Spaceflight-induced visual impairment and globe deformations in astronauts are linked to orbital cerebrospinal fluid volume increase

Noam Alperin, Ahmet M. Bagci

Research output: Chapter in Book/Report/Conference proceedingChapter

14 Scopus citations

Abstract

Objective: Most of the astronauts onboard the International Space Station (ISS) develop visual impairment and ocular structural changes that are not fully reversible upon return to earth. Current understanding assumes that the so-called visual impairments/intracranial pressure (VIIP) syndrome is caused by cephalad vascular fluid shift. This study assesses the roles of cerebrospinal fluid (CSF) and intracranial pressure (ICP) in VIIP. Materials and methods: Seventeen astronauts, 9 who flew a short-duration mission on the space shuttle (14.1 days [SD 1.6]) and 7 who flew a long-duration mission on the ISS (188 days [SD 22]) underwent MRI of the brain and orbits to assess the pre-to-post spaceflight changes in four categories: VIIP severity measures: globe flattening and nerve protrusion; orbital and ventricular CSF volumes; cortical gray and white matter volumes; and MR-derived ICP (MRICP). Results: Significant pre-to-post-flight increase in globe flattening and optic nerve protrusion occurred only in the long-duration cohort (0.031 [SD 0.019] vs −0.001 [SD 0.006], and 0.025 [SD 0.013] vs 0.001 [SD 0.006]; p < 0.00002 respectively). The increased globe deformations were associated with significant increases in orbital and ventricular CSF volumes, but not with increased tissue vascular fluid content. Additionally, a moderate increase in MRICP of 6 mmHg was observed in only two ISS astronauts with large ocular structure changes. Conclusions: These findings are evidence for the primary role of CSF and a lesser role for intracranial cephalad fluid-shift in the formation of VIIP. VIIP is caused by a prolonged increase in orbital CSF spaces that compress the globes’ posterior pole, even without a large increase in ICP.

Original languageEnglish (US)
Title of host publicationActa Neurochirurgica, Supplementum
PublisherSpringer-Verlag Wien
Pages215-219
Number of pages5
DOIs
StatePublished - Jan 1 2018

Publication series

NameActa Neurochirurgica, Supplementum
Volume126
ISSN (Print)0065-1419
ISSN (Electronic)2197-8395

Keywords

  • Cephalad fluid shift
  • Globe flattening
  • Optic nerve protrusion
  • Quantitative MRI
  • Visual impairment/intracranial pressure syndrome

ASJC Scopus subject areas

  • Surgery
  • Clinical Neurology

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    Alperin, N., & Bagci, A. M. (2018). Spaceflight-induced visual impairment and globe deformations in astronauts are linked to orbital cerebrospinal fluid volume increase. In Acta Neurochirurgica, Supplementum (pp. 215-219). (Acta Neurochirurgica, Supplementum; Vol. 126). Springer-Verlag Wien. https://doi.org/10.1007/978-3-319-65798-1_44