APOE4 predicts amyloid-ß in cortical brain biopsy but not idiopathic normal pressure hydrocephalus.

OBJECTIVE: To investigate the association of apolipoprotein E (APOE) genotype, especially the APOE4 allele, to (1) idiopathic normal pressure hydrocephalus (iNPH) and (2) amyloid-ß (Aß) plaques in cortical brain biopsies of presumed NPH patients with and without a final clinical diagnosis of Alzheimer's disease (AD). METHODS: 202 patients with presumed NPH were evaluated by intraventricular pressure monitoring and frontal cortical biopsy immunostained against Aß (134 semiquantified by Aß plaques/mm2). The 202 patients and 687 cognitively healthy individuals were genotyped for APOE. The final clinical diagnoses in a median follow-up of 3.9 years were: 113 iNPH (94 shunt responsive, 16 shunt non-responsive, three not shunted); 36 AD (12 mixed iNPH + AD); 53 others. RESULTS: The APOE genotypes distributed similarly in the 94 shunt responsive and 16 non-responsive iNPH patients and healthy controls. In multivariate analysis, the APOE4 allele correlated independently with Aß plaques in the cortical biopsies (OR 8.7, 95% CI 3.6 to 20, p<0.001). The APOE4 allele in presumed NPH predicted later AD as follows: sensitivity 61%; specificity 77%; positive predictive value 37%; negative predictive value 90%. CONCLUSION: In presumed NPH patients, APOE4 associates independently with the presence of Aß plaques in the frontal cortical biopsy. APOE4 is not a risk factor for iNPH and does not predict the response to shunt. Our data further support the view that the iNPH syndrome is a distinct dementing disease. TRIAL REGISTRATION NUMBER: Kuopio NPH Registry (http://www.uef.fi/nph).

Cortical brain biopsy in long-term prognostication of 468 patients with possible normal pressure hydrocephalus.

Normal pressure hydrocephalus (NPH) can be alleviated by cerebrospinal fluid shunting but the differential diagnosis and patient selection are challenging. Intraventricular intracranial pressure monitoring as part of the diagnostic workup as well as shunting enable to obtain cortical brain biopsies to detect amyloid-ß (Aß) and hyperphosphorylated tau (HPτ), the hallmark lesions of Alzheimer's disease (AD). In possible NPH, Aß alone indicates an increased risk of AD and when present with HPτ probable AD, but the effect of those brain lesions on survival is not known. The aim of this study was to evaluate the predictive value of brain biopsy for the long-term outcome of possible NPH. Between 1991 and 2006, the Neurosurgery Department of the Kuopio University Hospital evaluated 468 patients for possible NPH by intraventricular intracranial pressure monitoring and frontal cortical brain biopsy immunostained against Aß and HPτ. All patients were followed up until the end of 2008 (n = 201) or death (n = 267) with a median follow-up of 4.6 years (range 0-17). Logistic regression analysis with Cox models was applied. Out of the 468 cases, Aß was detected in 197 (42%) cortical biopsies, and together with HPτ in 44 (9%). Aß alone indicated increased risk of AD and with HPτ probable AD, but it did not affect survival. Vascular aetiology was the most frequent cause of death. Cortical biopsy findings indicate that NPH is at present a heterogeneous syndrome and has notable overlapping with AD. Brain biopsy did not predict survival but may open a novel research window to study the pathobiology of neurodegeneration.

Amyloid and tau proteins in cortical brain biopsy and Alzheimer's disease.

OBJECTIVE: Amyloid-ß(Aß) aggregates are presumed to be found in the brain at an early stage of Alzheimer's disease (AD) but have seldom been assessed by brain biopsy during life in often elderly patients. METHODS: Between 1991 and 2006 we evaluated 468 patients with suspected normal pressure hydrocephalus with intraventricular pressure monitoring and a right frontal cortical biopsy sample immunostained for Aß and hyperphosphorylated tau (HPτ). Adequate samples and the clinical follow-up data until death or the end of 2008, available in 433 cases, were reviewed for the clinical signs of dementia, including AD. Logistic regression analysis was used to analyze whether Aß and/or HPτ in the biopsy samples obtained during life predicted development of cognitive impairment, in particular, AD. RESULTS: Of the 433 frontal cortical samples, 42 (10%) displayed both Aß and HPτ, 144 (33%) Aß only, and 247 (57%) neither Aß nor HPτ. In a median follow-up time of 4.4 years, 94 patients (22%) developed clinical AD. The presence of both Aß and HPτ was strongly associated (odds ratio [OR], 68.2; 95% confidence interval [CI], 22.1-210) and Aß alone significantly associated (OR, 10.8; 95% CI, 4.9-23.8) with the clinical diagnosis of AD. INTERPRETATION: This is the largest follow-up study of patients assessed for the presence of Aß and HPτ in frontal cortical brain biopsy samples. 1) The presence of Aß and HPτ spoke strongly for the presence or later development of clinical AD; 2) Aß alone was suggestive of AD; and 3) the absence of Aß and HPτ spoke against a later clinical diagnosis of AD.

Incidence, Comorbidities, and Mortality in Idiopathic Normal Pressure Hydrocephalus.

OBJECT: To investigate the incidence, comorbidities, mortality, and causes of death in idiopathic normal pressure hydrocephalus (iNPH). METHODS: A cohort of 536 patients with possible NPH from a defined population with a median follow-up time of 5.1 years, (range 0.04-19.9 years) was included in the study. Patients were evaluated by brain imaging and intraventricular pressure monitoring, with a brain biopsy specimen immunostained against amyloid-ß and hyperphosphorylated τ. Hospital records were reviewed for vascular diseases and type 2 diabetes mellitus (T2DM). Death certificates and yearly population of the catchment area were obtained from national registries. RESULTS: A total of 283 patients had a clinical diagnosis of iNPH, leading to a median annual incidence of 1.58 iNPH patients per 100,000 inhabitants (range, 0.8-4.5). Alzeimer disease-related brain biopsy findings were less frequent in iNPH patients than in non-iNPH patients (P < 0.05). An overrepresentation of hypertension (52% vs. 33%, P < 0.001) and T2DM (23% vs. 13%, P = 0.002) was noted in iNPH patients. Age (hazard ratio [HR] 1.04/year, 95% confidence interval [CI] 1.03-1.06, P < 0.001) and T2DM (HR 1.63, 95% CI 1.23-2.16, P < 0.001) increased the risk of death in the iNPH patients and in the total population. iNPH was associated with decreased risk of death (HR 0.63, 95% CI 0.50-0.78, P < 0.001). The most frequent causes of death were cardiovascular and cerebrovascular disease. Dementia as a cause of death was more common in non-iNPH patients (27% vs. 10%, P < 0.001). CONCLUSIONS: Hypertension and T2DM are common in iNPH and the latter causes excess mortality in the affected patients.

Familial idiopathic normal pressure hydrocephalus.

Idiopathic normal pressure hydrocephalus (iNPH) is a late-onset surgically alleviated, progressive disease. We characterize a potential familial subgroup of iNPH in a nation-wide Finnish cohort of 375 shunt-operated iNPH-patients. The patients were questionnaired and phone-interviewed, whether they have relatives with either diagnosed iNPH or disease-related symptomatology. Then pedigrees of all families with more than one iNPH-case were drawn. Eighteen patients (4.8%) from 12 separate pedigrees had at least one shunt-operated relative whereas 42 patients (11%) had relatives with two or more triad symptoms. According to multivariate logistic regression analysis, familial iNPH-patients had up to 3-fold risk of clinical dementia compared to sporadic iNPH patients. This risk was independent from diagnosed Alzheimer's disease and APOE ε4 genotype. This study describes a familial entity of iNPH offering a novel approach to discover the potential genetic characteristics of iNPH. Discovered pedigrees offer an intriguing opportunity to conduct longitudinal studies targeting potential preclinical signs of iNPH.

Amyloid-ß and Tau Dynamics in Human Brain Interstitial Fluid in Patients with Suspected Normal Pressure Hydrocephalus.

BACKGROUND: Amyloid-ß (Aß1 - 42), total tau (T-tau), and phosphorylated tau (P-tau181) in the cerebrospinal fluid (CSF) are the most promising biomarkers of Alzheimer's disease (AD). Still, little is known about the dynamics of these molecules in the living brain. In a transgenic mouse brain, soluble Aß decreases with increasing age and advanced Aß pathology as seen similarly in CSF. OBJECTIVE: To assess the relationship between AD-related pathological changes in human brain tissue, ventricular and lumbar CSF, and brain interstitial fluid (ISF). METHODS: Altogether 11 patients with suspected idiopathic normal pressure hydrocephalus underwent frontal cortical brain biopsy, 24-h intraventricular pressure monitoring, and a microdialysis procedure. AD-related biomarkers were analyzed from brain tissue, CSF, and ISF. RESULTS: ISF T-tau levels decreased strongly within the first 12 h, then plateauing until the end of the experiment. Aß1 - 42 and P-tau181 remained stable during the experiment (n = 3). T-tau and P-tau were higher in the ISF than in ventricular or lumbar CSF, while Aß1 - 42 levels were within similar range in both CSF and ISF samples. ISF P-tau correlated with the ventricular CSF T-tau (r = 0.70, p = 0.017) and P-tau181 (r = 0.64, p = 0.034). Five patients with amyloid pathology in the brain biopsy tended to reveal lower ISF Aß1 - 42 levels than those six without amyloid pathology. CONCLUSIONS: This is the first study to report ISF Aß and tau levels in the human brain without significant brain injury. The set-up used enables sampling from the brain ISF for at least 24 h without causing adverse effects due to the microdialysis procedure to follow the dynamics of the key molecules in AD pathogenesis in the living brain at various stages of the disease.

Cerebrospinal fluid biomarker and brain biopsy findings in idiopathic normal pressure hydrocephalus.

BACKGROUND: The significance of amyloid precursor protein (APP) and neuroinflammation in idiopathic normal pressure hydrocephalus (iNPH) and Alzheimer's disease (AD) is unknown. OBJECTIVE: To investigate the role of soluble APP (sAPP) and amyloid beta (Aß) isoforms, proinflammatory cytokines, and biomarkers of neuronal damage in the cerebrospinal fluid (CSF) in relation to brain biopsy Aß and hyperphosphorylated tau (HPτ) findings. METHODS: The study population comprised 102 patients with possible NPH with cortical brain biopsies, ventricular and lumbar CSF samples, and DNA available. The final clinical diagnoses were: 53 iNPH (91% shunt-responders), 26 AD (10 mixed iNPH+AD), and 23 others. Biopsy samples were immunostained against Aß and HPτ. CSF levels of AD-related biomarkers (Aß42, p-tau, total tau), non-AD-related Aß isoforms (Aß38, Aß40), sAPP isoforms (sAPPα, sAPPß), proinflammatory cytokines (several interleukins (IL), interferon-gamma, monocyte chemoattractant protein-1, tumor necrosis factor-alpha) and biomarkers of neuronal damage (neurofilament light and myelin basic protein) were measured. All patients were genotyped for APOE. RESULTS: Lumbar CSF levels of sAPPα were lower (p<0.05) in patients with shunt-responsive iNPH compared to non-iNPH patients. sAPPß showed a similar trend (p = 0.06). CSF sAPP isoform levels showed no association to Aß or HPτ in the brain biopsy. Quantified Aß load in the brain biopsy showed a negative correlation with CSF levels of Aß42 in ventricular (r = -0.295, p = 0.003) and lumbar (r = -0.356, p = 0.01) samples, while the levels of Aß38 and Aß40 showed no correlation. CSF levels of proinflammatory cytokines and biomarkers of neuronal damage did not associate to the brain biopsy findings, diagnosis, or shunt response. Higher lumbar/ventricular CSF IL-8 ratios (p<0.001) were seen in lumbar samples collected after ventriculostomy compared to the samples collected before the procedure. CONCLUSIONS: The role of sAPP isoforms in iNPH seems to be independent from the amyloid cascade. No neuroinflammatory background was observed in iNPH or AD.