New research was presented at ISC 2019, the American Heart Association’s annual International Stroke Conference, from February 6-8 in Honolulu. The features below highlight some of the studies that emerged from the conference.
Gut Microbiome Linked With Dementia
Previous research indicates a relationship between the gut microbiome and several life-threatening conditions. While the gut microbiome might, therefore, represent a useful target for the prevention of dementia, this relationship has not been well studied. For a study, researchers assessed cognitive function, gut microbiome, demographics, risk factors, and activities of daily living among demented and non-demented patients of their memory clinic. They found that the number of Bacteroides (enterotype I) was lower and the number of ‘other’ bacteria (enterotype III) was higher in demented than non-demented patients. Multivariable analyses showed that the populations of enterotype I and enterotype III bacteria were strongly associated with dementia, independent of traditional dementia biomarkers. Additional research is needed to determine the mechanism underlying this association.
Targeting SBP in Ischemic Stroke Patients on IV Thrombolysis
Although thrombolytic treatment with IV alteplase is contraindicated in patients with acute ischemic stroke and systolic blood pressure (SBP) higher than 185 mm Hg, little is known regarding the target SBP for optimal outcomes. Among thrombolysis-eligible patients with acute ischemic stroke and SBP of 150 mm Hg or higher, study investigators assessed intensive BP lowering compared with guideline-recommended BP lowering within 6 hours of stroke onset for a study. At 90 days, functional status did not differ between the groups treated with either approach. However, the intracranial hemorrhage rate was 14.8% in the intensive group, compared with 18.7% in the guideline group. Serious adverse event rates did not differ significantly between the groups. No evidence was observed of an interaction of intensive BP lowering with dose (low vs standard) of alteplase with regard to functional status at 90 days.
Thrombectomy in Transferred Patients With Ischemic Stroke in the Late Window
Data are lacking on whether or not patients with ischemic stroke with large-vessel occlusion in the anterior circulation who are transferred from outside facilities and have penumbral imaging mismatch prior to endovascular thrombectomy have similar outcomes with thrombectomy in the late window as those who are directly admitted to thrombectomy-capable hospitals. To evaluate whether the imaging-based selection criteria used in the Endovascular Therapy Following Imaging Evaluation for Ischemic Stroke 3 (DEFUSE 3) trial would lead to comparable outcome rates and treatment benefits in transfer vs direct-admission patients, researchers assessed 90-day modified Rankin Scale scores among a subgroup of DEFUSE 3 participants. These scores did not differ between the direct and transfer groups. Overall functional independence rate, treatment effect, thrombectomy reperfusion rates, mortality, and symptomatic intracranial hemorrhage rates also did not differ between the groups. “These results have health care implications indicating transferring potential candidates for late-window thrombectomy is associated with substantial clinical benefits and should be encouraged,” write the study authors.
Advanced Neuroimaging & Mechanical Thrombectomy Patient Selection
Although clinical equipoise exists regarding the use of advanced imaging in the selection of acute ischemic stroke patients who are eligible for mechanical thrombectomy during the first 6 hours after symptom onset, recent research suggests that advanced neuroimaging appears to represent a vital and time-independent prognostic factor. To evaluate the impact of patient selection with advanced neuroimaging on 3-month functional independence, favorable functional outcomes, all-cause mortality, and functional improvement, study investigators performed a systematic review and meta-analysis of 10 randomized clinical trials with nearly 2,000 patients. The five studies that used advanced neuroimaging showed higher treatment effects of mechanical thrombectomy—when compared with studies using conventional neuroimaging—on functional independence (odds ratio [OR], 3.79 vs 1.76), favorable functional outcomes (OR, 3.16 vs 1.75), and functional improvement (crude OR 2.77 vs 1.60). When assessing only studies that looked at the early (0-8 hours) time window, advanced imaging selection was associated with better 3-month functional independence rates when compared with conventional imaging selection. No differences were observed between the imaging approaches in mortality or symptomatic intracranial hemorrhage rates. The study authors conclude that the use of advanced neuroimaging for both the selection and prediction of prognosis for mechanical thrombectomy candidates should not depend on the elapsed time from symptom onset.
White Matter Tracts After Ischemic Stroke
Post-acute ischemic stroke clinical assessment scores are moderately correlated with structural brain damage, as lesion location is an important confounding factor. Whereas multiple studies have assessed gray matter eloquence, data are lacking on the importance of specific white matter tract involvement. To investigate the eloquence of major white matter tracts with respect to 24 hours post-stroke NIH Stroke Scale (NIHSS) score, researchers manually segmented—and non-linearly registered to a common atlas—lesions in follow-up fluid-attenuated inversion recovery MRI datasets acquired 1-7 days after acute stroke onset due to proximal middle cerebral artery or internal carotid artery occlusion. Voxel-based lesion-symptom mapping (VLSM) using sparse canonical correlation analysis was used to generate a statistical eloquence map with normalized t-scores ranging from 0 to 1 with the 24-hour NIHSS as the outcome score. Multivariate variable length subnet masking resulted in a major left-hemispheric and smaller right-hemispheric cluster of significant voxels overlapping with four white matter tracts. The left corticospinal tract (motor function) showed an overlap of 3.52%, the right corticospinal tract an overlap of 7.33%, the left anterior thalamic radiation (sensory and motor relay) an overlap of 5.89%, and the inferior fronto-occipital fasciculus (auditory and visual association) an overlap of 21.31%. “The significantly affected WM tracts identified are related to motor and cognition function…, highlighting the importance of white matter tract involvement for recovery and rehabilitation,” conclude the study authors.