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Causes of Intracranial Hypertension (Grouped by Mechanism) 

Causes of Intracranial Hypertension (Grouped by Mechanism) 

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Increased intracranial pressure (ICP) is one of the major causes of secondary brain ischemia that accompanies a variety of pathological conditions, most notably, traumatic brain injury (TBI), stroke, and intracranial hemorrhages. However, aside from a few Level I trauma centers, ICP monitoring is rarely a part of the clinical management of patients...

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... There is a well-recognised clinical need for a practical non-invasive method of assessing intracranial pressure (ICP) (Zhang et al 2017, Evensen andEide 2020). Several techniques have been described, none of which have yet been widely adopted in patient applications (Popovic et al 2009, Khan et al 2017, Zhang et al 2017, Evensen and Eide 2020. The clinical uses of ICP measurement include long term monitoring of patients with chronic conditions such as cerebral spinal fluid (CSF) leaks, idiopathic intracranial hypertension and patients with ventricular peritoneal shunts. ...
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Objective: Evoked tympanic membrane displacement (TMD) measurements show a correlation with intracranial pressure (ICP). Attempts to use these measurements for non-invasive monitoring of ICP in patients have been limited by high measurement variability. Pulsing of the tympanic membrane at the cardiac frequency has been shown to be a significant source of the variability. In this study we describe a post processing method to remove the cardiac pulse waveform and assess the impact of this on the measurement and its repeatability. Approach: Three-hundred and sixteen healthy volunteers were recruited for evoked TMD measurements. The measurements were quantified by V m, defined as the mean displacement between the point of maximum inward displacement and the end of the stimulus. A sample of spontaneously pulsing TMDs was measured immediately before the evoked measurements. Simultaneous recording of the ECG allowed a heartbeat template to be extracted from the spontaneous data and subtracted from the evoked data. Intra-subject repeatability of V m was assessed from 20 repeats of the evoked measurement. Results with and without subtraction of the heartbeat template were compared. The difference was tested for significance using the Wilcoxon sign rank test. Main results: In left and right ears, both sitting and supine, application of the pulse correction significantly reduced the intra-subject variability of V m (p value range 4.0 × 10-27 to 2.0 × 10-31). The average improvement was from 98 ± 6 nl to 56 ± 4 nl. Significance: The pulse subtraction technique substantially improves the repeatability of evoked TMD measurements. This justifies further investigations to assess the use of TMD measurements in clinical applications where non-invasive tracking of changes in ICP would be useful.
... As a result, LP is no longer recommended for use in diagnosing ICH in neurocritical care settings and is reserved more often for use in hydrocephalus and idiopathic intracranial hypertension [3,29]. Guidelines regarding the accuracy of invasive ICP measurement have been outlined by The American National Standards Institute (ANSI)/Association for the Advancement of Medical Instrumentation (AAMI) and specify that ICP in the range of 0 − 20 mm Hg should maintain an accuracy of ±2 mm Hg, while ICP > 20 mm Hg should not exceed 10% error [31,32]. The relationship between pressure and volume within the intracranial compartment. ...
... Otoacoustic emissions (OAEs) are sounds generated by the inner ear in response to a loud sound, which can be evoked using a number of techniques [31,73]. The mangitude of these OAEs has been shown to be sensitive to changes in ICP [74][75][76][77][78]. ...
... Optical coherence tomography (OCT) is an imaging technique that acts effectively as an "optical ultrasound" and can be used to measure retinal nerve fiber layer (RNFL) thickness in papilledema [109]. Intracranial hypertension can result in swelling of the RNFL [31]. A patented method exists that uses OCT to measure RNFL thickness and thereby infer ICP values [110]. ...
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Measurement of intracranial pressure (ICP) is crucial in the management of many neurological conditions. However, due to the invasiveness, high cost, and required expertise of available ICP monitoring techniques, many patients who could benefit from ICP monitoring do not receive it. As a result, there has been a substantial effort to explore and develop novel noninvasive ICP monitoring techniques to improve the overall clinical care of patients who may be suffering from ICP disorders. This review attempts to summarize the general pathophysiology of ICP, discuss the importance and current state of ICP monitoring, and describe the many methods that have been proposed for noninvasive ICP monitoring. These noninvasive methods can be broken down into four major categories: fluid dynamic, otic, ophthalmic, and electrophysiologic. Each category is discussed in detail along with its associated techniques and their advantages, disadvantages, and reported accuracy. A particular emphasis in this review will be dedicated to methods based on the use of transcranial Doppler ultrasound. At present, it appears that the available noninvasive methods are either not sufficiently accurate, reliable, or robust enough for widespread clinical adoption or require additional independent validation. However, several methods appear promising and through additional study and clinical validation, could eventually make their way into clinical practice.
... Moreover, the maximum error should not exceed ± 10% in a range of 20-100 mmHg. With regard to nICP monitoring, the AAMI also states that when ICP is between 0 and 20 mmHg, a difference of 2 mmHg is acceptable when comparing nICP and ICP measurements, and when ICP is 20-100 mmHg, the difference should be less than 10% [83]. ...
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Sixty years have passed since neurosurgeon Nils Lundberg presented his thesis about intracranial pressure (ICP) monitoring, which represents a milestone for its clinical introduction. Monitoring of ICP has since become a clinical routine worldwide, and today represents a cornerstone in surveillance of patients with acute brain injury or disease, and a diagnostic of individuals with chronic neurological disease. There is, however, controversy regarding indications, clinical usefulness and the clinical role of the various ICP scores. In this paper, we critically review limitations and weaknesses with the current ICP measurement approaches for invasive, less invasive and non-invasive ICP monitoring. While risk related to the invasiveness of ICP monitoring is extensively covered in the literature, we highlight other limitations in current ICP measurement technologies, including limited ICP source signal quality control, shifts and drifts in zero pressure reference level, affecting mean ICP scores and mean ICP-derived indices. Control of the quality of the ICP source signal is particularly important for non-invasive and less invasive ICP measurements. We conclude that we need more focus on mitigation of the current limitations of today's ICP modalities if we are to improve the clinical utility of ICP monitoring.
... The invasiveness of the ICP measurement and the need for neurosurgical expertise to place such a catheter have motivated a variety of engineering approaches to make this important cranial vital sign available noninvasively [15], [16]. A particular class of approaches to continuous ICP estimation relies on waveform measurements of cerebral blood flow velocity (CBFV), recorded noninvasively using transcranial Doppler (TCD) ultrasonography, and radial arterial blood pressure (ABP), measured invasively through indwelling catheters [17]- [20]. ...
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Background: Intracranial pressure (ICP) normally ranges from 5 to 15 mmHg. Elevation in ICP is an important clinical indicator of neurological injury, and ICP is therefore monitored routinely in several neurological conditions to guide diagnosis and treatment decisions. Current measurement modalities for ICP monitoring are highly invasive, largely limiting the measurement to critically ill patients. An accurate noninvasive method to estimate ICP would dramatically expand the pool of patients that could benefit from this cranial vital sign. Methods: This work presents a spectral approach to model-based ICP estimation from arterial blood pressure (ABP) and cerebral blood flow velocity (CBFV) measurements. The model captures the relationship between the ABP, CBFV and ICP waveforms and utilizes a second-order model of the cerebral vasculature to estimate ICP. Results: The estimation approach was validated on two separate clinical datasets, one recorded from thirteen pediatric patients with a duration of around seven hours, and the other recorded from five adult patients, one hour and 48 minutes in duration. The algorithm was shown to have an accuracy (mean error) of 0.4 mmHg and -1.5 mmHg, and a precision (standard deviation of the error) of 5.1 mmHg and 4.3 mmHg, in estimating mean ICP (range of 1.3 mmHg to 24.8 mmHg) on the pediatric and adult data, respectively. These results are comparable to previous results and within the clinically relevant range. Additionally, the accuracy and precision in estimating the pulse pressure of ICP on a beat-by-beat basis were found to be 1.3 mmHg and 2.9 mmHg respectively. Conclusion: These contributions take a step towards realizing the goal of implementing a real-time noninvasive ICP estimation modality in a clinical setting, to enable accurate clinical-decision making while overcoming the drawbacks of the invasive ICP modalities.
... De plus, ils sont plus précis que ceux obtenus avec d'autres méthodes non invasives. D'après la revue scientifique (Popovic, Khoo, and Lee 2009) qui recense les méthodes disponibles, la meilleure précision, entre 3 et 5 mmHg, est réalisée avec un test d'ophtalmo-dynamométrie. La surveillance des variations de la PIC étant basée sur des mesures indirectes de la variation de pression intracochléaire, toutes les améliorations présentées en termes de précision, de stabilité des mesures et de possibilité de réduire l'influence de l'opérateur bénéficieront directement au test shift-OAE (pour les diagnostics de la maladie de Ménière). ...
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La mesure non invasive de la pression intracrânienne (PIC) est un sujet de recherche depuis des décennies, car les méthodes invasives comportent des risques d’hémorragies et d’infections. La surveillance non invasive par des réponses cochléaires a été suggérée comme étant une mesure fiable. Une des réponses couramment analysées dans ces méthodes est celle des produits de distorsion acoustique (PDA). La mesure du PDA est rapide et simple, car il suffit d'envoyer une stimulation sonore et d'enregistrer la réponse acoustique produit par les cellules ciliées externes à l'aide d'une seule sonde (comme une oreillette) dans le conduit auditif externe. Le déphasage du PDA est le paramètre qui nous permet de surveiller les variations de la PIC. Comme il s'agit d'une mesure relative, il est nécessaire de disposer d'une référence individuelle qui ne devrait pas être modifiée pendant ou entre les mesures. Cependant, les phases sont sensibles au positionnement de la sonde et (même de légères) variations de l'impédance de l'oreille. De plus, l’âge du patient influence les niveaux du PDA qui réduisent généralement avec le vieillissement. Ils sont aussi fragiles et très sensibles à l’environnement acoustique, en particulier le bruit généré par le patient. Le présent travail présente initialement le développement d'une méthode de traitement du signal basée sur l'analyse de la distribution du signal pour l'identification et la réjection automatique des sections bruyantes, afin d'améliorer la robustesse de l'extraction du signal du bruit de fond acoustique. La méthode mise au point a été comparée à la rejection de sections sur la base de seuils déterminés par l'opérateur à l'aide de l'analyse visuelle du spectre du signal (méthode standard). Les résultats ont indiqué un niveau de bruit statistiquement inférieur et des signaux plus stables lors de l'utilisation de la méthode automatique. Une deuxième étude présente une technique de détection du positionnement des sondes et des fuites d'air (AFPS), en utilisant l'analyse de la réponse en fréquence de la pression mesurée dans le conduit auditif externe après une stimulation large bande. Dans cette étude une table d'inclinaison a été utilisée pour induire une légère variation de la PIC dans quatre positions (60°, 0°, -20° et encore 60°) en deux séries de mesures. Nous avons analysé la reproductibilité entre les deux essais et les effets sur les résultats du test du déplacement de la sonde et des fuites d’air quand elles étaient identifiées. Ces analyses ont indiqué que la méthode AFPS est en mesure de classer correctement les signaux en fonction de la présence de fuites d'air ou du déplacement de la sonde. Pour la dernière expérience, les deux techniques (rejection automatique et AFPS) ont été adaptées pour être utilisées en temps réel, permettant d'identifier et de corriger les problèmes éventuels avant ou pendant le test. Nous avons comparé l'appareil modifié et l'appareil commercial en deux séances d'essai, de sorte que chaque appareil a été utilisé pour les deux oreilles. Dans chaque séance, trois tests ont été effectués (T1, T2 et T3), chacun avec cinq valeurs enregistrées pour chacune des trois positions (45°, 0° "position couchée" et -10°). Les trois tests ont été effectués afin de permettre l'analyse de la reproductibilité des mesures, sans et avec l’effet du remplacement de sonde, et sa précision (exprimée par l'écarttype des différences). La méthode AFPS augmente la robustesse, fournissant des valeurs plus cohérentes dans toutes les analyses, surtout en cas de repositionnement de la sonde. La réjection automatique réduit la variabilité entre les cinq mesures prises pour la même position, augmentant ainsi la stabilité et la précision des réponses.
... Since the use of invasive ICP measuring techniques has many limitations, noninvasive methods have been developed and proposed to evaluate ICP via related physiological vari-ables [55]. In this chapter we will focus on the most common noninvasive techniques available [56]. The predominant methodologies to assess noninvasive ICP ground their basis on the knowledge that the anatomical structures play an intricate part of the physiology that governs ICP. ...
... Another area that remains uncharted is how intracranial masses can change the measurements. Consequently, for clinical practice, this method may not be sufficiently precise [56]. ...
Chapter
As a part of the central nervous system, the optic nerve goes through the comparatively independent intraocular and retrobulbar pressurized cerebrospinal fluid cavity. Additionally, the central retinal vein and artery pass from the optic nerve head through the optic nerve and the orbital cerebrospinal fluid (CSF) space. The CSF pressure, as the counter pressure against intraocular pressure (IOP) from the opposite side of the lamina cribrosa, may have pathophysiologic importance for several intracranial and intraocular pressure gradient-related ophthalmic disorders, such as glaucomatous optic neuropathy associated with CSF pressure dysregulation [1–12], optic neuropathy secondary to idiopathic intracranial hypertension [13–19], visual impairment syndrome in space [20–22], and retinal vein occlusion [23].
... In addition, CSF indicates the brain health statues form intracranial diseases such as brain tissue infection, swelling, and intracranial tumors. CSF volume is about 130-150 milliliter and the normal value of ICP varies from 600 Pa to 2000 Pa for adults which is considered low (Figure 1) [1]. Since the skull is a rigid body that contain the brain tissue and CSF, the intracranial tissues can be compressed by the small amount of pressure. ...
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Intracranial pressure (ICP) monitoring methods can be categorized into invasive and non-invasive. Invasive methods increase the risks of bleeding and infection and need professional personnel; therefore, non-invasive methods are investigated more often. One non-invasive method is based on monitoring transcranial signals, which can be captured and processed from the skull. For this reason, the effects of cerebrospinal fluid (CSF) pressure increment on the natural frequencies of the skull have been investigated. In this paper, we model the human skull as a hemispherical shell employing skull bone mechanical characteristics. CSF will be considered as an incompressible and inviscid fluid with a pressure increase less than 2 kPa. Employing Finite Element (FE) numerical techniques, the fluid-solid interaction (FSI) of CSF-skull is discretized, and the eigenvalue problem is solved to obtain the first 50 natural frequencies and the associated skull vibrational mode-shapes. The results illustrate that rising in CSF pressure causes slightly decrement in the unsymmetrical and symmetrical vibration frequency modes. Moreover, the modes of skull vibration sensitivity with respect to CSF pressure variation are calculated. The sensitivity graph demonstrates that the skull vibration in higher frequencies modes is sensitive to ICP variation in comparison with the lower vibration modes.
... This is an inva- sive procedure, associated with risk of severe complications such as infection and hemorrhage in about 1-2% of patients 4 . Despite a 40-year history of research on non-invasive ICP, none of the presented methods are currently accurate enough to be used in clinical practice [5][6][7][8] . Therefore, ICP monitoring is restricted to patients with severe brain disease, in whom the invasiveness of the procedure is outweighed by the importance of measuring ICP. ...
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Abstract Time domain analysis of the intracranial pressure (ICP) waveform provides important information about the intracranial pressure-volume reserve capacity. The aim here was to explore whether the tympanic membrane pressure (TMP) waveform can be used to non-invasively estimate the ICP waveform. Simultaneous invasive ICP and non-invasive TMP signals were measured in a total of 28 individuals who underwent invasive ICP measurements as a part of their clinical work up (surveillance after subarachnoid hemorrhage in 9 individuals and diagnostic for CSF circulation disorders in 19 individuals). For each individual, a transfer function estimate between the invasive ICP and non-invasive TMP signals was established in order to explore the potential of the method. To validate the results, ICP waveform parameters including the mean wave amplitude (MWA) were computed in the time domain for both the ICP estimates and the invasively measured ICP. The patient-specific non-invasive ICP signals predicted MWA rather satisfactorily in 4/28 individuals (14%). In these four patients the differences between original and estimated MWA were
... However, when ICP is increased, the mean arterial pressure rises as a physiological response to maintain cerebral blood flow. Based on the former concepts, some studies have attempted to estimate ICP from waveform analysis of cerebral blood flow velocity along with arterial pressure, obtaining from moderate to very high correlation between estimated and invasively measured ICP values (Schmidt et al. 2002;Xu et al. 2010;Kashif et al. 2012 The velocity of blood flow in cerebral vessels is measured by transcranial Doppler (TCD) sonography, a technique that detects the frequency shift between an emitted ultrasonic wave and the reflected wave from blood flowing in an artery in the intracranial space (Lupetin et al. 1995;Golzan et al. 2009;Popovic et al. 2009). This frequency shift directly correlates with the speed of blood (given a constant insonation angle), so that the analysis of an artery with TCD can be used to produce the waveform of the flow velocity in that artery. ...
... changes in the volume of any intracranial element affect transit time of ultrasonic waves; Ragauskas et al. 2003), it has been aimed to estimate the ICP by comparing the characteristics (e.g. speed and attenuation) of an ultrasonic input wave against its characteristics after travelling through the head (Ragauskas & Daubaris 1995;Michaeli & Rappaport 2002;Ragauskas et al. 2003;Fountas et al. 2005;Popovic et al. 2009). To emit and detect ultrasonic waves through the brain, two transducers are located on the cranium opposite walls, or a single transducer may be used for both generating the incident wave and measuring the reflected wave (Popovic et al. 2009). ...
... speed and attenuation) of an ultrasonic input wave against its characteristics after travelling through the head (Ragauskas & Daubaris 1995;Michaeli & Rappaport 2002;Ragauskas et al. 2003;Fountas et al. 2005;Popovic et al. 2009). To emit and detect ultrasonic waves through the brain, two transducers are located on the cranium opposite walls, or a single transducer may be used for both generating the incident wave and measuring the reflected wave (Popovic et al. 2009). ...
Thesis
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Monitoring intracranial pressure (ICP) is vital to decide the appropriate clinical treatment of patients with conditions potentially causing high ICP (e.g. brain injury, cerebral tumor, and hydrocephalus). On the path for finding an alternative means to invasive ICP measurement, the only means to date for accurate ICP monitoring, this study investigates the relationship of ICP with systemic cardiovascular signals ─heart rate (HR), aortic blood pressure (aBP), and carotid blood flow (cBF)─ via rat experiments and signal analysis techniques. Whilst induced changes in aBP and cBF resulted in evident alterations of ICP magnitude, increases of mean ICP up to 49 mmHg showed minimal effect on HR, aBP, or cBF signals. Thus, a stepwise mixed-model regression proved that the cardiovascular parameters here studied have minimal but significant predictive value of ICP magnitude. Changes in HR were found to modify the waveforms observed in ICP, aBP, and cBF signals, without altering the magnitude or phase of transfer function models. The transfer function models were constructed as a function of mean ICP, mean aBP, and aBP or cBF waveforms, and they showed potential to reproduce the ICP waveform (Root Mean Square Error (RMSE)≤4 mmHg), being more accurate for mean aBP above 100 mmHg and mean ICP below 20 mmHg (RMSE≤0.5 mmHg). Likewise, estimation of pulse ICP showed a small error (<1±1.0 mmHg) for mean ICP below 20 mmHg across a range of mean aBP (70-130 mmHg), proving considerable accuracy improvement in relation to previous studies.
... Most non-invasive methods require initial invasive calibration [16] except transcranial Doppler ultrasound measurement of blood flows in the intra and extracranial segments of the ophthalmic artery. The estimate of absolute ICP given by this method is the pressure applied on the eyeball, such that blood flow in both segments of the ophthalmic artery is equalized [17,18]. ...
Article
Among possible causes of visual impairment or headache experienced by astronauts in microgravity or post-flight and that hamper their performance, elevated intracranial pressure (ICP) has been invoked, but never measured for lack of non-invasive methods. The goal of this work was to test two noninvasive methods of ICP monitoring using in-ear detectors of ICP-dependent auditory responses, acoustic and electric, in acute microgravity afforded by parabolic flights. The devices detecting these responses were hand-held tablets routinely used in otolaryngology for hearing diagnosis, customized for ICP extraction and serviceable by unskilled operators. These methods had been previously validated against invasive ICP measurements in neurosurgery patients. The two methods concurred in their estimation of ICP changes with microgravity, i.e., 11.0 {plus minus} 7.7 mmHg for the acoustic method (n = 7 subjects with valid results out of 30, auditory responses being masked by excessive in-flight noise in 23 subjects), and 11.3 {plus minus} 10.6 mmHg for the electric method (n = 10 subjects with valid results, out of 10 tested despite the in-flight noise). These results agree with recent publications using invasive access to cerebrospinal fluid in parabolic flights and suggest that acute microgravity has a moderate average effect on ICP, similar to body tilt from upright to supine, yet with some subjects undergoing large effects while others seem immune. The electric in-ear method would be suitable for ICP monitoring in circumstances and with subjects such that invasive measurements are excluded.