Testing of cerebrospinal compensatory reserve in shunted and non-shunted patients: a guide to interpretation based on an observational study.

OBJECTIVE--To design a computerised infusion test to compensate for the disadvantages of Katzman's lumbar infusion method: inadequate accuracy of estimation of the resistance to cerebrospinal fluid outflow and poor predictive value in normal pressure hydrocephalus. METHODS--Accuracy was improved by intracranial pressure signal processing and model analysis for measurement of cerebrospinal compensatory variable. These include the CSF outflow resistance, brain compliance, pressure-volume index, estimated sagittal sinus pressure, CSF formation rate, and other variables. Infusion may be made into the lumbar space, ventricles, or, when assessing shunt function in vivo, the shunt chamber. RESULTS AND CONCLUSIONS--The computerised test has been used for five years in a multicentre study in 350 hydrocephalic patients of various ages, aetiologies, and states of cerebrospinal compensation. The principles of using the test to characterise different types of CSF circulatory disorders in patients presenting with ventricular dilatation, including brain atrophy and normal and high pressure hydrocephalus, are presented and illustrated. Previous studies showed a positive correlation between cerebrospinal compensatory variables and the results of shunting, but such a prediction remains difficult in idiopathic normal pressure hydrocephalus, particularly in elderly patients. The technique is helpful in the assessment of shunt malfunction, including posture-related overdrainage, over-drainage related to the nocturnal B wave activity, and proximal or distal shunt obstruction. The appendix presents an introduction of the mathematical modelling of CSF pressure volume-compensation included in computerised infusion test software.     

Shunt operation versus endoscopic ventriculostomy in normal pressure hydrocephalus: diagnostics and outcome

In contrast to shunt operation the indication for an endoscopic ventriculostomy in patients diagnosed for normal pressure hydrocephalus is not scientifically established. From September 1997 to October 2001 we operated on 79 patients diagnosed for normal pressure hydrocephalus. Diagnosis was established by means of the intrathecal lumbal or ventricular infusion test, the cerebrospinal fluid tap test and MRI-CSF flow studies pre- and post-operatively. In 60 patients (76 %) we implanted a ventriculo-peritoneal shunt (Miethke Dual-Switch valve), and in 15 patients (19 %) we performed the endoscopic assisted third ventriculostomy. With our created NPH recovery rate and use of the clinical grading for normal pressure hydrocephalus created by Kiefer we compared the operative results of both patient groups. Immediately after the operation the results are the same for both treatments. In the follow-up examination after 12 and 27 months patients who underwent a ventriculostomy showed a better outcome, but the underdrainage rate was higher. Concerning the operation related complications the shunt treatment leaded to 10 revisions (17 %) because of four infections (7 %), two shunt insufficiencies (3 %), two overdrainages (3 %), two catheter dislocations (3 %). The ventriculostomy leaded to one case with a pneumatocephalus (7 %) and one ischemic thalamic lesion (7 %). In both operation methods we saw cases of underdrainages, three after valve implantation (5 %) and two after ventriculostomy (13 %). In that patients we performed a change of the implanted valve with a lower pressure level or rather an implantation of a valve system in the two cases who underwent a ventriculostomy. In patients with a pathologically increased resistance to CSF outflow in the lumbal infusion test a shunt implantation with the Miethke Dual-Switch valve is indicated. Patients whose outflow resistance is increased in the ventricular infusion test are suspected for a functional interventricular stenosis and should be treated by means of an endoscopic assisted ventriculostomy.     

The role of computerized rheoencephalography in the assessment of normal pressure hydrocephalus. Preliminary report

BACKGROUND AND PURPOSE: It is generally agreed that the positive result of lumbar cerebrospinal fluid (CSF) withdrawal offers a reliable means for selection of patients likely to respond to shunting in normal pressure hydrocephalus (NPH). However the studies of cerebral hemodynamics in NPH are performed Routinely only in few neurosurgical centers. We therefore studied the effect of CSF withdrawal on cerebrovascular autoregulation (CVA) in this condition by means of computerized rheoencephalography [REG]. MATERIAL AND METHODS: The study group consisted of 27 patients with presumed posttraumatic NPH. In each patient both the tap test and infusion test were performed. Psychometric tests and rheoencephalographic examinations were made twice: before and after CSF withdrawal. The obvious restoration of the functional state of CVA after CSF withdrawal was considered as a positive result of the tap test. RESULTS: Fourteen patients with a positive tap test and/or with resistance to CSF outflow (Rout) of more than 11 mmHg/ml/min were shunted. The improvement was obtained in 10 of them. Only one patient with a positive tap test did not improve. CONCLUSIONS: Our study suggests that restoration of CVA after CSF withdrawal is associated with high likelihood of shunt success, but not vice versa. Evaluation of CVA using REG seems to offer a new diagnostic tool in selecting patients likely to respond to shunting. Further studies are necessary to optimize the amount of CSF withdrawal, the delay between CSF withdrawal and control examinations and methodology of neuropsychological examinations.     

Meningeal Gadolinium Enhancement in Low-pressure Headaches

Three patients with headaches in erect but not recumbent positions had barely measurable cerebrospinal fluid (CSF) pressures and aseptic but abnormal CSF findings with variable pleocytosis and elevated protein content. The CSF glucose level was normal and there were no blasts or malignant cells. Gadolinium-enhanced magnetic resonance imaging (MRI) in all 3 showed diffuse meningeal enhancement. In 2, headaches and MRI abnormalities completely resolved spontaneously. The third patient, who had a prior ventriculoperitoneal shunt, improved after shunt revision.     

Low-pressure hydrocephalic state complicating hemispherectomy: a case report

Low-pressure hydrocephalic state (LPHS) has only recently been described as a distinct clinical entity occurring in patients with bioatrophic lesions of the brain. We report a patient in whom this syndrome developed after subtotal hemispherectomy for intractable epilepsy. METHODS: A 30-year-old man developed cerebrospinal fluid (CSF) rhinorrhea after subtotal hemispherectomy. After repair of the CSF dural fistula, clinical and radiological features of an LPHS developed. After external ventricular drainage for 26 days, a programmable low-pressure shunt system was instituted. RESULTS: Worsening neurologic status and ventriculomegaly in the face of normal intraventricular pressures is diagnostic of this condition. The clinical status clearly correlated with ventricular size and not ventricular pressure. CONCLUSION: LPHS is a clinically significant perioperative complication that rarely occurs after large brain excisions. Restoration of the baseline brain compliance is critical in the management of this condition.     

Communicating hydrocephalus in adults. Diagnostic tests and results of treatment with medium pressure shunts

In a study of 60 patients with communicating hydrocephalus, sources of error included lumbar cerebrospinal fluid (CSF) leakage, epidural infusion, and cerebrovascular reactions during the CSF infusion test; a high frequency of failing shunts; and initially undetected tumors in the group whose hydrocephalus was idiopathic. Though no sharp distinction could be made between positive and negative diagnositc tests, each variable indicated a certain probability of benefit, ranging from high to low, from shunting. CSF opening pressure in the lateral and sitting positions, the CSF infusion test, and cisternography were helpful in selecting patients for shunting. If clinical improvement was to take place, it did so within 3 months of shunting. Only patients with an opening pressure at or within the upper half of supposedly normal CSF pressure improved from a medium-pressure shunt. Improvement occurred in all patients having pressures of 580 mm H2O or more during an infusion test at a rate of 1.5 ml per minute. Neither preoperative signs and symptoms nor a single electroencephalogram had predictive value.     

Predictors of outcome in patients with normal pressure hydrocephalus

Despite emerging knowledge over 40 years, the postoperative results after shunt implantations in patients diagnosed for normal pressure hydrocephalus (NPH) did not improve significantly during the last decade. For that reason predictors have to be identified in order to predict preoperatively the course of disease. From 1982 until 2000 we examined in a prospective study 200 patients diagnosed for NPH. From the patients, who were surgically treated by a shunt implantation we could reexamine 155 (78%) in a meantime interval of seven month after the operation. The NPH was graduated according to the results of the intrathecal infusion test in an early state NPH (without brain atrophy) and late state NPH (with brain atrophy). In our study, we focussed the attention on the possible predictors: patients age, length of disease, clinical signs--like gait ataxia, dementia and bladder incontinence, aetiology idiopathic/secondary as well as implanted valve type and the value of resistance to cerebrospinal fluid outflow. To measure the outcome we used the NPH-Recovery-Rate, as statistical test the Chi-square according to Pearson. In 80 patients with an early stage NPH (without cerebral atrophy) a short course of disease (< 1 year), a just slight distinct of dementia and an implanted Miethke-Dual-Switch valve were significant predictors for a positive postoperative outcome. The outflow resistance measured in the intrathecal infusion test showed only a minimal relevance for the outcome. Those 75 patients with a late state NPH (with cerebral atrophy) had a better outcome when dementia was not present, the outflow resistance was above 20 mm Hg*min/ml, the CSF tap-test was positive and a Miethke-Dual-Switch valve was implanted.     

Pre- and postoperative cerebrospinal fluid absorption studies in patients with myelomeningocele shunted for hydrocephalus

Nine infants with myelomeningocele and hydrocephalus had cerebrospinal fluid formation and absorption studies before insertion of a ventriculoperitoneal shunt. Six were also tested postoperatively. The preshunt formation rate varied from 0.21-0.42 ml.min-1 and the cerebrospinal fluid absorption rate or CSF conductance (Ccsf) varied from 0.008 to 0.031 ml.min-1.mm Hg-1. The postoperative formation rate varied from 0.21 to 0.39 ml.min-1. The postoperative CSF conductance (Ct) was calculated as the sum of Ccsf and the shunt conductance (Cs). The relationship between the Ccsf and Cs curves was determined by matching the sum of these curves to the postoperative data points using the method of least-squares. The data suggests that the shunt may work directly or indirectly to establish a new resting pressure; the latter by stabilizing the sagittal sinus pressure which preoperatively increased concomitantly with the CSF pressure and thus enhanced an already-existing absorption deficit.     

Méthode et résultats du test de perfusion dans l’hydrocéphalie à pression normale : revue de la littérature

Introduction

The cerebrospinal (CSF) infusion test is used to analyze the dynamics of CSF circulation. We describe the technique and report test results obtained in subjects with normal pressure hydrocephalus.

State of the art

The CSF infusion test is based on pressure monitoring during a continuous infusion of saline solution into the CSF space via a lumbar puncture. The main parameters are: intracranial pressure, resistance to CSF outflow (Rout), and compliance of the cranial enclosure estimated by the pressure-volume index. Our review of the recent literature dealing with the results of infusion test in normal pressure hydrocephalus indicates that the positive predictive value is about 80 % for Rout greater than 12 mmHg/ml per minute, i.e. shunt response is observed in 80 % of patients. The information available in the literature for assessing negative predictive value of Rout and usefulness of compliance is limited.

Perspectives and conclusion

The CSF infusion test may be helpful for the diagnosis of normal pressure hydrocephalus, as supplemental testing when the diagnosis is not certain. We propose a procedure, which includes the infusion test, for identifying shunt-responsive patients.     

How does CSF dynamics change after shunting?

Objective –  Hydrocephalus is much more complex than a simple disorder of cerebrospinal fluid (CSF) circulation. Shunting primarily corrects disturbed fluid flow which may have an impact on cerebral blood flow and metabolism. We studied hydrocephalic patients before and after shunting to characterize changes in their CSF compensatory parameters.
Material and methods –  We selected 25 patients and studied them retrospectively. All patients had ventriculomegaly and clinical symptoms of normal pressure hydrocephalus. After shunting, they were still presenting with some adverse symptoms, mainly headaches, slow improvement or no improvement of ventriculomegaly. Therefore, they underwent further infusion studies to assess shunt function. In all cases, the shunts were confirmed to be draining CSF adequately. Parameters of CSF dynamics: baseline intracranial pressure (ICP), resistance to CSF outflow, cerebrospinal elasticity, content of vasogenic pressure waves (pulse, respiratory and B waves) and compensatory reserve assessed as moving correlation coefficient between mean CSF pressure and pulse amplitude (RAP), were compared before and after shunting.
Results –  Mean ICP and resistance to CSF outflow decreased ( P  < 0.003) after shunting. All vasogenic pressure waves decreased ( P  < 0.005). Compensatory reserve (RAP) significantly improved ( P  < 0.005).
Conclusion –  A functioning shunt has an important impact on CSF circulation and pressure–volume compensation. Infusion studies can demonstrate the return of disturbed CSF dynamics to normal values even if clinical or radiological changes are not dramatic.     

CSF pulsatility in hydrocephalus: respiratory effect on pulse wave slope as an indicator of intracranial compliance

The effect of inspiration and expiration on the systolic slope of the cerebrospinal fluid (CSF) pulse wave has been studied in 83 shunted and non-shunted patients undergoing diagnostic tests for suspected hydrocephalus. A ratio of the systolic CSF pulse slope on inspiration to the same in expiration (I/E ratio or index) has proved statistically valid in identifying non-hydrocephalic patients from hydrocephalic patients and in separating hydrocephalic patients into arrested, communicating and aqueductal stenosis hydrocephalus. The I/E ratio depends on the comparative damping effect of intracranial venous venting on the systolic CSF pulse slope during inspiration (I) when venous volume is evacuated from the cranium by negative mediastinal pressure, and during expiration (E) when cranial venous volume flow to heart is minimal due to positive mediastinal pressure. The low cranial venous outflow on expiration produces little effect on the normal damping of the systolic CSF pulse slope. The high venous outflow on inspiration produces a loss of damping, causing a high systolic CSF pulse slope. Therefore, exhausted cranial venous volume, or exhausted intracranial compliance, produces an I/E ratio approaching 1.0, whereas a normal I/E ratio is between 2.0 and 3.0. The I/E ratio can presumably be used to assess intracranial compliance changes occurring before the dangerous late intracranial pressure (ICP) upward surge related to the volume-pressure curve in all clinical problems of increasing ICP. The I/E ratio may be used likewise to assess the urgency of treatment for any hydrocephalus and increased intracranial pressure problem, i.e. the closer to unity the greater the urgency.     

The ventriculoomental bursa shunt

OBJECT: The aim of this study is to access the efficacy of the omental bursa (lesser sac) as a receptacle of cerebrospinal fluid (CSF) and to use it as an alternative to the ventriculoatrial or ventriculopleural shunts when the peritoneum reduces or loses its CSF absorption capacity. METHODS: Three patients with hydrocephalus presented with malfunctioning of ventriculoperitoneal shunts, secondary to peritoneal blockage caused by previous episodes of shunt infections in two and peritonitis in one patient. All patients underwent previous shunt revisions due to ventriculitis and shunt obstruction ranging from three to eight times. In order to keep the peritoneal cavity as the main receptacle of CSF absorption site, the distal catheter was inserted in the omental bursa, through the foramen of Winslow, jointly by a pediatric surgeon. We denominated this new technique of CSF diversion as ventriculoomental bursa (VOB) shunting. The children have been followed at least for 1 year (range 12 to 28 months) with no recurrence of shunt. CONCLUSIONS: VOB shunting may be considered an acceptable technique to CSF shunting when the anterior peritoneum loses or decreases its CSF absorption capacity.     

Unilateral hearing loss following shunt placement for normal pressure hydrocephalus with a unilateral patent cochlear aqueduct

Hearing loss in patients who have undergone shunt placement for a hydrocephalus is perhaps an underestimated complication rather than a rare event. There appears to be a correlation between the occurrence of hearing loss and patient characteristics consistent with excessive drainage of cerebrospinal fluid (CSF) and patent cochlear aqueduct (CA). We present the case of a 77-year-old man with unilateral dominant sensorineural hearing loss after a shunt placement for normal pressure hydrocephalus (NPH) combined with a patent cochlear aqueduct. Based on our experience and a review of the literature, we suggest an early restoration of the reduced CSF pressure using a programmable valve as a treatment strategy, which might prevent the persistent hearing loss.     

Cerebrospinal fluid absorption mechanism--based on measurement of CSF flow rate in shunt tube

The cerebrospinal fluid (CSF) absorption mechanism in cases of hydrocephalus was investigated on the basis of measurements of CSF flow in a shunt tube after ventriculo-peritoneal shunt surgery, monitoring of intracranial pressure, CT findings, radioisotope cisternography, cerebral blood flow, EEG, PSP tests and changes in neurological findings. The subjects were 6 males and 7 females aged from 18 to 70. CSF flow rates in the shunt tubes were between 0.01 and 1.93 ml/min. Calculating the daily volume of CSF flow, the subjects were divided into two groups: Group A (8 patients) with a volume of less than 150 ml/day (0.01-0.25 ml/min), and Group B (5 patients) with between 150 and 500 ml/day (0.01-1.93 ml/min). Monitoring of intracranial pressure prior to the shunt operation was performed in 10 cases. These pressure values ranged between 4 and 25 mmHg (mean: 7-8 mmHg), and there was no difference between the two groups. The pre-and post-operative radioisotope cisternography findings indicated improvement of ventricular dilatation, periventricular lucency and ventricular reflux. After the shunt operations, there was neurological improvement in 6 of the 8 Group A cases but only in 2 of the 5 Group B cases. Considering the CSF flow volumes of the two groups, it appears that in Group A the shunt tube is not the main CSF circulation pathway. This could mean that resistance to CSF absorption in the cerebrospinal space has decreased after the shunt operation and there has been recovery of the physiological CSF absorption pathways. In other words, neurological improvement can be expected in this group A.     

Cerebrospinal fluid dynamics and cerebrospinal fluid infusion in children. Part II: Clinical application of lumbar cerebrospinal fluid infusion in children with macrocephaly and normal growth rate of the head circumference

In fourteen children with macrocephaly and a normal growth rate of the head circumference, the CSF dynamics were studied by means of the lumbar CSF infusion test with constant flow. We discuss the significance of the outflow resistance together with the advantage of the Pressure Volume Index, which constitute the major parameters of the test. On the basis of computed tomography, we were able to show a differentiation in macrocephaly between megalencephaly, so-called external ventricular obstructive hydrocephalus and communicating hydrocephalus. We were not able to establish a disturbance of the CSF dynamics in megalencephaly and external ventricular obstructive hydrocephalus. In communicating hydrocephalus, CSF absorption was normal, whilst the Pressure Volume Index was elevated. As far as we have been able to ascertain, we are the first in the field to point to a positive correlation between ventricular size and Pressure Volume Index in children with moderately enlarged CSF-spaces.     

The CSF accumulator

The ability of the central nervous system (CNS) to store and release fluid energy plays an important role in both health and disease. The stored fluid energy is the product of the fluid volume and pressure. How changes in CNS fluid (CSF, blood, or extracellular fluid) energy are distributed is determined by the compliance of the fluid containers and their arrangement. Hydrocephalus and related diseases not only interfere with the absorption of CSF but also interfere with the exchange of CSF in response to positional changes, cardiorespiratory and intraperitoneal energy changes. While shunts allow for the diversion of CSF when the intracranial energy exceeds the absorbing receptacle energy, they do not normalize the return of CSF to the intracranial compartment as needed with the intracranial blood volume or pressure decreases (the accumulator function of the CNS's CSF). A CSF shunt that has an artificial accumulator proximal to the valve can potentially restore the accumulator function towards normal and prevent some of the complications associated with CSF overdrainage.     

The Delta Valve: a physiologic shunt system

PS Medical has advanced the state-of-the-art in hydrocephalus valve technology with the introduction of the Delta Valve. The Delta Valve is designed upon the premise that the shunted patient should have intracranial pressure (ICP) maintenance within a normal range regardless of cerebrospinal fluid (CSF) flow rate or body position. All previous valves have performance characteristics that are greatly influenced by the negative hydrostatic pressure caused by the gravitational effect on the vertical water column in the distal catheter. This negative pressure influence is non-physiologic and contributes directly to overdrainage that can cause slit ventricles, subdural hematoma, and proximal catheter occlusions. The Delta Valve is the only valve that maintains a near-constant pressure gradient regardless of flow rate or patient posture. It automatically adjusts for increasing negetive pressures in the distal catheter by proportionally increasing its resistance to flow, thus nullifying the adverse effects of the hydrostatic force on intracranial pressures. The result is a shunt system that provides for CSF drainage while allowing the patient's normal physiologic conditions to control ICP. The early use of the Delta Valve in the treatment of hydrocephalus may reduce the incidence of the dramatic complications associated with overdrainage.Presented at the Consensus Conference: Hydrocephalus '92, Assisi, Italy, 26–30 April 1992     

Predictors of outcome in patients with normal-pressure hydrocephalus.

Despite knowledge emerging over the last 40 years, the postoperative results after shunt implantation in patients diagnosed with normal-pressure hydrocephalus (NPH) have not improved significantly over the last decade. For that reason predictors have to be identified in order to preoperatively predict outcome. From 1982 to 2000 we prospectively studied 200 patients diagnosed with NPH. From the patients, who were surgically treated by a shunt implantation we reexamined 155 (78%) postoperatively a mean time interval of 7 months. The NPH was graded according to the results of the intrathecal infusion test in an early stage NPH (without brain atrophy) and late stage NPH (with brain atrophy). In our study, we focussed attention on the possible predictors: patients age, length of disease, clinical signs (gait ataxia, dementia and bladder incontinence), aetiology idiopathic/secondary as well as implanted valve type and the value of resistance to cerebrospinal fluid outflow. To measure the outcome we used the NPH recovery rate and as the statistical test the chi(2) according to Pearson. In 80 patients with an early stage NPH (without cerebral atrophy), a short course of disease (<1 year), a slight degree of dementia and an implanted Miethke-Dual-Switch valve were significant predictors for a positive postoperative outcome. The outflow resistance measured in the intrathecal infusion test showed only a minimal relevance to outcome. Those 75 patients with a late state NPH (with cerebral atrophy) had a better outcome when dementia was not present, the outflow resistance was above 20mm Hg/min/ml, the CSF tap-test was positive and a Miethke-Dual-Switch valve was implanted.     

Aneurysm Clips: Twenty Years Later

Abstract

The ability of the central nervous system (CNS) to store and release fluid energy plays an important role in both health and disease. The stored fluid energy is the product of the fluid volume and pressure. How changes in CNS fluid (CSF, blood, or extracellular fluid) energy are distributed is determined by the compliance of the fluid containers and their arrangement. Hydrocephalus and related diseases not only interfere with the absorption of CSF but also interfere with the exchange of CSF in response to positional changes, cardiorespiratory and intraperitoneal energy changes. While shunts allow for the diversion of CSF when the intracranial energy exceeds the absorbing receptacle energy, they do not normalize the return of CSF to the intracranial compartment as needed with the intracranial blood volume or pressure decreases (the accumulator function of the CNS’s CSF). A CSF shunt that has an artificial accumulator proximal to the valve can potentially restore the accumulator function towards normal and prevent some of the complications associated with CSF overdrainage. [Neural Res 2000; 22: 4-18]     

一种诊断脑室-腹腔分流装置梗阻的方法

目的 介绍一种诊断脑室腹腔分流装置梗阻的方法。方法 选择2014年8月至2018年3月收治的腹腔分流术后病人32例，其中分流装置梗阻16例（梗阻组），分流装置通畅16例（对照组）。病人先平躺1 h后改坐位，将0.1 ml 5%葡萄糖溶液注射入贮液囊，20 min后抽0.1 ml，用生理盐水将其稀释1倍后应用血糖仪检测葡萄糖浓度。结果 对照组贮液囊内葡萄糖浓度[（6.6±1.6）mmol/L]较梗阻组[（31.9±2.8）mmol/L]明显下降（P<0.05）。梗阻组病人入院后均行脑室-腹腔分流管调整术，手术证实分流装置梗阻，术后病人颅内压增高症状消失，术后3 d复查头颅CT结果显示脑室体积较术前减小11例，无明显变化5例。结论 此方法可检测分流管内脑脊液的流动情况，为诊断分流装置梗阻提供一种新的方法。