Quantitative EEG to Detect a Late-Onset Vasospasm After Subarachnoid Hemorrhage due to Basilar Artery Aneurysm: A Case Report.

Delayed cerebral ischemia remains a major cause of morbidity and mortality following subarachnoid hemorrhage. Early detection is crucial for improving outcomes, yet traditional imaging modalities may fail to identify evolving ischemic changes in real time. We report the case of a 44-year-old female who presented with a sudden severe headache. Initial computed tomography revealed a subarachnoid hemorrhage secondary to a serpentine aneurysm of a tortuous basilar artery. Continuous EEG (cEEG) monitoring demonstrated progressive hemispheric asymmetry and frequency slowing preceding clinical deterioration, consistent with evolving delayed cerebral ischemia (DCI). This case underscores the value of cEEG as a sensitive and noninvasive tool for the early detection of cerebral ischemia, allowing timely therapeutic intervention before irreversible injury occurs.