Understanding the relationship between intracranial pressure and spaceflight associated neuro-ocular syndrome (SANS): a systematic review.

Neuro-ocular changes, such as globe flattening, optic disc edema or chorioretinal folds, are a major worry when considering astronaut health. These findings are now known as Spaceflight Associated Neuro-Ocular Syndrome. This systematic review aims to discuss the possible mechanisms involved in the pathogenesis of this syndrome. Contemplating the different reports regarding the impact of intracranial pressure (ICP), cardiovascular system, hypercapnia or glymphatic system, we hypothesize that a relationship exists between variations in ICP and SANS development. A literature search of five databases was conducted using the PICO model. Twenty studies were subsequently included, and two main theories discussed. The first suggests that cerebrospinal fluid (CSF) shifts can lead to a rise in ICP, while the second supports the importance of CSF compartmentalization, independently of ICP variation. These hypotheses are not mutually exclusive and environmental factors may also be essential for the development of this syndrome.