On the Question of the Reflexotherapy Action Mechanisms in the Ischemic Stroke Acute Period (Literature Review)

A high degree of disability in stroke patients, along with severe social and economic losses, determine the enduring urgency of the problem of early rehabilitation for post-stroke patients. Despite the proven effectiveness of the various reflexotherapy techniques in rehabilitation of patients with ischemic stroke, the underlying mechanisms remain unclear. The aim of the review was to analyze the mechanisms of the acupuncture intervention effect on the main links of the ischemic stroke pathogenesis, on neurological deficit and the volume of cerebral infarction (based on publications in international databases). The use of acupuncture in the acute period of ischemic stroke can improve the ability to cerebrovascular reserve, reduce the severity of arterial stiffness and endothelial dysfunction, induce neuroprotection, inhibit cell apoptosis and stimulate neuroplasticity, alleviate the inflammatory response in acute cerebral ischemia, regulate mediators of inflammation and oxidative stress etc., thus improving cerebral blood flow. The analysis of literature data has shown that acupuncture induces multilevel regulation through complex mechanisms, and one factor may not be enough to explain the positive effect against cerebral ischemia.

Cerebrovascular Reserve Capacity as a Predictor of Postoperative Delirium: A Pilot Study

Introduction: Postoperative delirium is a common complication after cardiac surgery with cardiopulmonary bypass (CPB). Compromised regulation of the cerebral circulation may be a predisposing factor for delirium. However, the potential relationship between cerebrovascular reserve capacity and delirium is unknown. The aim of this study was to investigate if impaired cerebrovascular reserve capacity was associated with postoperative delirium.Methods: Forty-two patients scheduled for cardiac surgery with CPB were recruited consecutively. All patients underwent preoperative transcranial Doppler (TCD) ultrasound with calculation of breath-hold index (BHI). BHI < 0.69 indicated impaired cerebrovascular reserve capacity. In addition, patients were examined with preoperative neuropsychological tests such as MMSE (Mini Mental State Examination) and AQT (A Quick Test of cognitive speed). Postoperative delirium was assessed using Nursing Delirium Screening Scale (Nu-DESC) in which a score of ≥2 was considered as delirium.Results: Six patients (14%) scored high for postoperative delirium and all demonstrated impaired preoperative cerebrovascular reserve capacity. Median (25th−75th percentile) BHI in patients with postoperative delirium was significantly lower compared to the non-delirium group [0.26 (−0.08–0.44) vs. 0.83 (0.57–1.08), p = 0.002]. Preoperative MMSE score was lower in patients who developed postoperative delirium (median, 25th−75th percentile; 26.5, 24–28 vs. 28.5, 27–29, p = 0.024). Similarly, patients with postoperative delirium also displayed a slower performance during the preoperative cognitive speed test AQT color and form (mean ± SD; 85.8 s ± 19.3 vs. 69.6 s ± 15.8, p = 0.043).Conclusion: The present findings suggest that an extended preoperative ultrasound protocol with TCD evaluation of cerebrovascular reserve capacity and neuropsychological tests may be valuable in identifying patients with increased risk of developing delirium after cardiac surgery.

Acetazolamide-Challenged Arterial Spin Labeling Detects Augmented Cerebrovascular Reserve After Surgery for Moyamoya

Background and Purpose: Cerebrovascular reserve (CVR) inversely correlates with stroke risk in children with Moyamoya disease and may be improved by revascularization surgery. We hypothesized that acetazolamide-challenged arterial spin labeling MR perfusion quantifies augmentation of CVR achieved by revascularization and correlates with currently accepted angiographic scoring criteria. Methods: We retrospectively identified pediatric patients with Moyamoya disease or syndrome who received cerebral revascularization at ≤18 years of age between 2012 and 2019 at our institution. Using acetazolamide-challenged arterial spin labeling, we compared postoperative CVR to corresponding preoperative values and to postoperative perfusion outcomes classified by Matsushima grading. Results: In this cohort, 32 patients (17 males) with Moyamoya underwent 29 direct and 16 indirect extracranial-intracranial bypasses at a median 9.7 years of age (interquartile range, 7.6–15.7). Following revascularization, median CVR increased within the ipsilateral middle cerebral artery territory (6.9 mL/100 g per minute preoperatively versus 16.5 mL/100 g per minute postoperatively, P <0.01). No differences were observed in the ipsilateral anterior cerebral artery ( P =0.13) and posterior cerebral artery ( P =0.48) territories. Postoperative CVR was higher in the ipsilateral middle cerebral artery territories of patients who achieved Matsushima grade A perfusion, in comparison to those with grades B or C (25.8 versus 17.5 mL, P =0.02). The method of bypass (direct or indirect) did not alter relative increases in CVR (8 versus 3.8 mL/100 g per minute, P =0.7). Conclusions: Acetazolamide-challenged arterial spin labeling noninvasively quantifies augmentation of CVR following surgery for Moyamoya disease and syndrome.

Leptomeningeal collateral activation indicates severely impaired cerebrovascular reserve capacity in patients with symptomatic unilateral carotid artery occlusion

For patients with symptomatic unilateral internal carotid artery (ICA) occlusion, impaired cerebrovascular reactivity (CVR) indicates increased stroke risk. Here, the role of collateral activation remains a matter of debate, whereas angio-anatomical collateral abundancy does not necessarily imply sufficient compensatory flow provided. We aimed to further elucidate the role of collateral activation in the presence of impaired CVR. From a prospective database, 62 patients with symptomatic unilateral ICA occlusion underwent blood oxygenation-level dependent (BOLD) fMRI CVR imaging and a transcranial Doppler (TCD) investigation for primary and secondary collateral activation. Descriptive statistic and multivariate analysis were used to evaluate the relationship between BOLD-CVR values and collateral activation. Patients with activated secondary collaterals exhibited more impaired BOLD-CVR values of the ipsilateral hemisphere (p = 0.02). Specifically, activation of leptomeningeal collaterals showed severely impaired ipsilateral hemisphere BOLD-CVR values when compared to activation of ophthalmic collaterals (0.05 ± 0.09 vs. 0.12 ± 0.04, p = 0.005). Moreover, the prediction analysis showed leptomeningeal collateral activation as a strong independent predictor for ipsilateral hemispheric BOLD-CVR. In our study, ipsilateral leptomeningeal collateral activation is the sole collateral pathway associated with severely impaired BOLD-CVR in patients with symptomatic unilateral ICA occlusion.

Variable Temporal Cerebral Blood Flow Response to Acetazolamide in Moyamoya Patients Measured Using Arterial Spin Labeling

Cerebrovascular reserve capacity (CVR), an important predictor of ischaemic events and a prognostic factor for patients with moyamoya disease (MMD), can be assessed by measuring cerebral blood flow (CBF) before and after administration of acetazolamide (ACZ). Often, a single CBF measurement is performed between 5 and 20 min after ACZ injection. Assessment of the temporal response of the vasodilation secondary to ACZ administration using several repeated CBF measurements has not been studied extensively. Furthermore, the high standard deviations of the group-averaged CVRs reported in the current literature indicate a patient-specific dispersion of CVR values over a wide range. This study aimed to assess the temporal response of the CBF and derived CVR during ACZ challenge using arterial spin labeling in patients with MMD. Eleven patients with MMD were included before or after revascularisation surgery. CBF maps were acquired using pseudo-continuous arterial spin labeling before and 5, 15, and 25 min after an intravenous ACZ injection. A vascular territory template was spatially normalized to patient-specific space, including the bilateral anterior, middle, and posterior cerebral arteries. CBF increased significantly post-ACZ injection in all vascular territories and at all time points. Group-averaged CBF and CVR values remained constant throughout the ACZ challenge in most patients. The maximum increase in CBF occurred most frequently at 5 min post-ACZ injection. However, peaks at 15 or 25 min were also present in some patients. In 68% of the affected vascular territories, the maximum increase in CBF did not occur at 15 min. In individual cases, the difference in CVR between different time points was between 1 and 30% points (mean difference 8% points). In conclusion, there is a substantial variation in CVR between different time points after the ACZ challenge in patients with MMD. Thus, there is a risk that the use of a single post-ACZ measurement time point overestimates disease progression, which could have wide implications for decision-making regarding revascularisation surgery and the interpretation of the outcome thereof. Further studies with larger sample sizes using multiple CBF measurements post-ACZ injection in patients with MMD are encouraged.

The Utility of Cerebrovascular Reactivity MRI in Brain Rehabilitation: A Mechanistic Perspective

Cerebrovascular control and its integration with other physiological systems play a key role in the effective maintenance of homeostasis in brain functioning. Maintenance, restoration, and promotion of such a balance are one of the paramount goals of brain rehabilitation and intervention programs. Cerebrovascular reactivity (CVR), an index of cerebrovascular reserve, plays an important role in chemo-regulation of cerebral blood flow. Improved vascular reactivity and cerebral blood flow are important factors in brain rehabilitation to facilitate desired cognitive and functional outcomes. It is widely accepted that CVR is impaired in aging, hypertension, and cerebrovascular diseases and possibly in neurodegenerative syndromes. However, a multitude of physiological factors influence CVR, and thus a comprehensive understanding of underlying mechanisms are needed. We are currently underinformed on which rehabilitation method will improve CVR, and how this information can inform on a patient’s prognosis and diagnosis. Implementation of targeted rehabilitation regimes would be the first step to elucidate whether such regimes can modulate CVR and in the process may assist in improving our understanding for the underlying vascular pathophysiology. As such, the high spatial resolution along with whole brain coverage offered by MRI has opened the door to exciting recent developments in CVR MRI. Yet, several challenges currently preclude its potential as an effective diagnostic and prognostic tool in treatment planning and guidance. Understanding these knowledge gaps will ultimately facilitate a deeper understanding for cerebrovascular physiology and its role in brain function and rehabilitation. Based on the lessons learned from our group’s past and ongoing neurorehabilitation studies, we present a systematic review of physiological mechanisms that lead to impaired CVR in aging and disease, and how CVR imaging and its further development in the context of brain rehabilitation can add value to the clinical settings.

Cerebral hypoperfusion necessitating additional bypass following hunterian ligation of the internal carotid artery despite reassuring intraoperative challenges: Video case report

Background: Hunterian ligation has been adapted for complex intracranial aneurysm repair when other, more modern techniques are insufficient. Before drastic alteration of cerebral blood flow dynamics, intraoperative challenges and consideration of blood flow dynamics must be completed to ensure adequate perfusion postligation. On satisfaction, ligation may proceed; however, subtle changes related to hypoperfusion may not be immediately observed during intraoperative challenge under general anesthesia and/or before onset of the vasospasm window. Case Description: In this report, we describe a patient who presented with a Hunt-Hess Grade III subarachnoid hemorrhage (SAH), with a right internal carotid artery (ICA) occlusion and a ruptured giant left ICA aneurysm. Endovascular treatment of the aneurysm was aborted because the nominal, 9 mm diameter of the ICA was too large for any intracranial balloon or stent. Three days later, she underwent a left-sided “insurance” extracranial-tointracranial arterial bypass (EIAB) using the superficial temporal artery simultaneously with hunterian ligation of the left ICA following reassuring results on intraoperative occlusion challenge. Over several days, her neurologic condition declined concurrent with the vasospasm window, and a right-sided EIAB was required to augment vascular supply. Following a protracted hospital course, the patient became progressively more independent and is currently residing in an assisted living facility. Conclusion: We illustrate an ultimately successful microsurgical treatment option in the setting of acute SAH that highlights the importance of cerebrovascular reserve and blood flow replacement in the setting of a compromised circle of Willis, especially during the vasospasm window.