周围神经损伤
-
Figure 1｜Aquaporin distribution in ocular tissues.
Figure 2｜Anatomy of optic nerve subarachnoid space.
As the eye is an extension of the diencephalon in the CNS, the optic nerve and the retina bear resemblances to the brain from embryology to physiology in terms of high-rate metabolism, confinement within limited space, fluid homeostasis, fluid pressure ranges and immune privilege. In particular, the eye also lacks the classical lymphatic vessels for metabolic waste clearance. Therefore, researchers have been searching for glymphatic-like components in the eye and optic nerve that may facilitate paravascular clearance similar to the CNS (Hu et al., 2016; Mathieu et al., 2017; Wostyn et al., 2017; Jacobsen et al., 2019; Wang et al., 2020) (Figure 1). Along the optic nerve, the surrounding SAS contains an intricate system of arachnoid trabeculae and septae that are distinct architecturally between the bulbar segment, mid-orbital segment, and canalicular portion, which may play important roles in CSF dynamics (Figure 2) (Killer et al., 2003).
Figure 3｜Ex vivo imaging of the glymphatic system in the optic nerve.
Figure 4｜In vivo gadolinium-MRI of the cerebrospinal fluid dynamics in the mouse optic nerve.
Recent studies have employed various imaging modalities to suggest the existence of a glymphatic system in the visual pathways of wild-type rodents, AQP4-null rodents, and humans. This glymphatic system via the optic nerve has been explored both ex vivo (Figure 3) and in vivo (Figure 4).