Are cortical microvascular raspberries caused by cerebral hypoperfusion? An exploratory pathological study

Cortical microvascular raspberries and ageing: an independent but not exclusive relationship

INTRODUCTION

Raspberries are cerebral microvascular formations of unknown origin, defined as three or more transversally sectioned vascular lumina surrounded by a common perivascular space. We have previously demonstrated an increased raspberry density in the cortex of patients with vascular dementia and cerebral atherosclerosis, while studies by other authors on overlapping and synonymously defined vascular entities mainly associate them with advancing age. The aim of the present study was to examine the relationship between raspberries and age in a large study sample while including multiple potential confounding factors in the analysis.

MATERIALS AND METHODS

Our study sample consisted of 263 individuals aged 20-97 years who had undergone a clinical autopsy including a neuropathological examination. The cortical raspberry density had either been quantified as part of a previous study or was examined de novo in a uniform manner on haematoxylin- and eosin-stained tissue sections from the frontal lobe. The medical records and autopsy reports were assessed regarding neurodegeneration, cerebral infarcts, cerebral atherosclerosis and small vessel disease, cardiac hypertrophy, nephrosclerosis, hypertension, and diabetes mellitus. With the patients grouped according to 10-year age interval, non-parametric tests (the Kruskal-Wallis test, followed by pairwise testing with Bonferroni-corrected P values) and multiple linear regression models (not corrected for multiple tests) were performed.

RESULTS

The average raspberry density increased with advancing age. The non-parametric tests demonstrated statistically significant differences in raspberry density when comparing the groups aged 60-99 years and 70-99 years to those aged 20-29 years (P < 0.012) and 30-59 years (P < 0.011), respectively. The multiple linear regression models demonstrated positive associations with age interval (P < 0.001), cerebral atherosclerosis (P = 0.024), cardiac hypertrophy (P = 0.021), hypertension subgrouped for organ damage (P = 0.006), and female sex (P = 0.004), and a tendency towards a negative association with Alzheimer's disease neuropathologic change (P = 0.048).

CONCLUSION

The raspberry density of the frontal cortex increases with advancing age, but our results also indicate associations with acquired pathologies. Awareness of the biological and pathological context where raspberries occur can guide further research on their origin.

A neuropathologic feature of brain aging: multi-lumen vascular profiles

Cerebrovascular pathologies other than frank infarctions are commonly seen in aged brains. Here, we focus on multi-lumen vascular profiles (MVPs), which are characterized by multiple vessel lumens enclosed in a single vascular channel. Little information exists on the prevalence, risk factors, and co-pathologies of MVPs. Therefore, we used samples and data from the University of Kentucky Alzheimer's Disease Research Center (n = 91), the University of Kentucky Pathology Department (n = 31), and the University of Pittsburgh Pathology Department (n = 4) to study MVPs. Age at death was correlated with MVP density in the frontal neocortex, Brodmann Area 9 (r = 0.51; p < 0.0001). Exploratory analyses were performed to evaluate the association between conventional vascular risk factors (e.g., hypertension, diabetes), cardiovascular diseases (e.g., heart attack, arrhythmia), and cerebrovascular disease (e.g., stroke); the only nominal association with MVP density was a self-reported history of brain trauma (Prevalence Ratio = 2.1; 95 CI 1.1-3.9, before correcting for multiple comparisons). No specific associations were detected between neuropathological (e.g., brain arteriolosclerosis) or genetic (e.g., APOE) variables and MVP density. Using a tissue clearing method called SeeDB, we provide 3-dimensional images of MVPs in brain tissue. We conclude that MVPs are an age-related brain pathology and more work is required to identify their clinical-pathological correlation and associated risk factors.

On the regional distribution of cerebral microvascular 'raspberries' and their association with cerebral atherosclerosis and acute circulatory failure

Introduction

In this follow-up study, cerebral microvascular formations termed 'raspberries' were quantified according to cerebral atherosclerosis (C-ASCL) and acute circulatory failure (ACF). We also examined the regional distribution of raspberries throughout the brain.

Materials and methods

The study population consisted of adult individuals who had undergone a diagnostic neuropathological autopsy. Groups were formed to examine the association between raspberries, C-ASCL and ACF (control group, C-ASCL group, C-ASCL+ACF group [n = 47 per group] and a combined C-ASCL-tot group [n = 94]). To examine the regional distribution, additional groups were formed based on previously known raspberry densities of the frontal cortex (high-, medium- and low-density group [n = 6 per group]). Raspberries were quantified on scanned haematoxylin-eosin-stained sections.

Results

Cortical raspberry density did not differ at a statistically significant level between the control group, the C-ASCL group and the C-ASCL+ACF group (P = 0.10) but did so between the control group and the C-ASCL-tot group (P = 0.033). The total raspberry density of the high-, medium- and low-density groups differed at a statistically significant level (P = 0.005), which remained in group-to-group comparisons of the high- and medium-density groups (P = 0.015) and the high- and low-density groups (P = 0.002). Raspberries were rare in cerebral white matter and in the cerebellum.

Conclusion

An association between raspberry density and C-ASCL is supported but is weaker than previously indicated. An association with ACF is not indicated. The raspberry density of the frontal cortex provides an approximation of the brain's total raspberry density.