Hydrocephalus 2008, 17–20th September, Hannover Germany: a conference report

Hydrocephalus 2008 was held 17–20 September in Hannover, Germany, at the invitation of Petra M Klinge (President), co-hosted by Joachim K. Krauss (Vice President), and Madjid Samii (Honorary President). This meeting was a successor to Hydrocephalus 2006 held in Göteborg, Sweden, organised by Past-President, Carsten Wikkelso. The conference began with a general introductory session of six talks including three invited lectures, followed by eighteen parallel sessions. Subjects covered were hydrocephalus signs, symptoms and diagnosis, especially in normal pressure hydrocephalus; cerebrospinal fluid (CSF) physics and dynamics; CSF function and modelling of function; dementia and quality of life, economy, health care and rehabilitation; neuropsychology, cognition and outcome assessment; neuroimaging, functional imaging and non-invasive diagnostics; paediatric and adolescent hydrocephalus; intelligent shunt and valve design (e.g. telemetry, adjustable and antimicrobial shunts); endoscopic third ventriculostomy; technical advances and image-guided surgical approaches in the treatment of hydrocephalus; brain metabolism, biomarkers and biophysics; co-morbidity, classification and aetiology; epidemiology, registries and clinical trials; experimental hydrocephalus; and pharmaceutical modulation of central nervous system function (CNS drug delivery). Each session began with introductory talks from the invited chairpersons followed by six to eight submitted oral presentations. Overall, 136 oral presentations and 18 posters were presented, the abstracts of which were published elsewhere [1]. We present here an account of the introductory session, the invited chairperson's talks and the concluding remarks by Anthony Marmarou

Priorities for hydrocephalus research: report from a National Institutes of Health-sponsored workshop

Journal ArticleObject. Treatment for hydrocephalus has not advanced appreciably since the advent of cerebrospinal fluid (CSF) shunts more than 50 years ago. Many questions remain that clinical and basic research could address, which in turn could improve therapeutic options. To clarify the main issues facing hydrocephalus research and to identify critical advances necessary to improve outcomes for patients with hydrocephalus, the National Institutes of Health (NIH) sponsored a workshop titled "Hydrocephalus: Myths, New Facts, and Clear Directions." The purpose of this paper is to report on the recommendations that resulted from that workshop. Methods. The workshop convened from September 29 to October 1, 2005, in Bethesda, Maryland. Among the 150 attendees was an international group of participants, including experts in pediatric and adult hydrocephalus as well as scientists working in related fields, neurosurgeons, laboratory-based neuroscientists, neurologists, patient advocates, individuals with hydrocephalus, parents, and NIH program and intramural staff. Plenary and breakout sessions covered injury and recovery mechanisms, modeling, biomechanics, diagnosis, current treatment and outcomes, complications, quality of life, future treatments, medical devices, development of research networks and information sharing, and education and career development. Results. The conclusions were as follows: 1) current methods of diagnosis, treatment, and outcomes monitoring need improvement; 2) frequent complications, poor rate of shunt survival, and poor quality of life for patients lead to unsatisfactory outcomes; 3) investigators and caregivers need additional methods to monitor neurocognitive function and control of CSF variables such as pressure, flow, or pulsatility; 4) research warrants novel interdisciplinary approaches; 5) understanding of the pathophysiological and recovery mechanisms of neuronal function in hydrocephalus is poor, warranting further investigation; and 6) both basic and clinical aspects warrant expanded and innovative training programs. Conclusions. The research priorities of this workshop provide critical guidance for future research in hydrocephalus, which should result in advances in knowledge, and ultimately in the treatment for this important disorder and improved outcomes in patients of all ages

CSF Dynamics for Shunt Prognostication and Revision in Normal Pressure Hydrocephalus.

BACKGROUND: Despite the quantitative information derived from testing of the CSF circulation, there is still no consensus on what the best approach could be in defining criteria for shunting and predicting response to CSF diversion in normal pressure hydrocephalus (NPH). OBJECTIVE: We aimed to review the lessons learned from assessment of CSF dynamics in our center and summarize our findings to date. We have focused on reporting the objective perspective of CSF dynamics testing, without further inferences to individual patient management. DISCUSSION: No single parameter from the CSF infusion study has so far been able to serve as an unquestionable outcome predictor. Resistance to CSF outflow (Rout) is an important biological marker of CSF circulation. It should not, however, be used as a single predictor for improvement after shunting. Testing of CSF dynamics provides information on hydrodynamic properties of the cerebrospinal compartment: the system which is being modified by a shunt. Our experience of nearly 30 years of studying CSF dynamics in patients requiring shunting and/or shunt revision, combined with all the recent progress made in producing evidence on the clinical utility of CSF dynamics, has led to reconsidering the relationship between CSF circulation testing and clinical improvement. CONCLUSIONS: Despite many open questions and limitations, testing of CSF dynamics provides unique perspectives for the clinician. We have found value in understanding shunt function and potentially shunt response through shunt testing in vivo. In the absence of infusion tests, further methods that provide a clear description of the pre and post-shunting CSF circulation, and potentially cerebral blood flow, should be developed and adapted to the bed-space

Dynamics of cerebral fluids in patients suffering from hydrocephalus and pseudotumour cerebri

This dissertation is devoted to dynamics of brain liquids in patients with altered CSF circulation and pressure-volume compensation. Since the introduction of intracranial pressure (ICP) monitoring, the studies of CSF dynamics have revealed unique information about the intracranial circulation and opened new opportunities for diagnosis and treatment of hydrocephalus and pseudotumour cerebri. The adaptation of infusion tests in clinical practice over 45 years ago has introduced a practical tool to benefit both patients and research into altered CSF dynamics. Objective testing of intracranial circulation in patients with clinical symptoms constitutes a unique situation, where the discovery of new patterns and reasons for disturbed intracranial circulation can be quantified. Such macroscopic yet practical quantifications can easily be translated to clinically useful information, and back, in real time or alternative past and future synchronicities. The aim of this dissertation is to demonstrate the value of testing CSF dynamics in vivo and how it could provide pathophysiological and clinical insights into hydrocephalus and pseudotumour cerebri syndrome (PTCS). My intention was to describe and reflect the main themes involved in the study of CSF dynamics: a) their role in diagnosis and treatment, b) their use in understanding shunts and shunt malfunction c) the need to optimise our understanding of the contents of ICP, meaning that long-term ICP monitoring or dynamic tests are required in CSF disorders, not snapshot ICP measurements and finally d) the mapping and quantification of the interaction between CSF circulation and cerebral blood flow (CBF). As the above foundations and results of my work lead to the formation of a required, albeit expected, long doctoral treatise, I have structured the later in 9 chapters containing a comprehensive literature review of the Resistance to CSF outflow as well as a systematic literature review of the CBF and autoregulation of the CBF in NPH. I have also dedicated a methods chapter, Chapter 3, into introducing and explaining the variable tested during a CSF infusion test, such as the fundamental amplitude of ICP and the compensatory reserve indices. Following this is the presentation of the data and clinical material used for my original projects. Specifically, my results contain the following: I) Autoregulation of cerebral blood flow in hydrocephalus CSF infusion tests provide a unique setting where both ICP and cerebral blood flow and autoregulation can be measured in ambulatory patients utilising many different methods. Autoregulation has been studied by quantifying the interaction between the CSF and cerebral blood circulation has revealed diagnostic and outcome implications that could perhaps describe the natural course of a CSF disorder, or differentiate between a CSF disorder and a vascular disorder, or the coexistence of the two, opening new chapters to the comprehension of shunt responsive NPH. I have explored the state of global autoregulation in patients undergoing infusion tests, in an attempt to set out a reference for investigations related to NPH, Resistance, autoregulation and their clinical implications. In the 5th chapter, I have: • Described the relationship between Rout, cerebral autoregulation and arterial blood pressure. Rout demonstrates a negative linear relationship with global autoregulation. When I combined these parameters and accounted for the patients’ age, I was able to show a good correlation with outcome, much improved compared to Rout alone. II) CSF dynamics in normal pressure hydrocephalus and pseudotumour cerebri. CSF dynamics in different conditions have shown that parameters such as the Resistance to CSF outflow in NPH and ICP at baseline combined with compensatory reserve indices in PTCS, could provide important diagnostic and management information. This could be a valuable addition of objective evidence to imaging and clinical examination. Using large cohorts of patients, I have explored the Resistance to CSF outflow (Rout) in NPH in the context of different aetiologies of NPH, its relationship with age as well as its overall correlation with outcome after shunting. I have also explored these relationships in relevance to clinical practice. In PTCS, I have described the findings from infusion tests in both adult and paediatric patients and have highlighted the differences with hydrocephalus. In chapter 6, , I have described the following: • Davson’s equation in NPH: The so-called Davson’s equation describes the relationship between ICP, Rout, CSF formation rate and sagittal sinus pressure under physiological circumstances. I have validated the existence of such a linear relationship in NPH. • CSF dynamics in post-traumatic hydrocephalus: Traumatic brain injury, as a cause of secondary NPH, shows some differences in Rout and ICP amplitude compared to idiopathic NPH. I have also described the effect of decompressive craniectomy and of cranioplasty on CSF dynamics. In chapter 7, I have explored the CSF dynamics of PTCS and in particular: • The coupling between CSF pressure and Sagittal sinus pressure (SSp) in PTCS patients at baseline and during infusion tests. I have also shown how this relates to Davson’s equation under an unstable SSp and the possible pathophysiological consequences of this finding. • The CSF dynamics of paediatric patients with PTCS. Those included all patients assessed in Cambridge and classified as definite, probable and not PTCS. III) Shunt testing in vivo. Shunts are currently the mainstay for the management of hydrocephalus, as well as an important part of the management of PTCS. They change CSF dynamic parameters in a way that is easily assessed with shunt infusion tests. The knowledge of the post-shunting CSF circulation contains crucial information on the state of the shunt function, as well as the adequate restoration of the patients’ intracranial circulation. I have described how objective knowledge from shunt testing in vivo impacts clinical practice and patients’ outcomes. In chapter 8, I have presented two studies about testing shunt function in-vivo: • Shunt testing in vivo using infusion tests is important in avoiding unnecessary revisions of patent shunts and allows patients to be managed conservatively, with good outcomes. This also translates to financial benefits for healthcare systems. • In paediatric hydrocephalus, shunt infusion studies are an accurate and useful tool for investigating insidious shunt obstruction. IV) Slow waves of Intracranial Pressure. Reliable, long-term overnight monitoring is the gold standard in monitoring and analysing ICP and its contents. Slow waves, compensatory reserve and relationship with the venous circulation contain reliable information that are again correlated to clinical practice and can be compared and incorporated into the shorter-term infusion test. I have explored the behaviour of slow waves in anaesthetized patients In chapter 9, I have investigated the influence of general anaesthesia on slow waves of ICP in NPH and traumatic brain injury (TBI) patients. Conclusion: Infusion tests are a practical tool for research and possibly diagnosis and treatment in patients with PTCS and NPH. CSF dynamics provide a quantitative description of cerebral pathophysiology in CSF disorders, both for CSF and potentially for cerebral blood flow. After shunting, infusion tests are a reliable and cost-effective tool for identifying or excluding shunt malfunction. Further studies are needed to verify the clinical implications of CSF infusion tests and cerebral blood flow and autoregulation in those patients

Cerebrospinal fluid pulse pressure amplitude during lumbar infusion in idiopathic normal pressure hydrocephalus can predict response to shunting

<p>Abstract</p> <p>Background</p> <p>We have previously seen that idiopathic normal pressure hydrocephalus (iNPH) patients having elevated intracranial pressure (ICP) pulse amplitude consistently respond to shunt surgery. In this study we explored how the cerebrospinal fluid pressure (CSFP) pulse amplitude determined during lumbar infusion testing, correlates with ICP pulse amplitude determined during over-night ICP monitoring and with response to shunt surgery. Our goal was to establish a more reliable screening procedure for selecting iNPH patients for shunt surgery using lumbar intrathecal infusion.</p> <p>Methods</p> <p>The study population consisted of all iNPH patients undergoing both diagnostic lumbar infusion testing and continuous over-night ICP monitoring during the period 2002-2007. The severity of iNPH was assessed using our NPH grading scale before surgery and 12 months after shunting. The CSFP pulse was characterized from the amplitude of single pressure waves.</p> <p>Results</p> <p>Totally 62 iNPH patients were included, 45 of them underwent shunt surgery, in whom 78% were shunt responders. Among the 45 shunted patients, resistance to CSF outflow (R_out) was elevated (≥ 12 mmHg/ml/min) in 44. The ICP pulse amplitude recorded over-night was elevated (i.e. mean ICP wave amplitude ≥ 4 mmHg) in 68% of patients; 92% of these were shunt responders. In those with elevated overnight ICP pulse amplitude, we found also elevated CSFP pulse amplitude recorded during lumbar infusion testing, both during the opening phase following lumbar puncture and during a standardized period of lumbar infusion (15 ml Ringer over 10 min). The clinical response to shunting after 1 year strongly associated with the over-night ICP pulse amplitude, and also with the pulsatile CSFP during the period of lumbar infusion. Elevated CSFP pulse amplitude during lumbar infusion thus predicted shunt response with sensitivity of 88 and specificity of 60 (positive and negative predictive values of 89 and 60, respectively).</p> <p>Conclusions</p> <p>In iNPH patients, shunt response can be anticipated in 9/10 patients with elevated overnight ICP pulse amplitude, while in only 1/10 with low ICP pulse amplitude. Additionally, the CSFP pulse amplitude during lumbar infusion testing was elevated in patients with elevated over-night ICP pulse amplitude. In particular, measurement of CSFP pulse amplitude during a standardized infusion of 15 ml Ringer over 10 min was useful in predicting response to shunt surgery and can be used as a screening procedure for selection of iNPH patients for shunting.</p

Idiopathic normal pressure hydrocephalus in neurological practice : A study of epidemiology and methods for selection of patients for surgery

Aims:The aims of this thesis are to estimate the epidemiology of iNPH in a Norwegian population compared to the incidence of surgery for the condition, to assess whether lumbar measurements of cerebrospinal fluid pressure (CSFP) concurs with intracranial pressure (ICP), and with the clinical response to shunting, and finally to assess which of the lumbar hydrodynamic measurements that best can predict the clinical response to shunting. Methods:The thesis consists of six publications. Publication Iassesses the prevalence of iNPH in a Norwegian population. Publication IIassesses the five year incidence of surgery for iNPH in Norway. Publication III compareslumbarCSFP waves versus ICPwaves in iNPH. Publication IV compares ICPmeasured simultaneously within the brain parenchyma and cerebral ventricles.Publication Vassesses the role of lumbar infusion testing for referral of iNPH patients to neurosurgery. Publication VI assesses whether CSFP waveamplitude during lumbar infusion in iNPH can predict response to shunting. Results: We found a prevalence of probable iNPH of 21.9/100.000 inhabitants,and an incidence of 5.5/100.000/year. The total rate of surgery for iNPH was 1.09/100.000/year. The lumbar CSFP wave amplitude during lumbar infusion could be used to predict the ICP wave amplitude during over-night monitoring of the intracranial pressure. There is no pressure gradient between pressure wave amplitudes derived from brain parenchyma and ventricular CSF. Resistance to outflow (Rout) and CSFP wave amplitude derived from lumbar infusion related only weakly, while shunt response related highly to the quantitative distribution of CSFP wave amplitudes during infusion, giving false negative results in 16% of the patients. Elevated CSFP wave amplitudes during lumbar infusion predictedshunt response with asensitivity of 88 and aspecificity of 60. Conclusions:Our data suggest that too few patients are being offered surgical treatment for iNPH in Norway. Lumbar CSFP wave amplitudes concur to a great extent with ICP wave amplitudes and with clinical response to shunting. Lumbar CSFP wave amplitudes predict clinical response to shunting better than Rout, but further studies are advocated to address the problem of false negative results from lumbar hydrodynamic measurements

The pulsating brain: A review of experimental and clinical studies of intracranial pulsatility

The maintenance of adequate blood flow to the brain is critical for normal brain function; cerebral blood flow, its regulation and the effect of alteration in this flow with disease have been studied extensively and are very well understood. This flow is not steady, however; the systolic increase in blood pressure over the cardiac cycle causes regular variations in blood flow into and throughout the brain that are synchronous with the heart beat. Because the brain is contained within the fixed skull, these pulsations in flow and pressure are in turn transferred into brain tissue and all of the fluids contained therein including cerebrospinal fluid. While intracranial pulsatility has not been a primary focus of the clinical community, considerable data have accrued over the last sixty years and new applications are emerging to this day. Investigators have found it a useful marker in certain diseases, particularly in hydrocephalus and traumatic brain injury where large changes in intracranial pressure and in the biomechanical properties of the brain can lead to significant changes in pressure and flow pulsatility. In this work, we review the history of intracranial pulsatility beginning with its discovery and early characterization, consider the specific technologies such as transcranial Doppler and phase contrast MRI used to assess various aspects of brain pulsations, and examine the experimental and clinical studies which have used pulsatility to better understand brain function in health and with disease

Ultrasound-based non invasive intracranial pressure

Intracranial pressure (ICP) is an important monitoring modality in the clinical management of several neurological diseases carrying the intrinsic risk of potentially lethal intracranial hypertension (ICH). Considering that the brain is in an enclosed compartment, ICH leads to brain hypoperfusion and eventually ischaemia followed by irreversible neuronal damage. Traumatic brain injury (TBI), for instance, is a condition in which ICH is strongly associated with unfavourable outcome and death. Although ICP can guide patient management in neurocritical care settings, this parameter is not commonly monitored in many clinical conditions outside this environment. The invasive character of the standard methods for ICP assessment and their associated risks to the patient (like infections, brain tissue lesions, haemorrhage) contribute to this scenario. Such risks have prevented ICP assessment in a broad range of diseases like in patients with risk of coagulopathy, as well as in other conditions in which invasive assessment is not considered or outweighed by the risks of the procedure. Provided that knowledge of ICP can be crucial for the successful management of patients in many sub-critical conditions, non-invasive estimation of ICP (nICP) may be helpful when indications for invasive ICP assessment are not met and when it is not immediately available or even contraindicated. Several methods for non-invasive assessment of ICP (nICP) have been described so far. Transcranial Doppler (TCD), for instance, is primarily a technique for diagnosing various intracranial vascular disorders such as emboli, stenosis, or vasospasm, but has been broadly utilised for non-invasive ICP monitoring due to its ability to detect changes in cerebral blood flow velocity derived from ICP variations. Moreover, TCD allows monitoring of these parameters as they may change in time. Optic nerve sheath diameter ultrasonography (ONSD) is another non-invasive tool which gained interest in the last years. The optic nerve sheath is in continuous with the subarachnoid space, and when ICP increased, the diameter of ONSD enlarges proportionally to ICP. The focus of this thesis is on the assessment, applications and development of ultrasoundbased for nICP assessment in different clinical conditions where this parameter is relevant but in many circumstances not considered, including TBI and other neurological diseases ULTRASOUND BASED NON-INVASIVE INTRACRANIAL PRESSURE 17 associated with impairment of cerebral blood flow circulation. As main results, ONSD and TCD-based non-invasive methods could replicate changes in direct ICP across time confidently, and could provide reasonable accuracy in comparison to the standard invasive techniques. These findings support the use of ultrasound based non-invasive ICP methods in a variety of clinical conditions requiring management of intracranial pressure and brain perfusion. More importantly, the low costs associated with nICP methods, ultrasound machines are widely available medical devices, could contribute to its widespread use as a reliable alternative for ICP monitoring in everyday clinical practice

MR Elastography demonstrates reduced white matter shear stiffness in early-onset hydrocephalus

INTRODUCTION: Hydrocephalus that develops early in life is often accompanied by developmental delays, headaches and other neurological deficits, which may be associated with changes in brain shear stiffness. However, noninvasive approaches to measuring stiffness are limited. Magnetic Resonance Elastography (MRE) of the brain is a relatively new noninvasive imaging method that provides quantitative measures of brain tissue stiffness. Herein, we aimed to use MRE to assess brain stiffness in hydrocephalus patients compared to healthy controls, and to assess its associations with ventricular size, as well as demographic, shunt-related and clinical outcome measures. METHODS: MRE was collected at two imaging sites in 39 hydrocephalus patients and 33 healthy controls, along with demographic, shunt-related, and clinical outcome measures including headache and quality of life indices. Brain stiffness was quantified for whole brain, global white matter (WM), and lobar WM stiffness. Group differences in brain stiffness between patients and controls were compared using two-sample t-tests and multivariable linear regression to adjust for age, sex, and ventricular volume. Among patients, multivariable linear or logistic regression was used to assess which factors (age, sex, ventricular volume, age at first shunt, number of shunt revisions) were associated with brain stiffness and whether brain stiffness predicts clinical outcomes (quality of life, headache and depression). RESULTS: Brain stiffness was significantly reduced in patients compared to controls, both unadjusted (p ≤ 0.002) and adjusted (p ≤ 0.03) for covariates. Among hydrocephalic patients, lower stiffness was associated with older age in temporal and parietal WM and whole brain (WB) (beta (SE): -7.6 (2.5), p = 0.004; -9.5 (2.2), p = 0.0002; -3.7 (1.8), p = 0.046), being female in global and frontal WM and WB (beta (SE): -75.6 (25.5), p = 0.01; -66.0 (32.4), p = 0.05; -73.2 (25.3), p = 0.01), larger ventricular volume in global, and occipital WM (beta (SE): -11.5 (3.4), p = 0.002; -18.9 (5.4), p = 0.0014). Lower brain stiffness also predicted worse quality of life and a higher likelihood of depression, controlling for all other factors. CONCLUSIONS: Brain stiffness is reduced in hydrocephalus patients compared to healthy controls, and is associated with clinically-relevant functional outcome measures. MRE may emerge as a clinically-relevant biomarker to assess the neuropathological effects of hydrocephalus and shunting, and may be useful in evaluating the effects of therapeutic alternatives, or as a supplement, of shunting

Computerized analysis of intracranial pressure and cerebrospinal fluid dynamics in patients with idiopathic normal pressure hydrocephalus and positive clinical response to lumbar CSF drainage

Ziel dieser Arbeit war, bei Patienten mit idiopathischem Normaldruckhydrocephalus (iNPH), die als potentielle „Responder“ einer Therapie mit einem ventrickulo-peritonealen Shunt angesehen werden, mit Hilfe invasiver Methoden (computerisierte nächtliche Hirndruckanalyse und lumbale Infusionsstudie) nachzuweisen, dass eine erniedrigte intrakranielle Compliance vorliegt. Die momentan besterklärende pathophysiologische Hypothese zum iNPH geht davon aus, dass der Erkrankung eine über die erniedrigte Compliance bedingte Pulsatilitätsstörung von Blut und Liquor mit assoziierter Beeinträchtigung des zerebralen Blutflusses zugrunde liegt. Die 2. Hypothese der Arbeit war, daß eine dreitägige Lumbaldrainage, die zu einer klinischen Verbesserung des Patienten führt, mit einer Zunahme der intrakraniellen Compliance und Verbesserung der Reservekapazität einhergeht. Dies würde unsere Auffassung stärken, dass der wesentliche Effekt der Shunttherapie über die Verbesserung der Compliance vermittelt wird. Beide Hypothesen konnten in der Arbeit bestätigt werden. In Bezug auf die Korrelation des klinischen Scores (Kiefer Scale und der darauf basierenden NPH Recovery Rate) fanden wir keine überzeugende Korrelation zum Ausmaß der Besserung und dem Ausmaß der Veränderung der compliance assoziierten Messwerte. Neben der kleinen Patientenanzahl ist dies wahrscheinlich darin begründet, dass der Kiefer Scale unscharfe und subjektive Einschätzungen von Patient und Arzt beinhaltet. Eine deutlich bessere Korrelation fand sich zu objektiven Messverfahren wie Gangtest und Pegboard Test. Zusammenfassend konnte die Arbeit nachweisen, dass bei Patienten mit vermutetem iNPH eine erniedrigte cranio-spinale Compliance assoziiert ist mit einem guten Ansprechen auf eine dreitägige Liquorprobedrainage und nachfolgend einer Shunttherapie , und, dass die dabei bewirkte Entfernung vom Nervenwasser zu einer Erhöhung der intrakraniellen Compliance führt. Daraus folgt, dass die Kombination einer computerisierten Analyse des intrakraniellen Druckes und der cerebrospinal Liquordynamik (lumbale Infusionsstudie) eine aufwändige aber präzise pathophysiologisch orientierte Methode der Diagnose von jenen Normaldruckhydrocephalus Patienten ist, bei denen eine klinischen Verbesserung nach Shunt Implatantion zu erwarten ist. Zukünftige Arbeiten sollten zum Ziel haben, eine Simplifizierung der Diagnostik bei gleichbleibenden Aussagekraft, idealerweise unter Verwendung weniger invasiver Verfahren, zu erreichen