Ultrasonography of the optic nerve sheath diameter for diagnosis and monitoring of acute mountain sickness: A systematic review
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AIMS: Despite extensive research on acute mountain sickness (AMS), the underlying pathophysiology remains unclear. Ultrasonography studies have shown that optic nerve sheath diameter (ONSD) correlates with intracranial pressure (ICP) in critical care patients, and recent studies report elevated ONSD values at high altitude. The aim of this review was to elucidate whether 1. measurement of ONSD could shed light on the pathophysiology of AMS, and 2. ultrasonography of the ONSD could support the diagnosis of AMS. METHODS: Systematic search of MEDLINE (through Pubmed; from 1966 to 14 October 2014), Cochrane Central Register of Controlled Trials (CENTRAL), and EMBASE databases. RESULTS: Six studies with 436 subjects (139 women, 297 men; 406 mostly Caucasian; 30 Nepalese) were included. A marked variability in ONSD was found across studies both at baseline and at high altitude. CONCLUSION: The variability in ONSD across the included studies and within each study limit the utility of ONSD measurement in the diagnosis of AMS. ONSD measurements might be useful from a population perspective, but the accuracy of optic nerve ultrasonography for single subjects and single point-in-time assessment for diagnosing AMS is questionable due to high individual variability in ONSD.