, Thioredoxin-dependent peroxide reductase; p < 0.05) and increased expression of potential biomarkers (e.g. Neurogranin, Fatty acid-binding protein, heart p < 0.05) compared to focal TBI. Proteomics of human brain biopsies displayed considerable molecular heterogeneity among the different TBI subtypes with consequences for the pathophysiology and development of targeted treatments for TBI.

Intracranial Pressure: A Comparison of the Noninvasive HeadSense Monitor versus Lumbar Pressure Measurement

OBJECTIVE

To compare a new method of noninvasive intracranial pressure (nICP) measurement with conventional lumbar puncture (LP) opening pressure.

METHODS

In a prospective multicenter study, patients undergoing LP for diagnostic purposes underwent intracranial pressure measurements with HeadSense, a noninvasive transcranial acoustic device, and indirectly with LP. Noninvasive measurements were conducted with the head in a 30° tilt and in supine position before and after LP. The primary endpoint was the correlation between nICP measurement in supine position before LP and the LP opening pressure.

RESULTS

There was no correlation between supine nICPs before LP and the LP opening pressures (r = -0.211, P = 0.358). The 30° head-tilt nICPs correlated with the supine nICPs before LP (r = 0.830, P < 0.01). There was no correlation between supine nICPs before and after LP (r = 0.056, P = 0.831) or between 30° head-tilt nICPs and LP opening pressures (r = -0.038, P = 0.861).

CONCLUSIONS

There was no correlation between nICPs and LP opening pressures. Further development is warranted before transcranial acoustic HeadSense can become a clinical tool for investigating patients with neurologic conditions.

Non-invasive assessment of pulsatile intracranial pressure with phase-contrast magnetic resonance imaging

Invasive monitoring of pulsatile intracranial pressure can accurately predict shunt response in patients with idiopathic normal pressure hydrocephalus, but may potentially cause complications such as bleeding and infection. We tested how a proposed surrogate parameter for pulsatile intracranial pressure, the phase-contrast magnetic resonance imaging derived pulse pressure gradient, compared with its invasive counterpart. In 22 patients with suspected idiopathic normal pressure hydrocephalus, preceding invasive intracranial pressure monitoring, and any surgical shunt procedure, we calculated the pulse pressure gradient from phase-contrast magnetic resonance imaging derived cerebrospinal fluid flow velocities obtained at the upper cervical spinal canal using a simplified Navier-Stokes equation. Repeated measurements of the pulse pressure gradient were also undertaken in four healthy controls. Of 17 shunted patients, 16 responded, indicating high proportion of “true” normal pressure hydrocephalus in the patient cohort. However, there was no correlation between the magnetic resonance imaging derived pulse pressure gradient and pulsatile intracranial pressure (R = -.18, P = .43). Pulse pressure gradients were also similar in patients and healthy controls (P = .26), and did not differ between individuals with pulsatile intracranial pressure above or below established thresholds for shunt treatment (P = .97). Assessment of pulse pressure gradient at level C2 was therefore not found feasible to replace invasive monitoring of pulsatile intracranial pressure in selection of patients with idiopathic normal pressure hydrocephalus for surgical shunting. Unlike invasive, overnight monitoring, the pulse pressure gradient from magnetic resonance imaging comprises short-term pressure fluctuations only. Moreover, complexity of cervical cerebrospinal fluid flow and -pulsatility at the upper cervical spinal canal may render the pulse pressure gradient a poor surrogate marker for intracranial pressure pulsations.

Aspects on the Physiological and Biochemical Foundations of Neurocritical Care

Neurocritical care (NCC) is a branch of intensive care medicine characterized by specific physiological and biochemical monitoring techniques necessary for identifying cerebral adverse events and for evaluating specific therapies. Information is primarily obtained from physiological variables related to intracranial pressure (ICP) and cerebral blood flow (CBF) and from physiological and biochemical variables related to cerebral energy metabolism. Non-surgical therapies developed for treating increased ICP are based on knowledge regarding transport of water across the intact and injured blood-brain barrier (BBB) and the regulation of CBF. Brain volume is strictly controlled as the BBB permeability to crystalloids is very low restricting net transport of water across the capillary wall. Cerebral pressure autoregulation prevents changes in intracranial blood volume and intracapillary hydrostatic pressure at variations in arterial blood pressure. Information regarding cerebral oxidative metabolism is obtained from measurements of brain tissue oxygen tension (PbtO2) and biochemical data obtained from intracerebral microdialysis. As interstitial lactate/pyruvate (LP) ratio instantaneously reflects shifts in intracellular cytoplasmatic redox state, it is an important indicator of compromised cerebral oxidative metabolism. The combined information obtained from PbtO2, LP ratio, and the pattern of biochemical variables reveals whether impaired oxidative metabolism is due to insufficient perfusion (ischemia) or mitochondrial dysfunction. Intracerebral microdialysis and PbtO2 give information from a very small volume of tissue. Accordingly, clinical interpretation of the data must be based on information of the probe location in relation to focal brain damage. Attempts to evaluate global cerebral energy state from microdialysis of intraventricular fluid and from the LP ratio of the draining venous blood have recently been presented. To be of clinical relevance, the information from all monitoring techniques should be presented bedside online. Accordingly, in the future, the chemical variables obtained from microdialysis will probably be analyzed by biochemical sensors.

Safety profile and probe placement accuracy of intraspinal pressure monitoring for traumatic spinal cord injury: Injured Spinal Cord Pressure Evaluation study

OBJECTIVE

A novel technique for monitoring intraspinal pressure and spinal cord perfusion pressure in patients with traumatic spinal cord injury was recently described. This is analogous to monitoring intracranial pressure and cerebral perfusion pressure in patients with traumatic brain injury. Because intraspinal pressure monitoring is a new technique, its safety profile and impact on early patient care and long-term outcome after traumatic spinal cord injury are unknown. The object of this study is to review all patients who had intraspinal pressure monitoring to date at the authors' institution in order to define the accuracy of intraspinal pressure probe placement and the safety of the technique.

METHODS

At the end of surgery to fix spinal fractures, a pressure probe was inserted intradurally to monitor intraspinal pressure at the injury site. Postoperatively, CT scanning was performed within 48 hours and MRI at 2 weeks and 6 months. Neurointensive care management and complications were reviewed. The American Spinal Injury Association Impairment Scale (AIS) grade was determined on admission and at 2 to 4 weeks and 12 to 18 months postoperation.

RESULTS

To date, 42 patients with severe traumatic spinal cord injuries (AIS Grades A–C) had undergone intraspinal pressure monitoring. Monitoring started within 72 hours of injury and continued for up to a week. Based on postoperative CT and MRI, the probe position was acceptable in all patients, i.e., the probe was located at the site of maximum spinal cord swelling. Complications were probe displacement in 1 of 42 patients (2.4%), CSF leakage that required wound resuturing in 3 of 42 patients (7.1%), and asymptomatic pseudomeningocele that was diagnosed in 8 of 42 patients (19.0%). Pseudomeningocele was diagnosed on MRI and resolved within 6 months in all patients. Based on the MRI and neurological examination results, there were no serious probe-related complications such as meningitis, wound infection, hematoma, wound breakdown, or neurological deterioration. Within 2 weeks postoperatively, 75% of patients were extubated and 25% underwent tracheostomy. Norepinephrine was used to support blood pressure without complications. Overall, the mean intraspinal pressure was around 20 mm Hg, and the mean spinal cord perfusion pressure was around 70 mm Hg. In laminectomized patients, the intraspinal pressure was significantly higher in the supine than lateral position by up to 18 mm Hg after thoracic laminectomy and 8 mm Hg after cervical laminectomy. At 12 to 18 months, 11.4% of patients had improved by 1 AIS grade and 14.3% by at least 2 AIS grades.

CONCLUSIONS

These data suggest that after traumatic spinal cord injury intradural placement of the pressure probe is accurate and intraspinal pressure monitoring is safe for up to a week. In patients with spinal cord injury who had laminectomy, the supine position should be avoided in order to prevent rises in intraspinal pressure.

Noninvasive methods of detecting increased intracranial pressure

The detection of elevated intracranial pressure (ICP) is of paramount importance in the diagnosis and management of a number of neurologic pathologies. The current gold standard is the use of intraventricular or intraparenchymal catheters; however, this is invasive, expensive, and requires anesthesia. On the other hand, diagnosing intracranial hypertension based on clinical symptoms such as headaches, vomiting, and visual changes lacks sensitivity. As such, there exists a need for a noninvasive yet accurate and reliable method for detecting elevated ICP. In this review, we aim to cover both structural modalities such as computed tomography (CT), magnetic resonance imaging (MRI), ocular ultrasound, fundoscopy, and optical coherence tomography (OCT) as well as functional modalities such as transcranial Doppler ultrasound (TCD), visual evoked potentials (VEPs), and near-infrared spectroscopy (NIRS).

Characteristics of intracranial pressure (ICP) waves and ICP in children with treatment-responsive hydrocephalus

BACKGROUND

One important goal of modern treatment of pediatric hydrocephalus is to normalize the intracranial pressure (ICP) and ICP volume reserve capacity to optimize normal brain development. Better knowledge of the characteristics of ICP waves/ICP in pediatric hydrocephalus may provide new insight into the mechanisms behind modern hydrocephalus treatment. The aim of the present work was to characterize the ICP waves/ICP in children with either communicating or non-communicating hydrocephalus who improved clinically after surgery. The hydrocephalic children not treated surgically following ICP monitoring served as reference patients.

METHODS

The patient material includes all children with hydrocephalus and no previous surgical treatment who underwent diagnostic ICP wave/ICP monitoring during the period 2002-2011. We retrieved the information about the patients from the patient records and the digitally stored ICP waveforms. The ICP wave characteristics amplitude, rise time and rise time coefficient and the mean ICP were determined in the patients treated surgically for their hydrocephalus. The findings were compared with findings in children not treated surgically after ICP monitoring who served as reference patients.

RESULTS

The patient material includes 58 patients. Thirty-one (53%) were treated surgically after ICP monitoring, of whom all improved clinically. As compared to the reference patients, patients treated surgically presented with increased ICP wave amplitudes (MWA) and mean ICP. Alterations were comparable in communicating and non-communicating hydrocephalus. We found no apparent association between the ICP wave/ICP scores and presence of symptoms, indices of ventricular size or age.

CONCLUSIONS

Children with either communicating or non-communicating hydrocephalus improving clinically after surgery presented with elevated MWA and mean ICP. In particular, the levels of MWA were raised to a magnitude seen when intracranial compliance is impaired. Hence, the present observations may support the idea that improvement of intracranial compliance can be an important mechanism by which shunts work in pediatric hydrocephalus.

Intracranial pressure monitoring in pediatric and adult patients with hydrocephalus and tentative shunt failure: a single-center experience over 10 years in 146 patients

OBJECT In patients with hydrocephalus and shunts, lasting symptoms such as headache and dizziness may be indicative of shunt failure, which may necessitate shunt revision. In cases of doubt, the authors monitor intracranial pressure (ICP) to determine the presence of over- or underdrainage of CSF to tailor management. In this study, the authors reviewed their experience of ICP monitoring in shunt failure. The aims of the study were to identify the complications and impact of ICP monitoring, as well as to determine the mean ICP and characteristics of the cardiac-induced ICP waves in pediatric versus adult over- and underdrainage. METHODS The study population included all pediatric and adult patients with hydrocephalus and shunts undergoing diagnostic ICP monitoring for tentative shunt failure during the 10-year period from 2002 to 2011. The patients were allocated into 3 groups depending on how they were managed following ICP monitoring: no drainage failure, overdrainage, or underdrainage. While patients with no drainage failure were managed conservatively without further actions, over- or underdrainage cases were managed with shunt revision or shunt valve adjustment. The ICP and ICP wave scores were determined from the continuous ICP waveforms. RESULTS The study population included 71 pediatric and 75 adult patients. There were no major complications related to ICP monitoring, but 1 patient was treated for a postoperative superficial wound infection and another experienced a minor bleed at the tip of the ICP sensor. Following ICP monitoring, shunt revision was performed in 74 (51%) of 146 patients, while valve adjustment was conducted in 17 (12%) and conservative measures without any actions in 55 (38%). Overdrainage was characterized by a higher percentage of episodes with negative mean ICP less than -5 to -10 mm Hg. The ICP wave scores, in particular the mean ICP wave amplitude (MWA), best differentiated underdrainage. Neither mean ICP nor MWA levels showed any significant association with age. CONCLUSIONS In this cohort of pediatric and adult patients with hydrocephalus and tentative shunt failure, the risk of ICP monitoring was very low, and helped the authors avoid shunt revision in 49% of the patients. Mean ICP best differentiated overdrainage, which was characterized by a higher percentage of episodes with negative mean ICP less than -5 to -10 mm Hg. Underdrainage was best characterized by elevated MWA values, indicative of impaired intracranial compliance.