Supplementary Tests in Idiopathic Normal Pressure Hydrocephalus: A Single-Center Experience with a Combined Lumbar Infusion Test and Tap Test

Comparison Between Ventricular and Spinal Infusion Tests in Suspected Normal Pressure Hydrocephalus

Idiopathic normal pressure hydrocephalus (iNPH) is an often-overlooked or misdiagnosed brain disorder characterized by overt ventriculomegaly and associated with gait disturbances, cognitive impairment, and urinary incontinence. If correctly diagnosed, it is considered the only form of dementia treatable with surgery, namely through a ventriculoperitoneal or ventriculoatrial shunt with programmable valves.Among the 856 spinal and ventricular infusion tests performed from 2001 to 2017 at our institution, we analyzed 106 cases selected for suspected normotensive hydrocephalus. In all cases, Intracranial Elastance Index (IEI) and outflow resistance (Rout) values were calculated: 52 of these patients underwent Spinal Katzman Test (SKT), and the remaining 54 underwent an intraventricular infusion test (IVKT). Of the 40 patients in the SKT group with pathological elastance (71%), 17 also had a Rout >12 mmHg and 23 a Rout <12 mmHg. Of the 50 patients in the IVKT group with pathological elastance (92%), 38 also had a Rout >12 mmHg and 12 a Rout <12 mmHg.IVKT and SKT to date represent two useful tools in the diagnosis of normal pressure hydrocephalus. Despite being more invasive, IVKT, including both the intracranial elastance index (IEI) and Rout analysis, could be considered more reliable than SKT and therefore could be reserved for the most controversial cases.

Comparison of Noninvasive Measurements of Intracranial with Tap Test Results in Patients with Idiopathic Normal Pressure Hydrocephalus

Background

Normal pressure hydrocephalus is a disease directly related to the change in intracranial compliance and consequent repercussions in the brain parenchyma. Invasive monitoring of such parameters proves to be reliable especially for prognosis in neurocritical patients; however, it is not applicable in an outpatient service setting. The present study describes the comparison between the tap test results and the parameters obtained with a non-invasive sensor for monitoring intracranial compliance in patients with suspected NPH.

Methods

Twenty-eight patients were evaluated before and after lumbar puncture of 50mL of CSF (the tap test), comprising clinical assessment, magnetic resonance imaging, physical therapy assessment using the Timed Up and Go test, Dynamic Gait Index, BERG test, neuropsychological assessment, and recording of non-invasive intracranial compliance data using the Brain4care^® device in three different positions (lying, sitting, and standing) for 5 min each. The tap test results were compared to the Time to Peak and P2/P1 ratio parameters obtained by the device.

Results

The group that had a positive Tap test result presented a median P2/P1 ratio greater than 1.0, suggesting a change in intracranial compliance. In addition, there was also a significant difference between patients with positive, negative, and inconclusive results, especially in the lying position.

Conclusion

A non-invasive intracranial compliance device when used with the patient lying down and standing up obtained parameters that suggest correspondence with the result of the tap test.

The pathogenesis of idiopathic normal pressure hydrocephalus based on the understanding of AQP1 and AQP4

Idiopathic normal pressure hydrocephalus (iNPH) is a neurological disorder without a recognized cause. Aquaporins (AQPs) are transmembrane channels that carry water through cell membranes and are critical for cerebrospinal fluid circulation and cerebral water balance. The function of AQPs in developing and maintaining hydrocephalus should be studied in greater detail as a possible diagnostic and therapeutic tool. Recent research indicates that patients with iNPH exhibited high levels of aquaporin 1 and low levels of aquaporin 4 expression, suggesting that these AQPs are essential in iNPH pathogenesis. To determine the source of iNPH and diagnose and treat it, it is necessary to examine and appreciate their function in the genesis and maintenance of hydrocephalus. The expression, function, and regulation of AQPs in iNPH are reviewed in this article, in order to provide fresh targets and suggestions for future research.

Accuracy of MRI derived cerebral aqueduct flow parameters in the diagnosis of idiopathic normal pressure hydrocephalus

Idiopathic normal pressure hydrocephalus (iNPH) is a potentially reversible cause of dementia-like symptoms among the elderly. Current diagnostic guidelines for iNPH rely on clinical manifestations and ventricular morphology, which often lack accuracy. While magnetic resonance imaging (MRI) CSF flowmetry of the cerebral aqueduct provides a noninvasive aid to differential diagnosis, previous studies suffered from small sample sizes. This study compares the accuracy of different CSF flow parameters for iNPH diagnosis in a general patient population. From 2016 to 2018, a total of 216 subjects over 60 years of age were retrospectively enrolled, including 38 patients with iNPH and 178 patients with non-iNPH neurological conditions. All participants received phase-contrast MRI (PC-MRI) CSF flowmetry, with measurements performed independently by two radiologists. Flow parameters of iNPH and non-iNPH groups were compared along with their diagnostic accuracy. Absolute stroke volume (ABSV), forward flow, backward flow, mean flux and peak velocity were significantly higher in iNPH patients (P < 0.001, P < 0.001, P < 0.001, P = 0.008, P = 0.038, respectively). Backward flow had the highest diagnostic accuracy, followed by ABSV and forward flow. Net caudocranial aqueductal flow was observed in both groups, but with greater volume in the iNPH group. PC-MRI provides a non-invasive method of CSF flowmetry across the cerebral aqueduct and may aid in iNPH diagnosis. ABSV and its component flow values may provide better accuracy in identifying iNPH than other parameters.

The diagnostic value of the pulsatility curve to predict shunt responsiveness in patients with idiopathic normal pressure hydrocephalus

OBJECTIVE

The aim of this study was to investigate the diagnostic accuracy of the pulsatility curve to predict shunt response in patients with idiopathic normal pressure hydrocephalus (iNPH).

METHODS

Lumbar cerebrospinal fluid dynamics were derived from an automatic lumbar infusion test (LIT) protocol. All patients were treated with ventriculoperitoneal shunting and re-examined 6 months after shunting. Patient demographics and outcomes were gathered in a prospective, electronic database that spanned from January 2012 to January 2020. A validated iNPH scale was used to assess patients preoperatively and 6 months postoperatively. The relationship of the relative pulse pressure coefficient (RPPC), delta amplitude, successful lowering of amplitude, and the pressure-value at a hypothetical amplitude of zero (P₀), resistance to outflow (R_out), and outcome, were assessed using receiver operating characteristic (ROC) curves.

RESULTS

We included 38 patients. The RPPC, delta amplitude, successful lowering of amplitude, and P₀ parameters did not predict shunt response. Mean P₀ was 0.5 (IQR 0.4-0.9) in improved patients and 0.4 (IQR 0-1.2) in non-improved patients. The delta amplitude was 0.16 kPa (IQR 0.10-0.23) in improved patients and 0.18 kPa (IQR 0.11-0.24) in non-improved patients. Furthermore, we found a technical failure rate of pulsatility curve measurements of 32%.

CONCLUSION

Pulsatility curve results were not suitable in predicting shunt response in our cohort. The diagnostic value of LIT in case of normal pressure hydrocephalus should be subject to more rigorous research.

The Value of the Correlation Coefficient Between the ICP Wave Amplitude and the Mean ICP Level (RAP) Combined With the Resistance to CSF Outflow (Rout) for Early Prediction of the Outcome Before Shunting in Posttraumatic Hydrocephalus

Objective

To evaluate the value of the correlation coefficient between the ICP wave amplitude and the mean ICP level (RAP) and the resistance to CSF outflow (Rout) in predicting the outcome of patients with post-traumatic hydrocephalus (PTH) selected for shunting.

Materials and Methods

As a training set, a total of 191 patients with PTH treated with VP shunting were retrospectively analyzed to evaluate the potential predictive value of Rout, collected from pre-therapeutic CSF infusion test, for a desirable recovery level (dRL), standing for the modified rankin scale (mRS) of 0–2. Eventually, there were 70 patients with PTH prospectively included as a validation set to evaluate the value of Rout-combined RAP as a predictor of dRL. We calculated Rout from a CSF infusion test and collected RAP during continuous external lumbar drainage (ELD). Maximum RAP (RAPmax) and its changes relative to the baseline (ΔRAPmax%) served as specific parameters of evaluation.

Results

In the training set, Rout was proved to be a significant predictor of dRL to shunting, with the area under the curve (AUC) of 0.686 (p &lt; 0.001) in receiver-operating characteristic (ROC) analysis. In the validation set, Rout alone did not present a significant value in the prediction of desirable recovery level (dRL). ΔRAPmax% after 1st or 2nd day of ELD both showed significance in predicting of dRL to shunting with the AUC of 0.773 (p &lt; 0.001) and 0.786 (p &lt; 0.001), respectively. Significantly, Rout increased the value of ΔRAPmax% in the prediction of dRL with the AUC of 0.879 (p &lt; 0.001), combining with ΔRAPmax% after the 1st and 2nd days of ELD. RAPmax after the 1st and 2nd days of ELD showed a remarkable predictive value for non-dRL (Levels 3-6 in Modified Rankin Scale) with the AUC of 0.891 (p &lt; 0.001) and 0.746 (p &lt; 0.001).

Conclusion

Both RAP and Rout can predict desirable recovery level (dRL) to shunting in patients with PTH in the early phases of treatment. A RAP-combined Rout is a better dRL predictor for a good outcome to shunting. These findings help the neurosurgeon predict the probability of dRL and facilitate the optimization of the individual treatment plan in the event of ineffective or unessential shunting.

Evaluating the cerebrospinal fluid tap test with the Hellström iNPH scale for patients with idiopathic normal pressure hydrocephalus

BACKGROUND

The cerebrospinal fluid tap test (CSF TT) is used for selecting shunt surgery candidates among patients with idiopathic normal pressure hydrocephalus (iNPH). We aimed to evaluate the predictive value of the CSF TT, by using the Hellström iNPH scale for shunted iNPH patients with a standardized method.

METHODS

One hundred and sixteen shunt-operated iNPH patients were retrospectively included in this study. The gait and balance domains in the iNPH scale were used as outcome measures for the CSF TT and the total iNPH scale score as the postoperative outcome. A positive response to CSF TT was defined as a change of ≥ 5 points in the gait domain and ≥ 16 points in the balance domain. Differences between CSF TT responders and non-responders, sensitivity, specificity, positive and negative predictive values, accuracy, and correlations between changes from baseline to post CSF TT and from baseline to the postoperative follow-up, were calculated.

RESULTS

In the CSF TT there were 63.8% responders in the gait domain and correspondingly 44.3% in the balance domain. CSF TT responders had a significantly better postoperative outcome in the total scale score (gait P ≤ 0.001, balance P ≤ 0.012) and gait CSF TT responders improved more in gait (P ≤ 0.001) and balance CSF TT responders in balance (P ≤ 0.001). No differences between CSF TT gait or balance responders could be found in neuropsychological or urinary continence assessments postoperatively. The sensitivity and specificity of the CSF TT and the outcome of the total iNPH scale score postoperatively were 68.1% and 52.0% for gait and 47.8% and 68.0% for balance, respectively.

CONCLUSIONS

The CSF TT, with the Hellström iNPH scale as the outcome measure, has clear limitations in predicting postoperative results. The gait domain may be used to predict outcomes for gait, but the balance domain is too insensitive.

Intraventricular infusion test accuracy in predicting short- and long-term outcome of iNPH patients: a 10-year update of a three-decade experience at a single institution

OBJECTIVE

In a previous work, we found that an Intracranial Elastance Index (IEI) ≥0.3 at ventricular infusion test had a high accuracy in predicting shunt response at 6 and 12 months in idiopathic normal pressure hydrocephalus (iNPH). The aim of this study was to verify the accuracy of IEI to predict response to shunt at both short- and long-term follow-up.

METHODS

Retrospective evaluation of 64 patients undergoing ventriculo-peritoneal shunting for iNPH between 2006 and 2015 based on a positive ventricular infusion test (IEI≥0.3). Patients were classified according to Krauss scale and mRS preoperatively, at 1-year and at last follow-up. An improvement of at least one point at Krauss score or at mRS was considered as a good outcome; unchanged or worsened patients were grouped as poor outcome.

RESULTS

Mean follow-up was 6.6 years. Improvement at Krauss scale was seen in 62.5% and 64.3% of patients at 1-year and last follow-up, respectively. Patients in good functional status (mRS≤2) increased from 25 in the preoperative period to 57% at both 1-year and last follow-up. IEI was significantly associated with Krauss (p=0.041) and mRS (p=0.036) outcome at last follow-up. Patients with worse preoperative Krauss and mRS had higher chance to improve but higher overall scores after treatment. At ROC curves, IEI showed a good long-term prediction of change in mRS from first year to last follow-up.

CONCLUSIONS

IEI≥0.3 predicts outcomes at both short- and long-term, with more than 50% of patients being able to look after themselves after 6 years from treatment.

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.

The Pathogenesis Based on the Glymphatic System, Diagnosis, and Treatment of Idiopathic Normal Pressure Hydrocephalus

Idiopathic normal pressure hydrocephalus (iNPH) is a rare neurological disorder with no clear prevalence factors and is a significant danger to the elderly. The intracranial glymphatic system is the internal environment that maintains brain survival and metabolism, and thus fluid exchange changes in the glymphatic system under various pathological conditions can provide important insights into the pathogenesis and differential diagnosis of many neurodegenerative diseases such as iNPH. iNPH can be diagnosed using a combination of clinical symptoms, imaging findings and history, and cerebrospinal fluid biomarkers due to the glymphatic system disorder. However, only few researchers have linked the two. Shunt surgery can improve the glymphatic system disorders in iNPH patients, and the surgical approach is determined using a combination of clinical diagnosis and trials. Therefore, we have composed this review to provide a future opportunity for elucidating the pathogenesis of iNPH based on the glymphatic system, and link the glymphatic system to the diagnosis and treatment of iNPH. The review will provide new insights into the medical research of iNPH.

Usefulness of Brain Positron Emission Tomography with Different Tracers in the Evaluation of Patients with Idiopathic Normal Pressure Hydrocephalous

Idiopathic normal pressure hydrocephalus (iNPH) is the only form of dementia that can be cured by surgery. Its diagnosis relies on clinical and radiological criteria. Identifying patients who can benefit from surgery is challenging, as other neurological diseases can be concomitant or mimic iNPH. We performed a systematic review on the role of positron emission tomography (PET) in iNPH. We retrieved 35 papers evaluating four main functional aspects with different PET radiotracers: (1) PET with amyloid tracers, revealing Alzheimer's disease (AD) pathology in 20-57% of suspected iNPH patients, could be useful in predictions of surgical outcome. (2) PET with radiolabeled water as perfusion tracer showed a global decreased cerebral blood flow (CBF) and regional reduction of CBF in basal ganglia in iNPH; preoperative perfusion parameters could predict surgical outcome. (3) PET with 2-Deoxy-2-[18F]fluoroglucose ([18F]FDG ) showed a global reduction of glucose metabolism without a specific cortical pattern and a hypometabolism in basal ganglia; [18F]FDG PET may identify a coexisting neurodegenerative disease, helping in patient selection for surgery; postsurgery increase in glucose metabolism was associated with clinical improvement. (4) Dopaminergic PET imaging showed a postsynaptic D2 receptor reduction and striatal upregulation of D2 receptor after treatment, associated with clinical improvement. Overall, PET imaging could be a useful tool in iNPH diagnoses and treatment response.

Preoperative evaluation using external lumbar drainage for patients with posthemorrhagic hydrocephalus: A prospective, monocentric, randomized controlled trial

BACKGROUND

External lumbar drainage (ELD) remains the most common used methods with a higher sensitivity before lumboperitoneal shunt (LPS) implantation to predict the shunt outcomes in the treatment of idiopathic normal pressure hydrocephalus. However, the benefits of such supplemental test have not been tested in the treatment of post-hemorrhagic hydrocephalus (PHH).

METHODS AND DESIGN

In the current trial, 100 eligible patients with PHH will be recruited and randomly assigned to the ELD group (study group) and non-ELD group (control group). Lumbar puncture (LP) will be performed for participants in non-ELD group. LP plus ELD will be performed for participants in ELD group, those who will then be investigated the suitability of potential LPS 4 days after ELD. Two independent and practiced assessors will collect the baseline data and evaluate each participant 4 days after ELD or LP, 1 day after LPS, at the time of discharge and 1 month after LPS. The primary outcome is the shunting outcomes 1 month after surgery. The secondary outcomes include the complications related to ELD, complications related to LPS, and Evens index at each evaluation point. Meanwhile, serious adverse events occurring at any time is recorded to determine the safety of this trial.

DISCUSSION

The results of this trial will demonstrate whether preoperative evaluation using temporary ELD for patients with PHH could attenuate the risk of LPS failure.

TRIAL REGISTRATION NUMBER

ChiCTR2000034094; Pre-results.

Role of aquaporins in hydrocephalus: what do we know and where do we stand? A systematic review

INTRODUCTION

Glymphatic fluid circulation may be considered the lymphatic system of the brain and the main role of such system seems to be played by aquaporins (AQPs), a family of proteins which regulates water exchange, in particular AQP4 and 1. Alterations of glymphatic fluid circulation through AQPs variations are now emerging as central elements in the pathophysiology of different brain conditions, like hydrocephalus. This systematic review provides an insight about the role of AQPs in hydrocephalus establishment and compensation, investigating their possible role as diagnostic tools or therapeutic targets.

METHODS

PubMed database was screened searching for the relevant existing literature in English language published until February 29th 2020, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Statement.

RESULTS

A total of 40 articles met the inclusion criteria for our systematic analysis. AQP4 resulted the most studied water channel, followed by AQP1. The changes in cerebrospinal fluid (CSF), brain parenchyma and choroid plexus (CP) in different hydrocephalus type were analyzed. Moreover, important pharmacological interactions regarding AQP and molecules or conditions were discussed. A very interesting result is the general consensus on increase of AQP4 in hydrocephalic patients, unless in patients suffering from idiopathic normal pressure hydrocephalus, where AQP4 shows a tendency in reduction.

CONCLUSION

AQP seem to play a central role in the pathophysiology of hydrocephalus and in its compensation mechanisms. Further studies are required to definitively establish their precise roles and their quantitative changes to allow their utilization as diagnostic tools or therapeutic targets.

The Kuopio idiopathic normal pressure hydrocephalus protocol: initial outcome of 175 patients

BACKGROUND

The Kuopio University Hospital (KUH) idiopathic normal pressure hydrocephalus (iNPH) cerebrospinal fluid (CSF) shunting protocol is described together with the initial outcomes of 175 patients with probable iNPH treated according to this protocol from a defined population. Our secondary aim was to display the variety of differential diagnoses referred to the KUH iNPH outpatient clinic from 2010 until 2017.

METHODS

Patients were divided into four groups according to the prognostic tests: tap test (positive or negative) and infusion test (positive or negative). The short-term outcome was compared between groups. The 3-month outcome following shunt surgery was assessed by measuring gait speed improvement, using a 12-point iNPH grading scale (iNPHGS) and the 15D instrument.

RESULTS

From 341 patients suspected of iNPH, 88 patients were excluded from further research mostly due to deviation from the protocol's gait assessment guidelines. Hence 253 patients with suspected iNPH were included in the study, 177/253 (70%) of whom were treated with a CSF shunt. A favorable clinical outcome following surgery was observed in 79-93% of patients depending on the prognostic group. A moderate association (Cramer's V = 0.32) was found between the gait speed improvement rate and the prognostic group (X², p = 0.003). Patients with a positive tap test had the highest gait speed improvement rate (75%). In addition, an improvement in walking speed was observed in 4/11 patients who had both a negative tap test and a negative infusion test. Other outcome measures did not differ between the prognostic groups. Conditions other than iNPH were found in 25% of the patients referred to iNPH outpatient clinic, with the most prevalent being Alzheimer's disease.

CONCLUSIONS

Our results emphasize the importance of a systematic diagnostic and prognostic workup especially in cases with an atypical presentation of iNPH. Additional diagnostic testing may be required, but should not delay adequate care. Active surgical treatment is recommended in patients with a high clinical probability of iNPH. Other neurological conditions contributed to most of the non iNPH diagnoses.

Establishing a Preoperative Evaluation System for Lumboperitoneal Shunt: Approach to Attenuate the Risk of Shunt Failure

OBJECTIVE

Lumboperitoneal shunt (LPS) has been demonstrated an effective method for the treatment of communicating hydrocephalus in the presence of frequent shunt failure. The objective of the present study was to determine whether establishing a preoperative evaluation system could benefit patients, thus attenuating the risk of LPS failure.

METHODS

In this 3-year study, treated by LPS, patients undergoing preoperative evaluation were included into the study group and other individuals without preoperative evaluation were included into the control group. Perioperative conditions, including Keifer's hydrocephalus score, symptomatic control rate, Evans index, complications, long-term shunt revision rate, and quality of life, were synchronously investigated.

RESULTS

A total of 93 eligible patients were included in the study (study group, 51; control group, 42). The baseline characteristics of the 2 groups were basically similar. The results showed that patients in the study group had better short-term improvement in symptoms and imageology, including higher symptomatic control rate (median, 62.5% vs. 50%; P = 0.001), more reduction in Evans index (0.08 ± 0.05 vs. 0.05 ± 0.04; P = 0.002), and lower incidence of postoperative complications (median, 35.3% vs. 57.1%; P = 0.04). Similarly, the incidence of shunt revision in the study group was dramatically lower than in the control group (median, 15.7% vs. 40.9%; P = 0.006) in line with the revision-free curve (P = 0.002), which suggested that most of patients received revision, if needed, within 3 months. In addition, patients in the study group had better quality of life.

CONCLUSIONS

In conclusion, patients who underwent evaluation before LPS had better short-term and long-term outcomes, suggesting that it would be a promising strategy to correctly select patients for LPS with prolonged favorable shunt outcomes.