Introduction: Perimesencephalic subarachnoid hemorrhage is a rare neurologic condition of unclear etiology. Multiple mechanisms have been postulated as potential triggers, but none are universally accepted.
Methods: Single observational case report and review of the literature.
Results: We describe a patient who developed perimesencephalic subarachnoid hemorrhage in the setting of "hypoxic training" (breath-holding while swimming). We describe the plausible pathophysiologic events that caused the hemorrhage.
Conclusion: The occurrence of perimesencephalic subarachnoid hemorrhage during hypoxic training suggests that acute venous congestion may be a triggering factor. The increasing popularity of hypoxic training demands vigilance from health care providers.