BOLD fMRI of cerebrovascular reactivity in the middle cerebral artery territory: A 100 volunteers' study

Quantitative assessment of near-infrared spectroscopy time course under hypercapnia using an a priori model-based fitting

BACKGROUND

Partial arterial pressure of carbon dioxide (CO₂) modulates cerebral blood flow through a vasoreactivity mechanism. Near infrared spectroscopy (NIRS) can be used to record these changes in cerebral hemodynamics. However, no laterality comparison of the NIRS signal has been performed despite being a prerequisite for the use of such a method in a vasoreactivity monitoring context. We propose to investigate the NIRS signal laterality in response to a CO₂-inhalation-based hypercapnia paradigm in healthy volunteers.

METHODS

Eleven healthy volunteers (6 women, 5 men, mean age: 31 ± 11) underwent a 3-block-design inhalation paradigm: normoxia (5min, "baseline") - hypercapnia (2min, "stimulation") - normoxia (5min, "post-stimulation"). NIRS signal was measured using a two-channel oximeter (INVOS 5100C, Medtronic, USA) with sensors placed symmetrically on both left and right sides on each subject's forehead. Additional heart rate (HR) monitoring was performed simultaneously. Based on the NIRS mean signal pattern, an a priori model of parametric identification was applied for each channel to quantify parameters of interest (amplitude, time delay, excitation and post-stimulation time) for each inhalation block.

RESULTS

HR increased significantly during the stimulation block. The quality of the model was satisfactory: mean absolute errors between modeled and experimental signals were lower than the resolution of the device. No significant lateralization was found between left and right values of most of the parameters.

CONCLUSION

Due to the lack of lateralization, this parametric identification of NIRS responses to hypercapnia could bring light to a potential asymmetry and be used as a biomarker in patients with cerebrovascular diseases.

Measurement of cerebrovascular reserve by multimodal imaging for cerebral arterial occlusion or stenosis patients: protocol of a prospective, randomized, controlled clinical study

Background

Cerebrovascular reactivity (CVR) is the change in cerebral blood flow in response to a vaso-active stimulus, and may assist the treatment strategy of ischemic stroke. However, previous studies reported that a therapeutic strategy for stroke mainly depends on the degree of vascular stenosis with steady-state vascular parameters (e.g., cerebral blood flow and CVR). Hence, measurement of CVR by multimodal imaging techniques may improve the treatment of ischemic stroke.

Methods/design

This is a prospective, randomized, controlled clinical trial that aimed to examine the capability of multimodal imaging techniques for the evaluation of CVR to improve treatment of patients with ischemic stroke. A total of 66 eligible patients will be recruited from Renji Hospital, Shanghai Jiaotong University School of Medicine. The patients will be categorized based on CVR into two subgroups as follows: CVR > 10% group and CVR < 10% group. The patients will be randomly assigned to medical management, percutaneous transluminal angioplasty and stenting, and intracranial and extra-cranial bypass groups in a 1:1:1 ratio. The primary endpoint is all adverse events and ipsilateral stroke recurrence at 6, 12, and 24 months after management. The secondary outcomes include the CVR, the National Institute of Health stroke scale and the Modified Rankin Scale at 6, 12, and 24 months.

Discussion

Measurement of cerebrovascular reserve by multimodal image is recommended by most recent studies to guide the treatment of ischemic stroke, and thus its efficacy and evaluation accuracy need to be established in randomized controlled settings. This prospective, parallel, randomized, controlled registry study, together with other ongoing studies, should present more evidence for optimal individualized accurate treatment of ischemic stroke.

Trial registration

Chinese Clinical Trial Registry, ID: ChiCTR-IOR-16009635; Registered on 16 October 2016.

All items are from the World Health Organization Trial Registration Data Set and registration in the Chinese Clinical Trial Registry: ChiCTR-IOR-16009635.

A New Technique for the Assessment of Cerebral Vasodilatory Capacity as Part of Catheter-Based Cerebral Angiography

BACKGROUND

Previous studies have demonstrated the value of cerebral vasodilatory capacity assessment for risk stratification in patients with extracranial arterial stenosis or occlusion. We describe a new method that assesses cerebral vasodilatory capacity as part of catheter-based cerebral angiography.

METHODS

We assessed regional cerebral blood volume (rCBV) in the arterial distribution of interest using a controlled contrast injection through a diagnostic catheter placed in the common carotid or the subclavian artery. rCBV maps were created using predefined algorithm based on contrast distribution in the venous phase (voxel size 0.466 mm³) into high, intermediate, low, and no detectable rCBV regions. rCBV maps were acquired again after the administration of intra-arterial nicardipine (1.5-2.5 mg), and percentage increases of the area of various grades of rCBV were calculated.

RESULTS

Three patients with internal carotid artery stenosis (32% - 64% in severity) and 1 patient with extracranial vertebral artery stenosis (46% in severity) were assessed. There was a variable but consistent increase in the area of high rCBV in the ipsilateral hemisphere in 3 patients with internal carotid artery flow (5.5%-24.5%) and the cerebellum (9.6%) in 1 patient with vertebral artery flow assessments. The increase in high rCBV was most prominent in the patient who received 2.5 mg (24.5%) and least prominent in a patient who received 1.5 mg (5.5%) of intra-arterial nicardipine. There was a concurrent reduction in areas of intermediate and low rCBV (shift) in 3 patients, and there was an increase in all areas of rCBV grades (addition) in 1 patient.

CONCLUSIONS

Selective assessment of cerebral vasodilatory response in the affected arterial distribution is feasible during catheter-based cerebral angiography.

Modulation of the Emotional Response to Viewing Strabismic Children in Mothers-Measured by fMRI

PURPOSE

Strabismus influences not only the individual with nonparallel eyes but also the observer. It has previously been demonstrated by fMRI that adults viewing images of strabismic adults have a negative reaction to the images as demonstrated by limbic activation, especially activation of the left amygdala. The aim of this study was to see if mothers would have a similar reaction to viewing strabismic children and whether or not that reaction would be different in mothers of strabismic children.

METHODS

Healthy mothers of children with strabismus (n = 10, Group I) and without strabismus (n = 15, Group II) voluntarily underwent fMRI at 3T. Blood oxygen level dependent signal responses to viewing images of strabismic and non-strabismic children were analyzed.

RESULTS

Group II, while viewing images of strabismic children, showed significantly increased activation of the limbic network (p < 0.05) and bilateral amygdala activation. Group I showed considerably less limbic activation, compared to the group II, and had no amygdala activation. Both groups revealed statically significant activation in the FEF (frontal eye field) when they were viewing images of strabismic children as compared to when they were viewing children with parallel eyes. The activated FEF area for Group II was much larger than for group I.

CONCLUSION

Mothers of non-strabismic children showed similar negative emotional fMRI patterns as adults did while viewing strabismic adults. Strabismus is an interpersonal organic issue for the observer, which also impacts the youngest members of our society.

Intra- and extracranial atherosclerotic disease: casting a new light on emerging trends

Intra- and extracranial atherosclerotic stenosis has been shown to be associated with an increased risk of secondary stroke mortality. Advances in invasive and non-invasive imaging modalities have improved analysis of hemodynamic changes and allowed better delineation of the integrity of intracranial collateralization and plague morphology in patients with artery stenosis. This review focuses on new imaging modalities and clinical applications of currently available techniques, and provides significant insight into future directions in comprehensive analysis of intra- and extracranial atherosclerotic stenosis.