Cambios metabólicos corticales y resultado clínico en la hidrocefalia normotensiva después de la derivación ventrículo-peritoneal: nuestros resultados preliminares / Cortical metabolic changes and clinical outcome in normal pressure hydrocephalus after ventriculoperitoneal shunt: our preliminary results

INTRODUCCIÓN: Nuestro objetivo fue evaluar los cambios metabólicos corticales y el resultado clínico en los pacientes afectados por la hidrocefalia idiopática de presión normal (iNPH) después de la colocación de una derivación ventriculoperitoneal (VP). MATERIALES Y MÉTODOS: Diez pacientes afectados por la sospecha de iNPH se sometieron a una evaluación de la hidrodinámica del LCR basada en una prueba de infusión lumbar. El principal criterio de selección para la cirugía se basó en la elasticidad intracraneal (EI)>0,30. Todos los sujetos con una EI> 0,30 se sometieron a una exploración PET con 18 fluorodesoxiglucosa (18F-FDG) en la línea de base (PET1) y un mes después de la cirugía (PET2). Además, los mismos pacientes fueron sometidos a una evaluación clínica antes y un mes después de la cirugía mediante pruebas neuropsicológicas y análisis de la marcha. RESULTADOS: Se realizó un número total de 20 exploraciones de PET 18F-FDG en todos los pacientes reclutados. En comparación con la PET1, la PET2 mostró un aumento en el consumo de glucosa en el lóbulo frontal izquierdo y el lóbulo parietal izquierdo en la PET2 en comparación con la PET1 (p < 0,001). Todos los pacientes reclutados presentaron un aumento significativo en las puntuaciones neuropsicológicas (i.e. Batería de evaluación frontal y Evaluación cognitiva de Montreal) y han mejorado clínicamente en el análisis de la marcha. Se encontró una correlación significativa entre el aumento del consumo de glucosa cortical en el área parietal izquierda y la mejoría cognitiva detectable por la evaluación neuropsicológica. CONCLUSIONES: La mejora en 18F-FDG PET del metabolismo de la glucosa podría considerarse un marcador de imagen útil para la evaluación de la respuesta de la iNPH a la derivación ventriculoperitoneal

INTRODUCTION: Our objective was to evaluate the cortical metabolic changes and clinical outcome in patients affected by idiopathic normal pressure hydrocephalus (iNPH) after a placement of ventriculoperitoneal (VP) shunt. MATERIALS AND METHODS: 10 patients affected by suspected iNPH underwent a CSF hydrodynamics evaluation based on a lumbar infusion test (LIT). The main selection criterion for surgery was based on intracranial elasticity (IE)>0.30. All subjects with an IE>0.30 underwent a PET scan with 18 fluorodeoxiglucose (18F-FDG) at baseline (PET1) and 1 month after surgery (PET2). Furthermore, the same patients were submitted to clinical evaluation before and 1 month after surgery through neuropsychological tests and gait analysis. RESULTS: An overall number of 20 18F-FDG PET scans were performed in all the enrolled patients. As compared to PET1, PET2 showed an increase in glucose consumption in the left frontal and left parietal lobe in PET2 as compared to PET1 (P<.001). All the enrolled patients presented a significant increase in neuropsychological scores (i.e Frontal Assessment Battery and Montreal Cognitive Assessment) and have clinically improved at gait analysis. A significant correlation was found between the increase of cortical glucose consumption in the left parietal area and the cognitive improvement as detectable by neuropsychological assessment. CONCLUSIONS: Improvement in 18F FDG PET glucose metabolism could be considered a useful imaging marker for the assessment of iNPH response to VP shunting

Cortical metabolic changes and clinical outcome in normal pressure hydrocephalus after ventriculoperitoneal shunt: Our preliminary results. / Cambios metabólicos corticales y resultado clínico en la hidrocefalia normotensiva después de la derivación ventrículo-peritoneal: nuestros resultados preliminares.

INTRODUCTION: Our objective was to evaluate the cortical metabolic changes and clinical outcome in patients affected by idiopathic normal pressure hydrocephalus (iNPH) after a placement of ventriculoperitoneal (VP) shunt. MATERIALS AND METHODS: 10 patients affected by suspected iNPH underwent a CSF hydrodynamics evaluation based on a lumbar infusion test (LIT). The main selection criterion for surgery was based on intracranial elasticity (IE)>0.30. All subjects with an IE>0.30 underwent a PET scan with 18 fluorodeoxiglucose (18F-FDG) at baseline (PET1) and 1 month after surgery (PET2). Furthermore, the same patients were submitted to clinical evaluation before and 1 month after surgery through neuropsychological tests and gait analysis. RESULTS: An overall number of 20 18F-FDG PET scans were performed in all the enrolled patients. As compared to PET1, PET2 showed an increase in glucose consumption in the left frontal and left parietal lobe in PET2 as compared to PET1 (P<.001). All the enrolled patients presented a significant increase in neuropsychological scores (i.e Frontal Assessment Battery and Montreal Cognitive Assessment) and have clinically improved at gait analysis. A significant correlation was found between the increase of cortical glucose consumption in the left parietal area and the cognitive improvement as detectable by neuropsychological assessment. CONCLUSIONS: Improvement in 18F FDG PET glucose metabolism could be considered a useful imaging marker for the assessment of iNPH response to VP shunting.

Occurrence of CPPopt Values in Uncorrelated ICP and ABP Time Series.

OBJECTIVES: Optimal cerebral perfusion pressure (CPPopt) is a concept that uses the pressure reactivity (PRx)-CPP relationship over a given period to find a value of CPP at which PRx shows best autoregulation. It has been proposed that this relationship be modelled by a U-shaped curve, where the minimum is interpreted as being the CPP value that corresponds to the strongest autoregulation. Owing to the nature of the calculation and the signals involved in it, the occurrence of CPPopt curves generated by non-physiological variations of intracranial pressure (ICP) and arterial blood pressure (ABP), termed here "false positives", is possible. Such random occurrences would artificially increase the yield of CPPopt values and decrease the reliability of the methodology.In this work, we studied the probability of the random occurrence of false-positives and we compared the effect of the parameters used for CPPopt calculation on this probability. MATERIALS AND METHODS: To simulate the occurrence of false-positives, uncorrelated ICP and ABP time series were generated by destroying the relationship between the waves in real recordings. The CPPopt algorithm was then applied to these new series and the number of false-positives was counted for different values of the algorithm's parameters. RESULTS: The percentage of CPPopt curves generated from uncorrelated data was demonstrated to be 11.5%. CONCLUSION: This value can be minimised by tuning some of the calculation parameters, such as increasing the calculation window and increasing the minimum PRx span accepted on the curve.

Pressure Reactivity-Based Optimal Cerebral Perfusion Pressure in a Traumatic Brain Injury Cohort.

OBJECTIVES: Retrospective data from patients with severe traumatic brain injury (TBI) indicate that deviation from the continuously calculated pressure reactivity-based "optimal" cerebral perfusion pressure (CPPopt) is associated with worse patient outcome. The objective of this study was to assess the relationship between prospectively collected CPPopt data and patient outcome after TBI. METHODS: We prospectively collected intracranial pressure (ICP) monitoring data from 231 patients with severe TBI at Addenbrooke's Hospital, UK. Uncleaned arterial blood pressure and ICP signals were recording using ICM+® software on dedicated bedside computers. CPPopt was determined using an automatic curve fitting procedure of the relationship between pressure reactivity index (PRx) and CPP using a 4-h window, as previously described. The difference between an instantaneous CPP value and its corresponding CPPopt value was denoted every minute as ΔCPPopt. A negative ΔCPPopt that was associated with impaired PRx (>+0.15) was denoted as being below the lower limit of reactivity (LLR). Glasgow Outcome Scale (GOS) score was assessed at 6 months post-ictus. RESULTS: When ΔCPPopt was plotted against PRx and stratified by GOS groupings, data belonging to patients with a more unfavourable outcome had a U-shaped curve that shifted upwards. More time spent with a ΔCPPopt value below the LLR was positively associated with mortality (area under the receiver operating characteristic curve = 0.76 [0.68-0.84]). CONCLUSIONS: In a recent cohort of patients with severe TBI, the time spent with a CPP below the CPPopt-derived LLR is related to mortality. Despite aggressive CPP- and ICP-oriented therapies, TBI patients with a fatal outcome spend a significant amount of time with a CPP below their individualised CPPopt, indicating a possible therapeutic target.

ICP Versus Laser Doppler Cerebrovascular Reactivity Indices to Assess Brain Autoregulatory Capacity.

BACKGROUND: To explore the relationship between various autoregulatory indices in order to determine which approximate small vessel/microvascular (MV) autoregulatory capacity most accurately. METHODS: Utilizing a retrospective cohort of traumatic brain injury patients (N = 41) with: transcranial Doppler (TCD), intracranial pressure (ICP) and cortical laser Doppler flowmetry (LDF), we calculated various continuous indices of autoregulation and cerebrovascular responsiveness: A. ICP derived [pressure reactivity index (PRx)-correlation between ICP and mean arterial pressure (MAP), PAx-correlation between pulse amplitude of ICP (AMP) and MAP, RAC-correlation between AMP and cerebral perfusion pressure (CPP)], B. TCD derived (Mx-correlation between mean flow velocity (FVm) and CPP, Mx_a-correlation between FVm and MAP, Sx-correlation between systolic flow velocity (FVs) and CPP, Sx_a-correlation between FVs and MAP, Dx-correlation between diastolic flow index (FVd) and CPP, Dx_a-correlation between FVd and MAP], and LDF derived (Lx-correlation between LDF cerebral blood flow [CBF] and CPP, Lx_a-correlation between LDF-CBF and MAP). We assessed the relationship between these indices via Pearson correlation, Friedman test, principal component analysis (PCA), agglomerative hierarchal clustering (AHC), and k-means cluster analysis (KMCA). RESULTS: LDF-based autoregulatory index (Lx) was most associated with TCD-based Mx/Mx_a and Dx/Dx_a across Pearson correlation, PCA, AHC, and KMCA. Lx was only remotely associated with ICP-based indices (PRx, PAx, RAC). TCD-based Sx/Sx_a was more closely associated with ICP-derived PRx, PAx and RAC. This indicates that vascular-derived indices of autoregulatory capacity (i.e., TCD and LDF based) covary, with Sx/Sx_a being the exception, whereas indices of cerebrovascular reactivity derived from pulsatile CBV (i.e., ICP indices) appear to not be closely related to those of vascular origin. CONCLUSIONS: Transcranial Doppler Mx is the most closely associated with LDF-based Lx/Lx_a. Both Sx/Sx-a and the ICP-derived indices appear to be dissociated with LDF-based cerebrovascular reactivity, leaving Mx/Mx-a as a better surrogate for the assessment of cortical small vessel/MV cerebrovascular reactivity. Sx/Sx_a cocluster/covary with ICP-derived indices, as seen in our previous work.

Compensatory-Reserve-Weighted Intracranial Pressure and Its Association with Outcome After Traumatic Brain Injury.

OBJECTIVE: We introduced 'compensatory-reserve-weighted intracranial pressure (ICP),' named 'weightedICP' for brevity, as a variable that may better describe changes leading to mortality after traumatic brain injury (TBI) over the standard mean ICP. METHODS: ICP was monitored prospectively in over 1023 sedated and ventilated patients. The RAP coefficient (R-correlation, A-amplitude, and P-pressure) was calculated as the running correlation coefficient between slow changes in the pulse amplitude of ICP and the mean ICP. RAP has a value of 0 on the linear part of the pressure-volume curve and a value of + 1 on the ascending exponential part. Then, RAP decreases towards zero or even becomes negative when ICP increases further-a phenomenon thought to be related to the critical closing of cerebral vessels. In this study, we investigated a derived variable called weightedICP, calculated as ICP*(1 - RAP). RESULTS: Mortality after TBI was associated with both elevated ICP and weightedICP. Analysis of variance showed higher values of test statistics for weightedICP (K = 93) than for ICP (K = 64) in outcome categorization. Additionally, receiver operator curve analysis indicated greater area under the curve for weightedICP (0.71) than for ICP (0.67) with respect to associated mortality; however, the difference was not statistically significant (p = 0.12). The best threshold (maximizing sensitivity and specificity) was 19.5 mm Hg for mean ICP, and 8 mm Hg for weightedICP. Mortality rate expressed as a function of mean ICP and weightedICP showed an ascending profile in both cases. CONCLUSION: The proposed variable shows a significant association with mortality following head injury. It is sensitive to both the rising absolute ICP and to the critical deterioration of pressure-volume compensation.

Principles of intracranial pressure monitoring and treatment.

Intracranial pressure (ICP) is governed by volumes of intracranial blood, cerebrospinal fluid, and brain tissue. Expansion of any of these volumes will trigger compensatory changes in the other compartments, resulting in initially limited change in ICP. Due to the rigid skull, once compensatory mechanisms are exhausted, ICP rises very rapidly. Intracranial hypertension is associated with unfavorable outcome in brain-injured patients. This chapter discusses the pathophysiology of raised ICP, as well as typical waveforms, monitoring techniques, and clinical management. The dynamics of ICP are more important than the absolute value at any given time point, but mean ICP exceeding 20-25mmHg is usually treated aggressively. Algorithms based on data from patients with traumatic brain injury are applied also in other conditions. However, an understanding of the underlying pathophysiology allows adaptation of therapies to other pathologies. Typically, a three-staged approach is used, starting with restoration of systemic physiology, sedation, and analgesia. If these measures are insufficient, surgical options, such as drainage of cerebrospinal fluid or evacuation of mass lesions, are considered. In the absence of surgical options, stage 2 treatments are initiated, consisting of either mannitol or hypertonic saline. If these measures are insufficient, stage 3 therapies include hypothermia, metabolic suppression, or craniectomy.

Comparison of ventricular drain location and infusion test in hydrocephalus.

OBJECTIVES: Suspected cerebrospinal fluid shunt (CSF) dysfunction in hydrocephalic patients poses a diagnostic uncertainty. The clinical picture can be non-specific and CT imaging alone is not always pathognomonic. Infusion tests are an increasingly used investigation for real-time hydrodynamic assessment of shunt patency. We report the correlation between infusion test results with the quality of ventricular drain placement on CT scans in a large retrospective group of hydrocephalic patients. MATERIALS & METHODS: Three hundred and six infusion test results performed in 200 patients were correlated with 306 corresponding CT head scans. Nominal logistic regression was used to correlate shunt catheter position on CT imaging to patency of ventricular drain as determined by infusion tests. RESULTS: Infusion test results of shunt patency are statistically congruent with the analysis of shunt catheter position on CT head scans. Catheter tips completely surrounded by either parenchyma or CSF on CT imaging are strongly associated with evidence of occlusion or patency from infusion tests, respectively (χ² = 51.68, P < 0.0001, n = 306 and χ² = 31.04, P < 0.0001, n = 306). CONCLUSIONS: The most important anatomical factor for shunt patency is the catheter tip being completely surrounded by CSF. Infusion tests provide functional and reliable assessment of shunt patency in vivo and are strongly correlated with the position of the ventricular catheter on CT imaging.

Effects of pneumoperitoneum and Trendelenburg position on intracranial pressure assessed using different non-invasive methods.

BACKGROUND: The laparoscopic approach is becoming increasingly frequent for many different surgical procedures. However, the combination of pneumoperitoneum and Trendelenburg positioning associated with this approach may increase the patient's risk for elevated intracranial pressure (ICP). Given that the gold standard for the measurement of ICP is invasive, little is known about the effect of these common procedures on ICP. METHODS: We prospectively studied 40 patients without any history of cerebral disease who were undergoing laparoscopic procedures. Three different methods were used for non-invasive estimation of ICP: ultrasonography of the optic nerve sheath diameter (ONSD); transcranial Doppler-based (TCD) pulsatility index (ICPPI); and a method based on the diastolic component of the TCD cerebral blood flow velocity (ICPFVd). The ONSD and TCD were measured immediately after induction of general anaesthesia, after pneumoperitoneum insufflation, after Trendelenburg positioning, and again at the end of the procedure. RESULTS: The ONSD, ICPFVd, and ICPPI increased significantly after the combination of pneumoperitoneum insufflation and Trendelenburg positioning. The ICPFVd showed an area under the curve of 0.80 [95% confidence interval (CI) 0.70-0.90] to distinguish the stage associated with the application of pneumoperitoneum and Trendelenburg position; ONSD and ICPPI showed an area under the curve of 0.75 (95% CI 0.65-0.86) and 0.70 (95% CI 0.58-0.81), respectively. CONCLUSIONS: The concomitance of pneumoperitoneum and the Trendelenburg position can increase ICP as estimated with non-invasive methods. In high-risk patients undergoing laparoscopic procedures, non-invasive ICP monitoring through a combination of ONSD ultrasonography and TCD-derived ICPFVd could be a valid option to assess the risk of increased ICP.

Cerebral Critical Closing Pressure: Is the Multiparameter Model Better Suited to Estimate Physiology of Cerebral Hemodynamics?

BACKGROUND: Cerebral critical closing pressure (CrCP) is the level of arterial blood pressure (ABP) at which small brain vessels close and blood flow stops. This value is always greater than intracranial pressure (ICP). The difference between CrCP and ICP is explained by the tone of the small cerebral vessels (wall tension). CrCP value is used in several dynamic cerebral autoregulation models. However, the different methods for calculation of CrCP show frequent negative values. These findings are viewed as a methodological limitation. We intended to evaluate CrCP in patients with severe traumatic brain injury (TBI) with a new multiparameter impedance-based model and compare it with results found earlier using a transcranial Doppler (TCD)-ABP pulse waveform-based method. METHODS: Twelve severe TBI patients hospitalized during September 2005-May 2007. Ten men, mean age 32 years (16-61). Four had decompressive craniectomies (DC); three presented anisocoria. Patients were monitored with TCD cerebral blood flow velocity (FV), invasive ABP, and ICP. Data were acquired at 50 Hz with an in-house developed data acquisition system. We compared the earlier studied "first harmonic" method (M1) results with results from a new recently developed (M2) "multiparameter method." RESULTS: M1: In seven patients CrCP values were negative, reaching -150 mmHg. M2: All positive values; only one lower than ICP (ICP 60 mmHg/ CrCP 57 mmHg). There was a significant difference between M1 and M2 values (M1 < M2) and between ICP and M2 (M2 > ICP). CONCLUSION: M2 results in positive values of CrCP, higher than ICP, and are physiologically interpretable.

"Solid Red Line": An Observational Study on Death from Refractory Intracranial Hypertension.

The index of cerebrovascular pressure reactivity (PRx) correlates independently with outcome after traumatic brain injury (TBI). However, as an index plotted in the time domain, PRx is rather noisy. To "organise" PRx and make its interpretation easier, the colour coding of values, with green when PRx <0 and red when PRx> 0.3, has been introduced as a horizontal colour bar on the ICM+ screen. In rare cases of death from refractory intracranial hypertension, an increase in intracranial pressure (ICP) is commonly preceded by values of PRx >0.3, showing a "solid red line".Twenty patients after TBI and one after traumatic subarachnoid haemorrhage (SAH) from six centres in Europe and Australia have been studied. All of them died in a scenario of refractory intracranial hypertension. In the majority of cases the initial ICP was below 20 mmHg and finally increased to values well above 60 mmHg, resulting in cerebral perfusion pressure less than 20 mmHg. In three cases initial ICP was elevated at the start of monitoring. A solid red line was observed in all cases preceding an increase in ICP above 25 mmHg by minutes to hours and in two cases by 2 and 3 days, respectively. If a solid red line is observed over a prolonged period, it should be considered as an indicator of deep cerebrovascular deterioration.

Shunt Testing In Vivo: Observational Study of Problems with Ventricular Catheter.

Most shunt obstructions happen at the inlet of the ventricular catheter. Three hundred six infusion studies from 2007 to 2011 were classified as having a typical pattern of either proximal occlusion or patency. We describe different patterns of shunt ventricular obstruction.Solid block: Cerebrospinal fluid (CSF) aspiration was impossible. Baseline pressure was without pulse waveform (respiratory waveform may be visible). A quick increase of pressure to a level compatible with the shunt's setting was recorded in response to infusion. Distal occlusion of the shunt via transcutaneous compression resulted in a rapid increase in pressure to levels above 50 mmHg. This pattern was attributed to a solid ventricular block.Slit ventricles: At baseline, a pattern similar to that of the solid block was observed. After compression, the pressure increases, the pulse waveform appears, and the intracranial pressure is often stabilized at 25-40 mmHg. It is probable that previously slit ventricles were opened during the test.Partial block: In a partial block of the ventricular catheter by an in-growing choroid plexus, the pulse waveform at baseline was observed and CSF aspiration was possible. During infusion, the pressure increased, but the pulse amplitude disappeared. During the increase in the pressure in the shunt prechamber, the connection with the ventricles is disturbed by repositioning of the plexus.Infusion study via the shunt prechamber is able to visualize ventricular obstruction of the hydrocephalus shunt.

Non-invasive Monitoring of Intracranial Pressure Using Transcranial Doppler Ultrasonography: Is It Possible?

Although intracranial pressure (ICP) is essential to guide management of patients suffering from acute brain diseases, this signal is often neglected outside the neurocritical care environment. This is mainly attributed to the intrinsic risks of the available invasive techniques, which have prevented ICP monitoring in many conditions affecting the intracranial homeostasis, from mild traumatic brain injury to liver encephalopathy. In such scenario, methods for non-invasive monitoring of ICP (nICP) could improve clinical management of these conditions. A review of the literature was performed on PUBMED using the search keywords 'Transcranial Doppler non-invasive intracranial pressure.' Transcranial Doppler (TCD) is a technique primarily aimed at assessing the cerebrovascular dynamics through the cerebral blood flow velocity (FV). Its applicability for nICP assessment emerged from observation that some TCD-derived parameters change during increase of ICP, such as the shape of FV pulse waveform or pulsatility index. Methods were grouped as: based on TCD pulsatility index; aimed at non-invasive estimation of cerebral perfusion pressure and model-based methods. Published studies present with different accuracies, with prediction abilities (AUCs) for detection of ICP ≥20 mmHg ranging from 0.62 to 0.92. This discrepancy could result from inconsistent assessment measures and application in different conditions, from traumatic brain injury to hydrocephalus and stroke. Most of the reports stress a potential advantage of TCD as it provides the possibility to monitor changes of ICP in time. Overall accuracy for TCD-based methods ranges around ±12 mmHg, with a great potential of tracing dynamical changes of ICP in time, particularly those of vasogenic nature.

Non-invasive assessment of intracranial pressure.

Monitoring of intracranial pressure (ICP) is invaluable in the management of neurosurgical and neurological critically ill patients. Invasive measurement of ventricular or parenchymal pressure is considered the gold standard for accurate measurement of ICP but is not always possible due to certain risks. Therefore, the availability of accurate methods to non-invasively estimate ICP has the potential to improve the management of these vulnerable patients. This review provides a comparative description of different methods for non-invasive ICP measurement. Current methods are based on changes associated with increased ICP, both morphological (assessed with magnetic resonance, computed tomography, ultrasound, and fundoscopy) and physiological (assessed with transcranial and ophthalmic Doppler, tympanometry, near-infrared spectroscopy, electroencephalography, visual-evoked potentials, and otoacoustic emissions assessment). At present, none of the non-invasive techniques alone seem suitable as a substitute for invasive monitoring. However, following the present analysis and considerations upon each technique, we propose a possible flowchart based on the combination of non-invasive techniques including those characterizing morphologic changes (e.g., repetitive US measurements of ONSD) and those characterizing physiological changes (e.g., continuous TCD). Such an integrated approach, which still needs to be validated in clinical practice, could aid in deciding whether to place an invasive monitor, or how to titrate therapy when invasive ICP measurement is contraindicated or unavailable.

Assessment of non-invasive ICP during CSF infusion test: an approach with transcranial Doppler.

BACKGROUND: This study aimed to compare four non-invasive intracranial pressure (nICP) methods in a prospective cohort of hydrocephalus patients whose cerebrospinal fluid dynamics was investigated using infusion tests involving controllable test-rise of ICP. METHOD: Cerebral blood flow velocity (FV), ICP and non-invasive arterial blood pressure (ABP) were recorded in 53 patients diagnosed for hydrocephalus. Non-invasive ICP methods were based on: (1) interaction between FV and ABP using black-box model (nICP_BB); (2) diastolic FV (nICP_FVd); (3) critical closing pressure (nICP_CrCP); (4) transcranial Doppler-derived pulsatility index (nICP_PI). Correlation between rise in ICP (∆ICP) and ∆nICP and averaged correlations for changes in time between ICP and nICP during infusion test were investigated. RESULTS: From baseline to plateau, all nICP estimators increased significantly. Correlations between ∆ICP and ∆nICP were better represented by nICP_PI and nICP_BB: 0.45 and 0.30 (p < 0.05). nICP_FVd and nICP_CrCP presented non-significant correlations: -0.17 (p = 0.21), 0.21 (p = 0.13). For changes in ICP during individual infusion test nICP_PI, nICP_BB and nICP_FVd presented similar correlations with ICP: 0.39 ± 0.40, 0.39 ± 0.43 and 0.35 ± 0.41 respectively. However, nICP_CrCP presented a weaker correlation (R = 0.29 ± 0.24). CONCLUSIONS: Out of the four methods, nICP_PI was the one with best performance for predicting changes in ∆ICP during infusion test, followed by nICP_BB. Unreliable correlations were shown by nICP_FVd and nICP_CrCP. Changes of ICP observed during the test were expressed by nICP values with only moderate correlations.

Intracranial pressure, its components and cerebrospinal fluid pressure-volume compensation.

Clinical measurement of intracranial pressure (ICP) is often performed to aid diagnosis of hydrocephalus. This review discusses analysis of ICP and its components' for the investigation of cerebrospinal fluid (CSF) dynamics. The role of pulse, slow and respiratory waveforms of ICP in diagnosis, prognostication and management of hydrocephalus is presented. Two methods related to ICP measurement are listed: an overnight monitoring of ICP and a constant-rate infusion study. Due to the dynamic nature of ICP, a 'snapshot' manometric measurement of ICP is of limited use as it might lead to unreliable results. Therefore, monitoring of ICP over longer time combined with analysis of its waveforms provides more detailed information on the state of pressure-volume compensation. The infusion study implements ICP signal processing and CSF circulation model analysis in order to assess the cerebrospinal dynamics variables, such as CSF outflow resistance, compliance of CSF space, pressure amplitude, reference pressure, and CSF formation. These parameters act as an aid tool in diagnosis and prognostication of hydrocephalus and can be helpful in the assessment of a shunt malfunction.

Intraoperative non invasive intracranial pressure monitoring during pneumoperitoneum: a case report and a review of the published cases and case report series.

Non-invasive measurement of ICP (nICP) can be warranted in patients at risk for developing increased ICP during pneumoperitoneum (PP). Our aim was to assess available data on the application of nICP monitoring during these procedures and to present a patient assessed with an innovative combination of noninvasive tools. Literature review of nICP assessment during PP did not find any studies comparing different methods intraprocedurally and only few studies of any nICP monitoring were available: transcranial Doppler (TCD) studies used the pulsatility index (PI) as an estimator of ICP and failed to detect a significant ICP increase during PP, whereas two out of three optic nerve sheath diameter (ONSD) studies detected a statistically significant ICP increase. In the case study, we describe a 52 year old man with a high grade thalamic glioma who underwent urgent laparoscopic cholecystectomy. Considering the high intraoperative risk of developing intracranial hypertension, he was monitored through parallel ONSD ultrasound measurement and TCD derived formulae (flow velocity diastolic formula, FVdnICP, and PI). ONSD and FVdnICP methods indicated a significant ICP increase during PP, whereas PI was not significantly increased. Our experience, combined with the literature review, seems to suggest that PI might not detect ICP changes in this context, however we indicate a possible interest of nICP monitoring during PP by means of ONSD and of TCD derived FVdNICP, especially for patients at risk for increased ICP.