Hemodynamic Correlations of Internal Carotid and Vertebral Arteries at High Altitude

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Summary of  Journal of Applied Physiology https://doi.org/10.1152/japplphysiol.00434.2024 
Dr. Kazunobu Okazaki  et al.

Points

Researchers assessed cerebral hemodynamics in eight healthy men at sea level and during a three-day stay at the summit of Mount Fuji to investigate acute mountain sickness mechanisms.
Analysis showed that internal carotid artery diameter increased significantly across all three days while flow volume specifically peaked on the third day of high-altitude exposure.
Vertebral artery metrics demonstrated a transient response where flow volume and velocity increased during the first day before decreasing during the subsequent acclimatization period.
Repeated measures analysis revealed a significant positive correlation between the percentage change in internal carotid artery diameter and the reported intensity of altitude-induced headaches.
The findings suggest that high-altitude-induced increases in specific cerebrovascular perfusion metrics are key contributors to the worsening of headaches associated with acute mountain sickness pathogenesis.

Summary

This study investigated the hypothesis that regional cerebrovascular responses to high-altitude exposure are associated with the symptoms of acute mountain sickness (AMS). To assess this, researchers monitored the internal carotid artery (ICA) and vertebral artery (VA) hemodynamics, along with cardiorespiratory responses, in eight healthy male lowlanders (mean age, 34 years) at sea level and during a three-day sojourn at the summit of Mount Fuji (3,776 m). The primary objective was to elucidate the specific effects of regional cerebral blood flow on the pathogenesis of high-altitude headaches and AMS progression.

Physiological measurements indicated distinct vascular responses between the two arterial systems during acclimatization. Compared to sea level baselines, ICA diameter increased significantly across all three days (P < 0.001), while ICA flow increased specifically on day 3 (P = 0.009). Conversely, VA flow demonstrated an earlier, transient increase on days 1 and 2 (P = 0.008 and P = 0.018, respectively), with VA velocity increasing significantly only on day 1 (P = 0.044). Clinical assessments showed that while headache intensity increased over the three-day period (P = 0.011 to 0.048), overall AMS scores peaked significantly on day 3 (P = 0.001).

Repeated-measures correlation analysis established a significant link between vascular changes and symptom severity. Changes in headache intensity from the previous day correlated positively with the percent change in ICA diameter (r_rm = 0.596, P = 0.012), as well as VA flow (r_rm = 0.537, P = 0.026) and VA velocity (r_rm = 0.619, P = 0.008). These results suggest that high-altitude-induced increases in cerebrovascular perfusion contribute directly to the worsening of headaches, characterizing a key mechanism in AMS pathogenesis.

Link to the article: https://journals.physiology.org/doi/full/10.1152/japplphysiol.00434.2024#con1

References

Okazaki, K., Asano, K., & Horiuchi, M. (2025). Effect of short-term high-altitude acclimatization on the relationship between cerebral blood flow and symptoms of mild acute mountain sickness in males. Journal of Applied Physiology, 139(2), 571–581. https://doi.org/10.1152/japplphysiol.00434.2024