Effects of ventriculoperitoneal shunt removal on cerebral oxygenation and brain compliance in chronic obstructive hydrocephalus

A New Definition for Intracranial Compliance to Evaluate Adult Hydrocephalus After Shunting

The clinical application of intracranial compliance (ICC), ∆V/∆P, as one of the most critical indexes for hydrocephalus evaluation was demonstrated previously. We suggest a new definition for the concept of ICC (long-term ICC) where there is a longer amount of elapsed time (up to 18 months after shunting) between the measurement of two values (V1 and V2 or P1 and P2). The head images of 15 adult patients with communicating hydrocephalus were provided with nine sets of imaging in nine stages: prior to shunting, and 1, 2, 3, 6, 9, 12, 15, and 18 months after shunting. In addition to measuring CSF volume (CSFV) in each stage, intracranial pressure (ICP) was also calculated using fluid–structure interaction simulation for the noninvasive calculation of ICC. Despite small increases in the brain volume (16.9%), there were considerable decreases in the ICP (70.4%) and CSFV (80.0%) of hydrocephalus patients after 18 months of shunting. The changes in CSFV, brain volume, and ICP values reached a stable condition 12, 15, and 6 months after shunting, respectively. The results showed that the brain tissue needs approximately two months to adapt itself to the fast and significant ICP reduction due to shunting. This may be related to the effect of the “viscous” component of brain tissue. The ICC trend between pre-shunting and the first month of shunting was descending for all patients with a “mean value” of 14.75 ± 0.6 ml/cm H2O. ICC changes in the other stages were oscillatory (nonuniform). Our noninvasive long-term ICC calculations showed a nonmonotonic trend in the CSFV–ICP graph, the lack of a linear relationship between ICC and ICP, and an oscillatory increase in ICC values during shunt treatment. The oscillatory changes in long-term ICC may reflect the clinical variations in hydrocephalus patients after shunting.

Global Rostral Midbrain Syndrome (GRMS) and Corpus callosum infarction in the context of shunt overdrainage

We report 3 cases of Global rostral midbrain syndrome (GRMS) and Corpus Callosum (CC) infarction, in the context of hydrocephalus followed by shunt dysfunction and slit ventricles. Prior shunt implantation had been indicated for adult-onset hydrocephalus secondary to aqueductal stenosis of varying causes. All three patients had been stable for months before developing repeated shunt dysfunctions, ultimately progressing to parkinsonism, Parinaud syndrome, akinetic mutism, pyramidal signs, cognitive impairment, CC infarction and slit ventricles, in the context of CSF overdrainage. Parkinsonism-related symptoms responded to dopa in all cases, but Parinaud syndrome and cognitive impairment persisted. Although GRMS has been described in the context of a transtentorial pressure gradient after shunt blockage, in these three cases with similar clinical presentation, reverse transtentorial pressure gradient and slit ventricles due to shunt overdrainage was the likely cause. The authors discuss the role of CC infarction and provide a detailed analysis after gathering previously described data, to unify information under a recognizable clinical entity and better understand the underlying pathophysiology, treatment options and outcome.

A novel model of acquired hydrocephalus for evaluation of neurosurgical treatments

Background

Many animal models have been used to study the pathophysiology of hydrocephalus; most of these have been rodent models whose lissencephalic cerebral cortex may not respond to ventriculomegaly in the same way as gyrencephalic species and whose size is not amenable to evaluation of clinically relevant neurosurgical treatments. Fewer models of hydrocephalus in gyrencephalic species have been used; thus, we have expanded upon a porcine model of hydrocephalus in juvenile pigs and used it to explore surgical treatment methods.

Methods

Acquired hydrocephalus was induced in 33–41-day old pigs by percutaneous intracisternal injections of kaolin (n = 17). Controls consisted of sham saline-injected (n = 6) and intact (n = 4) animals. Magnetic resonance imaging (MRI) was employed to evaluate ventriculomegaly at 11–42 days post-kaolin and to plan the surgical implantation of ventriculoperitoneal shunts at 14–38-days post-kaolin. Behavioral and neurological status were assessed.

Results

Bilateral ventriculomegaly occurred post-induction in all regions of the cerebral ventricles, with prominent CSF flow voids in the third ventricle, foramina of Monro, and cerebral aqueduct. Kaolin deposits formed a solid cast in the basal cisterns but the cisterna magna was patent. In 17 untreated hydrocephalic animals. Mean total ventricular volume was 8898 ± 5917 SD mm³ at 11–43 days of age, which was significantly larger than the baseline values of 2251 ± 194 SD mm³ for 6 sham controls aged 45–55 days, (p < 0.001). Past the post-induction recovery period, untreated pigs were asymptomatic despite exhibiting mild-moderate ventriculomegaly. Three out of 4 shunted animals showed a reduction in ventricular volume after 20–30 days of treatment, however some developed ataxia and lethargy, from putative shunt malfunction.

Conclusions

Kaolin induction of acquired hydrocephalus in juvenile pigs produced an in vivo model that is highly translational, allowing systematic studies of the pathophysiology and clinical treatment of hydrocephalus.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12987-021-00281-0.

Hydrodynamic comparison of shunt and endoscopic third ventriculostomy in adult hydrocephalus using in vitro models and fluid-structure interaction simulation

OBJECTIVE

The comparison of the efficiency of shunt placement and endoscopic third ventriculostomy (ETV) in treating of adult hydrocephalus patients with various intensities and different obstruction intensities in the aqueduct of Sylvius (AS).

METHODS

In vitro models with separated ventricles were simulated and implemented for modeling shunt and ETV surgeries in one healthy subject and hydrocephalus patients with various intensities, as well as three different obstruction intensities in AS and under two cerebrospinal fluid (CSF) dynamic conditions. The fluid-structure interaction simulation was also carried out to validate in vitro results.

RESULTS

The efficiency of both methods in reducing the maximum CSF pressure in the subarachnoid space (MCPS) decreased by an increase in the patient's intensities. Contrary to shunting, the efficiency of ETV in reducing MCPS demonstrated a decline (8.3-16.4%) by an increase in obstruction levels in AS. Based on the findings, shunt efficiency in decreasing MCPS in patients with low intensity was more remarkable compared to ETV. However, ETV was more efficient than shunt in the patient with intracranial hypertension. Further, shunt placement and ETV led to a significant reduction in the amplitude of CSF pressure in the SAS (ACPS) in patients with sneezing, coughing, Valsalva maneuver, and exercising effects in contrast to other patients. Moreover, ACPS reduction was not related to the intensity of the disease in both treatment methods. In contrast to shunt, an increase in the obstruction level in AS led to a reduction in ACPS in ETV in both CSF dynamic conditions.

CONCLUSIONS

The noises from irregular disorders increased the discharging of CSF after shunt placement, and activities such as sneezing, coughing, Valsalva maneuvers, and exercising increased the risk of shunt overdrainage by 10.4~47.8%, especially in the patient with intracranial hypertension. Based on the proposed in vitro ETV and shunt models, an increase of head compliance was higher in ETV compared to the shunt. Eventually, an increase in the obstruction level of AS after ETV led to a decline in head compliance in contrast to shunt.

Comparing the Efficiency of Two Treatment Methods of Hydrocephalus: Shunt Implantation and Endoscopic Third Ventriculostomy

Introduction:

Hydrocephalus is one of the most common diseases in children, and its treatment requires brain operation. However, the pathophysiology of the disease is very complicated and still unknown.

Methods:

Endoscopic Third Ventriculostomy (ETV) and Ventriculoperitoneal Shunt (VPS) implantation are among the common treatments of hydrocephalus. In this study, Cerebrospinal Fluid (CSF) hydrodynamic parameters and efficiency of the treatment methods were compared with numerical simulation and clinical follow-up of the treated patients.

Results:

Studies have shown that in patients under 19 years of age suffering from hydrocephalus related to a Posterior Fossa Brain Tumor (PFBT), the cumulative failure rate was 21% and 29% in ETV and VPS operation, respectively. At first, the ETV survival curve shows a sharp decrease and after two months it gets fixed while VPS curve makes a gradual decrease and reaches to a level lower than ETV curve after 5.7 months. Post-operative complications in ETV and VPS methods are 17% and 31%, respectively. In infants younger than 12 months with hydrocephalus due to congenital Aqueduct Stenosis (AS), and also in the elderly patients suffering from Normal Pressure Hydrocephalus (NPH), ETV is a better treatment option. Computer simulations show that the maximum CSF pressure is the most reliable hydrodynamic index for the evaluation of the treatment efficacy in these patients. After treatment by ETV and shunt methods, CSF pressure decreases about 9 and 5.3 times, respectively and 2.5 years after shunt implantation, this number returns to normal range.

Conclusion:

In infants with hydrocephalus, initial treatment by ETV was more reasonable than implanting the shunt. In adult with hydrocephalus, the initial failure in ETV occurred sooner compared to shunt therapy; however, ETV was more efficient.

Melatonin Attenuates Histopathological Changes in the Hippocampus of Infantile Rats with Kaolin-Induced Hydrocephalus

OBJECTIVE/AIM

Hydrocephalus is defined as an incapacitating neurological disorder characterized by ventricular enlargement in children, but the effects of melatonin on this hydrocephalus have not yet been fully elucidated. In the present experiment, we attempted to investigate the effects of exogenous melatonin administration on hydrocephalus-induced hippocampal changes in infantile rats.

METHODS

In this study, we randomly divided 45 Swiss albino rats aged 2 weeks into 3 groups: group I, the control group received a sham injection with needle insertion only; groups II and III were given kaolin injections before treatment - group II, the hydrocephalus group, was treated with an isotonic NaCl solution, and group III, the hydrocephalus plus melatonin group, was treated with 0.5 mg/100 g body weight of exogenous melatonin. Both immunohistochemical and histological analyses were performed after hydrocephalus induction and melatonin administration. Immunohistochemical staining consisted anti-glial fibrillary acidic protein staining. The TUNEL technique was used for defining quantitate apoptosis.

RESULTS

Melatonin administration significantly attenuated chronic hydrocephalus-induced histopathological changes in the hippocampal subregions of infantile rats. Compared to hydrocephalic rats treated with saline solution, melatonin significantly decreased the number of apoptotic cells and pyknotic index values of each hippocampal subregion after the kaolin-induced hydrocephalus (p < 0.001).

CONCLUSION

The present results demonstrate that the chronic hydrocephalus-induced histopathological changes in the hippocampus were partially reversible with melatonin treatment, suggesting its neuroprotective effects in infantile rats. However, these findings need to be confirmed by further experimental studies and clinical trials.

The pathophysiology of chronic noncommunicating hydrocephalus: lessons from continuous intracranial pressure monitoring and ventricular infusion testing

OBJECTIVE The pathophysiology of chronic noncommunicating hydrocephalus (ncHC) is poorly understood. This present study explored whether lessons about the pathophysiology of this clinical entity might be retrieved from results of overnight monitoring of pulsatile and static intracranial pressure (ICP) and ventricular infusion testing. METHODS The study cohort included adult patients (> 20 years of age) with chronic ncHC due to aqueductal stenosis in whom symptoms had lasted a minimum of 6 months. A reference cohort consisted of age- and sex-matched patients managed for communicating HC (cHC). Information about symptoms and clinical improvement following surgery was retrieved from a quality register, and results of overnight ICP recordings and ventricular infusion testing were retrieved from the hospital ICP database. RESULTS The cohort with ncHC consisted of 61 patients of whom 6 (10%) were managed conservatively, 34 (56%) by endoscopic third ventriculostomy (ETV), and 21 (34%) using ETV and subsequent shunt surgery. In patients responding to surgery, pulsatile ICP (mean ICP wave amplitude) was significantly increased to a similar magnitude in patients with ncHC and the reference cohort (cHC). Furthermore, intracranial compliance (ICC) was reduced in clinical responders. The results of ventricular infusion testing provided evidence that patients responding to ETV have impaired ventricular CSF absorption, while those requiring shunt placement after ETV present with impaired CSF absorption both in the intraventricular and extraventricular compartments. CONCLUSIONS The study may provide some lessons about the pathophysiology of chronic ncHC. First, increased pulsatile ICP and impaired ICC characterize patients with chronic ncHC who respond clinically to CSF diversion surgery, even though static ICP is not increased. Second, in patients responding clinically to ETV, impaired ventricular CSF absorption may be a key factor. Patients requiring shunt placement for clinical response appear to have both intraventricular and extraventricular CSF absorption failure. A subgroup of patients with ncHC due to aqueductal stenosis has normal ventricular CSF absorption and normal ICC and may not be in need of surgical CSF diversion.

Radiological Assessment of Hydrocephalus: New Theories and Implications for Therapy

It is almost a century since Dandy made the first experimental studies on hydrocephalus, but its underlying mechanism has been unknown up to now. The conventional view is that cerebrospinal fluid (CSF) malabsorption due to hindrance of the CSF circulation causes either obstructive or communicating hydrocephalus. Analyses of the intracranial hydrodynamics related to the pulse pressure show that this is an over-simplification. The new hydrodynamic concept presented here divides hydrocephalus into two main groups, acute hydrocephalus and chronic hydrocephalus. It is still accepted that acute hydrocephalus is caused by an intraventricular CSF obstruction, in accordance with the conventional view. Chronic hydrocephalus consists of two subtypes, communicating hydrocephalus and chronic obstructive hydrocephalus. The associated malabsorption of CSF is not involved as a causative factor in chronic hydrocephalus. Instead, it is suggested that increased pulse pressure in the brain capillaries maintains the ventricular enlargement in chronic hydrocephalus. Chronic hydrocephalus is due to decreased intracranial compliance, causing restricted arterial pulsations and increased capillary pulsations. The terms “restricted arterial pulsation hydrocephalus” or “increased capillary pulsation hydrocephalus” can be used to stress the hydrodynamic origin of both types of chronic hydrocephalus. The new hydrodynamic theories explain why third ventriculostomy may cure patients with communicating hydrocephalus, a treatment incompatible with the conventional view.

The correlation between pulsatile intracranial pressure and indices of intracranial pressure-volume reserve capacity: results from ventricular infusion testing

OBJECTIVE The objective of this study was to examine how pulsatile and static intracranial pressure (ICP) scores correlate with indices of intracranial pressure-volume reserve capacity, i.e., intracranial elastance (ICE) and intracranial compliance (ICC), as determined during ventricular infusion testing. METHODS All patients undergoing ventricular infusion testing and overnight ICP monitoring during the 6-year period from 2007 to 2012 were included in the study. Clinical data were retrieved from a quality registry, and the ventricular infusion pressure data and ICP scores were retrieved from a pressure database. The ICE and ICC (= 1/ICE) were computed during the infusion phase of the infusion test. RESULTS During the period from 2007 to 2012, 82 patients with possible treatment-dependent hydrocephalus underwent ventricular infusion testing within the department of neurosurgery. The infusion tests revealed a highly significant positive correlation between ICE and the pulsatile ICP scores mean wave amplitude (MWA) and rise-time coefficient (RTC), and the static ICP score mean ICP. The ICE was negatively associated with linear measures of ventricular size. The overnight ICP recordings revealed significantly increased MWA (> 4 mm Hg) and RTC (> 20 mm Hg/sec) values in patients with impaired ICC (< 0.5 ml/mm Hg). CONCLUSIONS In this study cohort, there was a significant positive correlation between pulsatile ICP and ICE measured during ventricular infusion testing. In patients with impaired ICC during infusion testing (ICC < 0.5 ml/mm Hg), overnight ICP recordings showed increased pulsatile ICP (MWA > 4 mm Hg, RTC > 20 mm Hg/sec), but not increased mean ICP (< 10-15 mm Hg). The present data support the assumption that pulsatile ICP (MWA and RTC) may serve as substitute markers of pressure-volume reserve capacity, i.e., ICE and ICC.

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

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

Cerebral white matter oxidation and nitrosylation in young rodents with kaolin-induced hydrocephalus

Hydrocephalus is associated with reduced blood flow in periventricular white matter. To investigate hypoxic and oxidative damage in the brains of rats with hydrocephalus, kaolin was injected into the cisterna magna of newborn 7- and 21-day-old Sprague-Dawley rats, and ventricle size was assessed by magnetic resonance imaging at 7, 21, and 42 days of age. In-situ evidence of hypoxia in periventricular capillaries and glial cells was shown by pimonidazole hydrochloride binding. Biochemical assay of thiobarbituric acid reaction and immunohistochemical detection of malondialdehyde and 4-hydroxy-2-nonenal indicated the presence of lipid peroxidation in white matter. Biochemical assay of nitrite indicated increased nitric oxide production. Nitrotyrosine immunohistochemistry showed nitrosylated proteins in white matter reactive microglia and astrocytes. Activities of the antioxidant enzymes catalase and glutathione peroxidase were not increased, and altered hypoxia-inducible factor 1α was not detected by quantitative reverse transcription-polymerase chain reaction. Cerebral vascular endothelial growth factor expression determined by quantitative reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay was not changed, but vascular endothelial growth factor immunoreactivity was increased in reactive astrocytes of hydrocephalic white matter. To determine if nitric oxide synthase is involved in the pathogenesis, we induced hydrocephalus in 7-day-old wild-type and neuronal nitric oxide synthase-deficient mice. At 7 days, the wild-type and mutant mice exhibited equally severe ventriculomegaly and no behavioral differences, although increased glial fibrillary acidic protein was less in the mutant mice. We conclude that hypoxia, via peroxidation and nitrosylation, contributes to brain changes in young rodents with hydrocephalus and that compensatory mechanisms are negligible.

Imaging diagnosis--Ventriculo-peritoneal shunt associated infection in a dog

Ventriculo-peritoneal shunting is a surgical treatment for hydrocephalus. Complications of this procedure are not well described in dogs. The most common complication in humans is infection, which can be fatal if not diagnosed and treated quickly. We describe the magnetic resonance (MR) imaging characteristics of a shunt-associated cerebral infection in a dog. The MR features of the infection included hyperintensity of the lining of the ventricular system visible on a T2-weighted FLAIR sequence and marked linear contrast enhancement of the ependymal layer on T1-weighted sequences, similar to that described in people.

Alterations of pulsation absorber characteristics in experimental hydrocephalus

OBJECT

Analysis of waveform data in previous studies suggests that the pulsatile movement of CSF may play a role in attenuating strong arterial pulsations entering the cranium, and its effectiveness in attenuating these pulsations may be altered by changes in intracranial pressure (ICP). These findings were obtained in studies performed in canines with normal anatomy of the CSF spaces. How then would pulsation absorbance respond to changes in CSF movement under obstructive conditions such as the development of hydrocephalus? In the present study, chronic obstructive hydrocephalus was induced by the injection of cyanoacrylate gel into the fourth ventricle of canines, and pulsation absorbance was compared before and after hydrocephalus induction.

METHODS

Five animals were evaluated with simultaneous recordings of ICP and arterial blood pressure (ABP) before and at 4 and 12 weeks after fourth ventricle obstruction by cyanoacrylate. To assess how the intracranial system responds to the arterial pulsatile component, ABP and ICP waveforms recorded in a time domain had to be analyzed in a frequency domain. In an earlier study the authors introduced a particular technique that allows characterization of the intracranial system in the frequency domain with sufficient accuracy and efficiency. This same method was used to analyze the relationship between ABP and ICP waveforms recorded during several acute states including hyperventilation as well as CSF withdrawal and infusion under conditions before and after inducing chronic obstructive hydrocephalus. Such a relationship is reflected in terms of a gain, which is a function of frequency. The cardiac pulsation absorbance (CPA) index, which is simply derived from a gain evaluated at the cardiac frequency, was used to quantitatively evaluate the changes in pulsation absorber function associated with the development of hydrocephalus within each of the animals, which did become hydrocephalic. To account for normal and hydrocephalic conditions within the same animal and at multiple time points, statistical analysis was performed by repeated-measures ANOVA.

RESULTS

The performance of the pulsation absorber as assessed by CPA significantly deteriorated after the development of chronic hydrocephalus. In these animals the decrement in CPA was far more significant than other anticipated changes including those in ICP, compliance, or ICP pulse amplitude.

CONCLUSIONS

To the extent that the free CSF movement acts as a buffer of arterial pulsation input to flow in microvessels, alterations in the pulsation absorber may play a pathophysiological role. One measure of alterations in the way the brain deals with pulsatile input-the CPA measurement-changes dramatically with the imposition of hydrocephalus. Results in the present study suggest that CPA may serve as a complementary metric to the conventional static measure of intracranial compliance in other experimental and clinical studies.

Cerebral microdialysis and intracranial pressure monitoring in patients with idiopathic normal-pressure hydrocephalus: association with clinical response to extended lumbar drainage and shunt surgery

OBJECT

This study was performed in patients with idiopathic normal-pressure hydrocephalus (iNPH) to monitor cerebral metabolism with microdialysis (MD) and intracranial pressure (ICP) readings, and relate to the clinical responses to extended lumbar drainage (ELD) and shunt surgery.

METHODS

The baseline levels of MD metabolites and ICP were monitored overnight in 40 consecutive patients with iNPH. In a subset of 28 patients, monitoring was continued during 3 days of ELD. Thirty-one patients received a ventriculoperitoneal shunt. The clinical severity of iNPH was determined before and then 3 and 6-12 months after shunt surgery.

RESULTS

Altered levels of MD markers (lactate, pyruvate, lactate/pyruvate ratio, glutamate, and/or glycerol) were seen in all patients at baseline; these improved during ELD. Despite normal static ICP (mean ICP), the pulsatile ICP (the ICP wave amplitude) was increased in 24 patients (60%). Only the level of the ICP wave amplitude differentiated the ELD and/or shunt responders from nonresponders.

CONCLUSIONS

The MD monitoring indicated low-grade cerebral ischemia in patients with iNPH; during ELD, cerebral metabolism improved. The pulsatile ICP (the ICP wave amplitude) was the only variable differentiating the clinical responders from the nonresponders. The authors suggest that the pulsatile ICP reflects the intracranial compliance and that CSF diversion improves the biophysical milieu of the nerve cells, which subsequently may improve their biochemical milieu.

Dissociation between vascular endothelial growth factor receptor-2 and blood vessel density in the caudate nucleus after chronic hydrocephalus

Chronic hydrocephalus (CH) is characterized by the presence of ventricular enlargement, decreased cerebral blood flow (CBF), and brain tissue oxygen delivery. Although the underlying pathophysiological role of vascular endothelial growth factor (VEGF) is not clear, ischemic-hypoxic events in CH are known to trigger its release. Previously, we have shown increased VEGF receptor-2 (VEGFR-2) and blood vessel density (BVd) in the hippocampus after CH. We investigated changes in neuronal and glial VEGFR-2 density and BVd in the caudate nucleus in an experimental model of CH. Animals with CH were divided into short term (ST, 2 to 4 weeks) and long term (LT, 12 to 16 weeks) and were compared with surgical controls (SCs, 12 to 16 weeks). The cellular and BVds were estimated using immunohistochemical and stereological counting methods. Overall, percentage (%)VEGFR-2 neurons were approximately two times greater in CH (ST, LT) than in SC. By comparison, glial cell %VEGFR-2 was greater by 10% to 17% in ST and 4% to 11% lower in LT compared with that in SC. Blood vessel density was significantly lower in CH than in SC in the superficial caudate. Changes in cerebrospinal fluid ventricular volume and pressure, as well as in CBF did not correlate with either VEGFR-2 or BVd. These observed findings suggest that destructive forces may outweigh angiogenic forces and possibly show a disassociation between VEGFR-2 and BV expressions.

Ventricular dilation and elevated aqueductal pulsations in a new experimental model of communicating hydrocephalus

In communicating hydrocephalus (CH), explanations for the symptoms and clear-cut effective treatments remain elusive. Pulsatile flow through the cerebral aqueduct is often significantly elevated, but a clear link between abnormal pulsations and ventriculomegaly has yet to be identified. We sought to demonstrate measurement of pulsatile aqueductal flow of CSF in the rat, and to characterize the temporal changes in CSF pulsations in a new model of CH. Hydrocephalus was induced by injection of kaolin into the basal cisterns of adult rats (n = 18). Ventricular volume and aqueductal pulsations were measured on a 9.4 T MRI over a one month period. Half of the animals developed ventricular dilation, with increased ventricular volume and pulsations as early as one day post-induction, and marked chronic elevations compared to intact controls (volume: 130.15 +/- 83.21 microl vs. 15.52 +/- 2.00 microl; pulsations: 114.51 nl +/- 106.29 vs. 0.72 +/- 0.13 nl). Similar to the clinical presentation, the relationship between ventricular size and pulsations was quite variable. However, the pulsation time-course revealed two distinct sub-types of hydrocephalic animals: those with markedly elevated pulsations which persisted over time, and those with mildly elevated pulsations which returned to near normal levels after one week. These groups were associated with severe and mild ventriculomegaly respectively. Thus, aqueductal flow can be measured in the rat using high-field MRI and basal cistern-induced CH is associated with an immediate change in CSF pulsatility. At the same time, our results highlight the complex nature of aqueductal pulsation and its relationship to ventricular dilation.

An experimental in-vivo canine model for adult shunt infection

Background

Detailed human studies of the mechanisms and development of shunt infection in real time are not possible, and we have developed a canine hydrocephalus model to overcome this. The intention of this pilot study was to show that the canine hydrocephalus model could be shunted using conventional "human" shunts, and that a shunt infection could be established so that further studies could then be planned.

Methods

Hydrocephalus was induced in seven dogs (Canis familiaris) by fourth ventricle obstruction. Four weeks later they were shunted using a Hakim Precision valve. Four of the dogs received shunts whose ventricular catheter had been inoculated with Staphylococcus epidermidis, and three were uninoculated controls. Four weeks after shunting the dogs were sacrificed and necropsy was performed. Removed shunts and tissue samples were examined microbiologically and isolates were subjected to detailed identification and genomic comparison.

Results

All the dogs remained well after shunting. Examination of removed shunt components revealed S. epidermidis in the brain and throughout the shunt system in the four inoculated animals, but in two of these Staphylococcus intermedius was also found. S. intermedius was also isolated from all three "negative" controls. There were slight differences between S. intermedius strains suggesting endogenous infection rather than cross- infection from a point source.

Conclusion

Shunt infection was established in the canine model, and had the experiment been extended beyond four weeks the typical microbiological, pathological and clinical features might have appeared. The occurrence of unplanned shunt infections in control animals due to canine normal skin flora reflects human clinical experience and underlines the usual source of bacteria causing shunt infection.

Chronic hydrocephalus-induced hypoxia: increased expression of VEGFR-2+ and blood vessel density in hippocampus

Chronic hydrocephalus (CH) is a neurological disease characterized by increased cerebrospinal fluid volume and pressure that is often associated with impaired cognitive function. By and large, CH is a complex and heterogeneous cerebrospinal fluid (CSF) disorder where the exact site of brain insult is uncertain. Several mechanisms including neural compression, fiber stretch, and local or global hypoxia have been implicated in the underlying pathophysiology of CH. Specifically, the hippocampus, which plays a significant role in memory processing and is in direct contact with expanding CSF ventricles, may be involved. Using our model of chronic hydrocephalus, we quantified the density of vascular endothelial growth factor receptor 2 (VEGFR-2(+)) neurons, glial, endothelial cells, and blood vessels in hippocampal regions CA1, CA2-3, dentate gyrus and hilus using immunohistochemical and stereological methods. Density and %VEGFR-2(+) cell populations were estimated for CH animals (2-3 weeks vs. 12-16 weeks) and surgical controls (SC). Overall, we found approximately six- to eightfold increase in the cellular density of VEGFR-2(+) and more than double blood vessel density (BVd) in the hippocampus of CH compared with SC. There were no significant regional differences in VEGFR-2(+) cellular and BVd expression in the CH group. VEGFR-2(+) and BVds were significantly related to changes in CSF volume (P<or=0.05), and not intracranial pressure (ICP). The %VEGFR-2(+) was significantly greater in CH than SC (P<or=0.05), and was significantly correlated with BVd (P<or=0.05). These results showed that CH elicited a profound increase in VEGFR-2(+) in hippocampus that corresponded to increased BVd. It was unclear whether increased VEGFR-2(+) and blood vessel expression was related to focal compression alone or in combination with global ischemia/hypoxia conditions as previously described. These findings suggest that VEGFR-2 may play an adaptive role in angiogenesis after CH-induced hypoxia. Modulation of vascular endothelial growth factor/VEGFR-2(+) may be important in developing treatments for hypoxic conditions including hydrocephalus and other forms of cerebral ischemia.

Chronic hydrocephalus-induced changes in cerebral blood flow: mediation through cardiac effects

Decreased cerebral blood flow (CBF) in hydrocephalus is believed to be related to increased intracranial pressure (ICP), vascular compression as the result of enlarged ventricles, or impaired metabolic activity. Little attention has been given to the relationship between cardiac function and systemic blood flow in chronic hydrocephalus (CH). Using an experimental model of chronic obstructive hydrocephalus developed in our laboratory, we investigated the relationship between the duration and severity of hydrocephalus and cardiac output (CO), CBF, myocardial tissue perfusion (MTP), and peripheral blood flow (PBF). Blood flow measures were obtained using the microsphere injection method under controlled hemodynamic conditions in experimental CH (n=23) and surgical control (n=8) canines at baseline and at 2, 4, 8, 12, and 16 weeks. Cardiac output measures were made using the Swan-Ganz thermodilution method. Intracranial compliance (ICC) via cerebrospinal fluid (CSF) bolus removal and infusion, and oxygen delivery in CSF and prefrontal cortex (PFC) were also investigated. We observed an initial surgical effect relating to 30% CO reduction and approximately 50% decrease in CBF, MTP, and PBF in both groups 2 weeks postoperatively, which recovered in control animals but continued to decline further in CH animals at 16 weeks. Cerebral blood flow, which was positively correlated with CO (P=0.028), showed no significant relationship with either CSF volume or pressure. Decreased CBF correlated with oxygen deprivation in PFC (P=0.006). Cardiac output was inversely related with ventriculomegaly (P=0.019), but did not correlate with ICP. Decreased CO corresponded to increased ICC, as measured by CSF infusion (P=0.04). Our results suggest that CH may have more of an influence on CO and CBF in the chronic stage than in the early condition, which was dominated by surgical effect. The cause of this late deterioration of cardiac function in hydrocephalus is uncertain, but may reflect cardiac regulation secondary to physiologic response or brain injury. The relationship between cardiac function and CBF should be considered in the pathophysiology and clinical treatment of CH.

Neuronal damage in hydrocephalus and its restoration by shunt insertion in experimental hydrocephalus: a study involving the neurofilament-immunostaining method

OBJECT

The morphological and functional impairments of neurons and their connections caused by hydrocephalus, and their restoration by ventricular shunt placement were investigated in experimental hydrocephalus by the immunostaining of neurofilaments, which constitute the major component of the neuronal cytoskeleton.

METHODS

Progressive hydrocephalus was induced in 15 young mongrel dogs 1 to 2 months of age, 3 to 4 weeks after cisternal injection of kaolin. The dogs were divided into three groups of five animals each, a "preshunt," "post-shunt," and "nonshunt" group, depending on whether the hydrocephalic animals underwent a procedure to insert a ventriculoperitoneal shunt. Neurofilament, glial fibrillary acid protein (GFAP), and synaptophysin immunostaining were performed using samples of brain tissue from each hydrocephalic group and a fourth "control" group (five animals). In the cortex, morphological deformation and heterogeneous neurofilament immunoreactivity of the apical dendrites became pronounced in accordance with the progression of hydrocephalus (from the preshunt to the nonshunt group), and these changes remained after shunt insertion (postshunt group). In the periventricular white matter, swollen and fragmented axons increased in number along with hydrocephalic progression and were incompletely repaired by ventricular shunt placement. The GFAP-positive astrocytes observed around repaired axons in the postshunt group were seen more prominently than in the untreated hydrocephalic groups. In the internal capsule, fairly good recovery from axonal damage caused by the hydrocephalic condition was achieved by insertion of a ventricular shunt, compared with that seen in the periventricular white matter.

CONCLUSIONS

Cytoskeletal damage of neurons in hydrocephalus and its incomplete restoration by shunt placement were most significant in the periventricular white matter. This finding may account for the impaired cognitive function seen in children who have shunts and an apparently reconstituted cerebral mantle; therefore, neuronal protection in the early hydrocephalic state should be considered.

On the optimal opening pressure of hydrostatic valves in cases of idiopathic normal-pressure hydrocephalus: a prospective randomized study with 123 patients

Does the opening pressure of hydrostatic shunts influence the clinical outcome for patients suffering from idiopathic normal-pressure hydrocephalus (NPH)? Between September 1997 and January 2003, 123 patients with idiopathic NPH were surgically treated by implanting a hydrostatic shunt at the Departments of Neurosurgery of the Unfallkrankenhaus Berlin and the University Homburg/Saar. As part of a prospective randomized study, all patients were examined preoperatively, postoperatively, and 1 year after the intervention. Forty-three percent of the patients showed a very good outcome, 25% good outcome, 20% fair outcome, and 12% poor outcome 1 year after the shunt implantation. Patients treated with an opening pressure rating of 50 mmH2O in the low-pressure stage of the gravitational valve showed a better outcome than those with an opening pressure of 100 or 130 mmH2O. According to present knowledge, hydrostatic shunts with an opening pressure of 50 mmH2O for the low-pressure stage are the best option for patients with idiopathic NPH. Due to the prompt switching function when the patient changes posture (lying down, standing, sitting, slanting etc.), the Miethke gravity-assisted valve (GAV) is more suitable in such cases than the Miethke Dual-Switch valve (DSV).

Radiological assessment of hydrocephalus: new theories and implications for therapy

It is almost a century since Dandy made the first experimental studies on hydrocephalus, but its underlying mechanism has been unknown up to now. The conventional view is that cerebrospinal fluid (CSF) malabsorption due to hindrance of the CSF circulation causes either obstructive or communicating hydrocephalus. Analyses of the intracranial hydrodynamics related to the pulse pressure show that this is an over-simplification. The new hydrodynamic concept presented here divides hydrocephalus into two main groups, acute hydrocephalus and chronic hydrocephalus. It is still accepted that acute hydrocephalus is caused by an intraventricular CSF obstruction, in accordance with the conventional view. Chronic hydrocephalus consists of two subtypes, communicating hydrocephalus and chronic obstructive hydrocephalus. The associated malabsorption of CSF is not involved as a causative factor in chronic hydrocephalus. Instead, it is suggested that increased pulse pressure in the brain capillaries maintains the ventricular enlargement in chronic hydrocephalus. Chronic hydrocephalus is due to decreased intracranial compliance, causing restricted arterial pulsations and increased capillary pulsations. The terms "restricted arterial pulsation hydrocephalus" or "increased capillary pulsation hydrocephalus" can be used to stress the hydrodynamic origin of both types of chronic hydrocephalus. The new hydrodynamic theories explain why third ventriculostomy may cure patients with communicating hydrocephalus, a treatment incompatible with the conventional view.

[Gravity valves for idiopathic normal pressure hydrocephalus. A Prospective study of 60 patients]

OBJECTIVE

Are hydrostatic valves superior to conventional differential pressure shunts in patients with normal- pressure hydrocephalus, with regard to the postoperative results of treatment and possible complications?

METHODS

From September 1997 to January 2002, 60 patients with idiopathic normal-pressure hydrocephalus were treated by surgical implantation of a hydrostatic valve (Miethke dual-switch valve) at the Unfallkrankenhaus Berlin.

RESULTS

One year after the shunt operation, the clinical picture was very good for 33% of the patients, good for 33%, satisfactory for 17%, and poor for 17%. At 20%, the rate of postoperative complications (catheter dislocations, valve infections, underdrainage and overdrainage) is still relatively high. The opening pressure of the Miethke dual-switch valve did not correlate with the postoperative results of treatment.

CONCLUSION

According to our experience, hydrostatic Miethke dual-switch valves are superior to conventional differential pressure shunts without an additional gravity unit, especially with regard to the treatment of patients with idiopathic normal -pressure hydrocephalus, concerning both the postoperative results of the treatment and the incidence of possible complications. With differentiated diagnosis and therapy, a clinical improvement can be achieved for 83% of such patients.

Functional magnetic resonance imaging before and after ventriculoperitoneal shunting for hydrocephalus--case report

A 70-year-old man with hydrocephalus was examined with functional magnetic resonance (fMR) imaging before and after ventriculoperitoneal shunting. Preoperatively, activation by right hand exercise revealed only a slight signal increase in the peri-rolandic area. However, 3 months after ventriculoperitoneal shunting, a significant signal increase was observed. fMR imaging may detect activity-related improvement of cerebral blood flow responses in patients with hydrocephalus after surgical treatment.