The association between carotid blood flow and resting-state brain activity in patients with cerebrovascular diseases

 In my opinion they are not thinking about this properly. If the Circle of Willis is complete you measure the blood flow there to determine your information. Measuring carotid blood flow is just measuring an intermediate step so your are removed from valid measurements and conclusions. Since my right carotid artery artery was completely closed for 14 years this analysis would make the assumption I have no resting-state brain activity. But I'm not dead yet, so there.

The association between carotid blood flow and resting-state brain activity in patients with cerebrovascular diseases

• Takahiro Matsumoto,
• Hideyuki Hoshi,
• Yoko Hirata,
• Sayuri Ichikawa,
• Keisuke Fukasawa,
• Tomoyuki Gonda,
• Jesús Poza,
• Víctor Rodríguez-González,
• Carlos Gómez &
• Yoshihito Shigihara 

Scientific Reports volume 11, Article number: 15225 (2021) Cite this article

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Abstract

Cerebral hypoperfusion impairs brain activity and leads to cognitive impairment. Left and right common carotid arteries (CCA) are the major source of cerebral blood supply. It remains unclear whether blood flow in both CCA contributes equally to brain activity. Here, CCA blood flow was evaluated using ultrasonography in 23 patients with cerebrovascular diseases. Resting-state brain activity and cognitive status were also assessed using magnetoencephalography and a cognitive subscale of the Functional Independence Measure, respectively, to explore the relationships between blood flow, functional brain activity, and cognitive status. Our findings indicated that there was an association between blood flow and resting-state brain activity, and between resting-state brain activity and cognitive status. However, blood flow was not significantly associated with cognitive status directly. Furthermore, blood velocity in the right CCA correlated with resting-state brain activity, but not with the resistance index. In contrast, the resistance index in the left CCA correlated with resting-state brain activity, but not with blood velocity. Our findings suggest that hypoperfusion is important in the right CCA, whereas cerebral microcirculation is important in the left CCA for brain activity. Hence, this asymmetry should be considered when designing appropriate therapeutic strategies.

Introduction

Dementia is a syndrome characterised by progressive cognitive impairment due to diverse brain diseases. Alzheimer's disease is the most prevalent cause of dementia followed by cerebrovascular diseases, which are typically termed ‘vascular dementia’^1,2. Cerebrovascular diseases lead to cerebral hypoperfusion and stroke³. Hypoperfusion itself changes brain activity⁴ and leads to cognitive impairment^5,6,7. Cerebral blood supply depends on two pairs of arteries, namely, the left and right internal carotid arteries and the vertebral arteries, with three-quarters of the blood supplied by the internal carotid artery pair⁸. The internal carotid artery is a branch of the common carotid artery (CCA) and its blood flow velocity has been associated with cognition in older adults^9,10. Both sides of the CCA supply blood mainly to the ipsilateral side of the cerebral hemisphere, with each hemisphere contributing differently to cognitive status^11,12,13. In this context, we hypothesised that there was an asymmetrical association between the two sides (i.e. left and right) of the CCA in terms of brain activity and cognitive status.

Blood flow in the CCA can be measured using carotid ultrasonography, which is a non-invasive measurement method for hypoperfusion due to atherosclerosis. It provides information on blood flow velocities and other haemodynamic factors, such as downstream resistance. Resting-state brain activity can be measured using magnetoencephalography (MEG). Resting-state MEG measures spontaneous neural oscillations and is sensitive to cerebral hypoperfusion¹⁴, which reduces the amplitude and lowers the frequency of oscillatory activities^4,14. Changes in resting-state brain activity are also associated with cognitive impairment^15,16,17, which, in turn, is related to three major characteristic alterations: (1) enhanced low frequency oscillatory activity accompanied with attenuated high frequency oscillatory activity; (2) slowing down of the alpha peak frequency (so-called ‘shift-to-the-left of the alpha peak’); and (3) loss of irregularity of brain activity^15,17,18,19. Cognitive status is generally assessed using neuropsychological tests, such as the Functional Independence Measure (FIM)^20,21,22 and the Mini-Mental State Examination (MMSE)¹⁰. The FIM is used to evaluate the cognitive and motor status of patients with cerebrovascular diseases, especially during rehabilitation periods, whereas the MMSE is used for screening dementia in general. A previous study showed that cognitive impairments, due to cerebral hypoperfusion, affected the MMSE score¹⁰.

In this study, we aimed to determine whether there was an asymmetrical association between carotid artery blood flow, brain activity, and cognitive status. We investigated the association between carotid blood flow and both resting-state brain activity and cognitive status in patients with cerebrovascular diseases using carotid ultrasonography, MEG, and the FIM scale.