Abstract 1122‐000183: Assessing Meningeal Lymphatic MRI Biomarkers in Acute Large Vessel Occlusion Stroke Treated with Thrombectomy
Authors: Pham Richard , Chatterjee Rano 
Published: December 2021

Introduction
: Until recently, there was very little known about the brain’s waste removal system. Unlike the peripheral organ systems, the CNS lacked a clearly defined lymphatic vasculature and waste clearance mechanism. However, in 2015, the meningeal lymphatic system (MLS) was first visualized in the dura of humans (1). Since then, a number of studies have investigated the MLS’s potential impact on various neurological diseases, including Alzheimer’s, Parkinson’s, Multiple Sclerosis, hydrocephalus, and epilepsy (2‐6). Other studies have also demonstrated the MLS’s profound influence on stroke (7‐10). However, there is little research that characterizes MLS imaging biomarkers in relation to stroke. Our study evaluates currently proposed MLS MRI biomarkers in large vessel occlusion stroke treated with thrombectomy.

Methods
: Participants: We recruited twenty patients who had an acute ischemic stroke treated with mechanical thrombectomy (MT) in a large intracranial artery (middle cerebral artery, internal carotid artery, basilar and/or vertebral). The mean age of our population was 69.9 ± 15.5 years. 12 (60%) of our patients had been treated with a combined approach stentriever + aspiration catheter, 4 (20%) with stentriever only, and 4 (20%) with contact aspiration only. Study Design: Basic demographic data, clinical comorbidities, information related to the stroke, technical details about the MT and outcome were collected from electronic medical records. We implemented High Resolution MR Vessel Wall Imaging (HR‐VWI) with a black blood T1‐weighted sequence to characterize changes in the enhancing vessels around the superior sagittal sinus that have been described as potential markers for meningeal lymphatic vessels (1). Within 24 hours after the MT procedure, patients underwent a 45‐minute 3T‐ brain MRI with contrast using a 20‐channel head coil (MAGNETOM Skyra, Siemens) with a sagittal isotropic black blood sequence included with the standard protocol. Our field of view included the superior sagittal sinus. Coronal reconstructed pre‐and post‐contrast back blood T1 sequences were qualitatively evaluated by a board certified Neuroradiologist with 8 years of academic experience evaluating the cerebrovasculature for the presence of purported meningeal lymphatic prominence or asymmetry.

Results
: There was no significant prominence or asymmetric difference seen in the purported meningeal lymphatics based on 3D high‐resolution T1 black blood MRI sequences in acute stroke large vessel occlusion post‐MT subjects.

Conclusions
: While in our study no observable differences were seen in the purported meningeal lymphatics based on current MR techniques, it marks an important initial step in development of a useful biomarker for the CNS lymphatic system. Future studies are needed to evaluate alternative meningeal lymphatic quantitative biomarkers. Our study also highlights the need for improved standardization of biomarkers for the meningeal lymphatics. By continuing to evaluate imaging biomarkers, we can further understand the MLS’s potentially profound role in complex neurological diseases.