Cerebrospinal Fluid Biomarkers to Differentiate Idiopathic Normal Pressure Hydrocephalus from Subcortical Ischemic Vascular Disease.

BACKGROUND: Idiopathic normal pressure hydrocephalus (iNPH) remains a challenge to differentiate from subcortical ischemic vascular disease (SIVD). Despite major research efforts, the cerebrospinal fluid (CSF) biomarker profiles of the two diseases are still not known in detail. OBJECTIVE: To determine if novel CSF biomarkers, neurofilament light (NFL) reflecting axonal damage, the synaptic protein neurogranin (NG), and the astroglial marker chitinase-3-like protein 1 (YKL-40), and the core Alzheimer's disease (AD) biomarkers, amyloid-ß 42 (Aß42), total tau (t-tau), phosphorylated tau (p-tau), can differentiate iNPH from SIVD. Patients with AD and healthy controls (HC) were included for comparison purposes. METHODS: Patients with iNPH (n = 28), SIVD (n = 30), AD (n = 57), and HC (n = 33) were retrospectively included from the Danish Dementia Biobank. All patients with iNPH had effect of shunt surgery with a follow-up period of 4 to 69 months. CSF biomarkers were measured using immunoassays. RESULTS: Lower levels of NFL, NG, Aß42, and t-tau were found in patients with iNPH versus SIVD, while YKL-40 and p-tau were similar in the two diseases. NFL and Aß42 were the most reliable biomarkers to differentiate iNPH from SIVD with an area under the curve (AUC) on 0.82 and 0.80, respectively. Combining NFL with Aß42, t-tau, and p-tau resulted in an AUC of 0.90, which was equivalent to the diagnostic accuracy of all six biomarkers combined. CONCLUSION: An addition of NFL to the CSF panel of Aß42, t-tau, and p-tau may improve the differentiation of iNPH from SIVD.

Cerebrospinal Fluid Biomarkers in Idiopathic Normal Pressure Hydrocephalus versus Alzheimer's Disease and Subcortical Ischemic Vascular Disease: A Systematic Review.

BACKGROUND: The diagnostic workup of idiopathic normal pressure hydrocephalus (iNPH) can be challenging due to an overlap in symptoms and neuroimaging features with other disorders. Despite a growing interest, a cerebrospinal fluid (CSF) biomarker profile in iNPH has not yet been identified. OBJECTIVE: To determine the CSF biomarkers with the greatest evidence for differentiating iNPH from the most common differential diagnoses, Alzheimer's disease (AD) and subcortical ischemic vascular disease (SIVD). METHODS: A systematic literature search was conducted in PubMed to identify relevant articles up to July 2018 using the following MESH-terms: "Cerebrospinal fluid", "diagnos*", "hydrocephalus, normal pressure". Relevant data were extracted to assess the risk of bias in the included studies. RESULTS: Twenty-five studies including 664 patients with iNPH, 502 with AD, 57 with SIVD, 81 with other disorders, and 338 healthy controls (HC) were included. They investigated the diagnostic value of 92 CSF biomarkers. Most evidence existed for amyloid-ß 42 (Aß42), phosphorylated tau (p-tau), and total tau (t-tau) in iNPH versus AD and HC: Aß42 did not differ between iNPH and AD, but was lower than in HC subjects. T-tau and p-tau were lower in iNPH versus AD on a level comparable to HC subjects. There was moderate or limited evidence for 62 and 88 biomarkers, respectively. Several plausible biases characterize the literature including small sample sizes and inconsistent diagnostic criteria. CONCLUSION: T-tau and p-tau may differentiate iNPH from AD and Aß42 from HC. A combination of these biomarkers may improve the diagnostic accuracy in iNPH.