A PRISMA-ScR scoping review of 46 studies in adults with aneurysmal subarachnoid hemorrhage found that noninvasive tools can flag delayed cerebral ischemia before overt decline, with TCD AUCs of 0.59–0.81, NIRS up to 0.93, and multimodal combinations reaching 0.96. The review, covering studies from 2004 to January 2025, suggests EEG, TCD, and NIRS provide complementary signals that may open an earlier treatment window.

Why It Matters To Your Practice

• Delayed cerebral ischemia remains a major driver of poor outcomes after aSAH, and bedside noninvasive monitoring could help detect evolving injury sooner.

• TCD was the most studied modality, but its standalone performance was variable, underscoring the limits of relying on a single physiologic marker.

• For clinicians interested in AI-enabled practice, the review points toward multimodal integration and real-time predictive modeling as the next step rather than replacement of clinical assessment.

Clinical Implications

• TCD middle cerebral artery mean flow velocity was the most common metric, with reported AUCs from 0.59 to 0.81.

• EEG quantitative features, especially alpha/delta ratio, showed strong predictive value for DCI-related changes.

• NIRS studies using rSO₂ cutoffs around 65%–70% reported AUCs up to 0.93.

• Combining modalities or pairing TCD with biomarkers or qEEG features improved discrimination, with AUCs up to 0.96.

Insights

• These modalities appear to capture different aspects of DCI pathophysiology, including vasospasm, microcirculatory dysfunction, and neuroelectric disturbance.

• Signal changes may precede clinical DCI, which is the key rationale for continuous or serial monitoring in high-risk patients.

• Interpret performance cautiously: studies used heterogeneous DCI definitions and analytic methods, limiting direct comparison and threshold adoption.

• AI is most relevant here as a layer for integrating streaming physiologic data, standardizing thresholds, and improving early warning performance.

The Bottom Line

• No single noninvasive test is definitive for DCI, but EEG, TCD, and NIRS each add useful physiologic information.

• The strongest future use case for AI in this Disease of the nervous system is multimodal prediction that supports earlier intervention after aSAH.

• For now, clinicians should view these tools as complementary monitors whose value likely increases when combined and interpreted in clinical context.