The contribution of posterior circulation to memory function during the intracarotid amobarbital procedure

Vessel Distance Mapping: A novel methodology for assessing vascular-induced cognitive resilience

The association between cerebral blood supply and cognition has been widely discussed in the recent literature. One focus of this discussion has been the anatomical variability of the circle of Willis, with morphological differences being present in more than half of the general population. While previous studies have attempted to classify these differences and explore their contribution to hippocampal blood supply and cognition, results have been controversial. To disentangle these previously inconsistent findings, we introduce Vessel Distance Mapping (VDM) as a novel methodology for evaluating blood supply, which allows for obtaining vessel pattern metrics with respect to the surrounding structures, extending the previously established binary classification into a continuous spectrum. To accomplish this, we manually segmented hippocampal vessels obtained from high-resolution 7T time-of-flight MR angiographic imaging in older adults with and without cerebral small vessel disease, generating vessel distance maps by computing the distances of each voxel to its nearest vessel. Greater values of VDM-metrics, which reflected higher vessel distances, were associated with poorer cognitive outcomes in subjects affected by vascular pathology, while this relation was not observed in healthy controls. Therefore, a mixed contribution of vessel pattern and vessel density is proposed to confer cognitive resilience, consistent with previous research findings. In conclusion, VDM provides a novel platform, based on a statistically robust and quantitative method of vascular mapping, for addressing a variety of clinical research questions.

Evaluation of the density spectral array in the Wada test: report of six cases

Wada test is an invasive procedure used in the preoperative evaluation for epilepsy surgery to determine language lateralization, postoperative risk of amnesia syndrome, and to assess the risk of memory deficits. It involves injection of amobarbital into internal carotid artery of the affected hemisphere followed by the healthy hemisphere to shut down brain function. We performed an observational study evaluating the density spectral array (DSA) of the bilateral bispectral index VISTA™ Monitoring System (BVMS) in 6 patients with drug-resistant epilepsy undergoing Wada test. DSA revealed the presence of bifrontal alpha waves in absence of loss of consciousness in all patients.

Intracranial atherosclerosis on 7T MRI and cognitive functioning: The SMART-MR study

OBJECTIVE

To investigate the association between intracranial atherosclerosis (ICAS) and cognitive functioning in patients with a history of vascular disease.

METHODS

Within the Second Manifestations of Arterial Disease-Magnetic Resonance (SMART-MR) study, cross-sectional analyses were performed in 130 patients (mean ± SD age 68 ± 9 years) with 7T vessel wall MRI data. Vessel wall lesions were rated according to established criteria and summed into a circulatory and artery-specific ICAS burden. Associations between ICAS burden and Z scores of memory, executive functioning, working memory, and processing speed were estimated using linear regression analyses adjusted for age, sex, education, reading ability, and vascular risk factors.

RESULTS

A total of 125 patients (96%) had ≥1 vessel wall lesion; the mean ICAS burden was 8.5 ± 5.7. A statistically nonsignificant association was found between total ICAS burden and memory (b = -0.03 per +1 lesion; 95% confidence interval [CI] -0.05 to 0.00). No associations were found for the other domains. A statistically significant association was found for ICAS burden of the posterior cerebral artery (PCA) and memory (b = -0.12 per +1 lesion; 95% CI -0.23 to -0.01) and executive functioning (b = -0.10 per +1 lesion; 95% CI -0.19 to -0.01). Statistically nonsignificant associations were found for the anterior cerebral artery (ACA) burden and memory (b = -0.13 per +1 lesion; 95% CI -0.26 to 0.01) and executive functioning (b = -0.11 per +1 lesion; 95% CI -0.22 to 0.01). Additional adjustments for large infarcts, white matter hyperintensities, lacunes, and ≥50% carotid stenosis produced similar results.

CONCLUSIONS

Our results suggest an artery-specific vulnerability of memory and executive functioning to ICAS, possibly due to strategic brain regions involved with these cognitive domains, which are located in the arterial territory of the PCA and ACA.

Ipsilateral foetal-type posterior cerebral artery is associated with cognitive decline after carotid revascularisation

Background

Stenosis of the internal carotid artery has been associated with cognitive impairment and decline. However, studies testing the effect of carotid revascularisation on cognition have had conflicting results. This may in part be explained by variation in the flow territory of the carotid artery. In 12 to 36% of the patients, the posterior cerebral artery is mainly or exclusively supplied by the internal carotid artery via a foetal-type posterior cerebral artery. In these patients, ipsilateral carotid artery stenosis is likely to result in a larger area with hypoperfusion than in case of a normal posterior cerebral artery. Patients with a foetal-type posterior cerebral artery could therefore benefit more from revascularisation. We compared the effects of carotid revascularisation on cognition between patients with a foetal-type and those with a normal posterior cerebral artery.

Methods

Patients with symptomatic internal carotid artery stenosis ≥ 50%, enrolled in the International Carotid Stenting Study (ICSS) at a single centre, underwent detailed neuropsychological examinations before and 6 months after revascularisation. Cognitive test results were standardized into z-scores, from which a cognitive sumscore was calculated. The primary outcome was the change in cognitive sumscore between baseline and follow-up. Changes in cognitive sumscore were compared between patients with an ipsilateral foetal-type and those with a normal posterior cerebral artery, as assessed with CT or MR angiography.

Results

Of 145 patients enrolled in ICSS at the centre during the study period, 98 had both angiography at baseline and neuropsychological examination at baseline and at 6-months follow-up. The cognitive sum score decreased by 0.28 (95% confidence interval, 0.10 to 0.45) in 13 patients with an ipsilateral foetal-type posterior cerebral artery and by 0.07 (95% CI, 0.002 to 0.15) in 85 patients with a normal posterior cerebral artery (mean difference, -0.20; 95% CI, -0.40 to -0.01). This did not change essentially after adjustment for baseline factors.

Conclusion

An ipsilateral foetal-type posterior cerebral artery appears to increase cognitive decline after carotid revascularisation. Our findings have to be reproduced in an independent study before further implications can be made.