Brain blood flow pulse analysis may help to recognize individuals who suffer from hydrocephalus.

BACKGROUND: Normal pressure hydrocephalus (NPH) is often associated with altered cerebral blood flow. Recent research with the use of the ultrasonic method suggests specific changes in the shape of cardiac-related cerebral arterial blood volume (CaBV) pulses in NPH patients. Our study aims to provide a quantitative analysis of the shape of CaBV pulses, estimated based on transcranial Doppler ultrasonography (TCD) in NPH patients and healthy individuals. METHODS: The CaBV pulses were estimated using TCD cerebral blood flow velocity signals recorded from probable NPH adults and age-matched healthy individuals at rest. The shape of the CaBV pulses was compared to a triangular shape with 27 similarity parameters calculated for every reliable CaBV pulse and compared between patients and volunteers. The diagnostic accuracy of the most prominent parameter for NPH classification was evaluated using the area under the receiver operating characteristic curve (AUC). RESULTS: The similarity parameters were calculated for 31 probable NPH patients (age: 59 years (IQR: 47, 67 years), 14 females) and 23 healthy volunteers (age: 54 years (IQR: 43, 61 years), 18 females). Eighteen of 27 parameters were different between healthy individuals and NPH patients (p < 0.05). The most prominent differences were found for the ascending slope of the CaBV pulse with the AUC equal to 0.87 (95% confidence interval: 0.77, 0.97, p < 0.001). CONCLUSIONS: The findings suggest that in NPH, the ascending slope of the CaBV pulse had a slower rise, was more like a straight line, and generally was less convex than in volunteers. Prospective research is required to verify the clinical utility of these findings.

Is Lumbar Puncture Needed? - Noninvasive Assessment of ICP Facilitates Decision Making in Patients with Suspected Idiopathic Intracranial Hypertension.

PURPOSE: Idiopathic intracranial hypertension (IIH) usually occurs in obese women of childbearing age. Typical symptoms are headache and sight impairment. Lumbar puncture (LP) is routinely used for both diagnosis and therapy (via cerebrospinal fluid drainage) of IIH. In this study, noninvasively assessed intracranial pressure (nICP) was compared to LP pressure (LPP) in order to clarify its feasibility for the diagnosis of IIH. MATERIALS AND METHODS: nICP was calculated using continuous signals of arterial blood pressure and cerebral blood flow velocity in the middle cerebral artery, a method which has been introduced recently. In 26 patients (f = 24, m = 2; age: 33 ±â€Š11 years), nICP was assessed one hour prior to LPP. If LPP was > 20 cmH2O, lumbar drainage was performed, LPP was measured again, and also nICP was reassessed. RESULTS: In total, LPP and nICP correlated with R = 0.85 (p < 0.001; N = 38). The mean difference of nICP-LPP was 0.45 ±â€Š4.93 cmH2O. The capability of nICP to diagnose increased LPP (LPP > 20 cmH2O) was assessed by ROC analysis. The optimal cutoff for nICP was close to 20 cmH2O with both a sensitivity and specificity of 0.92. Presuming 20 cmH2O as a critical threshold for the indication of lumbar drainage, the clinical implications would coincide in both methods in 35 of 38 cases. CONCLUSION: The TCD-based nICP assessment seems to be suitable for a pre-diagnosis of increased LPP and might eliminated the need for painful lumbar puncture if low nICP is detected.

Development of normal pressure hydrocephalus following post-traumatic external hydrocephalus in an adult patient.

We report the case of 74-year-old patient suspected of post-traumatic external hydrocephalus (EH) following a mild traumatic brain injury with a progressive neurological decline and a concomitant enlargement of subarachnoid spaces without ventriculomegaly on CT scan. A lumbar puncture revealed raised ICP and a careful CSF withdrawal was performed, resulting in an immediate neurological improvement, confirming the diagnosis of EH. During the 20-month follow-up, the patient presented progressive signs of normal pressure hydrocephalus (NPH): gait and cognitive decline, ventriculomegaly and the lumbar infusion study confirmed disturbed CSF dynamics. The patient underwent a ventriculoperitoneal shunt surgery, resulting in a long-lasting improvement.

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.

Analysis of Intracranial Pressure Pulse-Pressure Relationship: Experimental Validation.

The slope of linear relationship between the amplitude of pulsations in intracranial pressure (ICP) versus mean ICP has recently been suggested as a useful guide for selecting patients for shunt surgery in normal pressure hydrocephalus (NPH). To better understand how the pathophysiology of cerebral circulation influences this parameter, we aimed to study the relationship between mean pressure and pulsation amplitude in a wide range of conditions affecting cerebrovascular tone and ICP in experimental conditions.We retrospectively analysed experimental material collected previously. Three physiological manoeuvres were studied in 29 New Zealand white rabbits: lumbar infusion with an infusion rate ≤0.2 mL/min to induce mild intracranial hypertension (n = 43), sympathetic blockade to induce arterial hypotension (n = 19), and modulation of the ventilator tidal volume, simultaneously influencing arterial carbon dioxide partial pressure (PaCO2) to induce hypocapnia or hypercapnia (n = 17). We investigated whether the slope of the pulse amplitude (AMP)-ICP line depended on PaCO2 and arterial blood pressure (ABP) changes.We found a linear correlation between AMP-ICP and ICP with positive slope. Regression of slope against mean ABP showed a negative dependence (p = 0.03). In contrast, the relationship between slope and PaCO2 was positive, although not reaching statistical significance (p = 0.18).The slope of amplitude-pressure line is strongly modulated by systemic vascular variables and therefore should be taken as a descriptor of cerebrospinal fluid dynamics with great care.

Global Cerebral Autoregulation, Resistance to Cerebrospinal Fluid Outflow and Cerebrovascular Burden in Normal Pressure Hydrocephalus.

INTRODUCTION: We previously examined the relationship between global autoregulation pressure reactivity index (PRx), mean arterial blood pressure (ABP), Resistance to cerebral spinal fluid (CSF) outflow (Rout) and their possible effects on outcome after surgery on 83 shunted patients. In this study, we aimed to quantify the relationship between all parameters that influence Rout, their interaction with the cerebral vasculature, and their role in shunt prognostication. METHODS: From 423 patients having undergone infusion tests for possible NPH, we selected those with monitored ABP and calculated its mean and PRx. After shunting, 6 months patients' outcome was marked using a simple scale (improvement, temporary improvement, and no improvement). We explored the relationship between age, different CSF dynamics variables, and vascular parameters using multivariable models. RESULTS: Rout had a weaker predictive value than ABP (Fisher Discrimination Ratio of 0.02 versus 0.42). ABP > 98 was an independent predictor of shunt outcome with odd ratio 6.4, 95% CI: 1.8-23.4 and p-value = 0.004. There was a strong and significant relationship between the interaction of age, PRx, ABP, and Rout (R = 0.53 with p = 7.28 × 10-0.5). Using our linear model, we achieved an AUC 86.4% (95% CI: 80.5-92.3%) in detecting shunt respondents. The overall sensitivity was 94%, specificity 75%, positive predictive value (PPV) of 54%, and negative predictive value of 97%. CONCLUSION: In patients with low Rout and high cerebrovascular burden, as described by high ABP and disturbed global autoregulation, response to shunting is less likely. The low PPV of high resistance, preserved autoregulation and absence of hypertension could merit further exploration.

Comparison of Assessment for Shunting with Infusion Studies Versus Extended Lumbar Drainage in Suspected Normal Pressure Hydrocephalus.

INTRODUCTION: Tools available for diagnosis of normal pressure hydrocephalus (NPH) and prediction of shunt-response are overnight ICP monitoring, infusion studies, and extended lumbar drainage (ELD). We investigated the shunt-response predictive value by infusion tests versus ELD. MATERIAL AND METHODS: We retrospectively recruited 83 patients who had undergone both infusion study and ELD assessments and compared infusion study hydrodynamics with improvement at clinic follow-up after ELD and after shunting. RESULTS: 62 patients had Rout >11 mmHg/mL/min. 28 Showed physiotherapy-documented improvement following ELD, and were selected for shunting, of which 21 were shunted. Of these, 19 showed improvement. Eight patients with Rout >20 mmHg/mL/min showed no response to ELD and were not shunted.There were 21 patients with Rout <11 mmHg/mL/min: five were shunted, showed improvement at follow-up, and had Rout >6 mmHg/mL/min. ICP amplitude did not differ at baseline or plateau between responders and non-responders. CONCLUSIONS: ELD response and CSF dynamics differed remarkably. All patients with Rout <6 mmHg/mL/min showed no improvement with ELD, indicating that ELD and shunting might be contraindicated in these subjects. High Rout patients with no response to ELD could merit further consideration.

The Role of Cerebrospinal Fluid Dynamics in Normal Pressure Hydrocephalus Diagnosis and Shunt Prognostication.

BACKGROUND: Over the years, there have been several reports and trials of the resistance to cerebrospinal fluid (CSF) outflow (Rout) in normal pressure hydrocephalus (NPH). This work aimed to revisit the utility of testing CSF circulation in a large population of patients clinically presenting with NPH. MATERIALS AND METHODS: We retrospectively analyzed the data of 369 NPH patients-either shunted or with endoscopic third ventriculostomy (ETV)-in Cambridge between 1992 and 2018. We determined the patients' outcomes (improvement versus no improvement at 6 months) by applying a threshold on R out values and compared our results with those of existing literature. We also conducted a correlation analysis between all variables and calculated Chi-Statistics (as a measure of separability between improvement and no improvement outcomes) to determine a subset of variables which achieved the highest accuracy in prediction of outcome. RESULTS: In our dataset, R out of 18 mmHg*min/mL achieved the highest Chi-statistics of 9.7 with p-value <0.01 when adjusted for age. In addition to R out, intracranial pressure (ICP) values at the baseline and plateau, CSF production rate and ICP amplitude to slope ratio showed significant Chi-Statistics values (more than 5). Using these variables, an overall accuracy of 0.70 ± 0.09 was achieved for prediction of the shunt outcome. CONCLUSION: Rout can be used for selecting patients for shunt surgery but not for excluding patients from treatment. Critical, multivariable approaches are required to comprehend CSF dynamics and pressure-volume compensation in NPH. Outcome definition and assessment could also be brought to question.

External Hydrocephalus After Traumatic Brain Injury: Retrospective Study of 102 Patients.

INTRODUCTION: External hydrocephalus (EH) refers to impairment of extra-axial cerebrospinal fluid flow with enlargement of the subarachnoid space (SAS) and concomitant raised intracranial pressure (ICP). It is often confused with a subdural hygroma and overlooked, particularly when there is no ventricular enlargement. In this study, we aimed to describe the epidemiology of EH in a large population of adults with traumatic brain injury (TBI). METHODS: This observational, retrospective cohort study was conducted in adult patients who were admitted with TBI to the Department of Clinical Neuroscience at Addenbrooke's Hospital (Cambridge, UK) over a period of 3 years (2014-2017). Patients were included in the study if they had ICP monitoring and at least three CT scans within the first 21 days to assess SAS evolution. Patients who underwent a decompressive craniectomy were excluded. SAS was assessed individually on each CT scan by two independent investigators. ICP data were analysed with ICM+ software (Cambridge Enterprise Ltd., Cambridge, UK). Short-term and 6-month outcomes were examined. The groups of patients with and without EH were compared. RESULTS: Of the 102 patients included in the study, 30.4% developed EH after a delay of 2.98 ± 2.4 days. The initial Glasgow Coma Scale (GCS) scores did not differ between patients with and without EH. Subarachnoid haemorrhage was found to be the main risk factor for EH. Patients with EH required a significantly longer period of mechanical ventilation (+6.9 days), were more likely to have a tracheostomy (55% versus 33%), and had a longer stay in the intensive care unit (+8.5 days). ICP was higher during the 48 h after diagnosis of EH than during the previous 48 h. EH survivors had a lower mean Glasgow Outcome Scale Extended (GOS-E) score (4.6 versus 5.9, P = 0.031) and were more likely to receive a permanent shunt for secondary hydrocephalus (17.4% versus 1.8%, odds ratio 7.1). CONCLUSION: In adults with TBI, EH remains insufficiently understood and probably underdiagnosed. This study showed that it is a frequent complication of TBI, with significant clinical consequences.

Lower Breakpoint of Intracranial Amplitude-Pressure Relationship in Normal Pressure Hydrocephalus.

The relationship between intracranial pulse amplitude (AMP) and mean intracranial pressure (ICP) has been previously described. Generally, AMP increases proportionally to rises in ICP. However, at low ICP a lower breakpoint (LB) of amplitude-pressure relationship can be observed, below which pulse amplitude stays constant when ICP varies. Theoretically, below this breakpoint, the pressure-volume relationship is linear (good compensatory reserve, brain compliance stays constant); above the breakpoint, it is exponential (brain compliance decreases with rising ICP).Infusion tests performed in 169 patients diagnosed for idiopathic normal pressure hydrocephalus (iNPH) during the period 2004-2013 were available for analysis. A lower breakpoint was observed in 62 patients diagnosed for iNPH. Improvement after shunt surgery in patients in whom LB was recorded was 77% versus 90% in patients where LB was absent (p < 0.02). There was no correlation between improvement and slope of amplitude-pressure line above LB.The detection of a lower breakpoint is associated with less frequent improvement after shunting in NPH. It may be interpreted that cerebrospinal fluid dynamics of patients working on the flat part of the pressure-volume curve and having a 'luxurious' compensatory reserve, are more frequently caused by brain atrophy, which is obviously not responding to shunting.

Differences in Cerebrospinal Fluid Dynamics in Posttraumatic Hydrocephalus Versus Atrophy, Including Effect of Decompression and Cranioplasty.

INTRODUCTION: Challenges in diagnosing post-traumatic hydrocephalus (PTH) have created a need for an accurate diagnostic tool. We aim to report CSF dynamics in PTH and atrophy, along with differences before and after cranioplasty. METHODS: We retrospectively analyzed traumatic brain injury patients with ventriculomegaly who had infusion studies. We divided patients depending on CSF dynamics into two groups: 'likely PTH' (A) and 'likely atrophy' (B). A group of idiopathic normal pressure hydrocephalus shunt-responsive patients was used for comparison (C). RESULTS: Group A consisted of 36 patients who were non-decompressed or had a cranioplasty in situ for over 1 month. Group B included 16 patients with low Rout, AMP, and dAMP, 9 of whom were decompressed. Rout and dAMP were significantly higher in Group A than B, but significantly lower than Group C (45 iNPH patients). RAP change during infusion in group A indicated depleted compensatory reserve compared to ample reserve in group B. Repeat studies in five decompressed patients post-cranioplasty showed all parameters increased. CONCLUSIONS: Infusion tests are not useful in decompressed patients, whilst cranioplasty allowed differentiation between possible PTH and atrophy. Rout and AMP were significantly lower in PTH compared to iNPH and did not always reflect the degree of hydrocephalus reported on imaging.

Single Center Experience in Cerebrospinal Fluid Dynamics Testing.

Normal pressure hydrocephalus is more complex than a simple disturbance of the cerebrospinal fluid (CSF) circulation. Nevertheless, an assessment of CSF dynamics is key to making decisions about shunt insertion, shunt malfunction, and for further management if a patient fails to improve. We summarize our 25 years of single center experience in CSF dynamics assessment using pressure measurement and analysis. 4473 computerized infusion tests have been performed. We have shown that CSF infusion studies are safe, with incidence of infection at less than 1%. Raised resistance to CSF outflow positively correlates (p < 0.014) with improvement after shunting and is associated with disturbance of cerebral blood flow and its autoregulation (p < 0.02). CSF infusion studies are valuable in assessing possible shunt malfunction in vivo and for avoiding unnecessary revisions. Infusion tests are safe and provide useful information for clinical decision-making for the management of patients suffering from hydrocephalus.

Compliance of the cerebrospinal space: comparison of three methods.

BACKGROUND: Cerebrospinal compliance describes the ability of the cerebrospinal space to buffer changes in volume. Diminished compliance is associated with increased risk of potentially threatening increases in intracranial pressure (ICP) when changes in cerebrospinal volume occur. However, despite various methods of estimation proposed so far, compliance is seldom used in clinical practice. This study aimed to compare three measures of cerebrospinal compliance. METHODS: ICP recordings from 36 normal-pressure hydrocephalus patients who underwent infusion tests with parallel recording of transcranial Doppler blood flow velocity were retrospectively analysed. Three methods were used to calculate compliance estimates during changes in the mean ICP induced by infusion of fluid into the cerebrospinal fluid space: (a) based on Marmarou's model of cerebrospinal fluid dynamics (CCSF), (b) based on the evaluation of changes in cerebral arterial blood volume (CCaBV), and (c) based on the amplitudes of peaks P1 and P2 of ICP pulse waveform (CP1/P2). RESULTS: Increase in ICP caused a significant decrease in all compliance estimates (p < 0.0001). Time courses of compliance estimators were strongly positively correlated with each other (group-averaged Spearman correlation coefficients: 0.94 [0.88-0.97] for CCSF vs. CCaBV, 0.77 [0.63-0.91] for CCSF vs. CP1/P2, and 0.68 [0.48-0.91] for CCaBV vs. CP1/P2). CONCLUSIONS: Indirect methods, CCaBV and CP1/P2, allow for the assessment of relative changes in cerebrospinal compliance and produce results exhibiting good correlation with the direct method of volumetric manipulation. This opens the possibility of monitoring relative changes in compliance continuously.

Cerebrospinal fluid dynamics in pediatric pseudotumor cerebri syndrome.

PURPOSE: There is a growing body of evidence highlighting the importance of comprehensive intracranial pressure (ICP) values in pseudotumor cerebri syndrome (PTCS). Due to the highly dynamic nature of ICP, several methods of ICP monitoring have been established, including the CSF infusion study. We have performed a retrospective review of the CSF dynamics measurements for all pediatric patients investigated for PTCS in our center and examined their diagnostic value compared with clinical classification. METHODS: We retrospectively recruited 31 patients under 16 years of age investigated for PTCS by CSF infusion test. We used the clinically provided Friedman classification 13/31 patients with definite PTCS (group A), 13/31 with probable PTCS (group B), and 5/31 not PTCS (group C), to compare CSF dynamics in the 3 groups. RESULTS: CSF pressure (CSFp) was significantly increased in group A (29.18 ± 7.72 mmHg) compared with B (15.31 ± 3.47 mmHg; p = 1.644e-05) and C (17.51 ± 5.87; p = 0.01368). The amplitude (AMP) was higher in the definite (2.18 ± 2.06 mmHg) than in group B (0.68 ± 0.37; p = 0.01382). There was no in either CSFp or AMP between groups B and C. No lower breakpoint of the AMP-P line was observed in group A but was present in 2/13 and 2/5 patients in groups B and C. In group A, sagittal sinus pressure (SSp) and elasticity were the only parameters above threshold (p = 4.2e-06 and p = 0.001953, respectively), In group B, only the elasticity was significantly higher than the threshold (p = 004257). Group C did not have any of the parameters raised. The AUC of CSFp, elasticity, and SSp for the 3 groups was 93.8% (84.8-100% CI). CONCLUSIONS: Monitoring of CSFp and its dynamics, besides providing a more precise methodology for measuring CSFp, could yield information on the dynamic parameters of CSFp that cannot be derived from CSFp as a number, accurately differentiating between the clinically and radiologically derived entities of PTCS.

Value of computerized shunt infusion study in assessment of pediatric hydrocephalus shunt function-a two center cross-sectional study.

BACKGROUND: Hydrocephalus shunt malfunction can-also in children-occur insidiously without clear symptoms of raised intracranial pressure (ICP) or changes in ventricular size, imposing a diagnostic challenge. Computerized shunt infusion studies enable quantitative shunt function assessment. We report on feasibility and results of this technique in children in a two center cross-sectional study. MATERIAL AND METHODS: Shunt infusion study (SIS) is performed with two needles inserted into a pre-chamber for ICP recording and CSF infusion. After baseline ICP recording, constant rate infusion is started until a new ICP plateau (ICPpl) is reached. Dedicated software containing the shunt's resistance characteristics calculates ICP and its amplitude outflow resistance and critical shunt pressure (CSP). Overall, 203 SIS were performed in 166 children. Shunts were defined as functional if ICPpl was 5 mmHg above CSP and borderline in between. RESULTS: Forty-one shunts (20.2%) were found obstructed, 26 (12.8%) had borderline characteristics, and 136 (67%) were functional. Baseline ICP in obstructed shunts was significantly above shunt operating pressure. CSF outflow resistance (Rout) and ∆ICP plateau were significantly elevated in obstructed shunts, with cut-off thresholds of 8.07 mmHg min/ml and 11.74 mmHg respectively. Subgroup analysis showed smaller ventricles in 69% of revised cases. CONCLUSION: SIS is a feasible, reliable, and radiation-free technique for quantitative shunt assessment to rule out or prove shunt malfunction. Dedicated software containing shunt hydrodynamic characteristics is necessary and small children may need short-term sedation. Due to the clinical and inherent economic advantages, SIS should be more frequently used in pediatric neurosurgery.

Correlation between the total number of features of paediatric pseudotumour cerebri syndrome and cerebrospinal fluid pressure.

PURPOSE: Accurate diagnosis of pseudotumour cerebri syndrome (PTCS) in children is challenging. We aimed to see if the clinical and radiological assessment that is carried out before lumbar puncture could predict subsequently recorded CSF pressures, and thus whether it could be used to increase diagnostic certainty of paediatric PTCS. METHODS: We used internationally recognised diagnostic criteria to derive a list of clinical, brain neuroimaging and venography features that were accepted to be associated with a diagnosis of PTCS. We performed a retrospective cohort study of children referred to our centre with suspected PTCS, identifying the presence or absence of those features for each child at initial presentation. The sum total scores of the features that were present were correlated with the child's recorded CSF pressure. RESULTS: The sum total scores were significantly positively correlated with recorded CSF pressures. The positive correlation was seen when clinical and brain neuroimaging features were included alone, and the correlation was slightly stronger when venography features were included in addition. CONCLUSION: Calculating the sum total of clinical, brain neuroimaging and venography features (where venography is performed) present at initial presentation can help in the management of children under investigation for PTCS. Children with high scores are more likely to have severely raised CSF pressures and thus may warrant more urgent LP investigations. By contrast, in children with subtle abnormalities in optic disc appearance such that disc oedema cannot be ruled out, a low score may add further reassurance and less urgency to proceed to LP.

Coupling of CSF and sagittal sinus pressure in adult patients with pseudotumour cerebri.

OBJECTIVE: Pseudotumour cerebri syndrome (PTCS including idiopathic intracranial hypertension) is characterised by the symptoms and signs of raised cerebrospinal fluid pressure (CSFp) in the absence of ventricular dilatation or an intracranial mass lesion. Its aetiology is unknown in the majority of cases but there is much evidence for impaired CSF absorption. Traditionally, sagittal sinus pressure has been considered to be independent of CSF pressure in adults. However, the discovery of stenoses of intracranial venous sinuses and introduction of venous sinus stenting has highlighted the importance of the venous drainage in PTCS. In this study, we have explored the relationship between CSFp and SSp before and during a CSF infusion test and during CSF drainage. MATERIALS AND METHODS: Ten patients (9 females:1 male) with PTCS underwent infusion studies in parallel with direct retrograde cerebral venography. Both SSp and CSFp were recorded at a baseline and during CSFp elevation in a course of a CSF infusion test. The drainage of CSF after the CSF infusion was performed in 7 patients. In 5 cases, jugular venous pressure was also measured. RESULTS: CSFp and SSp including their amplitudes correlated significantly and strongly both at baseline (R = 0.96; p = 0.001) and during infusion (R = 0.92; p = 0.0026). During drainage, this correlation was maintained until SSp reached a stable value, whereas CSFp continued to decrease. CONCLUSIONS: In this series of ten patients with PTCS, CSFp and SSp were coupled, both at baseline and during infusion. The implications of such coupling for the calculation of CSF outflow resistance are discussed.

Shunt infusion studies: impact on patient outcome, including health economics.

OBJECTIVES: The diagnosis of shunt malfunction is often not straightforward. We have explored, in symptomatic shunted patients with hydrocephalus or pseudotumour cerebri syndrome (PTCS), the accuracy of CSF infusion tests in differentiating a functioning shunt from one with possible problems, and the health economic consequences. METHODS: Participants: hydrocephalus/PTCS patients with infusion tests performed from January 2013 until December 2015. We followed patients up after 6 and 12 months from the test to determine whether they had improved, had persisting symptoms or had required urgent revision. We calculated the total cost savings of revision versus infusion tests and standard protocol of revision and ICP monitoring versus infusion tests. RESULTS: Three hundred sixty-five shunt infusion tests had been performed where a shunt prechamber/reservoir was present. For hydrocephalus patients, more than half of the tests (~ 55%, 155 out of 280) showed no shunt malfunction versus 125 with possible malfunction (ages 4 months to 90 years old). For PTCS patients aged 10 to 77 years old, 47 had possible problems and 38 no indication for shunt malfunction. Overall, > 290 unnecessary revisions were avoided over 3 years' time. Two hundred fifty-eight (> 85%) of those non-surgically managed, remained well, did not deteriorate and did not require surgery. No infections were associated with infusion studies. For Cambridge, the overall savings from avoiding revisions was £945,415 annually. CONCLUSIONS: Our results provide evidence of the importance of shunt testing in vivo to confirm shunt malfunction. Avoiding unnecessary shunt revisions carries a strong health benefit for patients that also translates to a significant financial benefit for the National Health Service and potentially for other healthcare systems worldwide.

Ventriculo-peritoneal shunting is a safe and effective treatment for idiopathic intracranial hypertension.

PURPOSE: To determine the outcome of ventriculo-peritoneal shunts as a treatment for idiopathic intracranial hypertension (IIH) Materials and Methods: Retrospective case series of 28 patients with IIH and evidence of raised intracranial pressure (ICP) who underwent shunt insertion. Patients were identified from a prospectively updated operative database. A case-notes review was performed and data on type of shunt, pre- and post-operative symptoms, ophthalmological findings and post-operative complications were recorded. RESULTS: All patients had symptoms of IIH that had failed medical management. Twelve patients had previous lumbo-peritoneal shunts and 2 patients had previous venous sinus stents. All patients had evidence of raised ICP as papilloedema and raised CSF pressure on lumbar puncture. Twenty-seven patients received a ventriculo-peritoneal shunt and 1 patient a ventriculo-atrial shunt. Twenty-six patients received Orbis Sigma Valves and 2 patients Strata valves. At follow-up all patients (100%) had improvement/resolution of papilloedema, 93% had improved visual acuity and 84% had improved headaches. Mean time to last follow-up was 15 (range 4-96) months. Complications occurred in 3 patients (11%): 2 patients required revision of their peritoneal catheters and 1 patient had an anti-siphon device inserted. CONCLUSIONS: Previous literature reported a ventricular shunt revision rate of 22-42% in the management of IIH. We demonstrate ventriculo-peritoneal shunts to be an effective treatment with a revision rate of 11% compared to the previously reported 22-42%.

ICP and Antihypertensive Drugs.

OBJECTIVES: Arterial hypertension is among the leading risks for mortality. This burden requires in hypertensive patients the use of single, double or more antihypertensive drugs. The relationship between intracranial pressure (ICP) and arterial blood pressure is complex and still under debate. The impact of antihypertensive drugs on ICP is unknown. We wanted to understand whether the use of antihypertensive drugs has a significant influence on ICP and cerebrospinal fluid (CSF)/brain related parameters. MATERIALS AND METHODS: In a cohort of 95 patients with suspected normal pressure hydrocephalus, we prospectively collected drug details according to the Anatomical Therapeutic Chemical (ATC) classification. Lumbar infusion studies were performed. Using ICM+ software, we calculated at baseline and plateau ICP and pulse amplitude, resistance to CSF outflow, elastance, and pressure in the sagittal sinus and CSF production rate. We studied the influence of the administration of 1, 2, 3 or more antihypertensive drugs on ICP-derived parameters. We compared the data using Student's and Mann-Whitney tests or Chi-squared and Fisher's exact test. RESULTS: Elastance is significantly higher in patients with at least one antihypertensive drug compared with patients without medication. On the contrary, pressure volume index (PVI) is significantly decreased in patients with antihypertensive drugs compared with patients not on these medications. However, the number of antihypertensive drugs does not seem to influence other ICP parameters. CONCLUSIONS: Patients on antihypertensive drugs seem to have a stiffer brain than those not on them.