[Relevance and therapy of intracranial arachnoidal cysts]

Intracranial arachnoidal cysts (AC) are relevant due to their space-demanding character. The pathophysiological sequelae are dependent on the size and location of the cyst and the patient's age. Direct pressure on surrounding tissue causes headaches (meninges) or rarely seizures (brain tissue). Cerebrospinal fluid (CSF) circulation disturbances resulting from brain mass displacement with occlusion of, for example, the foramen monroi or the aqueduct cause occlusive hydrocephalus, which can lead to an increase in intracranial pressure. Depending on age, the typical primary clinical symptoms or findings differ. In adults and older children, headaches are usually the first clinical symptom. Children, in whom skull growth is not yet complete, present with a head circumference above the 97th percentile. An abnormal one-sided deflection of the calotte in the region of the underlying AC may also be present. Cranial magnetic resonance imaging (cMRI), the first-line diagnostic tool of choice to demonstrate size and location of the cysts and the surrounding intracranial structures, is of utmost importance for therapy planning. In addition, further malformations can be detected. Moreover, cMRI may also be useful for a rough assessment of increased intracranial pressure (ICP). In most symptomatic AC, surgical treatment is unavoidable. The primarily goal is to establish communication between the CSF and the cysts' content in order to effect pressure equalization. If the CSF reabsorption capacity is insufficient, it may also be necessary to implant a CSF shunt. Asymptomatic arachnoidal cysts should be strictly followed clinically and by cMRI over time. The reasonable frequency for follow-up depends on the size and location of the cyst.

[Clinical symptoms of hydrocephalus]

CLINICAL ISSUE

A correct interpretation of radiological data in cases of suspected hydrocephalus is not possible when ignoring patient age and clinical symptoms.

STANDARD TREATMENT

An in-depth knowledge of clinical findings is accordingly essential.

INNOVATIONS

New pathophysiological findings and a detailed assignment of previously unrecognized or ignored clinical symptoms to various entities of the spectrum of hydrocephalus disorders allow a coherent diagnosis drawn from clinical and radiological data. For this purpose it is necessary to know the specific symptoms of hydrocephalus in relation to age. Especially in chronic hydrocephalus, this is of utmost importance to avoid misdiagnosis.

DIAGNOSTIC WORK-UP

The radiological method of choice depends on the age and the specific issue to be addressed.

ACHIEVEMENTS

The typical clinical symptoms of different hydrocephalus entities presented here must be considered as confirmed knowledge.

PRACTICAL RECOMMENDATIONS

Only the synopsis of clinical and radiological findings currently allows correct interpretation of imaging. There is a threat of misdiagnosis if interpretation is restricted purely to radiological findings as the sole predictive value of modern imaging is still too limited despite all innovations.

Is it possible to minimize overdrainage complications with gravitational units in patients with idiopathic normal pressure hydrocephalus? Protocol of the randomized controlled SVASONA Trial (ISRCTN51046698)

Overdrainage is a common complication observed after shunting patients with idiopathic normal-pressure hydrocephalus (iNPH), with an estimated incidence up to 25%. Gravitational units that counterbalance intracranial pressure changes were developed to overcome this problem. We will set out to investigate whether the combination of a programmable valve and a gravitational unit (proGAV, Aesculap/Miethke, Germany) is capable of reducing the incidence of overdrainage and improving patient-centered outcomes compared to a conventional programmable valve (Medos-Codman, Johnson & Johnson, Germany). SVASONA is a pragmatic randomized controlled trial conducted at seven centers in Germany. Patients with a high probability of iNPH (based on clinical signs and symptoms, lumbar infusion and/or tap test, cranial computed tomography [CCT]) and no contraindications for surgical drainage will randomly be assigned to receive (1) a shunt assistant valve (proGAV) or (2) a conventional, programmable shunt valve (programmable Medos-Codman).We will test the primary hypothesis that the experimental device reduces the rate of overdrainage from 25% to 10%. As secondary analyses, we will measure iNPH-specific outcomes (i.e., the Black grading scale and the NPH Recovery Rate), generic quality of life (Short Form 36), and complications and serious adverse events (SAE). One planned interim analysis for safety and efficacy will be performed halfway through the study. To detect the hypothesized difference in the incidence of overdrainage with a type I error of 5% and a type II error of 20%, correcting for multiple testing and an anticipated dropout rate of 10%, 200 patients will be enrolled.The presented trial is currently recruiting patients, with the first results predicted to be available in late 2008.

Infection rate with application of an antibiotic-impregnated catheter for shunt implantation in children - a retrospective analysis

BACKGROUND

The infection rate of hydrocephalus shunts in children amounts figures of up to 25% and the according mortality rate is alarming high nowadays yet. An antibiotic impregnated shunt-catheter (AIS) was designed to reduce the incidence of shunt infections.

PATIENTS AND METHOD

In a non randomized trial 56 children were examined between January 2002 inclusive December 2007. The minimal follow-up was six months. Only children were included, who were shunted for the first time. In the study group (n=34) AIS (Bactiseal ) Codman, Johnson & Johnson, MA, Boston, USA) were used, while the control group (n=22) was provided with conventional, not-antibiotic impregnated catheters. To compare the risk profile for shunt infections, we defined, - according to the literature -, some risk factors.

RESULTS

Despite the incidence of shunt infections has been supposed to be higher according to the higher risk profile of the AIS group compared with controls, the shunt infection rate of the AIS group was lower than the shunt infection rate in the control group.

CONCLUSIONS

Apparently, AIS can reduce the incidence of shunt infections in children. Further prospective trials with a larger cohort are necessary for a statistically significant prove.

Analysis of pulse waves in intracranial pressure

In the therapy of hydrocephalus the dynamic course of the intracranial pressure (ICP) is rarely considered, although it may contain valuable diagnostic information. Several models for intracranial pressure and fluid dynamics are described. Assuming a simplified model and deriving the intracranial pressure wave relationships, this model could be partially confirmed and a characteristic dataset could be given for every patient.

Accuracy of ultrasound-guided puncture of the ventricular system

OBJECTS

Puncture of the ventricular system as one of the most frequently performed operative procedures in neurosurgery is usually done in a freehand way without guiding devices. The objective of this study is to examine whether ultrasonic guidance is able to heighten the accuracy of ventricular tapping.

METHODS

Real-time imaging via a single burr hole approach is achieved by aid of a bajonet-like shaped transducer with a footprint of 8x8 mm only (EUP-NS32, Hitachi Medical Systems). The needle is advanced towards the frontal horn along a displayed guideline. 51 punctures in 48 patients were performed with ultrasonic guidance and compared to 85 punctures in 67 patients without a guiding device.

CONCLUSION

The presented ultrasound method was not able to heighten the access rate of ventricular tapping, but it improved correct positioning of the catheter tip inside the frontal horn of the ventricular system significantly.

Outcome predictors for normal-pressure hydrocephalus

The objective of this prospective study was to find outcome predictors for better selection for treatment of normal-pressure hydrocephalus (NPH) patients. A total of 125 patients were evaluated and provided with a gravitational shunt. Cerebrospinal fluid hydrodynamics provided better predictive values if an algorithm to shunt all patients with a pressure/volume index of < 30 mL or resistance to outflow > 13 mmHg/mL x min was used. In general, outcome became worse with increasing anamnesis duration, worse preoperative clinical state, and increasing comorbidity. If one of these parameters was lower than a critical value, the shunt-responder rate was about 90% and the normally negative influence of older age was not seen. The well-known paradigm of a worse prognosis with NPH is not the result of the hydrocephalus etiology itself, but the consequence of a typical accumulation of negative outcome predictors as a consequence of the misinterpretation of normal aging and delayed adequate treatment.

An experimental aneurysm model: a training model for neurointerventionalists

SUMMARY

Reproducible animal models not only facilitate the pre-clinical assessment of aneurysm therapy but can also help in training for interventional procedures. The objective of this study was to find an animal model that can be used to test different endovascular occlusion techniques. Aneurysms in the right common carotid artery were created in 35 NZW rabbits by distal ligation and intraluminal elastase infusion. A total of 27 aneurysms were occluded by endovascular embolization with GDC-Coils. The time needed for placement of the microcatheter into the aneurysm by a professional interventionalist, a semi-professional interventionalist and a trainee was measured. The percentage of occlusion (occlusion rate) of the aneurysms was determined angiographically after embolization and again three months later, followed by a histological examination. Aneurysms of 2-6 mm size were reliably created in all 35 animals; mean size was 3.0 mm in height and 5.5 mm in diameter. Occlusion was achieved in 27 animals. Five animals from the group of 35 were initially planned as a control group with no embolization. We added to the control group one animal whose aneurysm could not be occluded endovascularly because of partial thrombosis and small size of the aneurysm. The angiographically determined mean occlusion rate was 89.5% +/- 11.3% standard deviation. Histological evaluation of the six aneurysms of the control group showed that they remained patent. Aneurysms that underwent embolization showed organized thrombus formation with no signs of recanalization. Two animals died from anaesthesia related or embolic complications. The time needed by the professional did not significantly decrease, after a little practice the trainee was nearly as quick as the professional. The beginner showed extensive progress, reducing the time for catheter placement by more than 50%. This paper describes the angiographic and histopathologic findings and also demonstrates possible methods for training in interventional procedures. Animal models will play a vital part in the training of future interventionalists. This model has the capability of testing different embolization devices (GDC, Onyx(R))and methods. Histologic long-term prognosis and the physical effect of the coils can be evaluated with this model.

Gravitational valves: relevant differences with different technical solutions to counteract hydrostatic pressure

Two different technical principles of gravitational valves (G-valves) have been presented: counterbalancer and switcher G-valves. The objective of our prospective study was to look for clinically relevant differences between both. A total of 54 patients with normal-pressure hydrocephalus (NPH) were treated; 30 patients received an Aesculap-Miethke GA-Valve (GAV; counterbalancer), and in 24 patients an Aesculap-Miethke Dualswitch-Valve (DSV; switcher) was implanted. The opening pressure of the posture-independent valve was 5 cm H2O in both devices. The outcome was clearly better with the usage of the GAV than with the DSV. The frequency and severity of complications was pronounced in the DSV group. We recommend the Aesculap-Miethke-GAV valve with a low opening pressure in a posture-independent valve for patients with NPH.

Gravitational shunt management of long-standing overt ventriculomegaly in adult (LOVA) hydrocephalus

OBJECTIVES

Recently a new subtype of chronic hydrocephalus was described: long-standing overt ventriculomegaly in adults (LOVA). Experience to date has indicated that shunt therapy was contraindicated, due to over-drainage. Therefore we investigated whether this problem could be overcome using gravitational shunts.

MATERIALS AND METHODS

Thirty macrocephalic adults (17-72 years of age), suffering from progressive hydrocephalus were managed with two different gravitational shunts. The post-operative observation period was 5-87 months.

RESULTS

Only two patients developed hygromas, and only one of these required surgical shunt revision. Eighty-seven percent of patients had a long-lasting clinical improvement. Ventricular size was only slightly reduced in 29 patients. There was no correlation between reduction in ventricular size and clinical improvement.

CONCLUSION

Contrary to clinical guidelines issued to date, we demonstrate that LOVA can be treated reliably with gravitational shunts, making them a genuine alternative to endoscopic third ventriculostomy (ETV).

[A grading system for chronic hydrocephalus]

A generally accepted grading system for patients suffering from chronic hydrocephalus has not been established yet. Therefore we designed a new grading system, which focuses on five symptom categories: gait disturbances, mental disorder, incontinence, headache, dizziness. For each category clearly circumscribed degrees of handicaps are defined. For each degree a value between 0-6 points is assigned in concordance to the severity of handicap. To get a generally accepted validation of the obstruction, the assigned values were oriented on the values provided in Germany to evaluate the degree of obstruction for insurances.[nl]In contrast to the established gradings of Stein and Langfitt and the Black Rating Scale our grading allows a more exact acquisition of the clinical presentation of a patient. Our experiences with the grading seemingly indicate also, that it is reliable. Because the grading allows an incorporation of measurable data such as psychometric analysis or gait analysis, our grading is useful as well for everydays' practice as for scientific purpose.

[LOVA hydrocephalus - a new entity of chronic hydrocephalus]

The recently defined term "longstanding overt ventriculomegaly in adults" (LOVA) describes a unique entity of chronic occlusive hydrocephalus. The experiences so far using conventional DP valves were not encouraging because of a high percentage of overdrainage. The objective was to evaluate whether gravitational shunts could be used for this condition with an acceptable overdrainage risk. Twenty-three macrocephalic adults aged 17-72 years suffered from chronic progressive hydrocephalic conditions. They received two different types of gravitational shunt. Follow-up ranged from 6 months to 75 months. Only two patients presented small subdural effusions postoperatively, and only one required additional treatment for that. Eighty-two percent were shunt responders. Ventricular size was only marginally reduced in 22 of the 23 patients. There was no correlation between clinical benefit and the reduction in ventricular size. Gravitational shunts clearly have the potency for safe treatment of LOVA, significantly reducing the risk of overdrainage over conventional valves, and may be considered an equivalent alternative to third ventriculostomy.

Five years experience with gravitational shunts in chronic hydrocephalus of adults

OBJECTIVE

Gravitational shunts for management of chronic hydrocephalus are supposed to avoid or at least to reduce the risk of overdrainage. In order to find out if this hypothesis is correct, we did a prospective study and analysed the results of a series of 185 hydrocephalic adults, treated by using gravitational shunts. For the few cases in whom overdrainage occurred, we wanted to establish the reason for it. Especially it should be proven or excluded that overdrainage was caused by shortcomings of the principle of gravitational shunts. Another goal was to compare post-shunting changes of the ventricular size with clinical outcome. A comparably large study has not yet been published.

METHODS

185 adult patients who suffered from chronic hydrocephalus were shunted between 1996-2000, either using the combination of an adjustable Codmann Hakim Valve & Miethke Shunt Assistant (35 patients) or a Miethke Dual Switch Valve (150 patients). The clinical course of each patient has been followed until the end of 2000. Average follow-up time was 26 months (range 6-60 months).

RESULTS

88% of our patients were shunt responders, 70% had a good or excellent outcome. Overdrainage occurred in only 4%. It turned out that this complication was not a failure of the concept of gravitational shunts, but the result of a wrongly estimated intraperitoneal pressure. After shunting the ventricular size was reduced only marginally. In 92% of the patients the Evans-Index decreased less than 20% after the shunt insertion, but 69% of these patients had a good or excellent outcome. The most obvious difference comparing pre- and postoperative imaging was a better visibility of the high apical sulci after shunting.

CONCLUSION

In our series gravitational shunts proved to be effective in preventing overdrainage. The 4% negative exceptions are mainly avoidable. There was no correlation between outcome and ventricular size reduction, and as a rule ventricular size was only marginally reduced.

Vertex epidural hematoma with communicating bifrontal subgaleal hematomas treated by percutaneous needle aspiration

The case of an 11-year-old boy is presented who suffered a bicycle accident with a parasagittal skull fracture, a small vertex epidural hematoma, frontal contusions and a frontal subgaleal hematoma. Enlargement of the vertex epidural hematoma was diagnosed after development of a slight paraparesis on day 11 with the aid of MRI. Three percutaneous needle aspirations of the subgaleal hematoma with a total of 59 ml being evacuated led to quick recovery and disappearance of the subgaleal as well as the vertex epidural hematoma. It is speculated that both hematomas communicated via the skull fracture thus making the evacuation of the epidural hematoma by subgaleal punctures possible.

[The importance of hydrostatic valves in the treatment of adult chronic hydrocephalus]

BACKGROUND AND OBJECTIVE

Earlier designs of hydrocephalus valves, focusing on a reduction of the problem of overdrainage, were proved to be insufficiently. Since the middle of the 90's hydrostatic valve, constructions are available, which should solve this problem. The objective of the study was to evaluate, whether these gravitational shunts would indeed reduce the percentage of overdrainage in shunted patients.

METHODS

In 51 patients clinical evaluation and MRI was performed pre- and in regular intervals postoperatively. 21 received a Dual-Switch valve, 14 a programmable Codman Hakim plus Shuntassistent and 6 a combination of a conventional valve with Shuntassistent.

RESULTS

Over 90% of the patients had clear and persisting (over 24 months) clinical benefit from shunting. Only one suffered for some days after shunt implantation from headache in the upright position. No other clinical or imaging hints were given on an overdrainage. The ventricular size was unchanged in patients with a normal pressure hydrocephalus after shunting. In patients with occlusive hydrocephalus only a few showed a significant reduction of the ventricular wide.

CONCLUSION

Gravitational shunts seem to decrease the overdrainage linked to the treatment of chronic hydrocephalus in shunted patients, therefore its use should be standardised when treatment chronic hydrocephalus.

[Significance of hydrostatic valves in therapy of chronic hydrocephalus]

Earlier design changes in hydrocephalus valves focusing on reducing overdrainage failed. Since the middle of the 1990s, hydrostatic valve constructions have been available which are claimed to solve this problem. The objective of this study was to evaluate the efficiency of these constructions. Clinical status and ventricular size were evaluated in 45 patients with chronic hydrocephalus before and 1, 6, and 26 weeks after operation. In 35 of these, a Miethke dual-switch valve was implanted (treatment group 1), and the others received a combination of a programmable Codman-Hakim valve and a Miethke shunt assistant as the hydrostatic element of the configuration (treatment group 2). A third group (n = 6) had already been shunted but suffered from overdrainage symptoms which could not be overcome by conservative measures. In these cases, the only operative treatment was the implantation of a Miethke shunt assistant adjunctively to the existing valve. In groups 1 and 2, there was a significant permanent improvement in the clinical state in nearly 80% of cases and a moderate permanent improvement in about 10%. Mild clinical and radiological signs of overdrainage occurred in three patients during the first postoperative week but resolved without further operative measures within the next 5 weeks. Typically, the ventricular width was not or only marginally reduced in these 45 patients. In the patients treated for symptoms of overdrainage (group 3), complaints resolved within the first week after implantation of the shunt assistant. The study indicates that gravitational shunts may be very effective in preventing overdrainage in chronic hydrocephalus, and therefore these constructions could represent the gold standard in the treatment of chronic hydrocephalus.

The dynamic infusion test in rats

Although the hydrocephalic H-Tx rat is a widely used model, data on the cerebrospinal fluid (CSF) dynamics in hydrocephalic rats are rare or - as the pressure volume index (PVI) - not available. We used hydrocephalic and nonhydrocephalic H-Tx rats, a stock with a high percentage of inherited hydrocephalus, for the evaluation of such data. In addition, a new, simple mathematical algorithm ("dynamic infusion test"), which has not formerly been used in animal experiments, was used as a pathophysiological model of CSF dynamics. Compared with classical methods for evaluation of these data, the dynamic infusion test gives a deeper insight into the relation between ICP and CSF dynamics. It was found that the resistance to outflow (ROF) in hydrocephalic rats was at least twice that in nonhydrocephalic rats. The PVI measured was similar in hydrocephalic and nonhydrocephalic animals, but clearly higher than the values reported in the literature. This may be attributable to the fact that the classically used bolus test, in contrast to the "dynamic infusion test", is representative only for the CSF compartment which is directly exposed to the bolus application.

The ependyma in chronic hydrocephalus

H-Tx rats produce congenitally hydrocephalic offspring with varying severity of the condition. We used moderately hydrocephalic rats without evident clinical signs of hydrocephalus and normal controls from the same stock when they were at least 1.5 years old. Macroscopic anatomy was studied by MRI and in fixed brain slices and the ultrastructure of the ependyma, with REM. Apart from markedly stretched areas, where the ependyma was totally destroyed and subependymal structures directly exposed to the CSF, the density of ependymal microvilli and of tufts of cilia was reduced in proportion to the ventricular distension of a given area. A supraependymal "network"--never seen before in acute hydrocephalus--was found, whose purpose is probably to prevent further ventricular enlargement. We conclude that even in arrested hydrocephalus the ependymal sequelae of hydrocephalus are similar to those of the acute stage, illustrating the extremely limited potential for recovery, but the organism seems nevertheless to react with an internal stabilization of the ventricular system.

[Possibilities and limits of automatic detection of pathologic intracranial pressure waves with FFT]

Owing to the existence of "reserve spaces" varying individually in extent and expressed by the term compliance, space-consumption intracranial processes do not raise the intracranial pressure (ICP) primarily. Only when this compliance has been exhausted may ICP rise dramatically and may rapidly reach dangerously high levels. It has been shown in the past that "anticipatory" initiation of ICP-reducing measures--i.e. very early in the development of increasing mean ICP--may greatly benefit patient outcome. To recognize an imminent ICP crisis, the available compliance needs to be known. The classical method for determining this latter is the bolus test, which, however, has the disadvantage of being discontinuous and associated with the risk of infection. Another, less invasive and continuous, option is the recognition of pathological intracranial pressure waves. However, recognition of such patterns requires specialized knowledge, that is not widely available. Since, however, knowledge of the compliance is of general importance for intensive care, the idea of developing a PC-based automated system for the identification of pathological waves was followed up. During the course of our basic research effort, we investigated the suitability of the fast Fourier transformation (FFT) algorithm for this purpose. We were able to show that while the FFT is theoretically useful for the detection of pathological intracranial waves, its shortcomings in terms of its sensitivity to extraneous signals (noise) (of considerable importance for biological data handling) and errors in correctly estimating the amplitudes of pathological waves (of great importance for clinical evaluation) make FFT appear less than optimally suitable for this purpose.

[Pilocytic astrocytoma with subarachnoid dissemination]

Pilocytic Astrocytomas (WHO I) are histopathologically tumors of glial origin occurring predominantly in childhood and adolescence. Normally, they are characterized by a benign clinical course, with a long overall survival time and a high rate of complete remission. The rare case of pilocytic astrocytoma, primarily located in the third ventricular region, with generalized subarachnoidal spread is described. In the 10 years of follow-up, the histopathologic findings of the seedings remained those of a typical pilocytic astrocytoma; tumor progression did not occur.

[Dysembryoplastic neuroepithelial tumor (DNT). Pattern of neuroradiologic findings]

Dysembryoplastic neuroepithelial tumors (DNT) were first described as a new tumor entity by Daumas-Duport et al. in 1988 and were introduced into the revised WHO classification of brain tumors in 1993. The purpose of this study was to work out neuroradiological CT and MRT patterns of DNT. Five patients, aged 11-61 years (three female, two male) underwent complete presurgical neuroradiological exploration (5 CT, 4 MRT investigations, 2 angiography) because of brain tumor. Four cases complained of seizures and one of occipital-located headache. Total microsurgical excision was achieved in two cases. Two further lesions were resected subtotally after stereotactic biopsy diagnosis. In one case, stereotactic biopsy alone was carried out. All DNTs were localized cortically: two frontobasal medial in the gyrus rectus, two temporobasal in the gyrus occipitotemporalis lateralis and one infratentorial in the lobus caudalis cerebelli. They were sharply demarcated from the surrounding brain tissue. Cortical localization was better visualized by MRT, especially on coronal and sagittal images. CT scans showed a hypodense lesion, MRT a high-signal intensity in T2, low signal in T1 and in proton-weighted images a hyperintense rim with a slightly hyperintense small cyst. The multinodular tumor architecture was best seen in MRT. Two DNTs presented partial contrast enhancement, while three DNTs did not take up contrast. In two lesions there were focal calcifications. The infratentorial DNT was associated with a bony defect of the tabula interna into which the tumor expanded. Two angiographies showed no pathological tumor neovascularization. A hypodense sharply demarcated lesion with a multinodular pattern in MRT with cortical location and without space-occupying signs is, in combination with the clinical symptom of epileptic seizures, highly suggestive of DNT. As our results demonstrate, DNT can also occur in the infratentorial space.