Three decades of normal pressure hydrocephalus: are we wiser now?

Regulation of brain fluid volumes and pressures: basic principles, intracranial hypertension, ventriculomegaly and hydrocephalus

The principles of cerebrospinal fluid (CSF) production, circulation and outflow and regulation of fluid volumes and pressures in the normal brain are summarised. Abnormalities in these aspects in intracranial hypertension, ventriculomegaly and hydrocephalus are discussed. The brain parenchyma has a cellular framework with interstitial fluid (ISF) in the intervening spaces. Framework stress and interstitial fluid pressure (ISFP) combined provide the total stress which, after allowing for gravity, normally equals intracerebral pressure (ICP) with gradients of total stress too small to measure. Fluid pressure may differ from ICP in the parenchyma and collapsed subarachnoid spaces when the parenchyma presses against the meninges. Fluid pressure gradients determine fluid movements. In adults, restricting CSF outflow from subarachnoid spaces produces intracranial hypertension which, when CSF volumes change very little, is called idiopathic intracranial hypertension (iIH). Raised ICP in iIH is accompanied by increased venous sinus pressure, though which is cause and which effect is unclear. In infants with growing skulls, restriction in outflow leads to increased head and CSF volumes. In adults, ventriculomegaly can arise due to cerebral atrophy or, in hydrocephalus, to obstructions to intracranial CSF flow. In non-communicating hydrocephalus, flow through or out of the ventricles is somehow obstructed, whereas in communicating hydrocephalus, the obstruction is somewhere between the cisterna magna and cranial sites of outflow. When normal outflow routes are obstructed, continued CSF production in the ventricles may be partially balanced by outflow through the parenchyma via an oedematous periventricular layer and perivascular spaces. In adults, secondary hydrocephalus with raised ICP results from obvious obstructions to flow. By contrast, with the more subtly obstructed flow seen in normal pressure hydrocephalus (NPH), fluid pressure must be reduced elsewhere, e.g. in some subarachnoid spaces. In idiopathic NPH, where ventriculomegaly is accompanied by gait disturbance, dementia and/or urinary incontinence, the functional deficits can sometimes be reversed by shunting or third ventriculostomy. Parenchymal shrinkage is irreversible in late stage hydrocephalus with cellular framework loss but may not occur in early stages, whether by exclusion of fluid or otherwise. Further studies that are needed to explain the development of hydrocephalus are outlined.

Gait pattern analysis in the home environment as a key factor for the reliable assessment of shunt responsiveness in patients with idiopathic normal pressure hydrocephalus

Background

The identification of patients with gait disturbance associated with idiopathic normal pressure hydrocephalus (iNPH) is challenging. This is due to the multifactorial causes of gait disturbance in elderly people and the single moment examination of laboratory tests.

Objective

We aimed to assess whether the use of gait sensors in a patient's home environment could help establish a reliable diagnostic tool to identify patients with iNPH by differentiating them from elderly healthy controls (EHC).

Methods

Five wearable inertial measurement units were used in 11 patients with iNPH and 20 matched EHCs. Data were collected in the home environment for 72 h. Fifteen spatio-temporal gait parameters were analyzed. Patients were examined preoperatively and postoperatively. We performed an iNPH sub-group analysis to assess differences between responders vs. non-responders. We aimed to identify parameters that are able to predict a reliable response to VP-shunt placement.

Results

Nine gait parameters significantly differ between EHC and patients with iNPH preoperatively. Postoperatively, patients with iNPH showed an improvement in the swing phase (p = 0.042), and compared to the EHC group, there was no significant difference regarding the cadence and traveled arm distance. Patients with a good VP-shunt response (NPH recovery rate of ≥5) significantly differ from the non-responders regarding cycle time, cycle time deviation, number of steps, gait velocity, straight length, stance phase, and stance to swing ratio. A receiver operating characteristic analysis showed good sensitivity for a preoperative stride length of ≥0.44 m and gait velocity of ≥0.39 m/s.

Conclusion

There was a significant difference in 60% of the analyzed gait parameters between EHC and patients with iNPH, with a clear improvement toward the normalization of the cadence and traveled arm distance postoperatively, and a clear improvement of the swing phase. Patients with iNPH with a good response to VP-shunt significantly differ from the non-responders with an ameliorated gait pattern.

Hydrocephalus: A neuropsychological and theoretical primer

Hydrocephalus is a common neurological condition, the hallmark feature of which is an excess in production, or accumulation, of cerebrospinal fluid in the ventricles. Although it is associated with diffuse damage to paraventricular brain areas, patients are broadly typified by a particular pattern of cognitive impairments that include deficits in working memory, attention, and spatial abilities. There have, however, been relatively few neuropsychological accounts of the condition. Moreover, theories of the relationship between aetiology and impairment appear to have emerged in isolation of each other, and proffer fundamentally different accounts. In this primer, we aim to provide a comprehensive and contemporary overview of hydrocephalus for the neuropsychologist, covering cognitive sequelae and theoretical interpretations of their origins. We review clinical and neuropsychological assays of cognitive profiles, along with the few studies that have addressed more integrative behaviours. In particular, we explore the distinction between congenital or early-onset hydrocephalus with a normal-pressure variant that can be acquired later in life. The relationship between these two populations is a singularly interesting one in neuropsychology since it can allow for the examination of typical and atypical developmental trajectories, and their interaction with chronic and acute impairment, within the same broad neurological condition. We reflect on the ramifications of this for our subject and suggest avenues for future research.

Using smartphone-based accelerometers to gauge postoperative outcomes in patients with NPH: Implications for ambulatory monitoring

Background

The surgical treatment of normal pressure hydrocephalus (NPH) with shunting remains controversial due to the difficulty in distinguishing such pathology from other neurological conditions that can present similarly. Thus, patients with suspected NPH should be carefully selected for surgical intervention. Historically, clinical improvement has been measured by the use of functional grades, alleviation of symptoms, and/or patient/family-member reported surveys. Such outcome analysis can be subjective, and there is difficulty in quantifying cognition. Thus, a push for a more quantifiable and objective investigation is warranted, especially for patients with idiopathic NPH (INPH), for which the final diagnosis is confirmed with postoperative clinical improvement. We aimed to use Apple Health (Apple Inc., Cupertino, CA) data to approximate physical activity levels before and after shunt placement for NPH as an objective outcome measurement. The patients were contacted and verbally consented to export Apple Health activity data. The patient's physical activity data were then analyzed. A chart review from the patient's EMR was performed to understand and better correlate recovery.

Case Description

Our first patient had short-term improvements in activity levels when compared to his preoperative activity. The patient's activity level subsequently decreased at 6 months and onward. This decline was simultaneous to new-onset lumbar pain. Our second patient experienced sustained improvements in activity levels for 12 months after his operation. His mobility data were in congruence with his subjectively reported improvement in clinical symptoms. He subsequently experienced a late-decline that began at 48-months. His late deterioration was likely confounded by exogenous factors such as further neurodegenerative diseases coupled with old age.

Conclusion

The use of objective activity data offers a number of key benefits in the analysis of shunted patients with NPH/INPH. In this distinctive patient population, detailed functional outcome analysis is imperative because the long-term prognosis can be affected by comorbid factors or life expectancy. The benefits from using smartphone-based accelerometers for objective outcome metrics are abundant and such an application can serve as a clinical aid to better optimize surgical and recovery care.

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

BACKGROUND

Over the years, there have been several reports and trials of the resistance to cerebrospinal fluid (CSF) outflow (Rout) in normal pressure hydrocephalus (NPH). This work aimed to revisit the utility of testing CSF circulation in a large population of patients clinically presenting with NPH.

MATERIALS AND METHODS

We retrospectively analyzed the data of 369 NPH patients-either shunted or with endoscopic third ventriculostomy (ETV)-in Cambridge between 1992 and 2018. We determined the patients' outcomes (improvement versus no improvement at 6 months) by applying a threshold on R _out values and compared our results with those of existing literature. We also conducted a correlation analysis between all variables and calculated Chi-Statistics (as a measure of separability between improvement and no improvement outcomes) to determine a subset of variables which achieved the highest accuracy in prediction of outcome.

RESULTS

In our dataset, R _out of 18 mmHg*min/mL achieved the highest Chi-statistics of 9.7 with p-value <0.01 when adjusted for age. In addition to R _out, intracranial pressure (ICP) values at the baseline and plateau, CSF production rate and ICP amplitude to slope ratio showed significant Chi-Statistics values (more than 5). Using these variables, an overall accuracy of 0.70 ± 0.09 was achieved for prediction of the shunt outcome.

CONCLUSION

Rout can be used for selecting patients for shunt surgery but not for excluding patients from treatment. Critical, multivariable approaches are required to comprehend CSF dynamics and pressure-volume compensation in NPH. Outcome definition and assessment could also be brought to question.

Poroelastic Mechanical Properties of the Brain Tissue of Normal Pressure Hydrocephalus Patients During Lumbar Drain Treatment Using Intrinsic Actuation MR Elastography

RATIONALE AND OBJECTIVES

Hydrocephalus (HC) is caused by accumulating cerebrospinal fluid resulting in enlarged ventricles and neurological symptoms. HC can be treated via a shunt in a subset of patients; identifying which individuals will respond through noninvasive imaging would avoid complications from unsuccessful treatments. This preliminary work is a longitudinal study applying MR Elastography (MRE) to HC patients with a focus on normal pressure hydrocephalus (NPH).

MATERIALS AND METHODS

Twenty-two ventriculomegaly patients were imaged and subsequently received a lumbar drain placement for cerebrospinal fluid (CSF) drainage. NPH lumbar drain responders and NPH syndrome nonresponders were categorized by clinical presentation. Displacement images were acquired using intrinsic activation (IA) MRE and poroelastic inversion recovered shear stiffness and hydraulic conductivity values. A stable IA-MRE inversion protocol was developed to produce unique solutions for both recovered properties, independent of initial estimates.

RESULTS

Property images showed significantly increased shear modulus (p = 0.003 in periventricular region, p = 0.005 in remaining cerebral tissue) and hydraulic conductivity (p = 0.04 in periventricular region) in ventriculomegaly patients compared to healthy volunteers. Baseline MRE imaging did not detect significant differences between NPH lumbar drain responders and NPH syndrome nonresponders; however, MRE time series analysis demonstrated consistent trends in average poroelastic shear modulus values over the course of the lumbar drain process in responders (initial increase, followed by a later decrease) which did not occur in nonresponders.

CONCLUSION

These findings are indicative of acute mechanical changes in the brain resulting from CSF drainage in NPH patients.

Recent Advances in Rational Diagnosis and Treatment of Normal Pressure Hydrocephalus: A Critical Appraisal on Novel Diagnostic, Therapy Monitoring and Treatment Modalities

BACKGROUND

Normal pressure hydrocephalus (NPH) is a critical brain disorder in which excess Cerebrospinal Fluid (CSF) is accumulated in the brain's ventricles causing damage or disruption of the brain tissues. Amongst various signs and symptoms, difficulty in walking, slurred speech, impaired decision making and critical thinking, and loss of bladder and bowl control are considered the hallmark features of NPH.

OBJECTIVE

The current review was aimed to present a comprehensive overview and critical appraisal of majorly employed neuroimaging techniques for rational diagnosis and effective monitoring of the effectiveness of the employed therapeutic intervention for NPH. Moreover, a critical overview of recent developments and utilization of pharmacological agents for the treatment of hydrocephalus has also been appraised.

RESULTS

Considering the complications associated with the shunt-based surgical operations, consistent monitoring of shunting via neuroimaging techniques hold greater clinical significance. Despite having extensive applicability of MRI and CT scan, these conventional neuroimaging techniques are associated with misdiagnosis or several health risks to patients. Recent advances in MRI (i.e., Sagittal-MRI, coronal-MRI, Time-SLIP (time-spatial-labeling-inversion-pulse), PC-MRI and diffusion-tensor-imaging (DTI)) have shown promising applicability in the diagnosis of NPH. Having associated with several adverse effects with surgical interventions, non-invasive approaches (pharmacological agents) have earned greater interest of scientists, medical professional, and healthcare providers. Amongst pharmacological agents, diuretics, isosorbide, osmotic agents, carbonic anhydrase inhibitors, glucocorticoids, NSAIDs, digoxin, and gold-198 have been employed for the management of NPH and prevention of secondary sensory/intellectual complications.

CONCLUSION

Employment of rational diagnostic tool and therapeutic modalities avoids misleading diagnosis and sophisticated management of hydrocephalus by efficient reduction of Cerebrospinal Fluid (CSF) production, reduction of fibrotic and inflammatory cascades secondary to meningitis and hemorrhage, and protection of brain from further deterioration.

Does aqueductal stenosis influence the lumbar infusion test in normal-pressure hydrocephalus?

BACKGROUND

Late-onset idiopathic aqueductal stenosis may present with clinical features indistinct from idiopathic normal-pressure hydrocephalus (NPH). Moreover, aqueductal stenosis (AS) is not always detected by conventional magnetic resonance imaging (MRI). The aim of this study was to compare the hydrodynamic pattern among NPH patients according to the patency of the aqueduct.

METHODS

Fifty-six consecutive lumbar infusion tests were performed in patients with NPH syndrome. Precipitating causes of hydrocephalus were excluded, and aqueductal patency was examined through high-resolution, T2-weighted 3D MRI. Patients were classified into two groups: non-patent aqueduct and patent aqueduct. Mean values of pressure and pulse amplitude were obtained from basal and plateau stages of infusion studies.

RESULTS

Twelve of 56 patients with NPH-like symptoms presented with morphological AS (21.4 %). Patent aqueduct and non-patent aqueduct groups had similar values of mean opening lumbar pressure (8.2 vs. 8.1 mmHg), and mean opening pulse amplitude (3.1 vs. 2.9 mmHg). Mean pressure in the plateau stage (28.6 vs. 23.2 mmHg), and mean pulse amplitude in the plateau stage (12.5 vs. 10.6 mmHg) were higher in the patent aqueduct group. These differences were not statistically significant. Only Rout was significantly higher in the patent aqueduct group (13.6 vs. 10.1 mmHg/ml/min). One-third of NPH patients with AS presented Rout >12 mmHg/ml/min.

CONCLUSIONS

No differences in mean pressure or pulse amplitude during basal and plateau epochs of the lumbar infusion test in NPH patients were detected, regardless of aqueductal patency. However, Rout was significantly higher in patients with patent aqueduct.

Radiological Assessment of Hydrocephalus: New Theories and Implications for Therapy

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

The Role of the Craniocervical Junction in Craniospinal Hydrodynamics and Neurodegenerative Conditions

The craniocervical junction (CCJ) is a potential choke point for craniospinal hydrodynamics and may play a causative or contributory role in the pathogenesis and progression of neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, MS, and ALS, as well as many other neurological conditions including hydrocephalus, idiopathic intracranial hypertension, migraines, seizures, silent-strokes, affective disorders, schizophrenia, and psychosis. The purpose of this paper is to provide an overview of the critical role of the CCJ in craniospinal hydrodynamics and to stimulate further research that may lead to new approaches for the prevention and treatment of the above neurodegenerative and neurological conditions.

Aqueductal Stroke Volume: Comparisons with Intracranial Pressure Scores in Idiopathic Normal Pressure Hydrocephalus

BACKGROUND AND PURPOSE

Aqueductal stroke volume from phase-contrast MR imaging has been proposed for predicting shunt response in normal pressure hydrocephalus. However, this biomarker has remained controversial in use and has a lack of validation with invasive intracranial monitoring. We studied how aqueductal stroke volume compares with intracranial pressure scores in the presurgical work-up and clinical score, ventricular volume, and aqueduct area and assessed the patient's response to shunting.

MATERIALS AND METHODS

Phase-contrast MR imaging was performed in 21 patients with probable idiopathic normal pressure hydrocephalus. Patients were selected for shunting on the basis of pathologically increased intracranial pressure pulsatility. Patients with shunts were offered a second MR imaging after 12 months. Ventricular volume and transverse aqueductal area were calculated, as well as clinical symptom score.

RESULTS

No correlations between aqueductal stroke volume and preoperative scores of mean intracranial pressure or mean wave amplitudes were observed. Preoperative aqueductal stroke volume was not different between patients with shunts and conservatively treated patients (P = .69) but was correlated with ventricular volume (R = 0.60, P = .004) and aqueductal area (R = 0.58, P = .006) but not with the severity or duration of clinical symptoms. After shunting, aqueductal stroke volume (P = .006) and ventricular volume (P = .002) were reduced. A clinical improvement was seen in 16 of 17 patients who had shunts (94%).

CONCLUSIONS

Aqueductal stroke volume does not reflect intracranial pressure pulsatility or symptom score, but rather aqueduct area and ventricular volume. The results do not support the use of aqueductal stroke volume for selecting patients for shunting.

Endoscopic third ventriculostomy (ETV) for idiopathic normal pressure hydrocephalus (iNPH)

BACKGROUND

Idiopathic normal pressure hydrocephalus (iNPH) is a type of communicating hydrocephalus also known as non-obstructive hydrocephalus. This type of hydrocephalus is caused by impaired cerebrospinal fluid reabsorption without any obstruction in the ventricular system and is associated with normal cerebrospinal fluid pressure. It is characterised clinically by gait disturbance, cognitive dysfunction, and urinary incontinence (known as the Hakim-Adams triad). The exact cause of iNPH is unknown. It may be managed conservatively or treated surgically by inserting a ventriculoperitoneal (VP) or ventriculoatrial (VA) shunt. However, a substantial number of patients do not respond well to surgical treatment, complication rates are high and there is often a need for further surgery. Endoscopic third ventriculostomy (ETV) is an alternative surgical intervention. It has been suggested that ETV may lead to better outcomes, including fewer complications.

OBJECTIVES

To determine the effectiveness of ETV for treatment of patients with iNPH compared to conservative therapy, or shunting of CSF using VP or VA shunts.To assess the perioperative and postoperative complication rates in patients with iNPH after ETV compared to conservative therapy, VP or VA shunting.

SEARCH METHODS

We searched for eligible studies using ALOIS: a comprehensive register of dementia studies, The Cochrane Central Register of Controlled Trials (CENTRAL) and several bibliographic databases such as MEDLINE (Ovid SP), EMBASE (Ovid SP), PsycINFO (Ovid SP), CINAHL (EBSCOhost) and LILACS (BIREME).We also searched the Database of Abstracts of Reviews of Effects (DARE) to identify potentially relevant reviews. The search strategy was adapted for other databases, using the most appropriate controlled vocabulary for each. We did not apply any language or time restrictions. The searches were performed in August 2014.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of ETV treatment of iNPH. Patients had to have at least two symptoms of the Hakim-Adams triad. Exclusion criteria were obstructive causes of hydrocephalus, other significant intracranial pathology and other confirmed causes of dementia. The eligible comparators were conservative treatment or shunting using VP and VA shunts.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened search results, selected eligible studies, assessed risk of bias and extracted data. We contacted trial authors for additional data.

MAIN RESULTS

Only one study met the inclusion criteria: an RCT comparing effectiveness of ETV and non-programmable VP shunts in 42 patients with iNPH. The study was conducted in Brazil between 2009 and 2012. The overall study risk of bias was high. The primary outcome in the study was the proportion of patients with improved symptoms one year after surgery, determined as a change of at least two points on the Japanese NPH scale. Due to imprecision in the results, it was not possible to determine whether there was any difference between groups in the proportion of patients who improved 3 or 12 months after surgery (3 months: odds ration (OR) 1.12, 95% confidence interval (CI) 0.26 to 4.76, n = 42; 12 months: OR 2.5, 95% CI 0.62 to 10.11, n = 38). We were unable to estimate the effect of treatment on other efficacy outcomes (cognition, balance, function, gait and mobility) because they were inadequately reported. Of the 26 patients in the VP shunting group, 5 developed subdural hematoma postoperatively, while there were no complications among the 16 patients in the ETV group (OR 0.12, 95% CI 0.01 to 2.3, n = 42), but the estimate was too imprecise to determine whether this was likely to reflect a true difference in complication rates. This was also the case for rates of further surgical intervention (OR 1.4, 95% CI 0.31 to 6.24, n = 42). There were no deaths during the trial. We judged the quality of evidence for all outcomes to be very low because of a high risk of selection, attrition and reporting bias and serious imprecision in the results.

AUTHORS' CONCLUSIONS

The only randomised trial of ETV for iNPH compares it to an intervention which is not a standard practice (VP shunting using a non-programmable valve). The evidence from this study is inconclusive and of very low quality. Clinicians should be aware of the limitations of the evidence. There is a need for more robust research on this topic to be able to determine the effectiveness of ETV in patients with iNPH.

Deformation of the corona radiata and internal capsule in normal pressure hydrocephalus

BACKGROUND AND PURPOSE

The pathophysiology of the clinical manifestations in normal pressure hydrocephalus (NPH) remains obscure. Ventricular dilatation could generate forces on the paracentral fibers of the corona radiata (CR), hence interfering with their function and producing the classical clinical triad. The analysis of the regional displacement and deformation of the white matter bundles, forming the corona radiata and internal capsule, may clarify the relationship between ventricular dilatation and clinical manifestations in NPH.

METHOD

An experimental finite element (FE) analysis was used to simulate ventricular dilatation in 3 dimensions (3D) and to calculate the strain and deformation on the surrounding parenchyma. Magnetic resonance diffusion tensor imaging-based white matter tractography was then applied to retrieve the displacement and deformation exerted along various fiber bundles of the corona radiata and internal capsule. Anterior and posterior limb displacements and elongations were compared using a paired samples t-test.

RESULTS

The internal capsule, hence the corona radiata, of each cerebral hemisphere was segmented into anterior and posterior limbs. Mean displacements and elongations were calculated for each limb. Mean displacement was significantly larger in the anterior limb whereas mean deformation was larger in the posterior limb (P<0.01).

CONCLUSION

The present simulation demonstrates that ventricular dilatation does not have a homogeneous effect on the periventricular fibre tracts, with a particular load on the corticospinal tract. The affection of this tract remains thereby a potential factor in the generation of the NPH gait disorders.

Quantitative phase-contrast MRI study of cerebrospinal fluid flow: a method for identifying patients with normal-pressure hydrocephalus

OBJECTIVES

The aim of this study is to evaluate the use of phase-contrast MR imaging to diagnose normal pressure hydrocephalus (NPH) and differentiate it from other neurological disorders with similar clinical symptoms.

METHODS

The study included 108 subjects, of whom 61 were healthy controls and 47, patients; in the patient group, 19 had cerebrovascular disease (CVD) and 28 had NPH. All patients underwent a phase-contrast MRI study and several CSF flow and velocity parameters were measured at the aqueduct of Sylvius. Discriminant analyses were performed to evaluate the classification capacity of both individual parameters and the combination of different parameters.

RESULTS

Maximum diastolic velocity, mean flow, and stroke volume showed statistically significant differences that could be used to distinguish between NPH and CVD patients (P<.001). Stroke volume and mean flow showed no false positive results and successful classification rates of 86% and 79%, respectively. No other parameters or combination produced better results.

CONCLUSIONS

Phase-contrast MR imaging is a useful tool for the early diagnosis of patients with NPH. CSF flow quantitative parameters, along with morphological features in a conventional MR study, enable us to differentiate between NPH and CVD patients.

What is the appropriate shunt system for normal pressure hydrocephalus?

Normal pressure hydrocephalus (NPH) represents a common disorder among older people with mild elevation of cerebrospinal fluid pressure and certain clinical manifestations. We present a patient with such a disorder in whom a programmable valve was implanted. With the use of a lower opening pressure, the patient developed a subdural hematoma although the symptoms subsided. After evacuating the hematoma and by setting the valve pressure higher, the patient recovered without any symptomatology. We observed that only the higher pressure was the right one, although in two different pressure values the symptoms had subsided.

Antipsychotic sensitivity in normal pressure hydrocephalus

Normal pressure hydrocephalus is characterized by a clinically progressive triad of an abnormal gait, dementia and urinary incontinence, which might present as paranoid psychosis, mood disorder, obsessive-compulsive disorder and, occasionally, with frontal lobe symptoms. We are reporting a patient having schizophrenia with intolerance to even low dose of antipsychotics, who was subsequently revealed to be having communicating hydrocephalus.

Selection of patients with idiopathic normal-pressure hydrocephalus for shunt placement: a single-institution experience

OBJECT

The ability to predict outcome after shunt placement in patients with idiopathic normal-pressure hydrocephalus (NPH) represents a challenge. To date, no single diagnostic tool or combination of tools has proved capable of reliably predicting whether the condition of a patient with suspected NPH will improve after a shunting procedure. In this paper, the authors report their experience with 120 patients with the goal of identifying CSF hydrodynamics criteria capable of selecting patients with idiopathic NPH. Specifically, they focused on the comparison between CSF-outflow resistance (R-out) and intracranial elastance (IE).

METHODS

Between January 1977 and December 2005, 120 patients in whom idiopathic NPH had been diagnosed (on the basis of clinical findings and imaging) underwent CSF hydrodynamics evaluation based on an intraventricular infusion test. Ninety-six patients underwent CSF shunt placement: 32 between 1977 and 1989 (Group I) on the basis of purely clinical and radiological criteria; 44 between 1990 and 2002 (Group II) on the basis of the same criteria as Group I and because they had an IE slope > 0.25; and 20 between 2003 and 2005 (Group III) on the basis of the same criteria as Group II but with an IE slope > or = 0.30. Outcomes were evaluated by means of both Stein-Langfitt and Larsson scores. Patients' conditions were considered improved when there was a stable decrease (at 6- and 12-month follow-up) of at least 1 point in the Stein-Langfitt score and 2 points in the Larsson score.

RESULTS

Group I: while no statistically significant difference in mean R-out value between improved and unimproved cases was observed, a clear-cut IE slope value of 0.25 differentiated very sharply between unimproved and improved cases. Group II: R-out values in the 2 unimproved cases were 20 and 47 mm Hg/ml/min, respectively. The mean IE slope in the improved cases was 0.56 (range 0.30-1.4), while the IE slopes in the 2 unimproved cases were 0.26 and 0.27. Group III: the mean IE slope was 0.51 (range 0.31-0.7). The conditions of all patients improved after shunting. A significant reduction of the Evans ratio was observed in 34 (40.5%) of the 84 improved cases and in none of the unimproved cases.

CONCLUSIONS

Our strategy based on the analysis of CSF pulse pressure parameters seems to have a great accuracy in predicting surgical outcome in clinical practice.

Brain MRI as a predictor of CSF tap test response in patients with idiopathic normal pressure hydrocephalus

In this study, our objective was to identify the characteristic morphological features of brain MRI associated with a positive cerebrospinal fluid (CSF) tap test in patients with idiopathic normal pressure hydrocephalus (iNPH). Patients diagnosed with clinical suspected iNPH were evaluated. All patients underwent a mini-mental state examination, a brain MRI, and a CSF tap test. The severities of clinical symptoms were rated before and after the CSF tap test. Characteristic brain MRI findings including frontal convexity narrowing, parietal convexity narrowing, upward bowing of the corpus callosum, empty sella, narrowing of the CSF space at the high convexity, marked dilatation of the Sylvian fissure, and disproportion between narrowing of the CSF space at the high convexity and dilatation of the Sylvian fissure ("mismatch" sign) on T1-weighted or FLAIR image were analyzed. Forty-three patients (33 males/ten females, mean age 76.9 ± 6.9 years) with possible iNPH participated in this study. The presence versus absence of empty sella (52.4 vs. 14.3%, OR 6.6, 95% CI 1.5-29.4, p = 0.02) and "mismatch" sign (45.5 vs. 9.5%, OR 7.9, 95% CI 1.5-42.5, p = 0.02) were associated with positive CSF tap test responses. The sensitivity, specificity, positive predictive value, and negative predictive value of the presence of either of these two MRI features in the prediction of CSF tap response were 72.7, 81, 80, and 73.9%, respectively. Specific brain MRI features can be used as markers for the identification of potential CSF tap test responders in iNPH patients. These features may serve as supplemental evidence in the diagnosis of iNPH patients.

The neuropsychology of normal pressure hydrocephalus (NPH)

Normal pressure hydrocephalus (NPH) accounts for one of the few known forms of reversible dementia. Varied aetiology and clinical presentation contribute to difficulties with early or differential diagnoses, and delayed surgical treatment may be less efficacious. Clinical neuropsychology provides a means of determining a cognitive profile for NPH, assisting in differential diagnosis, tracking the disorder's progression and assessing the efficacy of treatment. This article will review possible applications of clinical neuropsychology and propose a clinical assessment protocol for NPH.

CEREBROSPINAL FLUID DRAINAGE AND DYNAMICS IN THE DIAGNOSIS OF NORMAL PRESSURE HYDROCEPHALUS

INTRODUCTION

Because of the difficulty in distinguishing idiopathic normal pressure hydrocephalus (INPH) from other neurodegenerative conditions unrelated to cerebrospinal fluid (CSF) dynamics, response to CSF shunting remains highly variable. We examined the utility of CSF drainage and CSF pressure (Pcsf) dynamics in predicting response to CSF shunting for patients with INPH.

METHODS

Fifty-one consecutive INPH patients underwent continuous lumbar Pcsf monitoring for 48 hours followed by 72 hours of slow CSF drainage before ventriculoperitoneal shunting. Response to CSF drainage and B-wave characteristics were assessed via multivariate proportional-hazards regression analysis.

RESULTS

Improvement in 1, 2, or all 3 INPH symptoms was observed in 35 (69%), 28 (55%), and 11 (22%) patients, respectively, after CSF shunt implantation by 12 months after surgery. A positive response to CSF drainage was found to be an independent predictor of shunt responsiveness (relative risk, 0.30; 95% confidence interval, 0.09–0.98; P = 0.05). There was no difference in Pcsf wave characteristics between the shunt-responsive and -nonresponsive groups, regardless of whether 1-, 2-, or 3-symptom improvement was used to define response to CSF shunting.

CONCLUSION

In this study of 51 INPH patients who underwent Pcsf monitoring with waveform analysis and CSF drainage followed by shunt surgery, there was no correlation between specific Pcsf wave characteristics and objective symptomatic improvement after shunt placement. Pcsf monitoring with B-wave analysis contributes little to the diagnostic dilemma with INPH patients. Clinical response to continuous CSF drainage over a 72-hour period suggests a high likelihood of shunt responsiveness.

Normal pressure hydrocephalus: Diagnostic and predictive evaluationon

In typical cases, normal pressure hydrocephalus (NPH) manifests itself with the triad of gait disturbance, which begins first, followed by mental deterioration and urinary incontinence associated with ventriculomegaly (on CT or MRI) and normal cerebrospinal fluid (CSF) pressure. These cases present minor diagnostic difficulties and are the most likely to improve after shunting. Problems arise when NPH shows atypical or incomplete clinical manifestations (25–50% of cases) or is mimicked by other diseases. In this scenario, other complementary tests have to be used, preferentially those that can best predict surgical outcome. Radionuclide cisternography, intracranial pressure monitoring (ICP) and lumbar infusion tests can show CSF dynamics malfunction, but none are able to confirm whether the patient will benefit from surgery. The CSF tap test (CSF-TT) is the only procedure that can temporarily simulate the effect of definitive shunt. Since the one tap CSF-TT has low sensitivity, it cannot be used to exclude patients from surgery. In such cases, we have to resort to a repeated CSF-TT (RTT) or continuous lumbar external drainage (LED). The most reliable prediction would be achieved if RTT or LED proved positive, in addition to the occurrence of B-waves during more than 50% of ICP recording time. This review was based on a PubMed literature search from 1966 to date. It focuses on clinical presentation, neuroimaging, complementary prognostic tests, and differential diagnosis of NPH, particularly on the problem of selecting appropriate candidates for shunt.

Endoscopic third ventriculostomy in idiopathic normal pressure hydrocephalus: an Italian multicenter study

OBJECTIVES

The aim of the report is to define the indications and results of endoscopic third ventriculostomy (ETV) in idiopathic normal pressure hydrocephalus and to discuss the physiopathological mechanism of this procedure.

METHODS

The cases of 110 patients with idiopathic normal pressure hydrocephalus who underwent ETV in four Italian neurosurgical centers were retrospectively reviewed. The postoperative outcome was correlated with patient age, length of clinical history, preoperative clinical score, symptoms of clinical onset, type of hydrocephalus, and intraoperative findings.

RESULTS

The follow-up period ranged from 2 to 12 years (average, 6.5 yr). The outcome evaluation was made 2 years after the procedure. Postoperative clinical improvement occurred in 76 (69.1%) of 110 patients. There was no correlation between success rate and patient age or type of ventricular enlargement (normal or enlarged fourth ventricle). Conversely, the rate of neurological improvement was higher in patients with shorter clinical history, better preoperative neurological score, and clinical onset with gait disturbances. Moreover, the intraoperative finding of the sudden reappearance of normal cerebral pulsations and significant downward and upward movements of the third ventricular floor after ETV was also correlated with a good outcome.

CONCLUSION

ETV results in a relatively high rate of clinical improvement and a low complication rate in patients with idiopathic normal pressure hydrocephalus. Therefore, it may be easily performed with the same approach used for intracranial pressure monitoring with low morbidity. However, our data must be confirmed by additional studies.

Nonlinear poroplastic model of ventricular dilation in hydrocephalus

Object

The mechanism of ventricular dilation in normal-pressure hydrocephalus remains unclear. Numerical finite-element (FE) models of hydrocephalus have been developed to investigate the biomechanics of ventricular enlargement. However, previous linear poroelastic models have failed to reproduce the relatively larger dilation of the horns of the lateral ventricles. In this paper the authors instead elaborated on a nonlinear poroplastic FE model of the brain parenchyma and studied the influence of the introduction of these potentially more realistic mechanical behaviors on the prediction of the ventricular shape.

Methods

In the proposed model the elasticity modulus varies as a function of the distension of the porous matrix, and the internal mechanical stresses are relaxed after each iteration, thereby simulating the probable plastic behavior of the brain tissue. The initial geometry used to build the model was extracted from CT scans of patients developing hydrocephalus, and the results of the simulations using this model were compared with the real evolution of the ventricular size and shape in the patients.

Results

The authors' model predicted correctly the magnitude and shape of the ventricular dilation in real cases of acute and chronic hydrocephalus. In particular, the dilation of the frontal and occipital horns was much more realistic.

Conclusions

This finding suggests that the nonlinear and plastic mechanical behaviors implemented in the present numerical model probably occur in reality. Moreover, the availability of such a valid FE model, whose mechanical parameters approach real mechanical properties of the brain tissue, might be useful in the further modeling of ventricular dilation at a normal pressure.

Aging effects on cerebral blood and cerebrospinal fluid flows

Phase-contrast magnetic resonance imaging (PC-MRI) is a noninvasive reliable technique, which enables quantification of cerebrospinal fluid (CSF) and total cerebral blood flows (tCBF). Although it is used to study hydrodynamic cerebral disorders in the elderly group (hydrocephalus), there is no published evaluation of aging effects on both tCBF and CSF flows, and on their mechanical coupling. Nineteen young (mean age 27+/-4 years) and 12 elderly (71+/-9 years) healthy volunteers underwent cerebral MRI using 1.5 T scanner. Phase-contrast magnetic resonance imaging pulse sequence was performed at the aqueductal and cervical levels. Cerebrospinal fluid and blood flow curves were then calculated over the cardiac cycle, to extract the characteristic parameters: mean and peak flows, their latencies, and stroke volumes for CSF (cervical and aqueductal) and vascular flows. Total cerebral blood flow was (P<0.01) decreased significantly in the elderly group when compared with the young subjects with a linear correlation with age observed only in the elderly group (R(2)=0.7; P=0.05). Arteriovenous delay was preserved with aging. The CSF stroke volumes were significantly reduced in the elderly, at both aqueductal (P<0.01) and cervical (P<0.05) levels, whereas aqueduct/cervical proportion (P=0.9) was preserved. This is the first work to study aging effects on both CSF and vascular cerebral flows. Data showed (1) tCBF decrease, (2) proportional aqueductal and cervical CSF pulsations reduction as a result of arterial loss of pulsatility, and (3) preserved intracerebral compliance with aging. These results should be used as reference values, to help understand the pathophysiology of degenerative dementia and cerebral hydrodynamic disorders as hydrocephalus.

Changing concepts of cerebrospinal fluid hydrodynamics: role of phase-contrast magnetic resonance imaging and implications for cerebral microvascular disease

Phase-contrast magnetic resonance imaging (PC-MRI) or flow-sensitive MRI can be used to noninvasively measure intracranial vascular and CSF flow. Monro-Kellie homeostasis is the complex compensatory mechanism for the increase in intracranial blood volume during systole. Through PC-MRI techniques, our understanding of Monro-Kellie homeostasis and the associated intracranial hydrodynamics has greatly improved. Failure of this homeostatic mechanism has been implicated in a wide range of cerebral disorders, including vascular and Alzheimer's dementia, late-onset depression, benign and secondary intracranial hypertension, communicating and normal pressure hydrocephalus, and age-related white matter changes. The most common mode of homeostatic failure is due to vascular disease with decreased cerebral arterial compliance. This has wide-reaching implications in the investigation of patients with cerebral vascular disease. Here we discuss the role of PC-MRI in the study of cerebral hydrodynamics and the current understanding of Monro-Kellie homeostasis in both healthy and disease states. Quantitative assessment of the changes in this homeostatic mechanism using PC-MRI has important implications in the development of biomarkers of vascular involvement in disease with application in diagnosis, treatment planning, phenotype identification, and outcome assessment in clinical trials.

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

OBJECT

The average 65-year-old patient with moderate dementia can look forward to only 1.4 quality-adjusted life years (QALYs), that is, longevity times quality of life. Some of these patients suffer from normal-pressure hydrocephalus (NPH) and respond dramatically to shunt insertion. Currently, however, NPH cannot be diagnosed with certainty. The authors constructed a Markov decision analysis model to predict the outcome in patients with NPH treated with and without shunts.

METHODS

Transition probabilities and health utilities were obtained from a review of the literature. A sensitivity analysis and Monte Carlo simulation were applied to test outcomes over a wide range of parameters. Using shunt response and complication rates from the literature, the average patient receiving a shunt would gain an additional 1.7 QALYs as a result of automatic shunt insertion. Even if 50% of patients receiving a shunt have complications, the shunt response rate would need to be less than 5% for empirical shunt insertion to do more harm than good. Authors of most studies have reported far better statistics.

CONCLUSIONS

In summary, many more patients with suspected NPH should be considered for shunt insertion.

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.

Normal pressure hydrocephalus: diagnosis and new approaches to treatment

Impairment of gait occurs commonly in the elderly and has a profound impact on individual functional capacity and quality of life. Dementia and urinary incontinence are other common problems encountered in the elderly. In many circumstances, these problems are mutually exclusive, with treatments chosen to address each disease entity separately. When they appear over time in the same patient, however, these symptoms raise the possibility of normal pressure hydrocephalus.

Diagnosis, treatment, and analysis of long-term outcomes in idiopathic normal-pressure hydrocephalus

OBJECTIVE

The response to shunt surgery for idiopathic normal-pressure hydrocephalus (INPH) is variable because INPH is difficult to distinguish from other conditions causing the same symptoms. To date, no clinical picture or diagnostic test can distinguish INPH or predict response to cerebrospinal fluid (CSF) shunt surgery. We reviewed our 10-year experience with INPH to characterize long-term outcome and to identify independent predictors of outcome after shunt surgery.

METHODS

Patients were classified as having INPH only if they had: 1) ventriculomegaly, 2) two or more INPH clinical features, 3) no risk factor for secondary normal-pressure hydrocephalus, 4) A- or B-waves on CSF pressure monitoring, and 5) clinical improvement during a 3-day CSF drainage trial via a spinal catheter. Independent predictors of outcome were assessed via a multivariate proportional hazards regression analysis.

RESULTS

One hundred thirty-two patients underwent 179 shunt surgeries. Forty-four (33%), 79 (60%), and 99 (75%) patients demonstrated objective improvement 3, 6, and 24 months after shunt surgery, respectively. Gait improved first in 88 (93%) patients. Dementia and urinary incontinence were twofold less likely to improve. Radiological evidence of corpus callosum distension, gait impairment as the primary symptom, and shorter duration of INPH symptoms predicted improvement. Duration of symptoms and gait as the primary symptom were independent predictors by multivariate analysis.

CONCLUSION

INPH can be diagnosed accurately with CSF pressure monitoring and CSF drainage via a spinal catheter. CSF shunting is safe and effective for INPH with a long-term shunt response rate of 75%. Independent predictors of improvement are the presence of gait impairment as the dominant symptom and shorter duration of symptoms.

Case report: optic disc edema without hydrocephalus in acoustic neuroma

Traditionally, visual disturbance and optic disc edema are regarded as late manifestations of acoustic neuromas indicating increased intracranial pressure as a result of obstructive hydrocephalus or a sizeable mass lesion. We report the case of a 56-year-old man who presented with visual disturbance and bilateral optic disc edema. Classic features of hydrocephalus were absent. Magnetic resonance imaging showed a large acoustic neuroma. However, there was no ventriculomegaly and at surgery intracranial pressure was normal. We suggest that cerebrospinal fluid protein may have a role in the formation of optic disc edema through a normal pressure communicating type of hydrocephalus. Furthermore, patients with acoustic neuromas and a visual disturbance related to optic disc edema may be inappropriate for treatment with stereotactic radiosurgery and should be offered early surgery to prevent visual deterioration.

The predictive value of external continuous lumbar drainage, with cerebrospinal fluid outflow controlled by medium pressure valve, in normal pressure hydrocephalus

BACKGROUND

Although sporadic studies have described temporary external cerebrospinal fluid (CSF) lumbar drainage as a highly accurate test for predicting the outcome after ventricular shunting in normal pressure hydrocephalus (NPH) patients, a more recent study reports that the positive predictive value of external lumbar drainage (ELD) is high but the negative predictive value is deceptively low. Therefore, we conducted a prospective study in order to evaluate the predictive value of a continuous ELD, with CSF outflow controlled by medium pressure valve, in NPH patients.

METHOD

Twenty-seven patients with presumed NPH were admitted to our department and CSF drainage was carried out by a temporary (ELD) with CSF outflow controlled by a medium pressure valve for five days. All patients received a ventriculoperitoneal shunt using a medium pressure valve based upon preoperative clinical and radiographic criteria of NPH, regardless of ELD outcome. Clinical evaluation of gait disturbances, urinary incontinence and mental status, and radiological evaluation with brain CT was performed prior to and after ELD test, as well as three months after shunting.

FINDINGS

Twenty-two patients were finally shunted and included in this study. In a three-month follow-up, using a previously validated score system, overall improvement after permanent shunting correlated well to improvement after ELD test (Spearman's rho = 0.462, p = 0.03). When considering any degree of improvement as a positive response, ELD test yielded high positive predictive values for all individual parameters (gait disturbances 94%, 95% CI 71%-100%, urinary incontinence 100%, 95% CI 66%-100%, and mental status 100%, 95% CI 66%-100%) but negative predictive values were low (< 50%) except for cognitive impairment (85%, 95% CI 55%-98%).

CONCLUSION

This study suggests that a positive ELD-valve system test should be considered a reliable criterion for preoperative selection of shunt-responsive NPH patients. In case of a negative ELD-valve system test, further investigation of the presumed NPH patients with additional tests should be performed.

Cerebral blood oxygenation after cerebrospinal fluid removal in hydrocephalus measured by near infrared spectroscopy

BACKGROUND

The cerebrospinal fluid (CSF) tap test has been used for the diagnosis of chronic hydrocephalus to identify the candidates for surgical CSF shunting. However, a high rate of false negative results limits it utility. The purpose of this study is to investigate whether the concomitant monitoring of cerebral hemodynamics by near infrared spectroscopy (NIRS) can improve the diagnostic accuracy of the tap test.

METHODS

Thirteen patients with dilated ventricular system were candidates for this study. We assessed for the patterns of cerebral blood oxygenation (CBO) change in hydrocephalus to determine whether CBO change after CSF removal is useful for selecting shunt candidates.

RESULTS

Patients who showed clinical improvement following CSF shunting had a characteristic CBO change with increases in the concentration of oxyhemoglobin (Oxy-Hb), and patients without improvement during continuous CSF drainage test showed no increase in Oxy-Hb.

CONCLUSION

The current data suggests that CBF increases after CSF removal in hydrocephalus. Although the patients utilized in the present study had secondary chronic hydrocephalus, we speculate that these data could be applied to patients with idiopathic chronic hydrocephalus. Further investigation would be of benefit.

Endoscopic third ventriculostomy in idiopathic normal pressure hydrocephalus

OBJECTIVE

To define the role and indications for an endoscopic third ventriculostomy (ETV) in patients with idiopathic normal pressure hydrocephalus (INPH). A series of 25 patients treated by endoscopic technique was analyzed, and the results were compared with those of 14 studies reporting patients treated by shunting.

METHODS

Twenty-five patients with INPH were treated by ETV from January 1994 through December 2000. All were younger than 75 years of age, had a preoperative clinical history of 1 year or less, had prevalence of gait disturbance with scarce or mild dementia, had marked ventricular enlargement on magnetic resonance imaging (MRI), and had intracranial pressure values ranging from 8 to 12 mm Hg. All were studied by a phase-contrast MRI flow study 1 month after ETV. The 14 reviewed series of patients treated by shunting (all published after 1980) each include more than 25 patients, for a total of 777 patients.

RESULTS

The overall rate of neurological improvement after ETV in our series was 72% (including two patients reoperated on because of absence of flow in the MRI scan); this percentage is slightly higher than that found in the 14 series of shunted patients (66%). Gait disturbance showed a high rate of improvement when compared with other symptoms, both in our ETV study and in other shunting series. Postoperative complications occurred only in one patient (4%) with an intracerebral frontal hemorrhage and in 37.9% of patients from the series including shunted patients.

CONCLUSION

In patients with INPH showing short duration of symptoms, prevalence of gait disturbance, and slight mental impairment, ETV provides similar results to those of shunting. We suggest performing ETV in these patients and reserving shunting only for those who do not improve after ETV, despite the presence of cerebrospinal fluid flow through the ventriculostomy on MRI flow studies. The good results after ETV in our series indirectly confirm that the cerebrospinal fluid absorption is good or at least sufficient in selected patients with INPH.

Magnetic resonance spectroscopic determination of a neuronal and axonal marker in white matter predicts reversibility of deficits in secondary normal pressure hydrocephalus

BACKGROUND

Normal pressure hydrocephalus (NPH) is considered to be a treatable form of dementia, because cerebrospinal fluid (CSF) shunting can lessen symptoms. However, neuroimaging has failed to predict when shunting will be effective.

OBJECTIVE

To investigate whether 1H (proton) magnetic resonance (MR) spectroscopy could predict functional outcome in patients after shunting.

METHODS

Neurological state including Hasegawa's dementia scale, gait, continence, and the modified Rankin scale were evaluated in 21 patients with secondary NPH who underwent ventriculo-peritoneal shunting. Outcomes were measured postoperatively at one and 12 months and were classified as excellent, fair, or poor. MR spectra were obtained from left hemispheric white matter.

RESULTS

Significant preoperative differences in N-acetyl aspartate (NAA)/creatine (Cr) and NAA/choline (Cho) were noted between patients with excellent and poor outcome at one month (p = 0.0014 and 0.0036, respectively). Multiple regression analysis linked higher preoperative NAA/Cr ratio, gait score, and modified Rankin scale to better one month outcome. Predictive value, sensitivity, and specificity for excellent outcome following shunting were 95.2%, 100%, and 87.5%. Multiple regression analysis indicated that NAA/Cho had the best predictive value for one year outcome (p = 0.0032); predictive value, sensitivity, and specificity were 89.5%, 90.0%, and 88.9%.

CONCLUSIONS

MR spectroscopy predicted long term post-shunting outcomes in patients with secondary NPH, and it would be a useful assessment tool before lumbar drainage.

Radiological assessment of hydrocephalus: new theories and implications for therapy

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

Is the placement of shunts in patients with idiopathic normal pressure hydrocephalus worth the risk? Results of a study based on continuous monitoring of intracranial pressure

Object. Data from many studies have demonstrated that shunt insertion in patients with idiopathic normal-pressure hydrocephalus (NPH) is associated with high morbidity and a lack of significant improvement; however, the use of strict diagnostic and treatment protocols can improve the results of surgery in these patients. The primary aim in this prospective study was to analyze the results of shunt placement in 43 patients with idiopathic NPH. A secondary aim was to determine the relationship between several clinical and neuroimaging factors, and patient outcome after surgery.

Methods. Thirty men and 13 women with a mean age of 71.1 ± 6.9 years participated in this study. All patients underwent clinical, neuropsychological, and radiological assessment before and 6 months after surgery. In all patients continuous monitoring of intracranial pressure was performed using a fiberoptic extradural sensor. In 31 patients cerebrospinal fluid dynamics were also determined. Eighty-six percent of patients showed clinical improvement after shunt insertion, 11.6% showed no change, and 2.3% exhibited some worsening. Gait improved in 81.4% of the patients, sphincter control in 69.8%, and cognitive dysfunction in 39.5%. There was no treatment-related death. Early or late postsurgical complications occurred in six patients (14%), although all of these complications were minor or were satisfactorily resolved. The complete clinical triad, cortical sulci size, and periventricular lucencies were related to outcome, whereas patient age, symptom duration, ventricular dilation, and the degree of presurgical dementia were unrelated to outcome.

Conclusions. Given the correct diagnosis, shunt insertion can produce marked improvement in patients with idiopathic NPH syndrome, causing few deaths and few clinically relevant complications.

Intracranial Fluid Dynamics in Normal and Hydrocephalic States

OBJECTIVE

To present a novel magnetic resonance (MR) method of analysis of cerebrospinal fluid (CSF) flow dynamics.

METHODS

Fifty-one subjects were explored with phase-contrast cine MR imaging. There were 36 volunteers, 9 patients with normal pressure hydrocephalus (NPH), and 6 patients with asymptomatic ventricular dilation (VD). The transfer function XFRA/CSF from the arterial pulse waves (APWs) and the CSF pulse waves (CSFPWs) and the transfer function XFRCSF/SS from the CSF pulse waves (CSFPWs) and the sagittal sinus pulse waves (SSPWs) were studied separately.

RESULTS

There was a significant difference in the amplitude spectrum of the XFRA/CSF of patients with VD and volunteers (P < 0.05) and in that of patients with NPH and volunteers (P = 0.005). The amplitude of the fundamental frequency was higher in the NPH group than in the VD group (P = 0.02). In patients with NPH, the amplitude spectrum of XFRCSF/SS showed an attenuation of the pulse wave components that significantly differed from the observed amplification in healthy subjects (P = 0.009) and patients with VD (P = 0.012).

CONCLUSION

This systems analysis method could help to detect increased venous compliance in VD and decreased venous compliance in NPH.

Multi-modal MRI in normal pressure hydrocephalus identifies pre-operative haemodynamic and diffusion coefficient changes in normal appearing white matter correlating with surgical outcome

Magnetic resonance techniques were used to investigate haemodynamic abnormalities and their consequences in normal pressure hydrocephalus (NPH) and to assess changes in these parameters following surgery. Eleven patients with NPH were studied pre- and post-operatively using perfusion and diffusion weighted imaging and compared with ten age-matched controls. Pre-operative periventricular relative cerebral blood volume (rCBV) was reduced in patients (0.76+/-0.11) compared with control (1.16+/-0.16, P<0.01). There was no difference between outcome groups and no change in haemodynamic parameters following surgery. The periventricular apparent diffusion coefficient (ADC) was elevated in the poor outcome group (1.67+/-0.3 x 10(-3) mm(2) s(-1)) compared with both controls (1.04+/-0.4 x 10(-3) mm(2) s(-1), P<0.05) and the good outcome group (0.99+/-0.3 x 10(-3) mm(2) s(-1), P<0.05) despite appearing normal on conventional imaging. In white matter hyperintensities (WMH), rCBV was reduced (0.70+/-0.12 vs. 1.00+/-0.10, P<0.01), and the ADC was increased (1.98+/-0.6 vs. 1.04+/-0.4 x 10(-3) mm(2) s(-1), P<0.05) compared with the same anatomical location in controls. As low rCBV and high ADC is characteristic of chronic infarction, the findings in WMH regions suggest they are irreversibly damaged. Normal appearing periventricular tissue rCBV was reduced, implying that significant haemodynamic consequences contribute to symptoms in NPH. The elevated pre-operative ADC of the same region, was correlated with poor outcome, and may, therefore, be useful in selecting patients for surgery.

Is a combination of Tc-SPECT or perfusion weighted magnetic resonance imaging with spinal tap test helpful in the diagnosis of normal pressure hydrocephalus?

OBJECTIVE

The aim of this study was to evaluate the combination of spinal tap test (STT) with cerebral perfusion measurement assessed either by Tc-bicisate-SPECT (Tc-SPECT) or perfusion weighted MRI (pwMRI), or both, for a better preoperative selection of promising candidates for shunt operations in suspected idiopathic normal pressure hydrocephalus.

METHODS

27 consecutive patients were examined with a standard clinical protocol (assessed by the Homburg Hydrocephalus Scale (HHS)) as well as with 99m Tc-bicisate-SPECT (n=27) or additionally by pwMRI (n=12) before and after STT. The results of these examinations were compared preoperatively for each patient and correlated with postoperative clinical outcome after shunt surgery.

RESULTS

Nine patients showed both, a clinical improvement, and increased cerebral perfusion after STT. They underwent shunt surgery with good to excellent results. In another nine patients increasing cerebral perfusion was detected although they did not show a clear clinical improvement after STT. Six of them also received a shunt operation with good to excellent outcome. Three patients of the last group could have an operation. Nine patients did not show any clinical improvement or any kind of increasing cerebral perfusion after STT. Therefore, they did not undergo surgery. The results of SPECT and pwMRI correlated in 92 % of the patients (11 of 12).

CONCLUSION

It is concluded that a combination of clinical assessment with SPECT or pwMRI is helpful in the preoperative selection of patients for shunting procedures with suspected NPH syndrome. This combination is a minimal invasive and objective test modality that is superior to STT alone. Further studies are necessary for a comparison of the described imaging techniques with different diagnostic tests in this difficult field of cerebral disease.

Acute subdural hematoma after lumboperitoneal shunt placement in patients with normal pressure hydrocephalus

Acute subdural hematoma (SDH) is a rare but disastrous complication after lumboperitoneal shunt placement. Four of 206 adult patients with normal pressure hydrocephalus (1.9%) who underwent lumboperitoneal shunt placement suffered acute SDH following head trauma. The interval between shunt placement and acute SDH was one month to 7 years. Two patients had subdural effusion on computed tomography (CT) at 2- and 6-month follow up. All four patients required assistance in their daily activities before acute SDH onset. The traumatic event was a fall. On admission, CT revealed a large SDH that required surgical removal in two patients, of whom one had manifested subdural effusion after shunt placement. The other two patients had a small SDH. None of the four patients had cerebral contusions. Patients with lumboperitoneal shunts, especially those not capable of independent daily activities, are at risk for acute SDH after even minor head trauma.

1H magnetic resonance spectroscopy in human hydrocephalus

PURPOSE

To evaluate cerebral metabolism in clinical hydrocephalus with (1)H magnetic resonance spectroscopy (MRS).

MATERIALS AND METHODS

In 24 children and adults with progressive, arrested, or normal pressure hydrocephalus, long-echo time (1)H MR spectra were acquired from periventricular white matter and intraventricular cerebrospinal fluid (CSF). Metabolite ratios, and the presence of lactate, were compared with 38 age-matched controls.

RESULTS

Metabolite ratios of patients were within the 95% confidence interval (CI) of controls. A small lactate resonance was detected in 20% of control and hydrocephalic subjects. Lactate was consistently visible in CSF spectra, though lactate concentrations were normal. The CSF lactate T(2) was long in comparison with the known intracellular metabolite T(2) relaxation times. In three neonates with hydrocephalus and spina bifida, 3-hydroxybutyrate was detected in CSF in vivo.

CONCLUSION

Within the limits of the present methods, (1)H MRS could not detect cerebral metabolic abnormalities in human hydrocephalus and provided no additional diagnostic information. The long T(2) of lactate in CSF explains its high visibility. Hence, the detection of lactate in spectra acquired from voxels that contain CSF does not necessarily imply cerebral ischemia.