Clinical Practice and Cases in Emergency Medicine

Introduction: Nontraumatic subarachnoid hemorrhage (SAH) is a life-threatening neurological emergency, accounting for 5-10% of strokes. While most cases result from aneurysm rupture, perimesencephalic nonaneurysmal SAH is a distinct subtype characterized by blood localized to the midbrain cisterns and a venous pathophysiology. Perimesencephalic nonaneurysmal SAH is often associated with activities increasing intracranial venous pressure. Reports linking it to low-impact exercise such as yoga are rare.

Case Report: A 45-year-old female with no significant medical history presented with acute onset of severe headache and subjective unilateral hearing loss. Symptoms began immediately after a sudden, startled hyperextension movement during a yoga session. Noncontrast computed tomography of the brain revealed hemorrhage localized to the perimesencephalic and basal cisterns (modified Fisher Grade 4). Magnetic resonance imaging confirmed hemorrhage extension into the fourth ventricle and communicating hydrocephalus. Comprehensive workup, including echocardiography and serial digital subtraction angiography, ruled out aneurysm, arteriovenous malformation, or cardiac source.

Conclusion: The patient was diagnosed with perimesencephalic nonaneurysmal subarachnoid hemorrhage, likely precipitated by an abrupt Valsalva-like maneuver during yoga. She was managed conservatively with strict blood pressure control, chemical thromboprophylaxis, and vasospasm prophylaxis, achieving a full recovery. This case highlights that neurovascular events can occur during low-impact activities in susceptible individuals. Recognition of a distinct radiological pattern of perimesencephalic nonaneurysmal—confirmed by negative serial angiography—is vital, as it carries a significantly more favorable prognosis than aneurysmal SAH, allowing for conservative management and reassurance.