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ARKA Clinical Decision Support is designed to meet all four criteria for Non-Device CDS under FD&C Act §520(o)(1)(E) and FDA's January 2026 final guidance on Clinical Decision Support Software. Recommendations support, not replace, the clinician's judgment. Every recommendation is anchored in a published guideline or peer-reviewed source, with the basis available for independent review. CLIN emphasizes imaging appropriateness at order entry.

This recommendation is intended to support, not replace, clinical judgment. It is generated by ARKA, software designed to meet the four criteria for Non-Device Clinical Decision Support under FD&C Act §520(o)(1)(E) and FDA's final guidance on Clinical Decision Support Software (January 2026). The clinician is responsible for the final decision.

Regulatory rationale Feature catalog Trust center

Evidence library

AIIE Evidence

Thunderclap headache — emergent subarachnoid hemorrhage workup

Head / Brain

Last reviewed 2026-06-01

Knowledge Matrix v1.0.0

Clinical bottom line

Treat thunderclap headache as an emergency: immediate non-contrast head CT, then LP or CTA when CT is negative beyond the early window.

Summary

Headache reaching maximal intensity within a minute is subarachnoid hemorrhage until proven otherwise. Non-contrast CT within six hours of onset is highly sensitive; the Ottawa SAH rule supports structured risk assessment, and CTA evaluates for aneurysm when hemorrhage is confirmed or suspicion persists.

Key points

Modern CT within 6 hours of onset approaches 100% sensitivity for aneurysmal SAH in neurologically intact patients.
The Ottawa SAH rule is a highly sensitive screen for which acute headaches need workup.
CTA follows positive CT or persistent suspicion to identify the culprit aneurysm.