Shunts in normal-pressure hydrocephalus: do we place too many or too few?

AUTOMATED VENTRICLE PARCELLATION AND EVAN'S RATIO COMPUTATION IN PRE- AND POST-SURGICAL VENTRICULOMEGALY

Normal pressure hydrocephalus (NPH) is a brain disorder associated with enlarged ventricles and multiple cognitive and motor symptoms. The degree of ventricular enlargement can be measured using magnetic resonance images (MRIs) and characterized quantitatively using the Evan's ratio (ER). Automatic computation of ER is desired to avoid the extra time and variations associated with manual measurements on MRI. Because shunt surgery is often used to treat NPH, it is necessary that this process be robust to image artifacts caused by the shunt and related implants. In this paper, we propose a 3D regions-of-interest aware (ROI-aware) network for segmenting the ventricles. The method achieves state-of-the-art performance on both pre-surgery MRIs and post-surgery MRIs with artifacts. Based on our segmentation results, we also describe an automated approach to compute ER from these results. Experimental results on multiple datasets demonstrate the potential of the proposed method to assist clinicians in the diagnosis and management of NPH.

Comparison of ventriculoperitoneal shunt to lumboperitoneal shunt in the treatment of idiopathic: A monocentric, assessor-blinded, randomized controlled trial

BACKGROUND

Ventriculoperitoneal shunt (VPS) and lumboperitoneal shunt (LPS) remain the mainstay of idiopathic normal pressure hydrocephalus (INPH). There are no randomized controlled trials completed to compare the efficacy of these 2 shunt techniques.

METHODS/DESIGN

We will conduct a monocentric, assessor-blinded, and randomized controlled trial titled "Comparison of Ventriculoperitoneal Shunt to Lumboperitoneal Shunt for the treatment of Idiopathic Normal Pressure Hydrocephalus: Phase I (COVLINPH-1)" trial and recruit patients at West China Hospital of Sichuan University since June 2021. And this trial is expected to end in December 2030. Eligible participants will be randomly assigned into LPS group and VPS group at ratio of 1:1 followed by evaluation before surgery, 1 month, 12 months, and 5 years after surgery. The primary outcome is the rate of shunt failure within 5 years. The secondary outcomes include modified Rankin Scale (mRS), INPH grading scale (INPHGS), mini-mental state examination (MMSE), and Evans index. We will calculate the rate of favorable outcome, which is defined as shunt success and an improvement of more than 1 point in the mRS at evaluation point. We will also analyze the complications throughout the study within 5 years after shunt insertion.

DISCUSSION

The results of this trial will provide state-of-the-art evidence on the treatment option for patients with INPH, and will also generate the discussion regarding this subject.

TRIAL REGISTRATION NUMBER

ChiCTR2000031555; Pre-results.

Guidelines for Management of Idiopathic Normal Pressure Hydrocephalus (Third Edition): Endorsed by the Japanese Society of Normal Pressure Hydrocephalus

Among the various disorders that manifest with gait disturbance, cognitive impairment, and urinary incontinence in the elderly population, idiopathic normal pressure hydrocephalus (iNPH) is becoming of great importance. The first edition of these guidelines for management of iNPH was published in 2004, and the second edition in 2012, to provide a series of timely, evidence-based recommendations related to iNPH. Since the last edition, clinical awareness of iNPH has risen dramatically, and clinical and basic research efforts on iNPH have increased significantly. This third edition of the guidelines was made to share these ideas with the international community and to promote international research on iNPH. The revision of the guidelines was undertaken by a multidisciplinary expert working group of the Japanese Society of Normal Pressure Hydrocephalus in conjunction with the Japanese Ministry of Health, Labour and Welfare research project. This revision proposes a new classification for NPH. The category of iNPH is clearly distinguished from NPH with congenital/developmental and acquired etiologies. Additionally, the essential role of disproportionately enlarged subarachnoid-space hydrocephalus (DESH) in the imaging diagnosis and decision for further management of iNPH is discussed in this edition. We created an algorithm for diagnosis and decision for shunt management. Diagnosis by biomarkers that distinguish prognosis has been also initiated. Therefore, diagnosis and treatment of iNPH have entered a new phase. We hope that this third edition of the guidelines will help patients, their families, and healthcare professionals involved in treating iNPH.

Extended lumbar drainage in idiopathic normal pressure hydrocephalus: a systematic review and meta-analysis of diagnostic test accuracy

BACKGROUND

When appropriately selected, a high proportion of patients with suspected idiopathic normal pressure hydrocephalus (iNPH) will respond to cerebrospinal fluid diversion with a shunt. Extended lumbar drainage (ELD) is regarded as the most accurate test for this condition, however, varying estimates of its accuracy are found in the current literature. Here, we review the literature in order to provide summary estimates of sensitivity, specificity, positive- and negative predictive value for this test through meta-analysis of suitably rigorous studies.

METHODS

Studies involving a population of NPH patients with predominantly idiopathic aetiology (>80%) in which the intention of the study was to shunt patients regardless of the outcome of ELD were included in the review. Various literature databases were searched to identify diagnostic test accuracy studies addressing ELD in the diagnosis of iNPH. Those studies passing screening and eligibility were assessed using the QUADAS-2 tool and data extracted for bivariate random effects meta-analysis.

RESULTS

Four small studies were identified. They showed disparate results concerning diagnostic test accuracy. The summary estimates for sensitivity and specificity were 94% (CI 41-100%) and 85% (CI 33-100%), respectively. The summary estimates of positive and negative predictive value were both 90% (CIs 65-100% and 48-100%, respectively).

CONCLUSION

Large, rigorous studies addressing the diagnostic accuracy of ELD are lacking, and little robust evidence exists to support the use of ELD in diagnostic algorithms for iNPH. Therefore, a large cohort study, or ideally an RCT, is needed to determine best practice in selecting patients for shunt surgery.

Brain ventricle parcellation using a deep neural network: Application to patients with ventriculomegaly

Numerous brain disorders are associated with ventriculomegaly, including both neuro-degenerative diseases and cerebrospinal fluid disorders. Detailed evaluation of the ventricular system is important for these conditions to help understand the pathogenesis of ventricular enlargement and elucidate novel patterns of ventriculomegaly that can be associated with different diseases. One such disease is normal pressure hydrocephalus (NPH), a chronic form of hydrocephalus in older adults that causes dementia. Automatic parcellation of the ventricular system into its sub-compartments in patients with ventriculomegaly is quite challenging due to the large variation of the ventricle shape and size. Conventional brain labeling methods are time-consuming and often fail to identify the boundaries of the enlarged ventricles. We propose a modified 3D U-Net method to perform accurate ventricular parcellation, even with grossly enlarged ventricles, from magnetic resonance images (MRIs). We validated our method on a data set of healthy controls as well as a cohort of 95 patients with NPH with mild to severe ventriculomegaly and compared with several state-of-the-art segmentation methods. On the healthy data set, the proposed network achieved mean Dice similarity coefficient (DSC) of 0.895 ± 0.03 for the ventricular system. On the NPH data set, we achieved mean DSC of 0.973 ± 0.02, which is significantly (p < 0.005) higher than four state-of-the-art segmentation methods we compared with. Furthermore, the typical processing time on CPU-base implementation of the proposed method is 2 min, which is much lower than the several hours required by the other methods. Results indicate that our method provides: 1) highly robust parcellation of the ventricular system that is comparable in accuracy to state-of-the-art methods on healthy controls; 2) greater robustness and significantly more accurate results on cases of ventricular enlargement; and 3) a tool that enables computation of novel imaging biomarkers for dilated ventricular spaces that characterize the ventricular system.

Shunt surgery in idiopathic normal pressure hydrocephalus is cost-effective-a cost utility analysis

Background

The objective was to evaluate the cost-effectiveness of shunt surgery in patients with idiopathic normal pressure hydrocephalus (iNPH).

Methods

Health-related quality of life was evaluated before and 6 months after surgery using the EQ-5D-3 L (EuroQOL group five-dimensions health survey) in 30 patients (median age, 71 years; range, 65–89 years) diagnosed with iNPH. The costs associated with shunt surgery were assessed by a detailed survey with interviews and extraction of register data concerning the cost of hospital care, primary care, residential care, home-care service and informal care. The cost of untreated patients was derived from the cost of dementia disorders in Sweden in 2012, as reported by the National Board of Health and Welfare. The cost effectiveness analysis used a decision-analytic Markov model. We used a societal perspective and a lifelong time horizon to estimate costs and effects. One-way sensitivity analysis and probabilistic sensitivity analysis were carried out to test the robustness of the model.

Results

The shunt surgery model as the standard treatment in iNPH resulted in a gain of 2.2 life years and 1.7 quality-adjusted life years (QALY), along with an incremental cost per patient of €7,500/QALY. The sensitivity analysis showed that the results were not sensitive to changes in uncertain parameters or assumptions.

Conclusions

Shunt surgery in iNPH, an underdiagnosed condition severely impairing elderly patients, is not only an effective medical treatment, it is also cost-effective, adding 2.2 additional life years and 1.7 QALYs at a low cost, a remarkable gain for an individual aged around 70 years.

[Normal pressure hydrocephalus]

CLINICAL ISSUE

Normal pressure hydrocephalus (NPH) is a disorder found mainly in the elderly (> 60 years) with an increasing prevalence with age and is one of the few treatable causes of dementia. If untreated NPH often leads to severe motor, psychomotor and irreversible cognitive deficits. The pathogenesis is not yet fully understood. Clinical symptoms consist of the (not always complete) classical triad of equilibrium and gait disturbances followed later by incontinence and dementia. Symptoms often show a gradual progression to irreversibility in non-treated patients; therefore, early diagnosis and treatment are mandatory. Important differential diagnoses are Parkinson's disease (similar gait), Alzheimer's disease and vascular dementia, not least due to the high comorbidity of these conditions with NPH.

STANDARD RADIOLOGICAL METHODS

The standard radiological method for evaluation of NPH is conventional cross-sectional imaging that typically shows ventriculomegaly (Evans' index > 0.3 and cella media index < 4) often combined with the so-called disproportionately enlarged subarachnoid space hydrocephalus (DESH) pattern (tight convexity sulci and enlarged sylvian fissure). These findings should be differentiated from ventriculomegaly in atrophy combined with enlarged convexity sulci.

METHODICAL INNOVATIONS

Special magnetic resonance imaging (MRI) techniques can be used to evaluate cerebrospinal fluid (CSF) flow but are not yet part of the diagnostic guidelines.

ACHIEVEMENTS/PRACTICAL RECOMMENDATIONS

Combined with cross-sectional imaging, well-established clinical and invasive diagnostic tests, such as repeated spinal tap or lumbar drainage with re-evaluation of clinical symptoms lead to a diagnosis and help with preoperative patient selection for CSF diversion. Ventriculoperitoneal CSF shunting has proven to be safe and is the only known successful therapy for NPH.

Segmentation and labeling of the ventricular system in normal pressure hydrocephalus using patch-based tissue classification and multi-atlas labeling

Normal pressure hydrocephalus (NPH) affects older adults and is thought to be caused by obstruction of the normal flow of cerebrospinal fluid (CSF). NPH typically presents with cognitive impairment, gait dysfunction, and urinary incontinence, and may account for more than five percent of all cases of dementia. Unlike most other causes of dementia, NPH can potentially be treated and the neurological dysfunction reversed by shunt surgery or endoscopic third ventriculostomy (ETV), which drain excess CSF. However, a major diagnostic challenge remains to robustly identify shunt-responsive NPH patients from patients with enlarged ventricles due to other neurodegenerative diseases. Currently, radiologists grade the severity of NPH by detailed examination and measurement of the ventricles based on stacks of 2D magnetic resonance images (MRIs). Here we propose a new method to automatically segment and label different compartments of the ventricles in NPH patients from MRIs. While this task has been achieved in healthy subjects, the ventricles in NPH are both enlarged and deformed, causing current algorithms to fail. Here we combine a patch-based tissue classification method with a registration-based multi-atlas labeling method to generate a novel algorithm that labels the lateral, third, and fourth ventricles in subjects with ventriculomegaly. The method is also applicable to other neurodegenerative diseases such as Alzheimer's disease; a condition considered in the differential diagnosis of NPH. Comparison with state of the art segmentation techniques demonstrate substantial improvements in labeling the enlarged ventricles, indicating that this strategy may be a viable option for the diagnosis and characterization of NPH.

Diagnosis and prognosis in idiopathic normal pressure hydrocephalus

Idiopathic normal pressure hydrocephalus (iNPH) is a communicating hydrocephalus, of unknown pathophysiology, characterized by the classical triad of dementia, urinary incontinence, and ataxia. The most popular treatment option is shunt surgery, although it is not a cure. The diagnosis of the disorder is challenging as it may mimic a lot of other neurological conditions and has no distinct biomarker. It becomes even more challenging as majority of the cases are diagnosed by invasive cerebrospinal fluid (CSF) removal tests. However, a careful history taking, a keen and detailed physical examination, and pertinent imaging studies can lead to an early diagnosis. The gait symptoms respond the most to surgery. The predictors deciding the postsurgical prognosis has been discussed. Improved shunting modalities and novel shunt materials with valve adjustments have improved the precision of the shunting procedures. Still we have lot more to achieve in terms of early diagnosis and definitive management of iNPH.

Prevalence of idiopathic normal-pressure hydrocephalus

OBJECTIVES

The aim of this study was to determine the prevalence of idiopathic normal-pressure hydrocephalus (iNPH) in elderly persons in a large population-based sample using radiologic and clinical examinations.

METHODS

We examined representative elderly populations aged 70 years and older that had undergone neuropsychiatric evaluations and CT of the brain between 1986 and 2000 (n = 1,238). Gait was evaluated by clinical examination and history of walking difficulty. Cognitive function was evaluated with the Mini-Mental State Examination and urinary incontinence by self-report. iNPH was diagnosed in concordance with the American-European iNPH guidelines. Exclusion criteria were history of meningitis, severe head trauma, and subarachnoid hemorrhage.

RESULTS

The prevalence of probable iNPH was 0.2% in those aged 70-79 years (n = 2) and 5.9% (n = 24) in those aged 80 years and older, with no difference between men and women. Only 2 of these persons had been treated for iNPH. Hydrocephalic ventricular enlargement, i.e., a CT image consistent with NPH, was found in 56 persons (4.5%). An Evans Index >0.3 was found in 256 (20.7%) and occluded sulci at the high convexity in 67 persons (5.4%). All of these findings were more common in the older age groups.

CONCLUSIONS

Many elderly possess clinical and imaging features of iNPH, especially those older than 80 years. The number of persons with iNPH is probably much higher than the number of persons currently treated.

Systematic review of the outcome of shunt surgery in idiopathic normal-pressure hydrocephalus

INTRODUCTION

Early surgical series of shunt insertion for idiopathic normal-pressure hydrocephalus reported a low rate of short-term improvement with a relatively high rate of mortality and morbidity; subsequently shunt insertion was recommended for patients in whom there is favourable risk-to-benefit ratio.

METHODS

Bibliographic search for studies that objectively assessed the outcome following shunt insertion in idiopathic normal-pressure hydrocephalus was done; the aim was to estimate the outcome of shunt insertion in terms of improvement rates and associated mortality and morbidity.

RESULTS

A total of 64 studies of 3,063 patients were reviewed. Positive improvement following shunt insertion was reported in an average of 71 % of patients with an average 1 % mortality. Results from studies published in the last 5 years showed 82 % improvement following shunt insertion, mortality of 0.2 %, and combined common complications rate of 8.2 %.

CONCLUSION

When patients are properly selected, shunt insertion is a safe and effective management of idiopathic normal-pressure hydrocephalus with a prolonged positive outcome.

One-year outcome in the European multicentre study on iNPH

OBJECTIVES

To assess the 1-year outcome after shunt surgery in patients with idiopathic normal pressure hydrocephalus (iNPH).

METHODS

Patients (n = 142) were prospectively included in the European multicentre study by 13 centres. Diagnoses were based solely on clinical and radiological findings. All received a programmable ventriculoperitoneal shunt. Re-examinations, 12 months after surgery, were performed in 115 patients, and the outcome was assessed by the modified Rankin scale (mRs) and a new iNPH grading scale. Improvement was defined as ≥1 step on the mRs and ≥5 points on the iNPH scale.

RESULTS

The scores on both scales were significantly improved after 1 year of shunt treatment (Ps < 0.001). Sixty-nine per cent of the patients were improved according to the mRs and 84% according to the iNPH scale. The proportion able to live independently (scores 0-2 on the mRs) was increased from 53% before to 82% 12 months after surgery (P < 0.001). Neither classification (typical or questionable) nor comorbidity affected the level of improvement. Patients not completing the study were worse off with regard to their clinical condition at entry than completers. Twenty-eight per cent of the patients experienced complications and were either conservatively (13%) or surgically (15%) treated.

CONCLUSION

The results of this prospective multicentre study on patients with iNPH diagnosed solely on clinical and radiological criteria support shunt surgery in patients presenting with symptoms and signs and MRI findings suggestive of iNPH.

Inclusion of asymptomatic degenerative discs in a two-level anterior cervical discectomy and fusion: a decision analysis

OBJECTIVE

To perform a decision analysis model to compare single-level fusion versus two-level fusion in patients with an asymptomatic disc adjacent to a symptomatic disc.

METHODS

Probabilities and utilities of alternative outcomes in the decision tree were assigned based on systematic review of the literature and expert opinion. Rollback analysis determined the optimal treatment. Sensitivity analyses and Monte Carlo simulations were performed to identify effects of varying model parameters.

RESULTS

Rollback analysis provided expected values of 0.92 versus 0.84 in favor of observation as the optimal decision. Sensitivity analysis identified the probability of developing adjacent segment disease (ASD) and the likelihood of surgery given a diagnosis of ASD as the most critical parameters influencing the decision. Observation was the preferred strategy at all values of probability of ASD < 100%. At a probability of ASD of 100%, fusion was the preferred strategy only when the probability of surgery for ASD was ≥ 66% or the utility assigned to successful nonoperative management was ≤ 0.84.

CONCLUSIONS

Observation was the preferred strategy for management of asymptomatic adjacent degenerative discs (AADDs) given the probabilities and utilities used in the decision analysis model. The study was limited by unavailability of precise estimates of the probability of development of ASD and the probability of surgery after diagnosis of ASD, the most critical factors influencing the decision. However, the conclusions were robust given wide ranges used for these parameters in the sensitivity analysis.

The differential diagnosis and treatment of normal-pressure hydrocephalus

BACKGROUND

Normal-pressure hydrocephalus (NPH) arises in adulthood and is characterized by a typical combination of clinical and radiological findings. The mean basal intracranial pressure is normal or mildly elevated. The typical signs of the disease are gait impairment, urinary incontinence, and dementia. The difficulty of distinguishing NPH from other neurodegenerative disorders is the likely reason why some 80% of cases remain unrecognized and untreated. According to current evidence, the spontaneous course of NPH ends, for the vast majority of patients, in dependence on nursing care.

METHODS

This review article is based on relevant publications retrieved by a selective search in Medline and on national and international guidelines for the management of NPH.

RESULTS

Studies with a high evidence level are lacking; thus, the current state of knowledge about NPH is derived from studies of low or intermediate evidence levels, e.g., observational studies. Modern forms of treatment lead to clinical improvement in 70% to 90% of treated patients. The treatment of choice is the implantation of a ventriculoperitoneal shunt. The differential diagnosis is complicated by the fact that three-quarters of patients with NPH severe enough to require treatment also suffer from another neurodegenerative disorder. Therefore, the clinical findings and imaging studies often do not suffice to establish the indication for surgery. To do this, a further, semi-invasive diagnostic procedure is recommended. Current risk/benefit analyses indicate that shunt operations improve outcome compared to the spontaneous course of the disease.

CONCLUSION

Normal pressure hydrocephalus should always enter into the differential diagnosis of patients who present with its characteristic manifestations. If the diagnosis of NPH is confirmed, it should be treated at an early stage.

Natural history of idiopathic normal-pressure hydrocephalus

Natural history of idiopathic normal-pressure hydrocephalus (INPH) is not clear. We performed a literature search for studies that looked into the outcome of unshunted INPH patients trying to answer the following questions: Do all INPH patients deteriorate without shunt? If yes, at what rate? Do some NPH patients improve without shunt? If yes, to what extent? Six studies objectively described the outcome of 102 INPH patients. Result shows that without surgery, most INPH patients had measurable deterioration as early as 3 months following initial assessment. A small number of patients might improve without shunt, however the extent of improvement is not clear. The homogeneity of the findings of the cohort studies provided high evidence supporting the rule of shunt surgery in INPH patients.

Extended long-term (> 5 years) outcome of cerebrospinal fluid shunting in idiopathic normal pressure hydrocephalus

BACKGROUND

Shunt surgery has been established as the only durable and effective treatment for idiopathic normal pressure hydrocephalus.

OBJECTIVE

We evaluated the "extended" long-term follow-up (> 5 years) in a prospective study cohort who underwent shunting between 1990 and 1995. A secondary objective was to determine the cause of death in these patients.

METHODS

Fifty-one patients were included after confirmation of the diagnosis by extensive clinical and diagnostic investigations. Surgery included ventriculoatrial or ventriculoperitoneal shunting with differential pressure valves in the majority of patients. For each of the cardinal symptoms, postoperative outcome was assessed separately with the Krauss Improvement Index, yielding a value between 0 (no benefit) and 1 (optimal benefit) for the overall outcome.

RESULTS

Mean age at surgery was 70.2 years (range, 50-87 years). Thirty patients were women, and 21 were men. Short-term (18.8 +/- 16.6 months) follow-up was available for 50 patients. The Krauss Improvement Index was 0.66 +/- 0.28. Long-term (80.9 +/- 51.6 months) follow-up was available for 34 patients. The Krauss Improvement Index was 0.64 +/-0.33. Twenty-nine patients died during the long-term follow-up at a mean age of 75.8 years (range, 55-95 years). The major causes of death were cardiovascular disorders: cardiac failure (n = 7) and cerebral ischemia (n = 12). Other causes were pneumonia (n = 2), acute respiratory distress syndrome (n = 1), pulmonary embolism (n = 1), cancer (n = 2), renal failure (n = 1), and unknown (n = 3). There was no shunt-related mortality.

CONCLUSION

Idiopathic normal pressure hydrocephalus patients may benefit from shunting over the long term when rigorous selection criteria are applied. Shunt-related mortality is negligible. The main cause of death is vascular comorbidity.

Working towards patient oriented outcome assessment in normal pressure hydrocephalus, what is the most important?

OBJECTIVE

To date, there is no standard outcome assessment scale for shunt treatment in normal pressure hydrocephalus (NPH). In designing such scale, the relative weight of each of the common presentations of the condition from the patient's or his/her carer's point of view should be taken into consideration.

METHODS

A questionnaire was sent to 24 patients treated for NPH and their family/carer, assessing the patient and carer categorization of the preoperative main complaint, the weight they give to each of the common presentations of NPH and their satisfaction with treatment.

RESULTS

Twenty-two patients and 20 carers replied. Gait disturbance was the main complaint from both patient's (86%) and carer's (75%) point of view. Similarly, gait disturbance was considered as the most important problem that needs improvement by both patients (77%) and carers (65%). Incontinence was considered the second most important area by 11 (50%) patients and seven (35%) carers. When asked to quantify their satisfaction out of 10, patients had a mean of 7.2 while carers gave a mean of 7.5. Comparing subjective perspective of improvement with that of objective improvement on 10 m walking test and neuropsychological assessment, all patients who improved objectively were perceived as improved to a satisfactory degree by carers.

CONCLUSION

Walking/balance should be given far greater weight than other components of the NPH triad in future outcome assessment scales in accordance with patient/family perception.

Five-year incidence of surgery for idiopathic normal pressure hydrocephalus in Norway

OBJECTIVES

We have previously determined the incidence and prevalence of idiopathic normal pressure hydrocephalus (iNPH) in the county of Vestfold in Norway. This study aimed at determining the incidence of surgeries for iNPH.

MATERIALS AND METHODS

Information about age, sex, operation year and operation type was collected retrospectively for all patients hospitalized from 2002 to 2006 with any diagnosis of iNPH and operated with insertion of a ventriculo-peritoneal or ventriculoatrial shunt system, or with endoscopic third ventriculostomy in any of Norway's five regional neurosurgical centers.

RESULTS

Two hundred fifty-two patients were operated during the 5-year period, making the total incidence 1.09/100,000/year. The yearly incidence ranged from a minimum of 0.84/100,000 in 2006 to a maximum of 1.47/100,000 in 2004. The incidence was highest in the age group 70-79 years. There were little regional differences regarding incidence, sex, and age and operation type.

CONCLUSIONS

The data suggest that too few patients are being offered surgical treatment for iNPH in Norway.

Endoscopic third ventriculostomy versus ventriculoperitoneal shunt in pediatric patients: a decision analysis

INTRODUCTION

Uncertainty persists on the best treatment for patients with obstructive hydrocephalus: endoscopic third ventriculostomy (ETV) or shunt, particularly in the younger age groups. We performed decision analysis for quality of life (QOL) outcomes comparing these two procedures.

MATERIALS AND METHODS

Frequency of outcome events for ETV was obtained from the Canadian Pediatric Neurosurgery Study Group (368 patients) and for shunts from two prospective randomized trials, the Shunt Design Trial and the Endoscopic Shunt Insertion Trial (647 patients combined). Quality-adjusted life year (QALY) estimates for various outcomes were obtained from the literature. Decision analysis was performed at 1 year of follow-up for specific age groups, e.g., <1 month, 1-6 months, etc.

RESULTS

Failure from cerebrospinal fluid (CSF) diversion from either procedure was a function of age with higher failures rates in younger patients. Expected QALY at 1 year were marginally higher for ETV for all age groups, but the outcomes were similar enough to be regarded as equivalent. The results, however, were highly sensitive to the assigned health utility value estimates for patients who are well with a functioning ETV or shunt and the severe complication rate from ETV.

CONCLUSION

Age is a major determinant of outcome from CSF diversion with worse outcomes in young patients. QALY estimates for either ETV or shunt are similar at 1 year.

Treatment of hydrocephalus in adults

The following patients with multiple complex diagnoses define the adult hydrocephalus population: (1) transition patients (previously treated for hydrocephalus as children), (2) adults with previously untreated congenital hydrocephalus, (3) adults with acquired hydrocephalus with an identifiable etiology, and (4) patients with suspected or proven idiopathic normal pressure hydrocephalus. Restricting the outpatient care or hydrocephalus clinic definition to a single hydrocephalus patient subpopulation limits our understanding of these patients and effectively abandons the remaining adult patients with hydrocephalus to a less focused and potentially less effective healthcare arrangement. A comprehensive adult hydrocephalus clinic model is described and recommended to advance our understanding of this diverse patient population, which will ultimately lead to the development and provision of a better standard of patient care.

Gray matter metabolism in acute and chronic hydrocephalus

Although hydrocephalus is usually considered a disorder of periventricular white matter, disturbance of gray matter is probably also involved. However, so far gray matter metabolism has not been studied in experimental hydrocephalus using high resolution in vivo magnetic resonance spectroscopy (MRS). Therefore 15 rats were made hydrocephalic by injection of 0.1 ml kaolin into the cisterna magna, whereas 10 sham-operated rats served as controls. (1)H MRS and magnetic resonance imaging were performed longitudinally in acute hydrocephalus 2 and 4 weeks after kaolin treatment and in chronic hydrocephalus after 6 weeks. Volumes of interest included the gray matter regions cortex, thalamus and hippocampus. In hydrocephalic animals, (1)H MRS revealed decreased glutamate levels in all examined areas at all time points. Moreover, in acute hydrocephalus disturbances were noted in the hippocampus with decreased concentrations of N-acetyl aspartate, creatine, inositol and taurine, and in the cortex with decreased taurine levels. A clear lactate peak was detected in CSF spectra from hydrocephalic rats. In addition, T2-weighted images showed increase of free water in the hippocampus. It can be concluded that glutamate metabolism is deranged in gray matter in acute and chronic hydrocephalus in rats. If confirmed in humans, early detection of glutamatergic disturbances and lactate accumulation using in vivo(1)H MRS might serve as an indication for surgical treatment of hydrocephalus before irreversible neuronal damage develops.

Normal pressure hydrocephalus: diagnosis and treatment

Normal pressure hydrocephalus (NPH) is a syndrome of gait dysfunction and enlarged cerebral ventricles in the absence of another cause. It is frequently accompanied by frontal and subcortical cognitive deficits and bladder detrusor overactivity. NPH is rare relative to other potential causes of these symptoms in the elderly, but timely diagnosis can lead to reversal of symptoms through ventricular shunting. There are many tests used to predict possible response to surgery, such as MRI of the brain, formalized neuropsychological and gait testing, large-volume lumbar puncture, and prolonged lumbar drainage, but no one test has been validated to rule out potential response to surgery.

Cerebrospinal fluid dynamics: disturbances and diagnostics

The pathophysiology of hydrocephalus can be modelled and described in terms of altered biomechanical parameters. Shunting is aimed to correct the patient's cerebrospinal fluid dynamics, compensating for inadequate cerebrospinal fluid re-absorption or insufficient volume buffering reserve. Computerized infusion studies implement intracranial pressure and arterial pressure signal processing and model analysis to allow the estimation of cerebrospinal dynamics variables such as cerebrospinal fluid outflow resistance, brain compliance and pressure-volume index, estimated sagittal sinus pressure, cerebrospinal fluid formation rate, compensatory reserve and cerebral vasoreactivity. Infusion studies can assist in the prognostication of normal pressure hydrocephalus and in the diagnosis of idiopathic intracranial hypertension. The technique is also helpful in the assessment of shunt malfunction, including posture-related over-drainage and shunt obstruction.

Brain metabolism in adult chronic hydrocephalus

Normal pressure hydrocephalus (NPH) is the most frequent form of chronic hydrocephalus in adults. NPH remains underdiagnosed although between 5% and 10% of all demented patients may suffer from this disorder. As dementia is an increasing demographic problem, treatable forms such as in NPH have become a central issue in neurology. Despite the traditional perception of hydrocephalus being a disorder of disturbed CSF dynamics, in NPH metabolic impairment seems at least as important. So far, the only valid animal model of NPH is chronic adult kaolin hydrocephalus. In this model, opening of alternative CSF outflow pathways leads to normal or near-normal intracranial pressure and CSF outflow resistance. Yet, various metabolic disturbances cause ongoing ventricular enlargement and characteristic symptoms including cognitive decline and gait ataxia. Delayed hippocampal neuronal death, accumulation of beta-amyloid and disturbed cholinergic neurotransmission may contribute to memory dysfunction. Compromised periventricular blood flow, decreased dopamine levels in the substantia nigra and damaged striatal GABAergic interneurons may reflect basal ganglia symptoms. At least in human hydrocephalus cerebrovascular co-morbidity of the white matter plays an important role as well. It seems that in hydrocephalus from a certain 'point of no return' metabolic impairment becomes decoupled from CSF dynamics and, at least partly, self-sustained. This is probably the reason why despite restored CSF circulation by shunting many patients with chronic hydrocephalus still suffer from severe neurological deficits. The present paper offers a comprehensive review of the experimental and clinical data suggesting metabolic disturbances in chronic hydrocephalus.

Have we made progress in preventing shunt failure? A critical analysis

OBJECT

The goal of this study was to determine whether failure rates of hydrocephalus shunts have fallen over the years as a result of experience or technical improvements.

METHODS

A structured search was performed of the English language literature for case series reporting failure rates after shunt insertion. A metaanalytic model was constructed to pool data from multiple studies and to analyze failure rates statistically for temporal trends. Separate models were used for children (< 17 years old) and adults.

RESULTS

In children, the shunt failure rate was 31.3% for the 1st year and 4.5% per year thereafter. There were no significant changes in either rate over time. Although 1st-year failure rates in adults have fallen slightly over time, late failure rates have risen.

CONCLUSIONS

Progress in preventing shunt failures has not been made over the last several decades. Any improvements made in shunt materials or insertion techniques have been overshadowed by biological and other factors.

Screening tests for normal-pressure hydrocephalus: sensitivity, specificity, and cost

Object

Many tests have been proposed to help choose candidates for shunt insertion in cases of suspected normal-pressure hydrocephalus (NPH). It is unclear what sensitivity and specificity a prospective test must have to improve outcomes, compared with the results of automatic shunt insertion.

Methods

The authors adapted the decision analysis model used in a companion article to allow for application of a screening test. Using the reported sensitivities and specificities of several such tests, they evaluated the effects such tests would have on the expected outcome of an average 65-year-old patient with moderate dementia. They also evaluated the cost-effectiveness of a theoretical screening test with superior sensitivity and specificity.

Conclusions

Although external lumbar drainage comes quite close, none of the screening tests reported to date have sufficient sensitivity and specificity to improve expected outcome in an average candidate, compared with the results of automatic shunt placement in cases of suspected NPH. In addition, even a theoretically improved test would need to be considerably less expensive than prolonged lumbar drainage to be cost-effective in clinical practice.