Diagnostic Tools in Hydrocephalus

Role of Diffusion Tensor Imaging in Diagnosis and Estimation of Shunt Effect for Hydrocephalus in Stroke Patients: A Narrative Review

Hydrocephalus is a dilatation of the brain ventricular system by the accumulation of cerebrospinal fluid within the ventricle caused by impaired cerebrospinal fluid circulation or clearance. A diagnosis of hydrocephalus at the chronic stage of stroke has been mainly made by clinical features and radiologic findings on brain computed tomography and magnetic resonance imaging. On the other hand, it could not determine the effect of hydrocephalus or shunt effect on the periventricular neural structures. By contrast, these effects on the periventricular neural structures can be estimated using diffusion tensor imaging (DTI). This article reviewed 10 DTI-based studies related to the diagnosis and estimation of the shunt effect for hydrocephalus in stroke patients. These studies suggest that DTI could be a useful diagnostic and estimation tool of the shunt effect for hydrocephalus in stroke patients. In particular, some studies suggested that fractional anisotropy value in the periventricular white matter could be a diagnostic biomarker for hydrocephalus. As a result, the role of DTI in diagnosing and estimating the shunt effect for hydrocephalus in stroke patients appears to be promising. However, the number of studies and patients of all reviewed studies were limited (10 studies including a total of 58 stroke patients with heterogenous brain pathologies).

High Periventricular T1 Relaxation Times Predict Gait Improvement After Spinal Tap in Patients with Idiopathic Normal Pressure Hydrocephalus

PURPOSE

The diagnosis of idiopathic normal pressure hydrocephalus (iNPH) can be challenging. Aim of this study was to use a novel T1 mapping method to enrich the diagnostic work-up of patients with suspected iNPH.

METHODS

Using 3T magnetic resonance imaging (MRI) we prospectively evaluated rapid high-resolution T1 mapping at 0.5 mm resolution and 4 s acquisition time in 15 patients with suspected iNPH and 8 age-matched, healthy controls. T1 mapping in axial sections of the cerebrum, clinical and neuropsychological testing were performed prior to and after cerebrospinal fluid tap test (CSF-TT). T1 relaxation times were measured in 5 predefined periventricular regions.

RESULTS

All 15 patients with suspected iNPH showed gait impairment, 13 (86.6%) showed signs of cognitive impairment and 8 (53.3%) patients had urinary incontinence. Gait improvement was noted in 12 patients (80%) after CSF-TT. T1 relaxation times in all periventricular regions were elevated in patients with iNPH compared to controls with the most pronounced differences in the anterior (1006 ± 93 ms vs. 911 ± 77 ms; p = 0.023) and posterior horns (983 ± 103 ms vs. 893 ± 68 ms; p = 0.037) of the lateral ventricles. Montreal cognitive assessment (MoCA) scores at baseline were negatively correlated with T1 relaxation times (r < -0.5, p < 0.02). Higher T1 relaxation times were significantly correlated with an improvement of the 3‑m timed up and go test (r > 0.6 and p < 0.03) after CSF-TT.

CONCLUSION

In iNPH-patients, periventricular T1 relaxation times are increased compared to age-matched controls and predict gait improvement after CSF-TT. T1 mapping might enrich iNPH work-up and might be useful to indicate permanent shunting.

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.

Paradigm-shift: radiological changes in the asymptomatic iNPH-patient to be: an observational study

BACKGROUND

Many radiological signs are known for the diagnosis of idiopathic normal pressure hydrocephalus (iNPH). However, there is little information about these signs in the pre-symptomatic phase. For pathophysiological investigative purposes we conducted a descriptive image analysis study on pre-symptomatic patients.

METHODS

Patients that had contact with either the neurological or neurosurgical department of the university hospital Tuebingen from 2010 through 2016 with magnetic resonance images > 3 years before onset of symptoms, were included. The date of onset and severity of symptoms, date of first imaging and birth date were recorded. Evan's index (EI), width of the third ventricle (3VW), tight high convexity (THC), Sylvian fissure, extent of white matter hyperintensities and aqueductal flow were assessed in images before and around symptom onset.

RESULTS

Ten patients were included. In all ten patients the first symptom was gait disturbance. Nine of ten pre-symptomatic images showed classic signs for iNPH. EI showed a significant increase between the pre-symptomatic and symptomatic phase. 3VW showed a trend for increase without significance. THC changed back and forth over time within some patients.

CONCLUSIONS

In accordance with the scarce literature available, radiological changes are present at least 3 years before onset of iNPH-symptoms. EI seems to be a robust measure for pre-symptomatic radiological changes. Extrapolating the data, the development of iNPH typical changes might be an insidious process and the development of THC might be a variable and non-linear process. Further studies with larger sample sizes are necessary to put these findings into the pathophysiological perspective for the development of iNPH.

Diffusion tensor tractography measurement of the distance between corticospinal tracts in patients with spontaneous intraventricular haemorrhage

Objective

The difference in the widest distance between corticospinal tracts (CST) on diffusion tensor tractography (DTT) in stroke patients with hydrocephalus was investigated retrospectively.

Methods

Distances were measured on an axial slice of the corona radiata, which provided the widest distance between CSTs. Two distances were measured, the absolute distance – the distance between the most medial point of the CSTs and the relative distance – calculated as a percentage of the absolute distance.

Results

The absolute distances of CSTs were 55.34 mm for the patient group and 46.75 mm for the control group. The relative distances of the CSTs were 44.12% and 35.96% for the patient group and the control group. Significant differences in the absolute and relative distances of CSTs were observed between the patient and the control group.

Conclusion

These results suggest that the absolute and relative distances between CSTs might be used to diagnose hydrocephalus in stroke patients.

Periventricular hyperintensity in children with hydrocephalus

BACKGROUND

Magnetic resonance images of children with hydrocephalus often include a rim of hyperintensity in the periventricular white matter (halo).

OBJECTIVE

The purpose of this study was to decide between the hypothesis that the halo is caused by cerebrospinal fluid (CSF) flow during the cardiac cycle, and the alternate hypothesis that the halo is caused by anatomical changes (stretching and compression of white matter).

MATERIALS AND METHODS

Participants were selected from a multicenter imaging study of pediatric hydrocephalus. We compared 19 children with hydrocephalus to a group of 52 controls. We quantified ventricle enlargement using the frontal-occipital horn ratio. We conducted qualitative and quantitative analysis of diffusion tensor imaging in the corpus callosum and posterior limb of the internal capsule. Parameters included the fractional anisotropy (FA), mean diffusivity, axial diffusivity and radial diffusivity.

RESULTS

The halo was seen in 16 of the 19 children with hydrocephalus but not in the controls. The corpus callosum of the hydrocephalus group demonstrated FA values that were significantly decreased from those in the control group (P = 4 · 10(-6)), and highly significant increases were seen in the mean diffusivity and radial diffusivity in the hydrocephalus group. In the posterior limb of the internal capsule the FA values of the hydrocephalus group were higher than those for the control group (P = 0.002), and higher values in the hydrocephalus group were also noted in the axial diffusivity. We noted correlations between the diffusion parameters and the frontal-occipital horn ratio.

CONCLUSION

Our results strongly support the hypothesis that the halo finding in hydrocephalus is caused by structural changes rather than pulsatile CSF flow.

Differentiating shunt-responsive normal pressure hydrocephalus from Alzheimer disease and normal aging: pilot study using automated MRI brain tissue segmentation

Evidence suggests that normal pressure hydrocephalus (NPH) is underdiagnosed in day to day radiologic practice, and differentiating NPH from cerebral atrophy due to other neurodegenerative diseases and normal aging remains a challenge. To better characterize NPH, we test the hypothesis that a prediction model based on automated MRI brain tissue segmentation can help differentiate shunt-responsive NPH patients from cerebral atrophy due to Alzheimer disease (AD) and normal aging. Brain segmentation into gray and white matter (GM, WM), and intracranial cerebrospinal fluid was derived from pre-shunt T1-weighted MRI of 15 shunt-responsive NPH patients (9 men, 72.6 ± 8.0 years-old), 17 AD patients (10 men, 72.1 ± 11.0 years-old) chosen as a representative of cerebral atrophy in this age group; and 18 matched healthy elderly controls (HC, 7 men, 69.7 ± 7.0 years old). A multinomial prediction model was generated based on brain tissue volume distributions. GM decrease of 33% relative to HC characterized AD (P < 0.005). High preoperative ventricular and near normal GM volumes characterized NPH. A multinomial regression model based on gender, GM and ventricular volume had 96.3% accuracy differentiating NPH from AD and HC. In conclusion, automated MRI brain tissue segmentation differentiates shunt-responsive NPH with high accuracy from atrophy due to AD and normal aging. This method may improve diagnosis of NPH and improve our ability to distinguish normal from pathologic aging.

Diffusion tensor imaging following shunt in a patient with hydrocephalus

We report on a patient with hydrocephalus who was evaluated by diffusion tensor imaging (DTI) follow-up study before and after a shunt operation. A 48-year-old male patient and 6 age-matched control subjects were evaluated. The patient presented with hydrocephalus due to hemorrhage caused by the rupture of a right middle cerebral artery bifurcation aneurysm. Three longitudinal DTIs were acquired from the patient (pre-shunt, post-shunt 2 weeks, and post-shunt 8 weeks). The fractional anisotrophy values in the adjacent structures of the lateral ventricle, which were increased before the shunt operation, were decreased after the shunt operation. We think that DTI could be a useful tool for the evaluation of hydrocephalus.

The role of the neurologist in the longitudinal management of normal pressure hydrocephalus

BACKGROUND

Since normal pressure hydrocephalus (NPH) was first described in 1965, neurologists have been involved in the initial diagnostic evaluation for it but have rarely followed patients specifically to monitor response to therapy after shunt surgery.

REVIEW SUMMARY

The potential role for the neurologist in the longitudinal management of NPH has broadened, partly because of improvement in the tools used to diagnose and treat NPH and partly because of progress in understanding how NPH mimics and interacts with other common disorders of the elderly. The interplay of Alzheimer dementia, vascular dementia, Parkinson disease, and spinal stenosis with NPH presents the clinician with a patient profile that may be challenging to assess. Neurologists also face a broad differential spectrum of less common neurologic diseases that may present with similar signs (including ventriculomegaly) and symptoms; these diseases include frontotemporal dementia, progressive supranuclear palsy, Lewy body disease, corticobasal degeneration, Huntington disease, spongiform encephalopathy, and multiple-system atrophy.

CONCLUSIONS

The neurologist is in a unique position to differentiate NPH from alternative diagnoses, to suggest management strategies for patients with concomitant NPH and another neurologic disorder, and to participate in longitudinal management of NPH.

Adjustable shunt valve-induced magnetic resonance imaging artifact: a comparative study

OBJECT

In this paper, the authors' goal was to compare the artifact induced by implanted (in vivo) adjustable shunt valves in spin echo, diffusion weighted (DW), and gradient echo MR imaging pulse sequences.

METHODS

The MR images obtained in 8 patients with proGAV and 6 patients with Strata II adjustable shunt valves were assessed for artifact areas in different planes as well as the total volume for different pulse sequences.

RESULTS

Artifacts induced by the Strata II valve were significantly larger than those induced by proGAV valve in spin echo MR imaging pulse sequence (29,761 vs 2450 mm(3) on T2-weighted fast spin echo, p = 0.003) and DW images (100,138 vs 38,955 mm(3), p = 0.025). Artifacts were more marked on DW MR images than on spin echo pulse sequence for both valve types.

CONCLUSIONS

Adjustable valve-induced artifacts can conceal brain pathology on MR images. This should influence the choice of valve implantation site and the type of valve used. The effect of artifacts on DW images should be highlighted pending the development of less MR imaging artifact-inducing adjustable shunt valves.

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.

Noninvasive MRI assessment of intracranial compliance in idiopathic normal pressure hydrocephalus

PURPOSE

To assess the state and dynamics of the intracranial system in idiopathic normal-pressure hydrocephalus (I-NPH), we determined intracranial compliance using magnetic resonance imaging (MRI).

MATERIALS AND METHODS

The intracranial compliance index (ICCI), which was defined as the ratio of the peak-to-peak intracranial volume change (ICVC(p-p)) to the peak-to-peak cerebrospinal fluid (CSF) pressure gradient (PG(p-p)) during the cardiac cycle, was obtained from the net transcranial blood and CSF flow measured with phase-contrast (PC) cine MRI. ICCI was determined in patients with I-NPH (N = 7), brain atrophy, or asymptomatic ventricular dilation (VD) (N = 6), and in healthy volunteers (control group; N = 11). The changes in ICCI indices were also analyzed after a CSF tap test (N = 2).

RESULTS

The ICCI in the I-NPH group was significantly lower than in the control and VD groups, whereas no difference was found between the control and VD groups. The ICVC(p-p) was also lower than in the control and VD groups. However, no significant difference was found in the PG(p-p) between groups. The ICCI increased after the tap test.

CONCLUSION

Intracranial compliance analysis with MRI makes it possible to noninvasively obtain more detailed information of intracranial biomechanics in the I-NPH and to assist in the diagnosis of I-NPH.

Papilledema in the Assessment of Ventriculomegaly

To determine whether ventriculomegaly is associated with ongoing increased intracranial pressure (ICP), physicians often rely on corroborative imaging features such as altered periependymal signal, distortion of ventricular shape, subarachnoid space flattening, and an increase in ventricular size over time. In 2 patients with new headache and altered mental status, symptoms and ventriculomegaly were dismissed as long-standing and not reflective of current ICP elevation. In the first patient, ICP was considered normal because there were no corroborative imaging features of elevated ICP. In the second patient, ICP was considered normal because ventricular size was stable over a 1-year period. The diagnosis of ICP elevation was finally made by ICP monitoring after papilledema was recognized. Ventriculoperitoneal shunting rapidly resolved the papilledema and markedly improved mentation. Brain imaging may often be an unreliable guide to the presence of elevated ICP. In such patients, the finding of papilledema is a critical determinant of management.

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.

Diagnosing idiopathic normal-pressure hydrocephalus

OBJECTIVE

The precise incidence and prevalence of idiopathic normal-pressure hydrocephalus (INPH) is not known, and evidence-based clinical diagnostic criteria have not been developed previously. This report contains evidence-based guidelines for clinical diagnosis of INPH that are intended to facilitate future epidemiological studies of INPH, promote earlier and more accurate diagnosis, and ultimately improve treatment outcome.

METHODS

The criteria for the diagnosis of INPH are based on evidence from the medical literature, supplemented as necessary by expert opinion. From 1966 to 2003, 653 publications on "normal-pressure hydrocephalus" were cited in MEDLINE, including 29 articles that met the more stringent criteria of including "idiopathic normal-pressure hydrocephalus" in their title. Additional studies were considered that explicitly identified INPH cases and/or specified the criteria for a diagnosis of INPH. Studies were graded according to the class of evidence and results summarized in evidentiary tables. For issues of clinical relevance that lacked substantive evidence from the medical literature, the opinions of consulting experts were considered and contributed to "Options."

RESULTS

Evidence-based guidelines for the clinical diagnosis of INPH have been developed. A detailed understanding of the range of clinical manifestations of this disorder and adherence to practice guidelines should improve the timely and accurate recognition of this disorder.

CONCLUSION

It is recommended that INPH be classified into probable, possible, and unlikely categories. We hope that these criteria will be widely applied in clinical practice and will promote greater consistency in patient selection in future clinical investigations involving INPH.

Surgical management of hydrocephalic dementia in Paget's disease of bone: the 6-year outcome of ventriculo-peritoneal shunting

Paget's disease of bone is a chronic progressive skeletal disorder usually occurring in the long bones and skull of older adults and elderly persons. In the skull, softening of the skull base may lead to basilar impression and consequently obstruction of the cerebrospinal fluid through the basilar cisterns, resulting ventricular enlargement in association with gait difficulties, incontinence and dementia: a syndrome resembling normal pressure hydrocephalus. The optimal management of hydrocephalus associated with Paget's disease of the skull is not well documented and is still debated. We report a patient with hydrocephalic dementia linked to Paget's disease of the skull who showed marked sustained improvement in her neurological condition after ventriculo-peritoneal shunt insertion. We have now followed this patient for 6 years. Our experience supports the view that ventricular shunting is the procedure of choice for treating hydrocephalus linked to the Paget's disease of bone and is best carried out in the early stages of the illness.

Signal-to-noise ratio behavior of steady-state free precession

Steady-state free precession (SSFP) is a rapid gradient-echo imaging technique that has recently gained popularity and is used in a variety of applications, including cardiac and real-time imaging, because of its high signal and favorable contrast between blood and myocardium. The purpose of this work was to examine the signal-to-noise ratio (SNR) behavior of images acquired with SSFP, and the dependence of SNR on imaging parameters such as TR, bandwidth, and image resolution, and the use of multi-echo sequences. In this work it is shown that the SNR of SSFP sequences is dependent only on pulse sequence efficiency, voxel dimensions, and relaxation parameters (T1 and T2). Notably, SNR is insensitive to bandwidth unless increases in bandwidth significantly decrease efficiency. Finally, we examined the relationship between pulse sequence performance (TR and efficiency) and gradient performance (maximum gradient strength and slew rate) for several imaging scenarios, including multi-echo sequences, to determine the optimum matching of maximum gradient strength and slew rate for gradient hardware designs. For standard modern gradient hardware (40 mT/m and 150 mT/m/ms), we found that the maximum gradient strength is more than adequate for the imaging resolution that is commonly encountered with rapid scouting (3 mm x 4 mm x 10 mm voxel). It is well matched for typical CINE and real-time cardiac imaging applications (1.5 mm x 2 mm x 6 mm voxel), and is inadequate for optimal matching with slew rate for high-resolution applications such as musculoskeletal imaging (0.5 x 0.8 x 3 mm voxel). For the lower-resolution methods, efficiency could be improved with higher slew rates; this provokes interest in designing methods for limiting dB/dt peripherally while achieving high switching rates in the imaging field of view. The use of multi-echo SSFP acquisitions leads to substantial improvements in sequence performance (i.e., increased efficiency and shorter TR).

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.

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.

Routine placement of a ventricular reservoir at endoscopic third ventriculostomy

OBJECTIVE

Endoscopic third ventriculostomy (ETV) failure may be abrupt in onset, causing a potentially life-threatening increase in intracranial pressure. ETV failure may also have a more insidious onset, and in these cases, diagnosis on clinical and radiological grounds can be difficult. This study evaluates the usefulness of routine ventricular reservoir placement at the time of ETV for subsequent emergency ventricular access or the diagnosis of ETV failure.

METHODS

A retrospective review of 84 consecutive patients undergoing ETV with routine insertion of a ventricular reservoir during a 4-year period (1996-2000) was undertaken. The mean follow-up period was 14.8 months. End points for ETV failure were shunt insertion or revision of ETV. The diagnostic and therapeutic use of the reservoir was quantified.

RESULTS

The reservoir was used in 32% of patients (n = 27). The reservoir allowed life-saving emergency ventricular access in two cases of acute recurrent hydrocephalus. In patients with symptoms but equivocal radiological evidence of recurrent hydrocephalus, the reservoir allowed for assessment of intracranial pressure (n = 19) and/or a therapeutic trial of cerebrospinal fluid aspiration (n = 5). Seven of these patients subsequently required revision ETV or shunt insertion. In the 14 patients who had normal intracranial pressure, conservative management was successful. The reservoir also facilitated intrathecal drug administration for postoperative ventriculitis (n = 2). No patients requested reservoir removal.

CONCLUSION

Routine insertion of a ventricular reservoir allows life-saving emergency therapeutic cerebrospinal fluid aspiration to be performed for sudden neurological deterioration caused by ventriculostomy failure. It also assists in the diagnosis of ETV failure and allows intrathecal drug administration.