Charlotte Zerna, MD, MSc
Now that endovascular treatment for acute ischemic stroke due to large vessel occlusion is the new standard of care, imaging features that are associated with the success of the procedure and the functional outcome of the patient are of great interest. Leptomeningeal collaterals status has been found to determine both recanalization rate and clinical outcome many years ago.1 However, our understanding of the variability of leptomeningeal collateral status is still in progress. Prior studies found that metabolic syndrome, hyperuricemia, older age and statin use corresponded to poorer leptomeningeal collateral status, but these studies have pre-dated the era of proven endovascular treatment for acute ischemic stroke.2, 3 With improved workflow and faster treatment times in recent years, these demographic and patient-related factors that might influence leptomeningeal collateral status need to be re-evaluated.
In this study by Fujita et al., the authors aimed to evaluate the effect of chronic hypertension on acute leptomeningeal collateral flow in patients with large vessel occlusion that had been confirmed with digital subtraction angiography.4 From October 2011 to December 2017, they were able to identify 100 patients with acute occlusion of the M1 segment of the middle cerebral artery in their institution. Chronic hypertension was determined to be present if it was recorded during a past encounter with the healthcare system before the index stroke or the patient was on antihypertensive medication at the time of presentation. Leptomeningeal collateral status was assessed using the American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology Collateral Flow Grading System and defined as either excellent (grade 3–4) or poor (grade 0–2). This dichotomized leptomeningeal collateral status was then assessed using multivariable logistic regression analysis.
The most important finding of the study was that chronic hypertension emerged as an independent predictor of poor leptomeningeal collateral status (odds ratio, 2.80; 95% CI, 1.08– 7.70; P=0.034). Furthermore, the proportion of patients with poor leptomeningeal collateral status increased from only 22% in patients with no chronic hypertension to 45% in patients with chronic hypertension taking antihypertensive medication to 80% in patients with chronic hypertension on no antihypertensive therapy. This trend was statistically significant (P<0.001).
The authors rightfully acknowledged that their sample size was low and very little is known about the duration of chronic hypertension, as well as how well controlled it was with antihypertensive medication, if the patient was taking any. However, it seems that chronic hypertension impairs vasoreactivity and specifically vasodilation of the leptomeningeal anastomoses between two pial arterial branches of different cortical territories. These findings further illustrate the importance of primary and secondary prevention of hypertension and also shift the focus away from leptomeningeal collateral status being determined by systolic blood pressure upon admission, which more likely is a marker of sympathetic nervous system activation in the setting of a medical emergency. Further research in a larger and more ethnically diverse patient cohort is warranted to confirm these findings, as the current study was done in Japanese patients only, which are known to have a higher rate of intracranial atherosclerosis.
References:
1. Bang OY, Saver JL, Kim SJ, Kim GM, Chung CS, Ovbiagele B, et al. Collateral flow predicts response to endovascular therapy for acute ischemic stroke. Stroke; a journal of cerebral circulation. 2011;42:693-699
2. Malik N, Hou Q, Vagal A, Patrie J, Xin W, Michel P, et al. Demographic and clinical predictors of leptomeningeal collaterals in stroke patients. Journal of stroke and cerebrovascular diseases: the official journal of National Stroke Association. 2014;23:2018-2022
3. Menon BK, Smith EE, Modi J, Patel SK, Bhatia R, Watson TW, et al. Regional leptomeningeal score on ct angiography predicts clinical and imaging outcomes in patients with acute anterior circulation occlusions. AJNR. American journal of neuroradiology. 2011;32:1640-1645
4. Fujita K, Tanaka K, Yamagami H, Ide T, Ishiyama H, Sonoda K, et al. Detrimental effect of chronic hypertension on leptomeningeal collateral flow in acute ischemic stroke. Stroke; a journal of cerebral circulation. 2019;50:1751-1757
