The influence of lumbar spinal drainage on diffusion parameters in patients with suspected normal pressure hydrocephalus using 3T MRI

Intravoxel incoherent motion magnetic resonance imaging in the assessment of brain microstructure and perfusion in idiopathic normal-pressure hydrocephalus

PURPOSE

To determine the relationship between intravoxel incoherent motion (IVIM) MRI parameters and clinical changes post-tap test (TT) in idiopathic normal-pressure hydrocephalus (iNPH) patients.

METHODS

Forty-four probable iNPH patients underwent 3 T MRI before and after TT. IVIM parameters were calculated from eight different bilateral regions of interest in basal ganglia, centrum semiovale, and corona radiata. Patients were categorized based on TT response into positive (group 1) and negative (group 2) groups. A Welch two-sample t-test was used to compare differences in D, D*, f, and ADC between the two groups, while a paired t-test was employed to assess the changes within each group before and after TT. These parameters were then correlated with clinical results.

RESULTS

In the lenticular and thalamic nuclei, D value was significantly lower in the group 1 compared to group 2 both pre- and post-TT (p = 0.002 and p = 0.007 respectively). Post-TT, the positive response group exhibited a notably reduced D* value (p = 0.012) and significantly higher f values (p = 0.028). In the corona radiata and centrum semiovale, a significant post-TT reduction in D* was observed in the positive response group (p = 0.017). Within groups, the positive response cohort showed a significant post-TT increase in ADC (p < 0.001) and a decrease in D* (p = 0.007).

CONCLUSION

IVIM permits the acquisition of important non-invasive information about tissue and vascularization in iNPH patients. Enhanced perfusion in the lenticular and thalamic nuclei may suggest the role of re-established microvascular and glymphatic pathways, potentially elucidating the functional improvement in motor function after TT in iNPH patients.

Lumbar and ventricular CSF concentrations of extracellular matrix proteins before and after shunt surgery in idiopathic normal pressure hydrocephalus

Background

Idiopathic normal pressure hydrocephalus (iNPH) is a reversible CNS disease characterized by disturbed cerebrospinal fluid (CSF) dynamics. Changes in the extracellular matrix (ECM) composition might be involved in the pathophysiology of iNPH. The aim of this study was to explore possible differences between lumbar and ventricular CSF concentrations of the ECM markers brevican and neurocan, matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinase-1 (TIMP-1) and their relation to clinical symptoms in iNPH patients before and after shunt surgery.

Methods

Paired lumbar and ventricular CSF was collected from 31 iNPH patients, before and four months after shunt surgery. CSF was analysed for concentrations of tryptic peptides originating from brevican and neurocan using a mass spectrometry-based panel, and for MMP-1, -2, -9, -10 and TIMP-1 using fluorescent or electrochemiluminescent immunoassays.

Results

Brevican and neurocan peptide levels were not influenced by CSF origin, but MMP-1, -2, -10 and TIMP-1 were increased (p ≤ 0.0005), and MMP-9 decreased (p ≤ 0.0003) in lumbar CSF compared with ventricular CSF. There was a general trend of ECM proteins to increase following shunt surgery. Ventricular TIMP-1 was inversely correlated with overall symptoms (rho = − 0.62, p < 0.0001). CSF concentrations of the majority of brevican and neurocan peptides were increased in iNPH patients with a history of cardiovascular disease (p ≤ 0.001, AUC = 0.84–0.94) compared with those without.

Conclusion

Levels of the CNS-specific proteins brevican and neurocan did not differ between the lumbar and ventricular CSF, whereas the increase of several CNS-unspecific MMPs and TIMP-1 in lumbar CSF suggests contribution from peripheral tissues. The increase of ECM proteins in CSF following shunt surgery could indicate disturbed ECM dynamics in iNPH that are restored by restitution of CSF dynamics.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12987-021-00256-1.

The role of diffusion tensor imaging in idiopathic normal pressure hydrocephalus: A literature review

Idiopathic normal pressure hydrocephalus (iNPH) is a syndrome that comprises a triad of gait disturbance, dementia and urinary incontinence, associated with ventriculomegaly in the absence of elevated intraventricular cerebrospinal fluid (CSF) pressure. It is important to identify patients with iNPH because some of its clinical features may be reversed by the insertion of a CSF shunt. The diagnosis is based on clinical history, physical examination and brain imaging, especially magnetic resonance imaging (MRI). Recently, some papers have investigated the role of diffusion tensor imaging (DTI) in evaluating white matter alterations in patients with iNPH. DTI analysis in specific anatomical regions seems to be a promising MR biomarker of iNPH and could also be used in the differential diagnosis from other dementias. However, there is a substantial lack of structured reviews on this topic. Thus, we performed a literature search and analyzed the most recent and pivotal articles that investigated the role of DTI in iNPH in order to provide an up-to-date overview of the application of DTI in this setting. We reviewed studies published between January 2000 and June 2020. Thirty-eight studies and four reviews were included. Despite heterogeneity in analysis approaches, the majority of studies reported significant correlations between DTI and clinical symptoms in iNPH patients, as well as different DTI patterns in patients with iNPH compared to those with Alzheimer or Parkinson diseases. It remains to be determined whether DTI could predict the success after CSF shunting.

Changes in Apparent Diffusion Coefficient (ADC) during Cardiac Cycle of the Brain in Idiopathic Normal Pressure Hydrocephalus Before and After Cerebrospinal Fluid Drainage

BACKGROUND

The causative mechanisms of idiopathic normal-pressure hydrocephalus (iNPH) symptoms are currently unknown.

PURPOSE

To assess the dynamic changes in the apparent diffusion coefficient (ADC) during the cardiac cycle (ΔADC) of the brain before and after the lumbar tap and shunt surgery for the purpose of determining changes in hydrodynamic and biomechanical properties in the brain after cerebrospinal fluid (CSF) drainage for iNPH.

STUDY TYPE

Retrospective.

SUBJECTS

Overall, 22 patients suspected to have iNPH were examined before and after the lumbar tap and were divided into patients who showed symptomatic improvements (positive group, n = 17) and those without improvement (negative group, n = 5) after the lumbar tap. Seven patients in the positive group were examined after the shunt surgery.

FIELD STRENGTH/SEQUENCE

1.5T, electrocardiographically synchronized single-shot diffusion echo-planar imaging.

ASSESSMENT

The frontal white matter ΔADC and mean ADC (ADC_mean ) were compared between before and 24 hours after lumbar tap and from 1 week to 1 month after the shunt surgery.

STATISTICAL TESTS

Wilcoxon signed-rank test was used. P < 0.05 was considered statistically significant.

RESULTS

The ΔADC after the lumbar tap in the positive group was significantly lower than that before (P < 0.05), whereas no significant difference was found in the negative group (P = 0.23). After the lumbar tap, ΔADC decreased in 16 of 17 patients in the positive group, whereas ADC_mean did not significantly change (P = 0.96). After the shunt surgery, ΔADC decreased in all seven patients (P < 0.05), whereas ADC_mean did not significantly change (P = 0.87).

DATA CONCLUSION

The frontal white matter ΔADC in iNPH decreased after the lumbar tap and shunt surgery. ΔADC analysis may provide detailed information regarding changes in the hydrodynamic and biomechanical properties through CSF drainage.

LEVEL OF EVIDENCE

4.

TECHNICAL EFFICACY STAGE

4.

MRI diffusion and perfusion alterations in the mesencephalon and pons as markers of disease and symptom reversibility in idiopathic normal pressure hydrocephalus

Introduction

Core symptomatology in idiopathic normal pressure hydrocephalus (iNPH) points at dysfunction in the mesencephalon and pons indicating pathological changes in these regions, but only a few studies have addressed the issue. The aim of this study was to investigate diffusion (ADC) and perfusion patterns pre- and postoperatively in these areas in iNPH.

Methods

Twenty iNPH patients and 15 healthy controls were included. Patients underwent a clinical examination and brain MRI pre- and 3–6 months postoperatively. The MRI-scan included diffusion and dynamic susceptibility contrast perfusion weighted sequences. Regions of interest in the mesencephalon and pons were drawn on a FLAIR sequence and co-registered to ADC maps and perfusion data.

Results

There were no significant differences in pre or postoperative ADC compared to the control group, however postoperative ADC increased by 10% (p = 0.026) in the mesencephalon and 6% (p = 0.016) in the pons in all patients and also in the subgroup of shunt responders by 11% (p = 0.021) and 4% (p = 0.020), respectively. Preoperative relative cerebral blood flow (rCBF) was similar in iNPH patients and controls. Postoperatively, rCBF increased in shunt responders by 6% (p = 0.02) in the mesencephalon and 11% (p = 0.004) in the pons. This increase correlated with the degree of clinical improvement (r_s = 0.80, p = 0.031 and r_s = 0.66, p = 0.021, respectively).

Conclusion

The postoperative increase in ADC and the correlation between postoperative increase in rCBF and clinical improvement in the mesencephalon and pons shown in this study point at an involvement of these areas in the core pathophysiology and its reversibility in iNPH.

Indication of Thalamo-Cortical Circuit Dysfunction in Idiopathic Normal Pressure Hydrocephalus: A Tensor Imaging Study

Idiopathic normal pressure hydrocephalus (iNPH) is a disorder with unclear pathophysiology. The diagnosis of iNPH is challenging due to its radiological similarity with other neurodegenerative diseases and ischemic subcortical white matter changes. By using Diffusion Tensor Imaging (DTI) we explored differences in apparent diffusion coefficient (ADC) and fractional anisotropy (FA) in iNPH patients (before and after a shunt surgery) and healthy individuals (HI) and we correlated the clinical results with DTI parameters. Thirteen consecutive iNPH-patients underwent a pre- and post-operative clinical work-up: 10 m walk time (w10mt) steps (w10ms), TUG-time (TUGt) and steps (TUGs); for cognitive function MMSE. Nine HI were included. DTI was performed before and 3 months after surgery, HI underwent DTI once. DTI differences analyzed by manually placing 12 regions-of-interest. In patients motor and balance function improved significantly after surgery (p = 0.01, p = 0.025). Higher nearly significant FA values found in the patients vs HI pre-operatively in the thalamus (p = 0.07) accompanied by an almost significant lower ADC (p = 0.08). Significantly FA and ADC-values were found between patients and HI in FWM (p = 0.02, p = 0.001) and almost significant (p = 0.057) pre- vs postoperatively. Postoperatively we found a trend towards the HIs FA values and a strong significant negative correlation between FA changes vs. gait results in the FWM (r = −0.7, p = 0.008). Our study gives a clear indication of an ongoing pathological process in the periventricular white matter, especially in the thalamus and in the frontal white matter supporting the hypothesis of a shunt reversible thalamo-cortical circuit dysfunction in iNPH.

The role of diffusion tensor imaging and fractional anisotropy in the evaluation of patients with idiopathic normal pressure hydrocephalus: a literature review

OBJECTIVE Diffusion tensor imaging (DTI) for the assessment of fractional anisotropy (FA) and involving measurements of mean diffusivity (MD) and apparent diffusion coefficient (ADC) represents a novel, MRI-based, noninvasive technique that may delineate microstructural changes in cerebral white matter (WM). For example, DTI may be used for the diagnosis and differentiation of idiopathic normal pressure hydrocephalus (iNPH) from other neurodegenerative diseases with similar imaging findings and clinical symptoms and signs. The goal of the current study was to identify and analyze recently published series on the use of DTI as a diagnostic tool. Moreover, the authors also explored the utility of DTI in identifying patients with iNPH who could be managed by surgical intervention. METHODS The authors performed a literature search of the PubMed database by using any possible combinations of the following terms: "Alzheimer's disease," "brain," "cerebrospinal fluid," "CSF," "diffusion tensor imaging," "DTI," "hydrocephalus," "idiopathic," "magnetic resonance imaging," "normal pressure," "Parkinson's disease," and "shunting." Moreover, all reference lists from the retrieved articles were reviewed to identify any additional pertinent articles. RESULTS The literature search retrieved 19 studies in which DTI was used for the identification and differentiation of iNPH from other neurodegenerative diseases. The DTI protocols involved different approaches, such as region of interest (ROI) methods, tract-based spatial statistics, voxel-based analysis, and delta-ADC analysis. The most studied anatomical regions were the periventricular WM areas, such as the internal capsule (IC), the corticospinal tract (CST), and the corpus callosum (CC). Patients with iNPH had significantly higher MD in the periventricular WM areas of the CST and the CC than had healthy controls. In addition, FA and ADCs were significantly higher in the CST of iNPH patients than in any other patients with other neurodegenerative diseases. Gait abnormalities of iNPH patients were statistically significantly and negatively correlated with FA in the CST and the minor forceps. Fractional anisotropy had a sensitivity of 94% and a specificity of 80% for diagnosing iNPH. Furthermore, FA and MD values in the CST, the IC, the anterior thalamic region, the fornix, and the hippocampus regions could help differentiate iNPH from Alzheimer or Parkinson disease. Interestingly, CSF drainage or ventriculoperitoneal shunting significantly modified FA and ADCs in iNPH patients whose condition clinically responded to these maneuvers. CONCLUSIONS Measurements of FA and MD significantly contribute to the detection of axonal loss and gliosis in the periventricular WM areas in patients with iNPH. Diffusion tensor imaging may also represent a valuable noninvasive method for differentiating iNPH from other neurodegenerative diseases. Moreover, DTI can detect dynamic changes in the WM tracts after lumbar drainage or shunting procedures and could help identify iNPH patients who may benefit from surgical intervention.

Longitudinal Changes in the Brain Following Third Ventriculostomy in a Child With Hydrocephalus: A Case Report

The goal of this study was to detect the long-term effect of shunting on the integrity of white matter in young children with hydrocephalus.The authors reported the case of a 6-month-old boy with hydrocephalus who was evaluated by diffusion tensor imaging (DTI) before and after a shunt operation.When compared with normal children, the structures of the corpus callosum, internal capsule, and corona radiata in the patient showed a decrease in fractional anisotropy and an increase in radial diffusivity values before the shunt operation. Following successful cerebrospinal fluid shunting, long-term follow-up DTI demonstrated a trend toward normalization of the fractional anisotropy and radial diffusivity values.Shunt treatment can prevent further damage to the brain and grossly reconstitute the distorted anatomy. DTI could be a useful tool in detecting longitudinal changes after a shunt operation. Further studies involving larger case numbers are needed to detect the long-term effect of shunting on the brains of children with hydrocephalus.

MRI assessment of the effects of acetazolamide and external lumbar drainage in idiopathic normal pressure hydrocephalus

Background

The objective was to identify changes in quantitative MRI measures in patients with idiopathic normal pressure hydrocephalus (iNPH) occurring in common after oral acetazolamide (ACZ) and external lumbar drainage (ELD) interventions.

Methods

A total of 25 iNPH patients from two clinical sites underwent serial MRIs and clinical assessments. Eight received ACZ (125-375 mg/day) over 3 months and 12 underwent ELD for up to 72 hours. Five clinically-stable iNPH patients who were scanned serially without interventions served as controls for the MRI component of the study. Subjects were divided into responders and non-responders to the intervention based on gait and cognition assessments made by clinicians blinded to MRI results. The MRI modalities analyzed included T1-weighted images, diffusion tensor Imaging (DTI) and arterial spin labelling (ASL) perfusion studies. Automated threshold techniques were used to define regions of T1 hypo-intensities.

Results

Decreased volume of T1-hypointensities and decreased mean diffusivity (MD) within remaining hypointensities was observed after ACZ and ELD but not in controls. Patients responding positively to these interventions had more extensive decreases in T1-hypointensites than non-responders: ACZ-responders (4,651 ± 2,909 mm³), ELD responders (2,338 ± 1,140 mm³), ELD non-responders (44 ± 1,188 mm³). Changes in DTI MD within T1-hypointensities were greater in ACZ-responders (7.9% ± 2%) and ELD-responders (8.2% ± 3.1%) compared to ELD non-responders (2.1% ± 3%). All the acetazolamide-responders showed increases in whole-brain-average cerebral blood flow (wbCBF) estimated by ASL (18.8% ± 8.7%). The only observed decrease in wbCBF (9.6%) occurred in an acetazolamide-non-responder. A possible association between cerebral atrophy and response was observed, with subjects having the least cortical atrophy (as indicated by a positive z-score on cortical thickness measurements) showing greater clinical improvement after ACZ and ELD.

Conclusions

T1-hypointensity volume and DTI MD measures decreased in the brains of iNPH patients following oral ACZ and ELD. The magnitude of the decrease was greater in treatment responders than non-responders. Despite having different mechanisms of action, both ELD and ACZ may decrease interstitial brain water and increase cerebral blood flow in patients with iNPH. Quantitative MRI measurements appear useful for objectively monitoring response to acetazolamide, ELD and potentially other therapeutic interventions in patients with iNPH.