Conductance to outflow of CSF in normal pressure hydrocephalus

Pseudohypoxic brain swelling and secondary hydrocephalus with pseudomeningocele after lumbar surgery: a case report

BACKGROUND

Postoperative intracranial complications are rare in spine surgery not including cranial procedures. We describe an uncommon case of pseudohypoxic brain swelling (PHBS) and secondary hydrocephalus after transforaminal lumbar interbody fusion (TLIF) presenting as impaired consciousness and repeated seizures.

CASE PRESENTATION

A 65-year-old man underwent L4-5 TLIF for lumbar spondylolisthesis and began experiencing generalized seizures immediately postoperatively. Computed tomography (CT) revealed diffuse cerebral edema-like hypoxic ischemic encephalopathy. He was transported to our hospital, at which time epidural drainage was halted and anti-edema therapy was commenced. His impaired consciousness improved. However, he suffered secondary hydrocephalus due to continuous bleeding from a dural defect and spinal epidural fluid collection 3 months later. Following the completion of dural repair and insertion of a ventriculoperitoneal shunt, his neurologic symptoms and neuroimaging findings improved significantly.

CONCLUSIONS

PHBS can be considered in patients with unexpected neurological deterioration following lumbar spine surgery even with the absence of documented durotomy. This might be due to postoperative intracranial hypotension-associated venous congestion, and to be distinguished from the more common postoperative cerebral ischemic events-caused by arterial or venous occlusions-or anesthetics complications.

Invasive Preoperative Investigations in Idiopathic Normal Pressure Hydrocephalus: A Comprehensive Review

Idiopathic normal pressure hydrocephalus (iNPH) is a neurological disorder characterized by the triad of gait disturbance, cognitive impairment, and urinary incontinence. The condition is diagnosed mainly in older adults and is associated with ventricular enlargement without an increase in cerebrospinal fluid pressure. The clinical assessment involves a detailed medical history, physical examination, and cognitive testing. Neuroimaging is an essential part of the diagnostic workup for iNPH. However, to determine the suitability of patients for shunt surgery, a range of invasive preoperative investigations are employed. This narrative review aims to provide a comprehensive analysis of the current literature on invasive preoperative investigations in iNPH, focusing primarily on the lumbar infusion test, cerebrospinal fluid drainage tests, and continuous intracranial pressure monitoring. The strengths and limitations of each method, as well as their potential impact on treatment outcomes, are discussed.

Prognostic value of the pulse pressure amplitudes, time to reach the plateau and the slope obtained in the lumbar infusion test for the study of idiophatic normal pressure hydrocephalus

BACKGROUND AND OBJECTIVE

To study the prognostic value of the resistance to the cerebrospinal fluid outflow (Rout) obtained in the lumbar infusion test in idiopathic normal pressure hydrocephalus (iNPH), as well as the pulse pressure amplitudes in the different periods of the test and other new variables extracted by Neuropicture® software.

MATERIAL AND METHODS

Patients with 'probable iNPH' who underwent a lumbar infusion test were retrospectively revised. The positive predictive values (PPV) of the cutoff point of the best prognostic accuracy of the Rout, the basal pulse pressure amplitude (AMPo), the pulse pressure amplitude during the first 10 min (AMP_10min), the plateau pulse pressure amplitude (AMPmes), the Rout pulse pressure amplitude (AMP_Rout), the time to reach the plateau (T), and the slope until reaching the plateau were determined. Patients were categorized either as responders or non-responders.

RESULTS

The study included 64 responders patients and 16 non-responders patients. The PPV of Rout > 15 mmHg/mL/min was 91.7%; AMPo > 2.34 mmHg: 91.3%; AMP_{10 min} > 4.34 mmHg: 83.3%; AMPmes > 12.44 mmHg: 84.6%; AMP_Rout > 6.34 mmHg: 85%; T < 634 s: 86.7%; p > 0.040 mmHg/s: 96.3%.

CONCLUSIONS

Rout is a valid criterion to indicate a ventricular shunt. Pulse pressure amplitudes in the different periods of the lumbar infusion test, in addition to T and P, are other variables whose positivity is indicative of shunt response and should be considered in the diagnostic protocol of the iNPH.

Prognostic value of the pulse pressure amplitudes, time to reach the plateau and the slope obtained in the lumbar infusion test for the study of idiophatic normal pressure hydrocephalus

BACKGROUND AND OBJECTIVE

To study the prognostic value of the resistance to the cerebrospinal fluid outflow (Rout) obtained in the lumbar infusion test in idiopathic normal pressure hydrocephalus (iNPH), as well as the pulse pressure amplitudes in the different periods of the test and other new variables extracted by Neuropicture® software.

MATERIAL AND METHODS

Patients with ́probable iNPH́ who underwent a lumbar infusion test were retrospectively revised. The positive predictive values (PPV) of the cutoff point of the best prognostic accuracy of the Rout, the basal pulse pressure amplitude (AMP0), the pulse pressure amplitude during the first 10minutes (AMP10min), the plateau pulse pressure amplitude (AMPmes), the Rout pulse pressure amplitude (AMPRout), the time to reach the plateau (T), and the slope until reaching the plateau were determined. Patients were categorized either as responders or non-responders.

RESULTS

The study included 64 responders patients and 16 non-responders patients. The PPV of Rout> 15mmHg/ml/min was 91.7%; AMP0> 2.34mmHg: 91.3%; AMP10min>4.34mmHg: 83.3%; AMPmes>12.44mmHg: 84.6%; AMPRout>6.34mmHg: 85%; T <634seconds: 86.7%; P>0.040mmHg/sec: 96.3%.

CONCLUSIONS

Rout is a valid criterion to indicate a ventricular shunt. Pulse pressure amplitudes in the different periods of the lumbar infusion test, in addition to T and P, are other variables whose positivity is indicative of shunt response and should be considered in the diagnostic protocol of the iNPH.

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

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

Timing of intraventricular infusion test for diagnosing idiopathic normal pressure hydrocephalus

BACKGROUND

Infusion tests, which measure resistance to outflow (R_out), are used in selecting patients suspected for idiopathic normal pressure hydrocephalus (iNPH) for shunt surgery. Infusion tests can be performed through an external ventricular drain (EVD). A 24-hour time gap from EVD insertion to an infusion test is a routine practice at our department due to concerns that the surgical procedure might influence the test results in the immediate postoperative period. The objective of the study was to investigate if timing of an intraventricular infusion test influences the results of the test in patients suspected for iNPH.

METHODS

Ten patients scheduled for an intraventricular infusion test were included. Measurements of baseline intracranial pressure (ICP) and plateau ICP were obtained during constant rate intraventricular infusion test performed at two time points (1 and 24 h after EVD insertion) and R_out was calculated from these measures and compared within patients.

RESULTS

Eight patients completed both infusion tests. In one of the 18 infusion tests performed, it was not possible to define an ICP plateau and this infusion test was excluded, leaving 7 paired infusion tests. Median R_out was 12.9 mmHg/ml/min (range 7.0-22.0) 1 h after EVD insertion and 11.3 mmHg/ml/min (range 7.8-18.1) after 24 h. Overall, there were no statistically significant differences in R_out (P = 0.83), baseline ICP (P = 0.70), or plateau ICP (P = 0.81) between the recordings performed 1 h and 24 h after EVD insertion. For two of the seven patients with paired infusion tests, there was poor agreement between R_out values at 1 and 24 h.

CONCLUSION

Overall, R_out estimates do not change significantly between 1 and 24 h after EVD insertion. We therefore propose that infusion tests can be performed shortly after surgery to reduce the period of indwelling EVD and duration of hospitalization.

Normal-pressure hydrocephalus: A critical review

Normal-pressure hydrocephalus (NPH) is a potentially reversible syndrome characterized by enlarged cerebral ventricles (ventriculomegaly), cognitive impairment, gait apraxia and urinary incontinence. A critical review of the concept, pathophysiology, diagnosis, and treatment of both idiopathic and secondary NPH was conducted. We searched Medline and PubMed databases from January 2012 to December 2018 using the keywords "normal-pressure hydrocephalus" / "idiopathic normal-pressure hydrocephalus" / "secondary normal-pressure hydrocephalus" / "NPH" / "ventriculoperitoneal shunt". The initial search produced 341 hits. After careful selection, a total of 54 articles were chosen and additional relevant studies were included during the process of writing this article. NPH is an important cause of potentially reversible dementia, frequent falls and recurrent urinary infections in the elderly. The clinical and imaging features of NPH may be incomplete or nonspecific, posing a diagnostic challenge for medical doctors and often requiring expert assessment to minimize unsuccessful surgical treatments. Recent advances resulting from the use of non-invasive MRI methods for quantifying cerebral blood flow, in particular arterial spin-labeling (ASL), and the frequent association of NPH and obstructive sleep apnea (OSA), offer new avenues to understand and treat NPH.

Revisiting secondary normal pressure hydrocephalus: does it exist? A review

OBJECTIVE There are several etiologies that can lead to the development of secondary normal pressure hydrocephalus (sNPH). The aim of this study was to evaluate the etiology, diagnosis, treatment, and outcome in patients with sNPH and to highlight important differences between the separate etiologies. METHODS A comprehensive review of the literature was performed to identify studies conducted between 1965 and 2015 that included data regarding the etiology, treatment, diagnosis, and outcome in patients with sNPH. Sixty-four studies with a total of 1309 patients were included. The inclusion criteria of this study were articles that were written in English, included more than 2 patients with the diagnosis of sNPH, and contained data regarding the etiology, diagnosis, treatment, or outcome of NPH. The most common assessment of clinical improvement was based on the Stein and Langfitt grading scale or equivalent improvement on other alternative ordinal grading scales. RESULTS The main etiologies of sNPH were subarachnoid hemorrhage (SAH) in 46.5%, head trauma in 29%, intracranial malignancies in 6.2%, meningoencephalitis in 5%, and cerebrovascular disease in 4.5% of patients. In 71.9% of patients the sNPH was treated with ventriculoperitoneal shunt placement, and 24.4% had placement of a ventriculoatrial shunt. Clinical improvement after shunt placement was reported in 74.4% and excellent clinical improvement in 58% of patients with sNPH. The mean follow-up period after shunt placement was 13 months. Improvement was seen in 84.2% of patients with SAH, 83% of patients with head trauma, 86.4% of patients with brain tumors, 75% of patients with meningoencephalitis, and 64.7% of patients with NPH secondary to stroke. CONCLUSIONS Secondary NPH encompasses a diverse group of clinical manifestations associated with a subset of patients with acquired hydrocephalus. The most common etiologies of sNPH include SAH and traumatic brain injury. Secondary NPH does indeed exist, and should be differentiated from idiopathic NPH based on outcome and on clinical, pathophysiological, and epidemiological characteristics, but should not be considered as a separate entity.

Hydrocephalus: an underrated long-term complication of microvascular decompression for trigeminal neuralgia. A single institute experience

BACKGROUND

Hydrocephalus is a common complication of posterior fossa surgery, but its real incidence after microvascular decompression (MVD) for idiopathic trigeminal neuralgia (TN) still remains unclear. The aim of this study was to focus on the potential association between MVD and hydrocephalus as a surgery-related complication.

METHODS

All patients who underwent MVD procedure for idiopathic TN at our institute between 2009 and 2014 were reviewed to search for early or late postoperative hydrocephalus.

RESULTS

There were 259 consecutive patients affected by idiopathic TN who underwent MVD procedure at our institution between 2009 and 2014 (113 men, 146 women; mean age 59 years, range 30-87 years; mean follow-up 40.92 months, range 8-48 months). Nine patients (3.47 %) developed communicating hydrocephalus after hospital discharge and underwent standard ventriculo-peritoneal shunt. No cases of acute hydrocephalus were noticed.

CONCLUSIONS

Our study suggests that late communicating hydrocephalus may be an underrated potential long-term complication of MVD surgery.

Repeated assessment of suspected normal pressure hydrocephalus in non-shunted cases. A prospective study based on the constant rate lumbar infusion test

BACKGROUND

Only a few reports have been published on the natural history of non-shunted patients suspected of having NPH. The aim of this study is to follow up a group of such cases.

METHODS

It was possible to follow up 27 patients who had not been qualified for shunting after the primary diagnosis. An assessment of Hakim's triad was performed, together with an analysis of radiological parameters and the results of lumbar infusion tests (LITs), both on admission and at the later date (on average, after 5.6 months). All parameters were analyzed with respect to periventricular lucency (PVL), atrophy, type of NPH, and the age of the patients.

RESULTS

There were no deteriorations and six patients improved. Those who were over 50 and who had no PVL or secondary NPH tended to improve more frequently. Significant improvement of dementia was noted (p = 0.042) in all cases, and in the group of patients without PVL (p = 0.04). The size of the ventricles did not change significantly. The values of the resistance to outflow (R), elastance (E), and ICP remained stable.

CONCLUSIONS

Analysis of our series revealed that the patients suspected of having NPH who had not been qualified for shunting did not deteriorate, while some of them even improved significantly as far as the level of dementia was concerned. As the CT and LIT parameters remained stable, there were no indications for repeating these examinations, at least within the period of nearly 6 months, which followed the primary diagnosis.

The Dynamic Gait Index in Evaluating Patients with Normal Pressure Hydrocephalus for Cerebrospinal Fluid Diversion

BACKGROUND

Diagnosing normal pressure hydrocephalus (NPH) remains challenging. Most clinical tests currently used to evaluate suspected NPH patients for shunt surgery are invasive, require inpatient admission, and are not without complications. An objective, noninvasive, and low-cost alternative would be ideal.

METHODS

A retrospective review was performed of prospectively collected dynamic gait index (DGI) scores, obtained at baseline and on every day of a 3- to 5-day lumbar cerebrospinal fluid (CSF) drainage trial on patients with suspected NPH at our institution.

RESULTS

Between 2003 and 2014, 170 patients were suspected to have primary NPH (166, 97.6%) or secondary NPH (4, 2.4%). Using responsiveness to lumbar CSF drainage and subsequent shunting as the reference standard, we found that a baseline DGI ≥ 7 was found to have significant ability in selecting patients for permanent CSF diverting shunt surgery: sensitivity of 84.2% (95% confidence interval [95% CI]: 75.6%-90.2%), specificity of 80.6% (95% CI 70.0%-88.0%), and diagnostic odds ratio of 22.1 (95% CI 9.9-49.3).

CONCLUSIONS

A baseline DGI ≥ 7 appears to provide an objective, low-cost, noninvasive measure to select patients with suspected NPH for a positive response to CSF diversion with high sensitivity, specificity and diagnostic odds ratio.

Repeatability of cerebrospinal fluid constant rate infusion study

OBJECTIVE

Infusion tests are important tools to assess cerebrospinal fluid (CSF)dynamics used in the preoperative selection of patients for shunt surgery, or to predict the scope of improvement from shunt revision. The aim of this study was to assess the repeatability of the key quantitative parameters describing CSF dynamics that are determined with infusion testing.

MATERIALS AND METHODS

Eighteen patients in whom a constant infusion test was repeated within 102 days, without any intermediate surgical intervention, were studied. From each test baseline ICP, baseline pulse amplitude, outflow resistance, elastance coefficient and slope of the amplitude-pressure line were calculated and investigated with a regression and Bland-Altman analysis.

RESULTS

Significant correlations (P < 0.01) were found for the outflow resistance (R = 0.96), the elastance coefficient (R = 0.778) and the slope of the amplitude-pressure line (R = 0.876). The estimated 95% confidence level for outflow resistance was 3 mmHg/ml min. Likewise, the elastance coefficient lay within a range of 0.16/ml and the slope of the amplitude-pressure line within 0.25. The most inconsistent parameter found were baseline ICP (R = 0.272) and baseline pulse amplitude (R = 0.171).

CONCLUSION

The results of this study imply that the parameters resulting from an infusion study have to be considered within a range rather than as an absolute value.

A randomised trial of high and low pressure level settings on an adjustable ventriculoperitoneal shunt valve for idiopathic normal pressure hydrocephalus: results of the Dutch evaluation programme Strata shunt (DEPSS) trial

BACKGROUND

In treating idiopathic normal pressure hydrocephalus (INPH) with a shunt there is always a risk of underdrainage or overdrainage. The hypothesis is tested whether patients treated using an adjustable valve preset at the highest opening pressure leads to comparable good clinical results with less subdural effusions than in a control group with an opening pressure preset at a low pressure level.

METHODS

A multicentre prospective randomised trial was performed on a total of 58 patients suspected of INPH. Thirty patients were assigned to (control) group 1 and received a Strata shunt (Medtronic, Goleta, USA) with the valve preset at a performance level (PL) of 1.0, while 28 patients were assigned to group 2 and received a Strata shunt with the valve preset at PL 2.5. In this group the PL was allowed to be lowered until improvement or radiological signs of overdrainage were met.

RESULTS

Significantly more subdural effusions were observed in the improved patients of group 1. There was no statistically significant difference in improvement between both groups overall.

CONCLUSIONS

On the basis of this multicentre prospective randomised trial it is to be recommended to treat patients with INPH with a shunt with an adjustable valve, preset at the highest opening pressure and lowered until clinical improvement or radiological signs of overdrainage occur although slower improvement and more shunt adjustments might be the consequence.

Pulsatility in CSF dynamics: pathophysiology of idiopathic normal pressure hydrocephalus

BACKGROUND

It is suggested that disturbed CSF dynamics are involved in the pathophysiology of idiopathic normal pressure hydrocephalus (INPH). The pulsatility curve describes the relationship between intracranial pressure (ICP) and the amplitude of cardiac related ICP pulsations. The position of baseline ICP on the curve provides information about the physiological state of the CSF dynamic system. The objective of the study was to investigate if shunt surgery modifies the pulsatility curve and the baseline position on the curve, and how this relates to gait improvement in INPH.

METHODS

51 INPH patients were investigated with lumbar CSF dynamic investigations preoperatively and 5 months after shunt surgery. During the investigation, ICP was measured at baseline, and then a CSF sample was removed, resulting in pressure reduction. After this, ICP was regulated with an automated infusion protocol, with a maximum increase of 24 mm Hg above baseline. The pulsatility curve was thus determined in a wide range of ICP values. Gait improvement was defined as a gait speed increase ≥0.1 m/s.

RESULTS

The pulsatility curve was unaltered by shunting. Baseline ICP and amplitude were reduced (-3.0±2.9 mm Hg; -1.1±1.5 mm Hg; p<0.05, n=51). Amplitude reduction was larger for gait improvers (-1.2±1.6 mm Hg, n=42) than non-improvers (-0.2±0.5 mm Hg, n=9) (p<0.05) although mean ICP reduction did not differ.

CONCLUSIONS

The pulsatility curve was not modified by shunt surgery, while the baseline position was shifted along the curve. Observed differences between gait improvers and non-improvers support cardiac related ICP pulsations as a component of INPH pathophysiology.

Ventricle equilibrium position in healthy and normal pressure hydrocephalus brains using an analytical model

The driving force that causes enlargement of the ventricles remains unclear in case of normal pressure hydrocephalus (NPH). Both healthy and NPH brain conditions are characterized by a low transparenchymal pressure drop, typically 1 mm Hg. The present paper proposes an analytical model for normal and NPH brains using Darcy's and Biot's equations and simplifying the brain geometry to a hollow sphere with an internal and external radius. Self-consistent solutions for the large deformation problem that is associated with large ventricle dilation are presented and the notion of equilibrium or stable ventricle position is highlighted for both healthy and NPH conditions. The influence of different biomechanical parameters on the stable ventricle geometry is assessed and it is shown that both CSF seepage through the ependyma and parenchymal permeability play a key role. Although very simple, the present model is able to predict the onset and development of NPH conditions as a deviation from healthy conditions.

Cognitive disturbances and neuropsychological changes after surgical treatment in a cohort of 185 patients with idiopathic normal pressure hydrocephalus

Although idiopathic normal pressure hydrocephalus (iNPH) is considered a treatable dementia, there is still some controversy regarding the cognitive improvement in these patients. The main aims of this study were to analyze baseline cognitive status and to study the neuropsychological changes after surgical treatment in a sample of 185 consecutive iNPH patients. An additional aim was to identify the variables that influenced the cognitive outcome. Specific tests assessing memory, attention, visual scanning, executive functions (EFs), and motor speed were used before and 6 months after shunting. The cognitive domains most affected at baseline were memory, EFs, attention, and psychomotor speed. After shunting, significant differences in the group as a whole were found in all tests except Digits Forward and Trail Making Part B. However, less than 50% of patients showed a significant improvement when analyzed individually. Previous global cognitive status assessed by Mini-Mental State Examination baseline scores was the best predictor for the cognitive outcome.

Comparison between 3 infusion methods to measure cerebrospinal fluid outflow conductance

OBJECT

There are several infusion methods available to estimate the outflow conductance (Cout) or outflow resistance (Rout=1/Cout) of the CSF system. It has been stated that for unknown reasons, the bolus infusion method estimates a higher C(out) than steady-state infusion methods. The aim of this study was to compare different infusion methods for estimation of Cout.

METHODS

The following 3 different infusion methods were used: the bolus infusion method (Cout bol); the constant flow infusion method, both static (Cout stat) and dynamic (Cout dyn) analyses; and the constant pressure infusion method (Cout cpi). Repeated investigations were performed on an experimental model with well-known characteristics, with and without physiological pressure variations (B-waves, breathing, and so on). All 3 methods were also performed in a randomized order during the same investigation in 20 patients with probable or possible idiopathic normal-pressure hydrocephalus; 6 of these patients had a shunt and 14 did not.

RESULTS

Without the presence of physiological pressure variations, the concordance in the experimental model was good between all methods. When they were added, the repeatability was better for the steady-state methods and a significantly higher Cout was found with the bolus method in the region of clinically relevant Cout (p<0.05). The visual fit for the bolus infusion was dependent on subjective assessment by the operator. This experimental finding was confirmed by the clinical results, where significant differences were found in the investigations in patients without shunts between Cout of the visual bolus method and Cout stat, Cout dyn, and Cout cpi (4.58, 4.18, and 6.12 μl/[second×kPa], respectively).

CONCLUSIONS

This study emphasized the necessity for standardization of Cout measurements. An experienced operator could partly compensate for difficulties in correctly estimating the pressure parameters for the bolus infusion method, but for the general user this study suggests a steady-state method for estimating Cout.

Real-time estimation of cerebrospinal fluid system parameters via oscillating pressure infusion

Hydrocephalus is related to a disturbed cerebrospinal fluid (CSF) system. For diagnosis, lumbar infusion test are performed to estimate outflow conductance, C (out), and pressure volume index, PVI, of the CSF system. Infusion patterns and analysis methods used in current clinical practice are not optimized. Minimizing the investigation time with sufficient accuracy is of major clinical relevance. The aim of this study was to propose and experimentally evaluate a new method, the oscillating pressure infusion (OPI). The non-linear model of the CSF system was transformed into a linear time invariant system. Using an oscillating pressure pattern and linear system identification methods, C (out) and PVI with confidence intervals, were estimated in real-time. Forty-two OPI and constant pressure infusion (CPI) investigations were performed on an experimental CSF system, designed with PVI = 25.5 ml and variable C (out). The ARX model robustly estimated C (out) (mean C (out,OPI) - C (out,CPI) = 0.08 μl/(s kPa), n = 42, P = 0.68). The Box-Jenkins model proved most reliable for PVI (23.7 ± 2.0 ml, n = 42). The OPI method, with its oscillating pressure pattern and new parameter estimation methods, efficiently estimated C (out) and PVI as well as their confidence intervals in real-time. The results from this experimental study show potential for the OPI method and supports further evaluation in a clinical setting.

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.

Priorities for hydrocephalus research: report from a National Institutes of Health-sponsored workshop

OBJECT

Treatment for hydrocephalus has not advanced appreciably since the advent of cerebrospinal fluid (CSF) shunts more than 50 years ago. Many questions remain that clinical and basic research could address, which in turn could improve therapeutic options. To clarify the main issues facing hydrocephalus research and to identify critical advances necessary to improve outcomes for patients with hydrocephalus, the National Institutes of Health (NIH) sponsored a workshop titled "Hydrocephalus: Myths, New Facts, and Clear Directions." The purpose of this paper is to report on the recommendations that resulted from that workshop.

METHODS

The workshop convened from September 29 to October 1, 2005, in Bethesda, Maryland. Among the 150 attendees was an international group of participants, including experts in pediatric and adult hydrocephalus as well as scientists working in related fields, neurosurgeons, laboratory-based neuroscientists, neurologists, patient advocates, individuals with hydrocephalus, parents, and NIH program and intramural staff. Plenary and breakout sessions covered injury and recovery mechanisms, modeling, biomechanics, diagnosis, current treatment and outcomes, complications, quality of life, future treatments, medical devices, development of research networks and information sharing, and education and career development.

RESULTS

The conclusions were as follows: 1) current methods of diagnosis, treatment, and outcomes monitoring need improvement; 2) frequent complications, poor rate of shunt survival, and poor quality of life for patients lead to unsatisfactory outcomes; 3) investigators and caregivers need additional methods to monitor neurocognitive function and control of CSF variables such as pressure, flow, or pulsatility; 4) research warrants novel interdisciplinary approaches; 5) understanding of the pathophysiological and recovery mechanisms of neuronal function in hydrocephalus is poor, warranting further investigation; and 6) both basic and clinical aspects warrant expanded and innovative training programs.

CONCLUSIONS

The research priorities of this workshop provide critical guidance for future research in hydrocephalus, which should result in advances in knowledge, and ultimately in the treatment for this important disorder and improved outcomes in patients of all ages.

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.

A mathematical model of survival in a newly inserted ventricular shunt

OBJECT

The object of this study was to mathematically model the prognosis of a newly inserted shunt in pediatric or adult patients with hydrocephalus.

METHODS

A structured search was performed of the English-language literature for case series reporting shunt failure, patient mortality, and shunt removal rates after shunt insertion. A metaanalytic model was constructed to pool data from multiple studies and to predict the outcome of a shunt after insertion. Separate models were used to predict shunt survival rates for children (patients < 17 years old) and adults.

RESULTS

Shunt survival rates in children and adults were calculated for 1 year (64.2 and 80.1%, respectively), 5 years (49.4 and 60.2%, respectively), and the median (4.9 and 7.3 years, respectively). The longer-term rates predicted by the model agree closely with those reported in the literature.

CONCLUSIONS

This model gives a comprehensive view of the fate of a shunt for hydrocephalus after insertion. The advantages of this model compared with Kaplan-Meier survival curves are discussed. The model used in this study may provide useful prognostic information and aid in the early evaluation of new shunt designs and techniques.

Course of disease in patients with idiopathic normal pressure hydrocephalus (iNPH): a follow-up study 3, 4 and 5 years following shunt implantation

BACKGROUND

In spite of recent advances in the diagnosis and treatment of iNPH, favorable outcomes following CSF diversion continue to be limited by complications, both valve dependent and valve independent, as well as by a reduction, over time, in the response to shunting.

MATERIALS AND METHODS

Between September 1997 and December 2006, 148 patients underwent ventriculo-peritoneal shunt surgery in our department. All patients underwent the implantation of gravitational valves. These patients were followed-up 3, 6 and 12 months after surgery and then at annual intervals.

FINDINGS

The mean age of the 94 men and 54 women in our study was 68 years. The perioperative mortality was 0.7% (one patient died from a pulmonary embolism). A further 23 patients died during the follow-up period from causes unrelated to iNPH or the surgery. This study reports on groups of patients followed-up for 2 years (n = 92), 3 years (n = 62), 4 years (n = 38) and 5 years (n = 21) postoperatively. Valve independent complications occurred postoperatively in 6% of patients (n = 10). Of these, five patients (3% of the total) had an infection and catheter displacement was recorded in a further five. Valve dependent complications occurred in 24 patients (16%), with overdrainage found in seven patients (5%) and underdrainage apparent in 17 (11%). Responder rates were 79% at 2 years, 79% at 3 years, 64% at 4 years and 60% at 5 years. The optimal valve opening pressure in programmable valves with a gravitational unit was between 30 and 70 mmHg.

CONCLUSIONS

Sixty percent of patients with iNPH who underwent a ventriculo-peritoneal shunt using a gravitational valve continue to benefit from surgery 5 years postoperatively.

The influence of co-morbidity on the postoperative outcomes of patients with idiopathic normal pressure hydrocephalus (iNPH)

BACKGROUND

A critical question in the diagnosis and treatment of idiopathic normal pressure hydrocephalus (iNPH) is that of which preoperative factors can most reliably predict outcomes following shunt insertion. The number and type of co-morbidities are increasingly being viewed as important predictive indicators.

METHODS

Between 1997 and 2004, 95 patients were implanted with a gravitational ventriculo-peritoneal shunt as treatment for iNPH. All coincident disease processes were recorded. Eighty-two of these patients underwent follow-up 2 years postoperatively. The results of this prospective follow-up examination (Kiefer Score, NPH Recovery Rate) were compared with the preoperative CoMorbidity Index (CMI).

FINDINGS

Of the patients with a CMI score of 0-1 (n = 18), 67% experienced an excellent outcome, 28% a good outcome and 5% and 0% a fair and poor outcome respectively. A CMI score of 2-3 was associated with markedly poorer outcomes (n = 33); 42% excellent, 30% good, 18% fair and 10% poor. A score of 4-5 was related to 14% excellent, 27% good, 23% fair and 36% poor outcomes (n = 22). Remarkably few patients scoring between 6 and 8 on the CMI scale experienced a favourable outcome. The outcomes for this latter group were 0% excellent, 10% good, 45% fair and 45% poor (n = 9) significant predictor of the quality of clinical outcome for patients with iNPH undergoing shunt therapy.

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

OBJECT

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

[Idiopathic normal-pressure hydrocephalus. Flow measurement of cerebrospinal fluid using phase contrast MRI and its diagnostics importance]

AIM

The measurement of CSF flow in the aqueduct has been a focus of interest since the development of MR imaging (MRI) techniques for this purpose in diagnosing idiopathic normal-pressure hydrocephalus (iNPH).The purpose of this prospective study was to determine the ability of this diagnostic tool to replace invasive methods in establishing the diagnosis of iNPH.

PATIENTS AND METHODS

Between January 2003 and April 2005, 61 patients with the Hakim triad of clinical symptoms and dilated ventricular systems underwent the intrathecal infusion test, cerebrospinal tap test, and phase-contrast MRI to measure CSF flow rate in the aqueduct. Shunted patients were controlled 12 months postoperatively. Pre- and postoperative clinical symptoms were evaluated with the Kiefer score. Outcome was calculated according to the NPH recovery rate.

RESULTS

According to these criteria the patients were classified into groups of 41 with iNPH and 20 with brain atrophy. Of the iNPH patients, 39 were shunted and two did not agree to surgery. The mean Kiefer score of the shunted patients was statistically significantly lower after surgery. The aqueductal CSF flow rate of these patients was statistically analyzed and showed that a flow rate of more than 24.5 ml/min is 95% specific to iNPH.

CONCLUSIONS

Measurement of the CSF flow rate in the aqueduct using phase-contrast MRI is a highly specific preselective method for diagnosing iNPH.

Continuous intraventricular pressure monitoring for diagnosis of normal-pressure hydrocephalus

OBJECTIVES

Normal-pressure hydrocephalus (NPH) syndrome is treatable by implantation of a cerebrospinal fluid (CSF) shunt. However, diagnosis of NPH by clinical and radiological findings alone is unreliable, and co-existing structural dementia can contribute to low success rates after shunt implantation. The aim of our study was to investigate whether long-term results after shunt implantation in NPH improve when surgical candidates are selected by continuous intraventricular pressure monitoring (CIPM).

PATIENTS AND METHODS

Ninety-two consecutive patients who were admitted with suspected NPH received CIPM for 48 h including an intraventricular steady-state infusion test to determine the resistance outflow. With positive CIPM, shunt implantation was performed and the patients were prospectively followed up for 1 to 10 years (median 6.5 years).

RESULTS

CIPM was negative in 37 patients. Fifty-five patients had a positive CIPM and received CSF shunt. 96.1% of them improved from gait disturbance, 77.1% from cognitive impairment and 75.7% from urinary dysfunction. Clinical improvement remained during long-term follow-up in all but 3 patients who showed a decline at 4, 5 and 7 years, respectively. CIPM-related complications (ventriculitis) occurred in only one patient.

CONCLUSION

CIPM is a safe and valuable tool to establish a reliable diagnosis of NPH and to identify promising surgical candidates.

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.

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.

Outcome of shunting in idiopathic normal-pressure hydrocephalus and the value of outcome assessment in shunted patients

OBJECTIVE

To develop guidelines for assessing shunt outcome in patients with idiopathic normal-pressure hydrocephalus (INPH). To date, the literature available on this topic has been marked by disparate definitions of clinical improvement, varying postoperative follow-up protocols and periods, and substantial differences in the postoperative management. Because specific criteria for defining clinical improvement are seldom reported, conclusions drawn about shunt outcome may be subjective.

METHODS

A MEDLINE search back to 1966 was undertaken using the query NPH, normal-pressure hydrocephalus, shunting, shunt treatment, shunt response, outcome, and clinical outcome. The criteria for selection were studies that included INPH from 1966 to the present in which the outcome of INPH was reported in patient groups of 20 or more.

RESULTS

To date, there is no standard for outcome assessment of shunt treatment in INPH. The variable improvement rates reported are not only because of different criteria for selection of patients but also because of different postoperative assessment procedures and follow-up intervals.

CONCLUSION

Studies that have established fixed protocols for follow-up have shown that short- and long-term periods after shunting are determined by many factors. Whereas short-term results were more likely to be influenced by shunt-associated risks, long-term results were independent of factors inherent to the shunt procedure and shunt complications, i.e., death and morbidity related to concomitant cerebrovascular and vascular diseases. Studies have shown that beyond 1 year after surgery, these factors definitely influence the clinical effect of shunting, making the 1-year postshunt period a potential determinant of the shunt outcome. Guidelines for outcome assessment were developed on the basis of the available evidence and consensus of expert opinion.

On the optimal opening pressure of hydrostatic valves in cases of idiopathic normal-pressure hydrocephalus: a prospective randomized study with 123 patients

Does the opening pressure of hydrostatic shunts influence the clinical outcome for patients suffering from idiopathic normal-pressure hydrocephalus (NPH)? Between September 1997 and January 2003, 123 patients with idiopathic NPH were surgically treated by implanting a hydrostatic shunt at the Departments of Neurosurgery of the Unfallkrankenhaus Berlin and the University Homburg/Saar. As part of a prospective randomized study, all patients were examined preoperatively, postoperatively, and 1 year after the intervention. Forty-three percent of the patients showed a very good outcome, 25% good outcome, 20% fair outcome, and 12% poor outcome 1 year after the shunt implantation. Patients treated with an opening pressure rating of 50 mmH2O in the low-pressure stage of the gravitational valve showed a better outcome than those with an opening pressure of 100 or 130 mmH2O. According to present knowledge, hydrostatic shunts with an opening pressure of 50 mmH2O for the low-pressure stage are the best option for patients with idiopathic NPH. Due to the prompt switching function when the patient changes posture (lying down, standing, sitting, slanting etc.), the Miethke gravity-assisted valve (GAV) is more suitable in such cases than the Miethke Dual-Switch valve (DSV).

Is it possible to optimize treatment of patients with idiopathic normal pressure hydrocephalus by implanting an adjustable Medos Hakim valve in combination with a Miethke shunt assistant?

A better course of the disease after implantation of a low-pressure valve in patients with idiopathic normal pressure hydrocephalus normally comes at the cost of a distinctly higher rate of overdrainage. Can combining an adjustable valve with a gravity unit produce optimization of treatment results? In a prospective observation of the course of the disease, 18 patients with idiopathic normal pressure hydrocephalus were surgically treated with the aforementioned valve combination during the period January to June 2004 at the Unfallkrankenhaus Berlin and examined after 6 and 12 months. The course of the disease correlates with the opening pressure level of the valve. The controlled setting of the valve from 100 mmH2O to 70 mmH2O, then to 50 mmH2O after 3 months permits the brain to adapt optimally to the implanted valve without complications from overdrainage. In our view, combining an adjustable differential pressure valve with a gravity unit currently represents the optimal treatment variant for patients with idiopathic normal pressure hydrocephalus. In the future, the gravity valve should also be adjustable.

Clinical outcome of patients with idiopathic normal pressure hydrocephalus three years after shunt implantation

OBJECTIVE

To investigate the outcomes of surgical treatment of idiopathic normal pressure hydrocephalus (iNPH).

PATIENTS AND METHODS

We prospectively investigated 51 patients treated for iNPH by insertion of a ventriculoperitoneal shunt with gravitational valve.

RESULTS

The proportion of excellent, good, and satisfactory outcomes immediately following surgery was 80%; the same clinical outcome was later verified in 67% of patients on average of 34 months postoperatively. These results are similar to those reported in the literature. Ventricle volume decreased minimally during the course of treatment using Evans' index, which was concordant with recent literature and with current understanding of hydrocephalus treatment.

CONCLUSIONS

A gravitational valve for treatment of iNPH is the logical implementation of current knowledge of the pathophysiology of this illness enabling us to solve the problem of cerebrospinal fluid drainage with the lowest possible opening pressure while simultaneously protecting from overdrainage. The use of programmable valves, in combination with a gravitational component, is the next evolutionary stage, potentially making revision operations unnecessary.

First clinical experiences in patients with idiopathic normal-pressure hydrocephalus with the adjustable gravity valve manufactured by Aesculap (proGAV(Aesculap))

OBJECTIVE

Improved clinical outcomes after implantation of a low pressure valve in patients with idiopathic normal-pressure hydrocephalus is usually achieved at the expense of a higher overdrainage rate. Can an adjustable valve with a gravitational unit provide optimal results?

METHOD

In a prospective clinical outcome study conducted in the Unfallkrankenhaus Berlin, 30 patients with idiopathic normal-pressure hydrocephalus were treated surgically between June 2004 and May 2005 with the valve combination described above, and reexamination 3 months or 6 months postoperatively.

RESULTS

Clinical outcome correlates with opening pressure level of the valve. Controlled adjustment of the valve from 100 mmH2O to 70 mmH2O, and then to 50 mmH2O after 3 months, permits optimum adaptation of the brain to the implanted valve without overdrainage complications.

CONCLUSIONS

Advantages of this programmable gravity valve include: 1) the absence of unintentional readjustment through external magnets, and 2) the possibility of controlling the valve setting using an accessory instrument without the need for x-ray monitoring. A significant disadvantage is adjusting the valve after implantation. From the clinical point of view, this new "proGAV(Aesculap)" valve is a necessary development in the right direction, but at the moment it is still beset with technical problems.

Assessment of cerebrospinal fluid outflow conductance using constant-pressure infusion—a method with real time estimation of reliability

The outflow conductance (C(out)) of the cerebrospinal fluid (CSF) system is a parameter considered to be predictive in selection for hydrocephalus surgery. C(out) can be determined through an infusion test. A new apparatus for performing infusion tests in a standardized and automated way was developed. The objective was to evaluate repetitiveness as well as to propose and evaluate a method for real time estimation of the reliability of individual C(out) investigations. Repeated investigations were performed on an experimental model simulating the CSF system, and on 14 patients with hydrocephalus. DeltaC(out), calculated as the 95% confidence interval of C(out), was introduced as an estimate of the reliability of individual C(out) investigations. On the model, no significant difference was found between DeltaC(out) and the actual C(out) variation in repeated investigations (p = 0.135). The correlation between the first and the second patient investigation was high (R = 0.99, p < 0.05), although there was a significant difference between the investigations (p < 0.05). The standard deviation of difference was 2.60 microl (s kPa)(-1). The repetitiveness of C(out) with the new apparatus was high, and DeltaC(out) reflected the reliability of each investigation. This feature has to be taken into account in every individual case, before making a decision or performing research based on measurements of C(out) in the future.

Good outcome in patients with normal-pressure hydrocephalus and factors indicating poor prognosis

OBJECT

The authors set out to describe the outcome in a subgroup of patients with normal-pressure hydrocephalus (NPH) in whom prognostic factors were poor. This subgroup of patients who had received shunts was selected according to strict criteria.

METHODS

From a cohort of 56 patients with NPH in whom shunts were placed, the authors selected a subgroup with four of the factors traditionally considered to indicate poor prognosis: idiopathic type, cortical atrophy, longstanding symptoms, and presence of dementia in addition to old age. Twelve patients met the inclusion criteria. After receiving shunts, 92% of the patients showed clinical improvement on the NPH scale; gait improved in 100% of patients, sphincter control in 90%, and dementia in 33%. Improvement was significant for gait and sphincter control, general NPH score, and most daily life activity scales. No significant differences regarding clinical, cognitive, or functional changes following surgery were found in comparison with the rest of patients (the good prognosis subgroup).

CONCLUSIONS

The clinical condition of patients with NPH who present with traditionally accepted markers of poor prognosis can improve after surgery, especially as regards gait and sphincter control. The authors assert that the presence of these markers should not be considered to be an absolute criterion for ruling out shunt surgery in cases of NPH syndrome.

Intraventricular or lumbar infusion test in adult communicating hydrocephalus? Practical consequences and clinical outcome of shunt operation

BACKGROUND

To investigate the therapeutic consequences of restricting the CSF dynamic evaluation to a lumbar infusion test (LIT), as opposed to our formerly applied intraventricular assessment (VIT), in patients with communicating hydrocephalus (CH).

METHOD

All patients over 18 years of age referred with clinical and radiological indication of treatment-requiring secondary CH (n = 50) or idiopathic normal-pressure hydrocephalus (INPH, n = 33) were subjected to a LIT. Subsequently, a combination of the results of the LIT (mainly the resistance to CSF outflow) and the clinical presentation determined whether to proceed with (a) VIT before a decision about shunt surgery, (b) shunt surgery or (c) no further diagnostic investigation or surgery.

FINDINGS

In 88 percent of the patients with secondary CH and 80 percent of the patients with INPH the decision on shunt surgery was made after performing exclusively a LIT. The shunting success rate was 90 percent in patients with secondary CH and 82 percent in patients with INPH, which however in the latter group decreased to 76 percent, when including the patients undergoing an additional VIT. The achieved shunt success rates are equal or better, compared to the results from previous studies using intraventricular assessment.

CONCLUSIONS

LIT and VIT are equally reliable for selecting shunt responsive patients with CH, using clinical improvement rate as the main criterion for comparison. The practical and economic consequences are substantial: the LIT can be performed in an outpatient setting, whereas VIT necessitates hospitalisation for 1-2 days including occupation of the neurosurgical theatre and postoperative neuro-intensive monitoring.