Marked cerebrospinal fluid void: indicator of successful shunt in patients with suspected normal-pressure hydrocephalus

Morphologic features and flow void phenomenon in normal pressure hydrocephalus and other dementias: are they really significant?

RATIONALE AND OBJECTIVE

The aim of this study was to determine the distinctive features of normal-pressure hydrocephalus (NPH) and other dementias on routine T1-weighted and T2-weighted magnetic resonance (MR) images. Also, the contribution of these parameters to the diagnosis and treatment of NPH was investigated.

MATERIALS AND METHODS

Routine MR images were used to investigate the morphologic features (dilatation of Sylvian cisterns, narrowness of convexity sulci, thickness of corpus callosum (TCC), and dilatation of perihippocampal fissures) and the flow void phenomenon (FVP) in patients with idiopathic NPH (INPH) and other dementias. Routine MR images of 18 patients with INPH, 11 with dementias other than INPH, and 20 controls were retrospectively examined. Morphologic features and the FVP were graded subjectively. The TCC was measured quantitatively. Morphologic parameters, the FVP, and the shunt response were assessed using Kruskal-Wallis and Mann-Whitney U tests.

RESULTS

The mean FVP score was significantly higher in patients with INPH (2.89 +/- 0.75) than in controls and patients with other dementias (1.1 +/- 0.85 and 1.09 +/- 0.83, respectively) (P < .001). There was significant difference in terms of TCC between patients with INPH (3 +/- 0.7 mm), those with other dementias (1.9 +/- 0.7 mm), and controls (5.2 +/- 0.8 mm) (P < .001). Significant differences in terms of other morphologic features were found between patients with INPH and those with other dementias (P < .05). No significant difference was found between morphologic parameters and the FVP and the outcome of cerebrospinal fluid diversion (P > .05).

CONCLUSIONS

Intense FVP is a signature of but is not pathognomonic for INPH. The morphologic analysis of MR images can be distinctive for the diagnosis of INPH or dementias other than INPH. Detailed evaluation of morphologic features and the FVP in routine MR workup of dementia will be useful for accurate diagnosis.

Idiopathic Normal Pressure Hydrocephalus: Correlating Magnetic Resonance Imaging Biomarkers with Clinical Response

Idiopathic Normal Pressure Hydrocephalus (NPH) is a debilitating condition of the elderly. The patient is typically “wet, wobbly and wonky”, to different degrees of the triad. The diagnosis is supported by the radiologic finding of dilated ventricles, determined by an elevated Evan’s Index (EI) without a demonstrable cause. Patients with newly diagnosed NPH typically respond to ventriculo-peritoneal shunting (VPS). NPH-related dementia is possibly the only surgically reversible dementia. An elevated cerebrospinal fluid (CSF) flow rate (FR) is associated with a positive response to shunting. However, post-shunting EI and FRs are unpredictable. Of late, intracranial apparent diffusion coefficient (ADC) quantification via Diffusion Weighted Imaging (DWI) has been emerging as a possible marker in NPH diagnosis. A local study, conducted on a national level, to study the relationship of EI, FR and ADC to pre- and post-shunt clinical measurements has just ended. This review seeks to reconcile the current thinking of NPH, magnetic resonance imaging (MRI) quantification and clinical evaluation, and in the process shed some light on major pathophysiological determinants of the disease.

Noninvasive biomarkers in normal pressure hydrocephalus: evidence for the role of neuroimaging

Object

Normal pressure hydrocephalus (NPH) represents a treatable form of dementia. Recent estimates of the incidence of this condition are in the region of 5% of patients with dementia. The symptoms of NPH can vary among individuals and may be confused with those of patients with multi-infarct dementia, dementia of the Alzheimer type, or even Parkinson disease. Traditionally the diagnosis of NPH could only be confirmed postoperatively by a favorable outcome to surgical diversion of CSF. The object of this literature review was to examine the role of structural and functional imaging in providing biomarkers of favorable surgical outcome.

Methods

A Medline search was undertaken for the years 1980–2006, using the following terms: normal pressure hydrocephalus, adult hydrocephalus, chronic hydrocephalus, imaging, neuroimaging, imaging studies, outcomes, surgical outcomes, prognosis, prognostic value, sensitivity, specificity, positive predictive value, negative predictive value, and accuracy.

Results

The query revealed 16 studies that correlated imaging with surgical outcomes offering accuracy results. Three studies fulfilled the statistical criteria of a biomarker. A dementia Alzheimer-type pattern on SPECT in patients with idiopathic NPH, the presence of CSF flow void on MR imaging, and the N-acetylaspartate/choline ratio in patients with the secondary form are able to predict surgical outcomes with high accuracy.

Conclusions

There is at present Level A evidence for using MR spectroscopy in patients with secondary NPH, and Level B evidence for using SPECT and phase-contrast MR imaging to select patients with idiopathic NPH for shunt placement. The studies, however, need to be repeated by other groups. The current work should act as a platform to design further studies with larger sample sizes.

Models of the pulsatile hydrodynamics of cerebrospinal fluid flow in the normal and abnormal intracranial system

Images obtained from magnetic resonance imaging have helped to ascertain that both the cerebrospinal fluid (CSF) and brain move in a pulsatile manner within the cranium. However, these images are not able to reveal any quantitative information on the physiological forces that are associated with pulsatile motion. Understanding both the pressure and velocity flow field of CSF in the ventricles is important to help understand the mechanics of hydrocephalus. Four separate fluid structure interaction models of the ventricular system in the sagittal plane were created for this purpose. The first model was of a normal brain. The second and third models were pathological brain models with aqueductal stenosis at various locations along the fluid pathway. The fourth model was of a hydrocephalic brain. Results revealed the hydrodynamics of CSF pulsatile flow in the ventricles of these models. Most importantly, it has also revealed the different changes in CSF pulsatile hydrodynamics caused by the various locations of fluid flow obstructions.

Guidelines for management of idiopathic normal pressure hydrocephalus

With the rapid aging of Japanese society, medical care of the elderly has become an important social issue. Among various disorders manifesting dementia, gait disturbance, and urinary incontinence in the elderly population, normal pressure hydrocephalus (NPH), especially of idiopathic type (iNPH), is becoming noteworthy. The Guidelines for management of iNPH in Japan are created in compliance with the evidence-based medicine methods and published in 2004. This English version is made to show the diagnosis and treatment of iNPH with reference to the socio-medical background in Japan and to promote the international research on iNPH. They propose three diagnostic levels; possible, probable, and definite. They indicate the diagnostic importance of high convexity tightness and dilated sylvian fissure with mild to moderate ventriculomegaly on coronal magnetic resonance imaging. The cerebrospinal fluid tap test is regarded as an important diagnostic test because of its simplicity to perform and high predictability of the shunt efficacy. The use of programmable valves at shunt surgeries is recommended. Flowcharts for diagnosis, preoperative assessment, and prevention for complications of shunt surgery are made to promote a wide use of them.

Measurement of peak CSF flow velocity at cerebral aqueduct, before and after lumbar CSF drainage, by use of phase-contrast MRI: utility in the management of idiopathic normal pressure hydrocephalus

OBJECTIVE

Since it was first described, normal pressure hydrocephalus (NPH) and its treatment by means of cerebrospinal fluid (CSF) shunting have been the focus of much investigation. Whatever be the cause of NPH, it has been hypothesized that in this disease there occurs decreased arterial expansion and an increased brain expansion leading to increased transmantle pressure. We cannot measure the latter, but fortunately the effect of these changes (increased peak flow velocity through the aqueduct) can be quantified with cine phase-contrast magnetic resonance imaging (MRI). This investigation was thus undertaken to characterize and measure CSF peak flow velocity at the level of the aqueduct, before and after lumbar CSF drainage, by means of a phase-contrast cine MRI and determine its role in selecting cases for shunt surgery.

PATIENTS AND METHODS

37 patients with clinically suspected NPH were included in the study. Changes in the hyperdynamic peak CSF flow velocity with 50 ml lumbar CSF drainage (mimicking shunt) were evaluated in them for considering shunt surgery.

RESULTS

14 out of 15 patients who were recommended for shunt surgery, based on changes peak flow velocity after lumbar CSF drainage, improved after shunt surgery. None of the cases which were not recommended for shunt surgery, based on changes in CSF peak flow velocity after lumbar CSF drainage, improved after shunt surgery (2 out of 22 cases).

CONCLUSION

The study concluded that the phase-contrast MR imaging, done before and after CSF drainage, is a sensitive method to support the clinical diagnosis of normal pressure hydrocephalus, selecting patients of NPH who are likely to benefit from shunt surgery, and to select patients of NPH who are not likely to benefit from shunt surgery.

Normal pressure hydrocephalus

Doctors find the management of normal pressure hydrocephalus (NPH) difficult because their diagnosis often is uncertain and the treatment with shunt surgery carries a significant risk. With the aim of bringing to the attention of physicians the useful, but largely anecdotal, information available regarding this problem, this article discusses the epidemiology, reasons why the diagnosis is difficult, differential diagnosis, features of the history, examination, neuropsychologic assessment, radiologic evaluation, and special tests that may help clinicians with management.

Changes in aqueductal CSF stroke volume and progression of symptoms in patients with unshunted idiopathic normal pressure hydrocephalus

BACKGROUND AND PURPOSE

Idiopathic normal pressure hydrocephalus (iNPH) represents a diagnostic challenge, given its variable presentation and progression. Stroke volume (SV), defined as the mean volume of CSF passing through the aqueduct during both systole and diastole, greater than or equal to 42 muL, serves as a selection criterion for patients with good probabilities of improvement after ventriculoperitoneal shunt surgery (VPS). In this study, we evaluated the changes in SV during the progression of clinical symptoms in patients with suspected NPH.

MATERIALS AND METHODS

Nine patients who presented with clinical and radiologic evidence of NPH, but refused treatment with VPS, were evaluated every 6 months for up to 2 years for progression in their clinical symptoms and changes in their SV, as measured by phase-contrast cine MR imaging (PCCMR).

RESULTS

SV seems to increase between the onset of the symptoms and the following 18 to 20 months, then seems to plateau, followed in the next 18 to 20 months by a slight decline, and finally to a more precipitous drop in the next 12 months. During this time, however, the patient's clinical symptoms progressively worsen.

CONCLUSION

Patients with a low SV have not necessarily had brain atrophy and can show, in the following months, a progressive increase in SV, which qualifies them as good candidates for VPS. The progressive reduction of the SV in untreated patients with worsening clinical symptoms may be a sign of a progressive cerebral ischemic injury, which renders the NPH irreversible.

Value of phase contrast magnetic resonance imaging for investigation of cerebral hydrodynamics

OBJECTIVE

Phase Contrast Magnetic Resonance Imaging (PCMRI) is a noninvasive technique that can be used to quantify variations of flow during the cardiac cycle. PCMRI allows investigations of blood flow dynamics in the main arteries and veins of the brain but also the dynamics of cerebrospinal fluid. These cerebral flow investigations provide a description of the regulation mechanisms of intracranial pressure during the cardiac cycle. The objective of this paper is to describe the contribution of this technique in diseases related to disorders of cerebral hydrodynamics in the light of 5 clinical cases.

METHOD

Flow measurements were performed using PCMRI sequences on a 1.5 Tesla MR imager in 4 patients with symptomatic ventricular dilation and 1 patient with a syringomyelic cavity.

RESULTS

Flow quantification in these 5 patients, representative of the diseases mainly concerned by cerebral hydrodynamics, is useful to guide the indication for ventricular shunting in patients with hydrocephalus, to demonstrate obstruction of the cerebral aqueduct, to demonstrate recirculation of ventricular CSF after ventriculostomy and to characterize the dynamic features of CSF inside a spinal cavity.

CONCLUSION

PCMRI, now available to neurosurgeons, is complementary to morphological MR and provides quantitative information on cerebral hydrodynamics. This information is mainly used to confirm alteration of CSF flow in the cerebral and spinal compartments. PCMRI is also a functional tool to better understand the pathophysiology of hydrocephalus and syringomyelia.

IS AQUEDUCTAL STROKE VOLUME, MEASURED WITH CINE PHASE-CONTRAST MAGNETIC RESONANCE IMAGING SCANS USEFUL IN PREDICTING OUTCOME OF SHUNT SURGERY IN SUSPECTED NORMAL PRESSURE HYDROCEPHALUS?

OBJECTIVE

To evaluate clinical usefulness of cerebrospinal fluid stroke volume (SV) assessed in the cerebral aqueduct, via cine phase-contrast magnetic resonance imaging, for predicting outcome after shunt surgery in suspected normal pressure hydrocephalus.

METHODS

Thirty-eight patients with suspected normal pressure hydrocephalus were included. SV was assessed using cine phase-contrast magnetic resonance imaging, and the results were kept blinded until postoperative follow-up after 7 ± 5.8 months (mean ± standard deviation). Selection to surgery was based on a positive lumbar infusion test or cerebrospinal fluid tap test, and outcome was evaluated with objective tests.

RESULTS

Six patients were excluded from SV measurements because of technical difficulties. Eight patients were not operated (negative lumbar infusion test and cerebrospinal fluid tap test). SV in the not operated patients (mean, 66 ± 53 μl) did not differ from the operated patients (95 ± 78 μl; P= 0.335). Operated patients showed statistically significant improvements in walk (P= 0.020), reaction time (P= 0.006), and memory (P= 0.001) tests. Patients were divided into three groups according to SV range: low (0–50 μl), middle (51–100 μl), and high (&gt;100 μl). No statistically significant (P&gt; 0.05) improvements in any of the objective tests were found in any of the SV ranges. The numbers of individually improved patients were similar in the different SV ranges: six out of seven in the low, nine out of nine in the middle, and five out of eight in the high range. Weak correlations were found between SV and the initial pulse amplitude (Rs= 0.043; P= 0.014) as well as the plateau pulse amplitude (Rs= 0.043; P= 0.014) as measured with the lumbar infusion test.

CONCLUSION

The data from this study show no evidence that cine phase-contrast magnetic resonance imaging measurements of SV in the cerebral aqueduct are useful for selecting patients with normal pressure hydrocephalus symptoms to shunt surgery.

Idiopathic normal pressure hydrocephalus may be a “Two Hit” disease: Benign external hydrocephalus in infancy followed by deep white matter ischemia in late adulthood

PURPOSE

To determine if normal pressure hydrocephalus (NPH) could result from decreased resorption of cerebrospinal fluid (CSF) by the arachnoidal villi, leading to benign external hydrocephalus [BEH] in infancy, followed by deep white matter ischemia (DWMI) in late adulthood (the more hydrophilic environment increasing resistance to CSF flow through the extracellular space (ECS) of the brain).

MATERIALS AND METHODS

CSF outflow via the fourth ventricle and the ECS of the brain was mathematically modeled using a parallel electrical circuit analog. The apparent diffusion coefficient (ADC) was measured as a surrogate of the amount of water in the ECS in normals, patients with symptomatic NPH, and patients with dilated ventricles without symptoms of NPH ("pre-NPH").

RESULTS

The electrical circuit model demonstrates increasing ventricular volume with increasing resistance to flow through the ECS of the brain. ADC measurements performed in the centrum semiovale are significantly higher in patients with NPH and "pre-NPH" than in age-matched controls (P<0.05), controlling for the same degree of DWMI indicating increased fluid in the ECS of the brain.

CONCLUSION

The electrical circuit analog and finding of increased periventricular ADC support the theory that NPH is a "two hit" disease.

Magnetic resonance imaging flow void changes after cerebrospinal fluid shunt in post-traumatic hydrocephalus: clinical correlations and outcome

The assessment of the flow-void in the cerebral aqueduct of patients with post-traumatic hydrocephalus on magnetic resonance imaging (MRI) evaluation could concur the right diagnosis and have a prognostic value. We analysed prospectively 28 patients after a severe head injury (GCS<or=8), with radiological or clinical suspicion of post-traumatic hydrocephalus and a fast flow-void signal in the cerebral acqueduct on T2-weighted and proton density MRI. Twenty-two patients were shunted (n=19) or revised (n=3). Six patients were followed-up without surgery. Twenty out of 22 shunted patients (91%) showed variable reduction of the fast flow-void. Eighteen of the operated patients (82%) presented a significant clinical improvement at 6-month follow-up. All patients (n=2) who had no change of the fast flow-void after surgery did not clinically improve. The six non-shunted patients did not present any clinical or radiological improvement. In head-injured patients, fast flow-void in the cerebral aqueduct is diagnostic for post-traumatic hydrocephalus and its reduction after ventriculo-peritoneal shunt is correlated with a neurological improvement. In already shunted patients, a persistent fast flow-void is associated with a lack of or very slow clinical improvement and it should be considered indicative of under-drainage.

Pathological aging of the brain: an overview

The number of elderly people is increasing rapidly and, therefore, an increase in neurodegenerative and cerebrovascular disorders causing dementia is expected. Alzheimer disease (AD) is the most common cause of dementia. Vascular dementia, dementia with Lewy bodies, and frontotemporal dementia are the most frequent causes after AD, but a large proportion of patients have a combination of degenerative and vascular brain pathology. Characteristic magnetic resonance (MR) imaging findings can contribute to the identification of different diseases causing dementia. The MR imaging protocol should include axial T2-weighted images (T2-WI), axial fluid-attenuated inversion recovery (FLAIR) or proton density-weighted images, and axial gradient-echo T2*-weighted images, for the detection of cerebrovascular pathology. Structural neuroimaging in dementia is focused on detection of brain atrophy, especially in the medial temporal lobe, for which coronal high resolution T1-weighted images perpendicular to the long axis of the temporal lobe are extremely important. Single photon emission computed tomography and positron emission tomography may have added value in the diagnosis of dementia and may become more important in the future, due to the development of radioligands for in vivo detection of AD pathology. New functional MR techniques and serial volumetric imaging studies to identify subtle brain abnormalities may also provide surrogate markers for pathologic processes that occur in diseases causing dementia and, in conjunction with clinical evaluation, may enable a more rigorous and early diagnosis, approaching the accuracy of neuropathology.

Brain energy metabolism and intracranial pressure in idiopathic adult hydrocephalus syndrome

BACKGROUND

The symptoms in idiopathic adult hydrocephalus syndrome (IAHS) are consistent with pathology involving the periventricular white matter, presumably reflecting ischaemia and CSF hydrodynamic disturbance.

OBJECTIVE

To investigate whether a change in intracranial pressure (ICP) can affect energy metabolism in deep white matter.

METHODS

A microdialysis catheter, a brain tissue oxygen tension probe, and an ICP transducer were inserted into the periventricular white matter 0-7 mm from the right frontal horn in 10 patients with IAHS. ICP and intracerebral Ptio2 were recorded continuously during lumbar CSF constant pressure infusion test. ICP was raised to pressure levels of 35 and 45 mm Hg for 10 minutes each, after which CSF drainage was undertaken. Microdialysis samples were collected every three minutes and analysed for glucose, lactate, pyruvate, and glutamate.

RESULTS

When raising the ICP, a reversible drop in the extracellular concentrations of glucose, lactate, and pyruvate was found. Comparing the values during baseline to values at the highest pressure level, the fall in glucose, lactate, and pyruvate was significant (p < 0.05, Wilcoxon sign rank). There was no change in glutamate or the lactate to pyruvate ratio during ICP elevation. Ptio2 did not decrease during ICP elevation, but was significantly increased following CSF drainage.

CONCLUSIONS

Raising intracranial pressure induces an immediate and reversible change in energy metabolism in periventricular white matter, without any sign of ischaemia. Theoretically, frequent ICP peaks (B waves) over a long period could eventually cause persisting axonal disturbance and subsequently the symptoms noted in IAHS.

Chronic hydrocephalus in adults

Chronic hydrocephalus is a complex condition, the incidence of which increases with increasing age. It is characterised by the presence of ventricular enlargement in the absence of significant elevations of intracranial pressure. The clinical syndrome may develop either as a result of decompensation of a "compensated" congenital hydrocephalus, or it may arise de novo in adult life secondary to a known acquired disturbance of normal CSF dynamics. The latter may be due to late onset acqueductal stenosis or disruption of normal CSF absorptive pathways following subarachnoid hemorrhage or meningitis ("secondary" normal pressure hydrocephalus (NPH)). In some cases the cause of the hydrocephalus remains obscure ("idiopathic" NPH). In all forms of chronic hydrocephalus the clinical course of the disease is heavily influenced by changes in the brain associated with aging, in particular cerebrovascular disease. Recent research has challenged previously held tenets regarding the CSF circulatory system and this in turn has led to a radical rethinking of the pathophysiological basis of chronic hydrocephalus.

Cerebrospinal fluid dynamics

Hydrocephalus is far more complicated than a simple disorder of CSF circulation. Historically, it has been diagnosed using clinical and psychomotor assessment plus brain imaging. The role of physiological measurement to aid diagnosis becomes more appreciated in current clinical practice. This has been reflected by recently formulated guidelines for the management of normal pressure hydrocephalus. Clinical measurement in hydrocephalus is mainly related to intracranial pressure (ICP) and cerebral blood flow. This review lists and discusses most common forms of the methods: CSF infusion study, overnight ICP monitoring, assessment of slow ICP waves, testing pressure reactivity, cerebral autoregulation, CO2 reactivity and PET-CBF studies combined with MRI co-registration. The basics of CSF dynamics modelling are presented and the principles of the assessment of functioning of the implanted hydrocephalus shunts are also discussed. The descriptions of multiple forms of measurement along with clinical illustrations are mainly based on in-house experience of a multidisciplinary group of scientists and clinicians from Cambridge, UK.

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.

Differential effects of diabetes on rat choroid plexus ion transporter expression

Though diabetes is a disease with vascular complications, little is known about its effects on the blood-brain barrier or the blood-cerebrospinal fluid barrier (BCSFB). The BCSFB is situated at choroid plexuses located in the lateral, third, and fourth ventricles. Choroid plexuses are the primary site of cerebrospinal fluid (CSF) production and express numerous ion transporters. Previous studies have shown a perturbation of ion transport in the periphery and brain during diabetes. In this study, we investigated the effect of diabetes on ion transporters in the choroid plexuses of streptozotocin (STZ)-induced diabetic rats. Diabetes was induced in male Sprague-Dawley rats by intraperitoneal injection of STZ (60 mg/kg in citrate buffer, confirmed by glucose analysis: 601 +/- 22 mg/dl diabetic rats, 181 +/- 46 mg/dl age-matched controls); and at 28 days, rats were killed, choroid plexuses harvested, and protein extracted. Western blot analyses were carried out using antibodies for ion transporters, including Na(+)-K(+)-2Cl(-) cotransporter and the Na(+)-K(+)-ATPase alpha1-subunit. The efflux of the K(+) analog (86)Rb(+) from choroid plexus was also studied. Diabetic rats showed an increase in expression of the Na(+)-K(+)-2Cl(-) cotransporter and the Na(+)-K(+)-ATPase alpha1-subunit, as compared with age-matched controls, a decrease in Na(+)-H(+) exchanger expression, and no change in Na(+)-K(+)-ATPase beta1- or beta2-subunit. The net effect of these changes was a 66% increase in (86)Rb(+) efflux from diabetic choroid plexus compared with controls. These changes in expression may affect choroid plexus ion balance and thus significantly affect CSF production in diabetic rats.

Intracerebral microdialysis and CSF hydrodynamics in idiopathic adult hydrocephalus syndrome

BACKGROUND

In idiopathic adult hydrocephalus syndrome (IAHS), a pathophysiological model of "chronic ischaemia" caused by an arteriosclerotic process in association with a CSF hydrodynamic disturbance has been proposed.

OBJECTIVE

To investigate whether CSF hydrodynamic manipulation has an impact on biochemical markers related to ischaemia, brain tissue oxygen tension (PtiO(2)), and intracranial pressure.

METHODS

A microdialysis catheter, a PtiO(2) probe, and an intracerebral pressure catheter were inserted into the periventricular white matter 0-7 mm from the right frontal horn in 10 patients with IAHS. A subcutaneous microdialysis probe was used as reference. Intracranial pressure and intracerebral PtiO(2) were recorded continuously. Samples were collected for analysis between 2 and 4 pm on day 1 (baseline) and at the same time on day 2, two to four hours after a lumbar CSF hydrodynamic manipulation. The concentrations of glucose, lactate, pyruvate, and glutamate on day 1 and 2 were compared.

RESULTS

After CSF drainage, there was a significant rise in the intracerebral concentration of lactate and pyruvate. The lactate to pyruvate ratio was increased and remained unchanged after drainage. There was a trend towards a lowering of glucose and glutamate. Mean intracerebral PtiO(2) was higher on day 2 than on day 1 in six of eight patients.

CONCLUSIONS

There is increased glucose metabolism after CSF drainage, as expected in a situation of postischaemic recovery. These new invasive techniques are promising tools in the future study of the pathophysiological processes in IAHS.

Agreement between CSF flow dynamics in MRI and ICP monitoring in the diagnosis of normal pressure hydrocephalus. Sensitivity and specificity of CSF dynamics to predict outcome

OBJECTIVES

The aims of the study were 1) to assess the degree of agreement between CSF flow dynamics determined by MR and ICP monitoring in the diagnosis of NPH, and 2) to determine the sensitivity and specificity of CSF flow dynamics studied by MR in predicting improvement after shunting.

PATIENTS AND METHODS

A prospective study was carried out in 35 consecutive patients with suspected NPH. CSF velocity (Phase Contrast) through the aqueduct was determined in sagittal plane. Patients were classified as "normal" or hyperdynamic in comparison with a control group of 27 healthy volunteers. Continuous extradural ICP monitoring was performed for at least 72 hours and patients were classified as having active, compensated, or ex-vacuo hydrocephalus. Patients with active or compensated hydrocephalus were shunted.

RESULTS

The degree of agreement between MR dynamics and ICP monitoring was 82%. Sensitivity of CSF velocity was 90% and specificity was 50%.

CONCLUSIONS

The degree of agreement between ICP monitoring and CSF velocity is high. High CSF velocity through the aqueduct is a good predictor of improvement after surgery. However, patients with normal velocity in MR required additional tests before a diagnosis of NPH is ruled out.

White matter changes in normal pressure hydrocephalus and Binswanger disease: specificity, predictive value and correlations to axonal degeneration and demyelination

OBJECTIVES

To analyse the diagnostic and prognostic value of periventricular hyperintensity (PVH) and deep white matter hyperintensity (DWMH) magnetic resonance imaging (MRI) changes and their relation to symptoms and cerebrospinal fluid (CSF) markers of demyelination (sulphatide) and axonal degeneration [neurofilament triplet protein (NFL)] in a large series of patients with normal pressure hydrocephalus (NPH) and Binswanger disease (BD).

MATERIALS AND METHODS

PVH and DWMH were determined by a semi-automatic segmentation method on T2-weighted images in 29 patients with NPH and 17 patients with BD. CSF analyses, psychometric testing and quantification of balance, gait and continence were performed in all patients and also postoperatively in NPH patients.

RESULTS

No MRI variable could identify NPH or BD patients. Abundant PVH and DWMH preoperatively correlated with improvement in gait, balance and psychometric performance after shunt surgery (P < 0.05). CSF sulphatide correlated positively with the amount of DWMH (P < 0.05) while NFL was correlated to both PVH and DWMH (P < 0.05). Abundant PVH correlated with poor psychometric performance while DWMH correlated with gait disturbance (P < 0.05). Postoperative reduction in PVH correlated with improvement in gait, balance and psychometric performance.

CONCLUSION

In spite of a refined quantification method, NPH and BD patients exhibited similar MRI changes. MRI had a predictive value in NPH patients. DWMH might relate to demyelination and PVH to neuronal axonal dysfunction. NPH and BD share the major part of symptoms and MRI changes, indicating a common pathophysiological pattern, and we raise the question of how to treat BD patients.

Use of cerebrospinal fluid flow rates measured by phase-contrast MR to predict outcome of ventriculoperitoneal shunting for idiopathic normal-pressure hydrocephalus

OBJECTIVE

To determine whether favorable clinical response and magnitude of improvement are associated with increased aqueductal cerebrospinal fluid (CSF) flow rates in patients who undergo ventriculoperitoneal shunting (VPS) for idiopathic normal-pressure hydrocephalus (NPH).

PATIENTS AND METHODS

Between January 1995 and June 2000, 49 patients (14 men and 35 women; mean age, 72.9 years; range, 54-88 years) underwent magnetic resonance quantification of aqueductal CSF flow followed by VPS for presumed idiopathic NPH at the Mayo Clinic, Rochester, Minn. Logistic regression models for the odds of any improvement in score as a function of aqueductal CSF flow and separate models for any improvement in gait, incontinence, cognition, and total score were constructed.

RESULTS

Forty-two patients (86%) had improvement in gait at postoperative follow-up (mean, 10 months). Of the 32 patients with incontinence, 27 (69%) improved. Of the 36 patients with cognitive impairment, 16 (44%) improved. In univariate and fully adjusted models, increased CSF flow through the aqueduct was not significantly associated with improvement or the magnitude of improvement in gait, cognition, or incontinence. Thirty-six patients underwent high-volume lumbar puncture preoperatively, of whom 5 (14%) had no response. The aqueductal CSF flow rates of these 5 patients were significantly higher than those of the patients who improved after lumbar puncture. Postoperative complications occurred in 15 patients. The aqueductal CSF flow rates in these 15 patients were not significantly different from those of patients who experienced no complications.

CONCLUSION

Among patients who underwent VPS for the treatment of NPH, measurement of CSF flow through the cerebral aqueduct did not reliably predict which patients would improve after shunting or the magnitude of improvement.

The value of temporary external lumbar CSF drainage in predicting the outcome of shunting on normal pressure hydrocephalus

OBJECTIVE

It has been reported that temporary external lumbar CSF drainage (ELD) is a very accurate test for predicting the outcome after ventricular shunting in patients with normal pressure hydrocephalus (NPH). However, only a limited number of patients have been studied for assessing the predictive accuracy of ELD. Therefore, the value of ELD in predicting the outcome after a ventriculoperitoneal shunt in patients with presumed NPH was assessed.

METHODS

All patients with presumed NPH were invited to participate in this study. Clinical assessment, MRI, and neuropsychological evaluation were followed by a lumbar CSF tap test consisting of removing 40 ml CSF. When this test resulted in marked clinical improvement of gait impairment, mental disturbances, or both, the patient was shunted without further tests. In patients with either questionable or no improvement after the CSF tap test, ELD was carried out. The value of ELD for predicting the outcome after shunting was calculated by correlating the results of ELD with that of ventriculoperitoneal shunting.

RESULTS

Between January 1994 and December 2000, 49 presumed NPH patients from three institutes were included. Forty three had idiopathic, and the remaining six had secondary NPH. Forty eight patients were shunted; 39 had an ELD of whom 38 completed the test. After 2 months 35 of the 48 (73%) shunted patients had improved. The predictive value of a positive ELD was 87% (95% confidence interval (95% CI) 62-98) and that of a negative ELD 36% (95% CI 17-59). In two patients serious test related complications (meningitis) occurred without residual deficit.

CONCLUSION

The study suggests that although the predictive value of a positive ELD is high, that of a negative ELD is deceptively low because of the high rate of false negative results. The costs and invasiveness of the test and the possibility of serious test related complications further limits its usefulness in managing patients with presumed NPH.

Measurement of cerebrospinal fluid flow at the cerebral aqueduct by use of phase-contrast magnetic resonance imaging: technique validation and utility in diagnosing idiopathic normal pressure hydrocephalus

OBJECTIVE

We analyzed the reliability of a protocol for measuring quantitative cerebrospinal fluid (CSF) flow at the cerebral aqueduct and established the range of CSF flows in normal elderly patients, patients with Alzheimer's and other forms of dementia, and patients with idiopathic normal pressure hydrocephalus (NPH).

METHODS

A constant flow phantom was used to establish the accuracy of the CSF flow measurement. The clinical variability of the measurement was estimated by calculating the standard deviations and coefficients of variation of intra- and interobserver and intertrial data sets derived from three normal volunteers. A total of 236 patients were studied, including 47 normal elderly patients, 115 patients with cognitive impairment (9 with mild cognitive impairment, 46 with Alzheimer's disease, and 60 with other cognitive impairment), 31 patients in whom NPH was suspected but ultimately excluded, and 43 patients with a final clinical diagnosis of NPH.

RESULTS

The intraobserver, interobserver, and intertrial measurement variations of 6.4, 5.4, and 8.8%, respectively, were substantially smaller than the wide variation observed among subjects. There was no statistically significant difference in flow between normal elderly patients and patients with cognitive impairment (P = 0.91). When these populations were pooled, the average flow was 8.47 ml/min (standard deviation, 4.23; range, 0.9-18.5 ml/min). The average flow rate in patients with a final clinical diagnosis of NPH was 27.4 ml/min (standard deviation, 15.3; range, 3.13-62.2 ml/min). This was significantly higher than the flow rate in each of the other three groups (all, P < 0.001).

CONCLUSION

CSF flow measurements of less than 18 ml/min with a sinusoidal flow pattern are normal. CSF flow of greater than 18 ml/min suggests idiopathic NPH.

Cerebrospinal fluid flow waveforms: MR analysis in chronic adult hydrocephalus

Henry-Feugeas MC, Idy-Peretti I, Baledent O, et al. Cerebrospinal fluid flow waveforms: MR analysis in chronic adult hydrocephalus. Invest Radiol 2001;36:146-154.

RATIONALE AND OBJECTIVES

To analyze changes in cerebrospinal fluid (CSF) hydrodynamics in chronic adult hydrocephalus.

METHODS

Phase-contrast cine-MR acquisitions were used to explore the ventricular system and the upper ventral cervical spaces of 16 patients. The aqueductal jet was explored in 32 control subjects.

RESULTS

The duration of pulsatile caudal CSF flow (ie, CSF systole) was abnormally short in patients with active idiopathic and obstructive hydrocephalus. The duration of CSF cervical systole was normal in patients with stable hydrocephalus. The aqueductal stroke volume could be increased in stable communicating hydrocephalus. Patients who responded to shunting had shortened CSF systoles and hyperpulsatile ventricular patterns. Successful CSF diversion resulted in longer CSF systoles and CSF ventricular patterns that were no longer hyperpulsatile.

CONCLUSIONS

Magnetic resonance analysis of CSF flow can show craniospinal dissociation and limitation of CSF outflow from the ventricles in both obstructive and communicating hydrocephalus; it should help determine the response to shunting in communicating hydrocephalus.

Shunt-responsive dementia in sarcoid meningitis: role of magnetic resonance imaging and cisternography

The authors report a patient with progressive cognitive and gait decline in association with sarcoid meningitis. The patient had evidence of active inflammation as determined by cerebrospinal fluid examination and was steroid dependent. Magnetic resonance imaging and radionucleotide cisternography were complementary in establishing the diagnosis of communicating hydrocephalus, and suggested that the patient would be shunt responsive.

Normal pressure hydrocephalus: developments in determining surgical prognosis

Research into normal pressure hydrocephalus has often focused on the clinical dilemma of selecting patients who will benefit from cerebrospinal fluid diversion. Recent developments in imaging and lumbar infusion tests are throwing light on the underlying pathophysiology, providing researchers with new avenues for the development of reliable investigative tools.

Adult patients with "asymptomatic" and "compensated" hydrocephalus benefit from surgery

OBJECTIVES

There exists no consensus regarding the appropriate treatment of the group of adult hydrocephalus patients often denoted as "arrested"/ "compensated", "asymptomatic" or "symptomatic congenital". Our case series describes the results of CSF diversion in these patients.

MATERIAL AND METHODS

During the period of 1984 to 1994, 23 consecutive adult patients with "asymptomatic" (n = 10), "compensated" (n = 7) and "symptomatic congenital" (n = 6) hydrocephalus were prospectively evaluated. All patients showed signs of motor or psychometric impairment, had indications of an infantile or childhood debut, and had previously been ignored. In 15 patients the ventricular enlargement was a coincidental finding. Seventeen patients underwent shunt surgery or endoscopic third ventriculostomy.

RESULTS

All but one operated upon improved. Six patients declined surgery, but have been followed with 1 showing deterioration, the remaining being unchanged.

CONCLUSION

In addition to patients with "symptomatic congenital" most adult "asymptomatic" and "arrested"/"compensated" hydrocephalus patients can benefit from surgery despite a considerable duration of disease.

Cine MR CSF flow study in hydrocephalus: what are the valuable parameters?

To evaluate the changes of intracranial cerebrospinal fluid (CSF) dynamics in hydrocephalus, we studied the various parameters of cine phase contrast (PC) magnetic resonance (MR) CSF flow images in cases of acutely progressive hydrocephalus, comparing them with those in normal CSF circulation. The MR images were obtained with 1.5 T unit using the 2 dimensional cine PC sequence with cardiac gating in 10 non-obstructive hydrocephalus (NOH), 3 obstructive hydrocephalus (OH), and 10 controls. The temporal velocity information from the anterior and posterior cervical pericord spaces, third and fourth ventricles, and aqueduct were plotted as wave form. The wave forms were analyzed for configurations, amplitude parameters (Smax, Smin, Sdif), and temporal parameters (R-S, R-SMV, R-D, R-DMV). The statistical significance of each parameter was examined with paired t-test. All patients with OH underwent endoscopic thrid ventriculostomy, whereas all NOH underwent shunting procedures. In 5 ROIs, distinct reproducible configuration features were obtained at aqueductal and cervical pericord spaces. Statistically significant differences between control and hydrocephalus only in temporal parameters were determined. In NOH, the graph showed R-DMV shortening (p < 0.01) at anterior cervical pericord space. In OH, there were R-DMV shortening (p < 0.05) at anterior cervical pericord space, R-SMV shortening (p < 0.02) at posterior cervical pericord space. Also the level of obstructions could be determined in all OHs. The analysis of MR CSF flow images may give us valuable information on the site of obstruction, explaining the cause of hydrocephalus, thus deciding the necessity of shunting procedures using in vivo images.

Cine phase-contrast MR imaging in normal pressure hydrocephalus patients: relation to surgical outcome

Phase-contrast cine MR flow imaging through the aqueduct was used to establish the diagnosis of normal pressure hydrocephalus (NPH), and to predict outcome after shunting. From 1990-1994 16 patients, who were participants in the Dutch Normal Pressure Hydrocephalus Study [3], were studied. The patients included in this study met clinical and CT-scan criteria as described in this study, underwent cine phase-contrast MR imaging prior to placement of a CSF shunt, and had a follow-up 12 months after the operation. Claustrophobic patients, patients with a pacemaker or extremely agitated patients were excluded. Normal Flux was calculated in each patients, as the average difference in caudal and rostral flux (Fdiff) +2 times standard deviation (0.97 cc/sec) [2]. The clinical outcome was measured with a modified scale of activities of daily living (ADL) as described by Rankin. Of the 16 patients, 8 could not be evaluated due to restlessness during MR measurements, disabling cerebral vascular accidents or death before the end of the follow-up period. Of the remaining 8 patients, 5 had a normal flux, of which only one improved. Two patients had a Fdiff twice the normal range, which improved in both patients. One patient had no measurable flux, consistent with an aqueduct stenosis; he too improved. Overall, there was a concordance of MR findings with final outcome after shunting in 7 out of 8 patients. This pilot study, therefore, support the need to further evaluate flow with MR imaging techniques to select patients with shunt responsive NPH.