Multiple sclerosis affects more than 2 million people worldwide and is currently incurable. A number of interventions to modify the course of multiple sclerosis have been developed that offer new insight into disease mechanisms.

Here, we report the existence of meningeal lymphatic vessels in human and nonhuman primates (common marmoset monkeys) and the feasibility of noninvasively imaging and mapping them in vivo with high-resolution, clinical MRI. On T2-FLAIR and T1-weighted black-blood imaging, lymphatic vessels enhance with gadobutrol, a gadolinium-based contrast agent with high propensity to extravasate across a permeable capillary endothelial barrier, but not with gadofosveset, a blood-pool contrast agent. The topography of these vessels, running alongside dural venous sinuses, recapitulates the meningeal lymphatic system of rodents. In primates, meningeal lymphatics display a typical panel of lymphatic endothelial markers by immunohistochemistry. This discovery holds promise for better understanding the normal physiology of lymphatic drainage from the central nervous system and potential aberrations in neurological diseases.

Multiple sclerosis (MS) is a chronic neuroinflammatory and neurodegenerative disease.¹ Despite the availability of multiple treatment options, many patients live with disability or experience progressive symptoms that limit their quality of life and longevity. Even if pathobiological causes of disability accrual and disease progression are not completely understood, individual lesion-type patterns might account for clinical and prognostic variability.^2-4 After the acute phase of inflammatory demyelination at lesion onset, chronic lesions can show different pathological and repair outcomes, namely “chronic active/slowly expanding/smoldering,” “chronic inactive,” and, when repair is successful, “remyelinated.”^5,6 As personalized treatment paradigms emerge, imaging the distribution of different lesion types within individuals may prove critical.