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Comment & Response
March 21, 2019

Brain Upward Shift and Spaceflight-Associated Neuro-Ocular Syndrome—Reply

Author Affiliations
  • 1Department of Ophthalmology, Lariboisière Hospital, Assistance Publique–Hôpitaux de Paris, Paris Diderot University, Paris, France
  • 2Department of Electronic Science and Engineering, Kyoto University, Nishikyo, Kyoto, Japan
  • 3Department of Neurology, Osaka University Graduate School of Medicine, Suita, Japan
JAMA Ophthalmol. 2019;137(5):586-587. doi:10.1001/jamaophthalmol.2019.0223

In Reply In the letter by Mader et al, the idiopathic intracranial hypertension mechanism–like theory and possible ball-valve effect are focused on to explain optic nerve sheath (ONS) diameter expansion and globe flattening in spaceflight-associated neuro-ocular syndrome (SANS). In this commentary, we reply to their opinion and argue that brain upward shift is the major origin for SANS.

The diagnostic criteria of idiopathic intracranial hypertension include papilledema and increased cerebrospinal fluid pressure (>18 mm Hg) measured using lumbar puncture, and its typical symptoms include daily headache, diplopia, transient visual obscurations, pulse-synchronous tinnitus, and photophobia.1 In SANS, however, there is no complaint of these symptoms, suggesting that the origins of idiopathic intracranial hypertension and SANS are less likely to be shared.2