Optic Nerve Sheath Ultrasonography: A Novel Way to Assess Intracranial Pressure in Acute Mountain Sickness

Increased intracranial pressure is suspected in the pathogenesis of acute mountain sickness (AMS), but no studies have correlated it with the presence or severity of AMS. We sought to determine whether increased optic nerve sheath diameter, a surrogate measure of intracranial pressure, is associated with the presence and severity of AMS. We performed a cross-sectional study of travelers ascending through Pheriche, Nepal (4,240 m), from March 3 to May 14, 2006. AMS was assessed using the Lake Louise score. Optic nerve sheath diameter was measured by ultrasound. Ultrasound exams were performed and read by separate blinded observers. Two-hundred eighty seven subjects were enrolled. Ten of these underwent repeat examination. Mean optic nerve sheath diameter was 5.34 mm [95% confidence interval (CI) 5.18–5.51 mm] in the 69 subjects with AMS vs. 4.46 mm (95% CI 4.39–4.54 mm) in the 218 other subjects ( P < 0.0001). There was also a positive association between optic nerve sheath diameter and total Lake Louise score ( P for trend < 0.0001). In a multivariate logistic regression model of factors associated with AMS, optic nerve sheath diameter was strongly associated with AMS (odds ratio 6.3; 95% CI, 3.7–10.8; P < 0.001). In 10 subjects with repeat examinations, change in Lake Louise score had a strong positive correlation with change in optic nerve sheath diameter ( R2 = 0.84, P < 0.001). Optic nerve sheath diameter, a proxy for intracranial pressure, is associated with the presence and severity of AMS.

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Optic nerve sheath diameter, intracranial pressure and acute mountain sickness on Mount Everest: a longitudinal cohort study

British Journal of Sports Medicine ◽

10.1136/bjsm.2007.045286 ◽

2008 ◽

Vol 42 (3) ◽

pp. 183-188 ◽

Cited By ~ 41

Author(s):

A I Sutherland ◽

D S Morris ◽

C G Owen ◽

A J Bron ◽

R C Roach

Keyword(s):

Cohort Study ◽

Optic Nerve ◽

Intracranial Pressure ◽

Acute Mountain Sickness ◽

Optic Nerve Sheath Diameter ◽

Optic Nerve Sheath ◽

Longitudinal Cohort Study ◽

Mount Everest ◽

Nerve Sheath ◽

Mountain Sickness

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Optic nerve sheath diameter changes at high altitude and in acute mountain sickness: meta-regression analyses

British Journal of Ophthalmology ◽

10.1136/bjophthalmol-2020-317717 ◽

2020 ◽

pp. bjophthalmol-2020-317717

Author(s):

Tou-Yuan Tsai ◽

George Gozari ◽

Yung-Cheng Su ◽

Yi-Kung Lee ◽

Yu-Kang Tu

Keyword(s):

Optic Nerve ◽

High Altitude ◽

Acute Mountain Sickness ◽

Optic Nerve Sheath Diameter ◽

Optic Nerve Sheath ◽

Cochrane Library ◽

Regression Analyses ◽

Spline Regression ◽

Nerve Sheath ◽

Mountain Sickness

Background/aimsTo assess changes in optic nerve sheath diameter (ONSD) at high altitude and in acute mountain sickness (AMS).MethodsCochrane Library, EMBASE, Google Scholar and PubMed were searched for articles published from their inception to 31st of July 2020. Outcome measures were mean changes of ONSD at high altitude and difference in ONSD change between subjects with and without AMS. Meta-regressions were conducted to investigate the relation of ONSD change to altitude and time spent at that altitude.ResultsEight studies with 248 participants comparing ONSD from sea level to high altitude, and five studies with 454 participants comparing subjects with or without AMS, were included. ONSD increased by 0.14 mm per 1000 m after adjustment for time (95% CI: 0.10 to 0.18; p<0.01). Restricted cubic spline regression revealed an almost linear relation between ONSD change and time within 2 days. ONSD was greater in subjects with AMS (mean difference=0.47; 95% CI: 0.14 to 0.80; p=0.01; I2=89.4%).ConclusionOur analysis shows that ONSD changes correlate with altitude and tend to increase in subjects with AMS. Small study number and high heterogeneity are the limitations of our study. Further large prospective studies are required to verify our findings.

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