Time Trends of Cerebrospinal Fluid Biomarkers of Neurodegeneration in Idiopathic Normal Pressure Hydrocephalus

Association between ventricular CSF biomarkers and outcome after shunt surgery in idiopathic normal pressure hydrocephalus

INTRODUCTION

The relationship between neurochemical changes and outcome after shunt surgery in idiopathic normal pressure hydrocephalus (iNPH), a treatable dementia and gait disorder, is unclear. We used baseline ventricular CSF to explore associations to outcome, after shunting, of biomarkers selected to reflect a range of pathophysiological processes.

METHODS

In 119 consecutive patients with iNPH, the iNPH scale was used before and after shunt surgery to quantify outcome. Ventricular CSF was collected perioperatively and analyzed for biomarkers of astrogliosis, axonal, amyloid and tau pathology, and synaptic dysfunction: glial fibrillary acidic protein (GFAP), chitinase-3-like protein 1 (YKL40/CHI3L1), monocyte chemoattractant protein-1 (MCP-1) neurofilament light (NfL), amyloid beta 38 (Aβ38), Aβ40, Aβ42, amyloid beta 42/40 ratio (Aβ42/40), soluble amyloid precursor protein alfa (sAPPα), sAPPβ, total tau (T-tau), phosphorylated tau (P-tau), growth-associated protein 43 (GAP43), and neurogranin.

RESULTS

The neurogranin concentration was higher in improved (68%) compared to unimproved patients (median 365 ng/L (IQR 186-544) vs 330 (205-456); p = 0.046). A linear regression model controlled for age, sex and vascular risk factors including neurogranin, T-tau, and GFAP, resulted in adjusted R2 = 0.06, p = 0.047. The Aβ42/40 ratio was bimodally distributed across all samples, as well as in the subgroups of improved and unimproved patients but did not contribute to outcome prediction. The preoperative MMSE score was lower within the low Aβ ratio group (median 25, IQR 23-28) compared to the high subgroup (26, 24-29) (p = 0.028). The T-Tau x Aβ40/42 ratio and P-tau x Aβ40/42 ratio did not contribute to shunt response prediction. The prevalence of vascular risk factors did not affect shunt response.

DISCUSSION

A higher preoperative ventricular CSF level of neurogranin, which is a postsynaptic marker, may signal a favorable postoperative outcome. Concentrations of a panel of ventricular CSF biomarkers explained only 6% of the variability in outcome. Evidence of amyloid or tau pathology did not affect the outcome.

Plasma and cerebrospinal fluid concentrations of neurofilament light protein correlate in patients with idiopathic normal pressure hydrocephalus

BACKGROUND

Neurofilament light chain protein (NFL), a marker of neuronal axonal degeneration, is increased in cerebrospinal fluid (CSF) of patients with idiopathic normal pressure hydrocephalus (iNPH). Assays for analysis of NFL in plasma are now widely available but plasma NFL has not been reported in iNPH patients. Our aim was to examine plasma NFL in iNPH patients and to evaluate the correlation between plasma and CSF levels, and whether NFL levels are associated with clinical symptoms and outcome after shunt surgery.

METHODS

Fifty iNPH patients with median age 73 who had their symptoms assessed with the iNPH scale and plasma and CSF NFL sampled pre- and median 9 months post-operatively. CSF plasma was compared with 50 healthy controls (HC) matched for age and gender. Concentrations of NFL were determined in plasma using an in-house Simoa method and in CSF using a commercially available ELISA method.

RESULTS

Plasma NFL was elevated in patients with iNPH compared to HC (iNPH: 45 (30-64) pg/mL; HC: 33 (26-50) (median; Q1-Q3), p = 0.029). Plasma and CSF NFL concentrations correlated in iNPH patients both pre- and postoperatively (r = 0.67 and 0.72, p < 0.001). We found only weak correlations between plasma or CSF NFL and clinical symptoms and no associations with outcome. A postoperative NFL increase was seen in CSF but not in plasma.

CONCLUSIONS

Plasma NFL is increased in iNPH patients and concentrations correlate with CSF NFL implying that plasma NFL can be used to assess evidence of axonal degeneration in iNPH. This finding opens a window for plasma samples to be used in future studies of other biomarkers in iNPH. NFL is probably not a very useful marker of symptomatology or for prediction of outcome in iNPH.

Concordance of Alzheimer's Disease-Related Biomarkers Between Intraventricular and Lumbar Cerebrospinal Fluid in Idiopathic Normal Pressure Hydrocephalus

BACKGROUND

Alzheimer's disease cerebrospinal fluid (CSF) biomarkers amyloid-β 1-42 (Aβ42), total tau (T-tau), and phosphorylated tau 181 (P-tau181) are widely used. However, concentration gradient of these biomarkers between intraventricular (V-CSF) and lumbar CSF (L-CSF) has been demonstrated in idiopathic normal pressure hydrocephalus (iNPH), potentially affecting clinical utility.

OBJECTIVE

Here we aim to provide conversion factors for clinical and research use between V-CSF and L-CSF.

METHODS

Altogether 138 iNPH patients participated. L-CSF samples were obtained prior to shunt surgery. Intraoperative V-CSF samples were obtained from 97 patients. Post-operative follow-up L- and V-CSF (shunt reservoir) samples of 41 patients were obtained 1-73 months after surgery and then after 3, 6, and 18 months. CSF concentrations of Aβ42, T-tau, and P-tau181 were analyzed using commercial ELISA assays.

RESULTS

Preoperative L-CSF Aβ42, T-tau, and P-tau181 correlated to intraoperative V-CSF (ρ= 0.34-0.55, p < 0.001). Strong correlations were seen between postoperative L- and V-CSF for all biomarkers in every follow-up sampling point (ρs Aβ42: 0.77-0.88, T-tau: 0.91-0.94, P-tau181: 0.94-0.96, p < 0.0001). Regression equations were determined for intraoperative V- and preoperative L-CSF (Aβ42: V-CSF = 185+0.34*L-CSF, T-tau: Ln(V-CSF) = 3.11+0.49*Ln(L-CSF), P-tau181: V-CSF = 8.2+0.51*L-CSF), and for postoperative V- and L-CSF (Aβ42: V-CSF = 86.7+0.75*L-CSF, T-tau: V-CSF = 86.9+0.62*L-CSF, P-tau181: V-CSF = 2.6+0.74*L-CSF).

CONCLUSION

Aβ42, T-tau, and P-tau181 correlate linearly in-between V- and L-CSF, even stronger after CSF shunt surgery. Equations presented here, provide a novel tool to use V-CSF for diagnostic and prognostic entities relying on the L-CSF concentrations and can be applicable to clinical use when L-CSF samples are not available or less invasively obtained shunt reservoir samples should be interpreted.

Ventricular volume in relation to lumbar CSF levels of amyloid-β 1–42, tau and phosphorylated tau in iNPH, is there a dilution effect?

Background

Levels of the biomarkers amyloid-β 1–42 (Aβ42), tau and phosphorylated tau (p-tau) are decreased in the cerebrospinal fluid (CSF) of patients with idiopathic normal pressure hydrocephalus (iNPH). The mechanism behind this is unknown, but one potential explanation is dilution by excessive CSF volumes. The aim of this study was to investigate the presence of a dilution effect, by studying the relationship between ventricular volume (VV) and the levels of the CSF biomarkers.

Methods

In this cross-sectional observational study, preoperative magnetic resonance imaging (MRI) and lumbar CSF was acquired from 136 patients with a median age of 76 years, 89 men and 47 females, selected for surgical treatment for iNPH. The CSF volume of the lateral and third ventricles was segmented on MRI and related to preoperative concentrations of Aβ42, tau and p-tau.

Results

In the total sample VV (Median 140.7 mL) correlated weakly (rs = − 0.17) with Aβ42 (Median 534 pg/mL), but not with tau (Median 216 pg/mL) nor p-tau (Median 31 pg/mL). In a subgroup analysis, the correlation between VV and Aβ42 was only present in the male group (rs = − 0.22, p = 0.038). Further, Aβ42 correlated positively with tau (rs = 0.30, p = 0.004) and p-tau (rs = 0.26, p = 0.012) in males but not in females.

Conclusions

The findings did not support a major dilution effect in iNPH, at least not in females. The only result in favor for dilution was a weak negative correlation between VV and Aβ42 but not with the other lumbar CSF biomarkers. The different results between males and females suggest that future investigations of the CSF pattern in iNPH would gain from sex-based subgroup analysis.

Update on the Cognitive Presentations of iNPH for Clinicians

This mini-review focuses on cognitive impairment in iNPH. This symptom is one of the characteristic triad of symptoms in a condition long considered to be the only treatable dementia. We present an update on recent developments in clinical, neuropsychological, neuroimaging and biomarker aspects. Significant advances in our understanding have been made, notably regarding biomarkers, but iNPH remains a difficult diagnosis. Stronger evidence for permanent surgical treatment is emerging but selection for treatment remains challenging, particularly with regards to cognitive presentations. Encouragingly, there has been increasing interest in iNPH, but more research is required to better define the underlying pathology and delineate it from overlapping conditions, in order to inform best practise for the clinician managing the cognitively impaired patient. In the meantime, we strongly encourage a multidisciplinary approach and a structured service pathway to maximise patient benefit.

Tap Test Can Predict Cognitive Improvement in Patients With iNPH-Results From the Multicenter Prospective Studies SINPHONI-1 and -2

Background: We analyzed the predictive value of the tap test (TT) on the outcome of cerebrospinal fluid (CSF) shunting in patients with idiopathic normal pressure hydrocephalus (iNPH) and cognitive impairment up to 12 months postoperatively. Methods: We analyzed the data of two prospective multicenter studies on ventriculoperitoneal shunt (VPS) and lumboperitoneal shunt (LPS) use in iNPH patients. We selected patients with Mini-Mental State Examination (MMSE) scores ≤ 26 points as study subjects. We used a multivariate logistic regression model to obtain the optimal threshold of MMSE scores after TT to predict the score improvement at 12 months following shunting and that helped to control for confounding factors such as age and MMSE scores before TT. We used logistic regression models to identify variables with age-adjusted odds ratio (A-OR) and multivariate-adjusted OR (M-OR). Results: For an improvement of ≥3 points in the MMSE score cutoff 7 days following TT in VPS and LPS cohort studies, the MMSE scores improved by 6 points after 12 months. The VPS cohort had sensitivity, specificity, and area under the curve (AUC) of 69.2, 73.7, and 0.771%, respectively; however, for the LPS cohort, they were 86.2, 90.9, and 0.906%, respectively. For MMSE scores that improved by ≥3 points in patients after the TT, the possibility of an improvement by 6 points at 12 months following CSF shunt had A-OR 7.77 and M-OR 6.3 times for the VPS, and A-OR 62.3 and M-OR 59.6 times for the LPS cohort. Conclusion: CSF shunting contributes to improved cognitive function in iNPH patients. Furthermore, MMSE score evaluation at the TT can sensitively predict improvement in postoperative MMSE scores following LPS intervention. Clinical Trial Registration: SINPHONI-1 (ClinicalTrials.gov, no. NCT00221091), first posted: September 22, 2005. SINPHONI-2 [University Hospital Medical Information Network (UMIN) Clinical Trials no. UMIN000002730], the posted: February 1, 2010.