Clinical relevance of cerebral small vessel diseases in cognitive impairment, neurodegeneration and stroke

Cerebral small vessel diseases are common age-related processes associated with two important and highly prevalent clinical syndromes: stroke and dementia. Whilst our ability to define a specific small vessel disease neuropathologically (most usually post-mortem) is excellent, it is still difficult to reach a definitive diagnosis during life; there remains an unmet need to accurately classify and quantify different subtypes, especially if effective therapeutic trials are ever to be implemented. Thus, two important outstanding questions regarding cerebral small vessel diseases are: how do these processes contribute to cognitive decline and clinical prognosis, and how can we better recognise small vessel disease subtype and severity during life? The programme of research described in this PhD thesis has three key aims. The first is to explore the role of cerebral small vessel diseases and their neuroimaging markers in specific patient populations. These include patients with cognitive impairment and dementia (a “memory clinic” population), patients with spontaneous (“primary”) intracerebral haemorrhage, and those presenting with cardioembolic ischaemic stroke or TIA (transient ischaemic attack). The second aim is to identify how and whether different small vessel disease subtypes (defined on the basis of intracerebral haemorrhage location) and their burden are associated with particular outcomes in patients with intracerebral haemorrhage. The outcomes of interest are recurrent intracerebral haemorrhage, subsequent cerebral ischaemic events (either ischaemic stroke or TIA), and death. The final aim is to present work from a prospective observational pilot study designed to identify new biomarkers for cerebral amyloid angiopathy, one of the most common cerebral small vessel diseases. In addition to describing the protocol and the recruitment process, results from body fluid analyses (cerebrospinal fluid and blood) and positron emission tomography (using the amyloid ligand 18F-florbetapir) scanning will be presented. The implications and limitations of this work will then be discussed, together with proposals for future work in this field

Clinical considerations in early-onset cerebral amyloid angiopathy

Cerebral amyloid angiopathy (CAA) is an important cerebral small vessel disease associated with brain haemorrhage and cognitive change. The commonest form, sporadic amyloid-beta CAA, usually affects people in mid- to later life. However, early-onset forms, though uncommon, are increasingly recognised and may result from genetic or iatrogenic causes that warrant specific and focussed investigation and management. In this review, we firstly describe the causes of early-onset CAA, including monogenic causes of amyloid-beta CAA (APP missense mutations and copy number variants; mutations of PSEN1 and PSEN2) and non-amyloid-beta CAA (associated with ITM2B, CST3, GSN, PRNP and TTR mutations), and other unusual sporadic and acquired causes including the newly-recognised iatrogenic subtype. We then provide a structured approach for investigating early-onset CAA, and highlight important management considerations. Improving awareness of these unusual forms of CAA amongst healthcare professionals is essential for facilitating their prompt diagnosis, and an understanding of their underlying pathophysiology may have implications for more common, late-onset, forms of the disease

Prevalence, patterns, and predictors of patient-reported non-motor outcomes at 30 days after acute stroke: prospective observational hospital cohort study

Background: Adverse non-motor outcomes are common after acute stroke and likely to substantially affect quality of life, yet few studies have comprehensively assessed their prevalence, patterns, and predictors across multiple health domains.// Aims: We aim to identify the prevalence, patterns and the factors associated with non-motor outcomes 30 days after stroke.// Methods: This prospective observational hospital cohort study (Stroke Investigation in North and Central London (SIGNAL) identified patients with acute ischaemic stroke or intracerebral haemorrhage (ICH) admitted to the Hyperacute Stroke Unit (HASU) University College Hospital (UCH), London, between August 1st 2018 and August 31st 2019. We assessed non-motor outcomes (anxiety, depression, fatigue, sleep, participation in social roles and activities, pain, bowel, and bladder function) at 30-day follow-up using the Patient Reported Outcome Measurement Information System-Version 29 (PROMIS-29) scale and Barthel Index scale.// Results: We obtained follow-up data for 605/719 (84.1%) eligible patients (mean age 72.0 years; 48.3% female; 521 with ischaemic stroke, 84 with ICH). Anxiety (57.0%), fatigue (52.7%), bladder dysfunction (50.2%), reduced social participation (49.2%), and pain (47.9%) were the commonest adverse non-motor outcomes. The rates of adverse non-motor outcomes in ≥1, ≥2 and ≥3 domains were 89%, 66.3% and 45.8%, respectively; in adjusted analyses, stroke due to ICH (compared to ischaemic stroke) and admission stroke severity were the strongest and most consistent predictors. There were significant correlations between; bowel dysfunction and bladder dysfunction (κ= 0.908); reduced social participation and bladder dysfunction (κ= 0.844); and anxiety and fatigue (κ= 0.613). We did not identify correlation for other pairs of non-motor domains.// Conclusions: Adverse non-motor outcomes are very common at one month after stroke, affecting nearly 90% of evaluated patients in at least one health domain, about two-thirds in two or more domains, and almost 50% in three or more domains. Stroke due to ICH and admission stroke severity were the strongest and most consistent predictors. Adverse outcomes occur in pairs of domains such as with anxiety and fatigue.Our findings emphasise the importance of a multi-domain approach to effectively identify adverse non-motor outcomes after stroke to inform the development of more holistic patient recovery programs

Effect of small-vessel disease on cognitive trajectory after atrial fibrillation-related ischaemic stroke or TIA

Post-stroke dementia is common but has heterogenous mechanisms that are not fully understood, particularly in patients with atrial fibrillation (AF)-related ischaemic stroke or TIA. We investigated the relationship between MRI small-vessel disease markers (including a composite cerebral amyloid angiopathy, CAA, score) and cognitive trajectory over 12 months. We included patients from the CROMIS-2 AF study without pre-existing cognitive impairment and with Montreal Cognitive Assessment (MoCA) data. Cognitive impairment was defined as MoCA < 26. We defined "reverters" as patients with an "acute" MoCA (immediately after the index event) score < 26, who then improved by ≥ 2 points at 12 months. In our cohort (n = 114), 12-month MoCA improved overall relative to acute performance (mean difference 1.69 points, 95% CI 1.03-2.36, p < 0.00001). 12-month cognitive impairment was associated with increasing CAA score (per-point increase, adjusted OR 4.09, 95% CI 1.36-12.33, p = 0.012). Of those with abnormal acute MoCA score (n = 66), 59.1% (n = 39) were "reverters". Non-reversion was associated with centrum semi-ovale perivascular spaces (per-grade increase, unadjusted OR 1.83, 95% CI 1.06-3.15, p = 0.03), cerebral microbleeds (unadjusted OR 10.86, 95% CI 1.22-96.34, p = 0.03), and (negatively) with multiple ischaemic lesions at baseline (unadjusted OR 0.11, 95% CI 0.02-0.90, p = 0.04), as well as composite small-vessel disease (per-point increase, unadjusted OR 2.91, 95% CI 1.23-6.88, p = 0.015) and CAA (per-point increase, unadjusted OR 6.71, 95% CI 2.10-21.50, p = 0.001) scores. In AF-related acute ischaemic stroke or TIA, cerebral small-vessel disease is associated both with cognitive performance at 12 months and failure to improve over this period

Association of Presence and Pattern of MRI Markers of Cerebral Small Vessel Disease With Recurrent Intracerebral Hemorrhage.

BACKGROUND Assessing the risk of recurrent intracerebral hemorrhage (ICH) is of high clinical importance. MRI-based cerebral small vessel disease (SVD) markers may help establish ICH etiological subtypes (including cryptogenic ICH) relevant for recurrence risk. METHODS We investigated the risk of recurrent ICH in a large cohort of consecutive ICH survivors with available MRI at baseline. Patients with macrovascular, structural or other identified secondary causes (other than SVD) were excluded. Based on MRI findings, ICH etiology was defined as probable cerebral amyloid angiopathy (CAA) according to the Boston 2.0 criteria, arteriolosclerosis (non-lobar ICH and additional markers of arteriolosclerosis, absent lobar hemorrhagic lesions), mixed SVD (mixed deep and lobar hemorrhagic changes) or cryptogenic (no MRI markers of SVD). Recurrent ICH was determined using electronic health records and confirmed by neuroimaging. Data from an independent multi-center cohort (CROMIS-2 ICH) was used to confirm core findings. RESULTS Of 443 patients with ICH (mean age 67±13 years, 41% female), ICH etiology was mixed SVD in 36.7%, arteriolosclerosis in 23.6%, CAA in 23.0%, and cryptogenic in 16.7%. During a median follow-up period of 5.7 years (IQR 2.9-10.0, 2682 patient-years), recurrent ICH were found in 59 individual patients (13.3%). The highest recurrence rate per 100 person-years was detected in patients with CAA (8.5, 95% CI 6.1-11.7), followed by mixed SVD (1.8, 95% CI 1.1-2.9) and arteriolosclerosis (0.6, 95% CI 0.3-1.5). No recurrent ICH occurred in patients with cryptogenic ICH during 510 person-years follow-up (97.5% CI, 0-0.7); this finding was confirmed in an independent cohort (CROMIS-2 ICH, n=216), in which there was also no recurrence in patients with cryptogenic ICH. In patients with CAA, cortical superficial siderosis was the imaging feature strongest related with ICH recurrence (hazard ratio 5.7, 95% CI 2.4-13.6). CONCLUSIONS MRI-based etiological subtypes are helpful in determining the recurrence risk of ICH; while the highest recurrence risk was found in CAA, recurrence risk was low for arteriolosclerosis, and negligible for cryptogenic ICH

Association of Presence and Pattern of MRI Markers of Cerebral Small Vessel Disease With Recurrent Intracerebral Hemorrhage

BACKGROUND: Assessing the risk of recurrent intracerebral hemorrhage (ICH) is of high clinical importance. MRI-based cerebral small vessel disease (SVD) markers may help establish ICH etiological subtypes (including cryptogenic ICH) relevant for recurrence risk. METHODS: We investigated the risk of recurrent ICH in a large cohort of consecutive ICH survivors with available MRI at baseline. Patients with macrovascular, structural or other identified secondary causes (other than SVD) were excluded. Based on MRI findings, ICH etiology was defined as probable cerebral amyloid angiopathy (CAA) according to the Boston 2.0 criteria, arteriolosclerosis (non-lobar ICH and additional markers of arteriolosclerosis, absent lobar hemorrhagic lesions), mixed SVD (mixed deep and lobar hemorrhagic changes) or cryptogenic (no MRI markers of SVD). Recurrent ICH was determined using electronic health records and confirmed by neuroimaging. Data from an independent multi-center cohort (CROMIS-2 ICH) was used to confirm core findings. RESULTS: Of 443 patients with ICH (mean age 67±13 years, 41% female), ICH etiology was mixed SVD in 36.7%, arteriolosclerosis in 23.6%, CAA in 23.0%, and cryptogenic in 16.7%. During a median follow-up period of 5.7 years (IQR 2.9-10.0, 2682 patient-years), recurrent ICH were found in 59 individual patients (13.3%). The highest recurrence rate per 100 person-years was detected in patients with CAA (8.5, 95% CI 6.1-11.7), followed by mixed SVD (1.8, 95% CI 1.1-2.9) and arteriolosclerosis (0.6, 95% CI 0.3-1.5). No recurrent ICH occurred in patients with cryptogenic ICH during 510 person-years follow-up (97.5% CI, 0-0.7); this finding was confirmed in an independent cohort (CROMIS-2 ICH, n=216), in which there was also no recurrence in patients with cryptogenic ICH. In patients with CAA, cortical superficial siderosis was the imaging feature strongest related with ICH recurrence (hazard ratio 5.7, 95% CI 2.4-13.6). CONCLUSIONS: MRI-based etiological subtypes are helpful in determining the recurrence risk of ICH; while the highest recurrence risk was found in CAA, recurrence risk was low for arteriolosclerosis, and negligible for cryptogenic ICH

A Small Molecule p75NTR Ligand, LM11A-31, Reverses Cholinergic Neurite Dystrophy in Alzheimer's Disease Mouse Models with Mid- to Late-Stage Disease Progression

Degeneration of basal forebrain cholinergic neurons contributes significantly to the cognitive deficits associated with Alzheimer's disease (AD) and has been attributed to aberrant signaling through the neurotrophin receptor p75 (p75NTR). Thus, modulating p75NTR signaling is considered a promising therapeutic strategy for AD. Accordingly, our laboratory has developed small molecule p75NTR ligands that increase survival signaling and inhibit amyloid-β-induced degenerative signaling in in vitro studies. Previous work found that a lead p75NTR ligand, LM11A-31, prevents degeneration of cholinergic neurites when given to an AD mouse model in the early stages of disease pathology. To extend its potential clinical applications, we sought to determine whether LM11A-31 could reverse cholinergic neurite atrophy when treatment begins in AD mouse models having mid- to late stages of pathology. Reversing pathology may have particular clinical relevance as most AD studies involve patients that are at an advanced pathological stage. In this study, LM11A-31 (50 or 75 mg/kg) was administered orally to two AD mouse models, Thy-1 hAPPLond/Swe (APPL/S) and Tg2576, at age ranges during which marked AD-like pathology manifests. In mid-stage male APPL/S mice, LM11A-31 administered for 3 months starting at 6–8 months of age prevented and/or reversed atrophy of basal forebrain cholinergic neurites and cortical dystrophic neurites. Importantly, a 1 month LM11A-31 treatment given to male APPL/S mice (12–13 months old) with late-stage pathology reversed the degeneration of cholinergic neurites in basal forebrain, ameliorated cortical dystrophic neurites, and normalized increased basal forebrain levels of p75NTR. Similar results were seen in female Tg2576 mice. These findings suggest that LM11A-31 can reduce and/or reverse fundamental AD pathologies in late-stage AD mice. Thus, targeting p75NTR is a promising approach to reducing AD-related degenerative processes that have progressed beyond early stages

Small vessel disease burden and intracerebral haemorrhage in patients taking oral anticoagulants

OBJECTIVE We investigated the contribution of small vessel disease (SVD) to anticoagulant-associated intracerebral haemorrhage (ICH). METHODS Clinical Relevance of Microbleeds in Stroke-2 comprised two independent multicentre observation studies: first, a cross-sectional study of patients with ICH; and second, a prospective study of patients taking anticoagulants for atrial fibrillation (AF) after cerebral ischaemia. In patients with ICH, we compared SVD markers on CT and MRI according to prior anticoagulant therapy. In patients with AF and cerebral ischaemia treated with anticoagulants, we compared the rates of ICH and ischaemic stroke according to SVD burden score during 2 years follow-up. RESULTS We included 1030 patients with ICH (421 on anticoagulants), and 1447 patients with AF and cerebral ischaemia. Medium-to-high severity SVD was more prevalent in patients with anticoagulant-associated ICH (CT 56.1%, MRI 78.7%) than in those without prior anticoagulant therapy (CT 43.5%, p<0.001; MRI 64.5%, p=0.072). Leukoaraiosis and atrophy were more frequent and severe in ICH associated with prior anticoagulation. In the cerebral ischaemia cohort (779 with SVD), during 3366 patient-years of follow-up the rate of ICH was 0.56%/year (IQR 0.27-1.03) in patients with SVD, and 0.06%/year (IQR 0.00-0.35) in those without (p=0.001); ICH was independently associated with severity of SVD (HR 5.0, 95% CI 1.9 to 12.2,p=0.001), and was predicted by models including SVD (c-index 0.75, 95% CI 0.63 to 0.85). CONCLUSIONS Medium-to-high severity SVD is associated with ICH occurring on anticoagulants, and independently predicts ICH in patients with AF taking anticoagulants; its absence identifies patients at low risk of ICH. Findings from these two complementary studies suggest that SVD is a contributory factor in ICH in patients taking anticoagulants and suggest that anticoagulation alone should no longer be regarded as a sufficient 'cause' of ICH. TRIAL REGISTRATION NCT02513316