Subarachnoid Hemorrhage Diagnostic Testing

Obtain immediate noncontrast head CT for a patient with sudden severe headache when the presentation is concerning for nontraumatic SAH. Delayed diagnosis is associated with worse outcomes, and thunderclap headache also warrants consideration of intracranial hemorrhage and other vascular disorders. BMJBMJAssessment and investigation of thunderclap headache - The BMJ

The Ottawa SAH Rule can identify patients at very low risk among the rule's intended acute-headache population, but a positive rule result should be understood as an imaging trigger rather than evidence of hemorrhage. In pooled validation data, sensitivity was 99.5% (95% CI, 90.8%-100%) but specificity only 24% (95% CI, 15.5%-34.4%), so broad application substantially increases testing. BMJ+1BMJsystematic review of diagnostic accuracy studiesBMJManagement of patients presenting to the emergency department with sudden onset severe headache: systematic review of diagnostic accuracy studies | Emergency Medicine Journal

Do not use a normal neurologic examination alone to end the evaluation. The strongest early-CT evidence applies specifically to neurologically intact patients with a high-quality CT obtained promptly after headache onset and interpreted by an experienced reader. AHA JournalsAHA JournalsTreatment of Spontaneous Subarachnoid Hemorrhage

For suspected SAH, obtain noncontrast CT before lumbar puncture because CT detects acute hemorrhage and rapidly identifies alternative structural emergencies. In a systematic review of diagnostic studies, CT performed within 6 hours had pooled sensitivity of 98.7% (95% CI, 96.5%-100%) and specificity of 100% (95% CI, 99.7%-100%). BMJ+1BMJsystematic review of diagnostic accuracy studiesBMJManagement of patients presenting to the emergency department with sudden onset severe headache: systematic review of diagnostic accuracy studies | Emergency Medicine Journal

The early-CT rule-out approach requires more than a clock time. The cited clinical framework specifies a third-generation or higher CT scanner, imaging within 6 hours of onset, a neurologically intact patient, and a scan read as normal by a neuroradiologist; under those conditions, further testing was considered unnecessary. AHA JournalsAHA JournalsTreatment of Spontaneous Subarachnoid Hemorrhage

After 6 hours, negative CT is materially less reassuring. The pooled review found sensitivity of 90% or less in the two studies evaluating later imaging; proceed to CSF testing or a selected CTA-based approach when the clinical concern remains meaningful. BMJ+1BMJsystematic review of diagnostic accuracy studiesBMJManagement of patients presenting to the emergency department with sudden onset severe headache: systematic review of diagnostic accuracy studies | Emergency Medicine Journal

CT technique and interpretation remain operationally important. In the prospective early-CT cohort, scanners were third-generation multislice systems, and sites used 5-7.5 mm brain cuts with 2.5-5 mm posterior-fossa cuts after 2002; do not automatically extrapolate early-CT performance to nondiagnostic studies, poor-quality scans, or settings without routine brain-imaging expertise. BMJBMJSensitivity of computed tomography performed within six hours of onset of headache for diagnosis of subarachnoid haemorrhage: prospective cohort study

After a negative noncontrast CT obtained beyond 6 hours, perform lumbar puncture when the residual probability of SAH justifies an invasive test. In pooled diagnostic data, LP with spectrophotometric CSF analysis after negative CT had sensitivity of 100% and specificity of 95% (95% CI, 86.0%-98.5%). BMJ+1BMJsystematic review of diagnostic accuracy studiesBMJManagement of patients presenting to the emergency department with sudden onset severe headache: systematic review of diagnostic accuracy studies | Emergency Medicine Journal

Request CSF xanthochromia assessment using spectrophotometry when available and clinically applicable. Spectrophotometric analysis is the method evaluated in the pooled high-sensitivity LP studies; visual xanthochromia and red-cell counts have different limitations and should not be treated as interchangeable assays. BMJ+2BMJsystematic review of diagnostic accuracy studiesBMJManagement of patients presenting to the emergency department with sudden onset severe headache: systematic review of diagnostic accuracy studies | Emergency Medicine JournalScienceDirectControversies in the Diagnosis of Subarachnoid Hemorrhage - ScienceDirect

Interpret CSF red blood cells cautiously because traumatic taps are common and may be difficult to distinguish from SAH. A review cites a final-tube RBC threshold of 2,000 × 10^6/L with sensitivity 93% and specificity 93% for aneurysmal SAH, whereas lower final-tube thresholds trade sensitivity for specificity; therefore, a low or falling RBC count alone should not override the clinical and xanthochromia context. ScienceDirectScienceDirectControversies in the Diagnosis of Subarachnoid Hemorrhage - ScienceDirect

LP can also redirect the diagnosis toward meningitis or another disorder when CT is negative. This broader diagnostic yield is a practical advantage over a vascular-only strategy, particularly when fever, meningismus, immunocompromise, or altered mental status broadens the differential. BMJBMJManagement of patients presenting to the emergency department with sudden onset severe headache: systematic review of diagnostic accuracy studies | Emergency Medicine Journal

Obtain CTA after CT-confirmed SAH to identify an aneurysm or another vascular cause and to guide urgent cerebrovascular treatment planning. AHA/ASA guidance emphasizes management in centers with dedicated neurocritical care, multidisciplinary expertise, and experience treating aneurysms, which should influence early transfer decisions when these services are unavailable. AHA JournalsAHA Journals2023 Guideline for the Management of Patients With Aneurysmal Subarachnoid Hemorrhage: A Guideline From the American Heart Association/American Stroke Association | Stroke

For CT-negative thunderclap headache, CTA can be an alternative to LP in selected cases, especially when LP is difficult or unacceptable, but it should be chosen deliberately. CTA can identify vascular causes of thunderclap headache, whereas MRI/MRA may reveal alternative diagnoses such as cerebral venous thrombosis or reversible cerebral vasoconstriction syndrome and may also produce incidental findings with uncertain management implications. BMJ+1BMJAssessment and investigation of thunderclap headache - The BMJAHA JournalsTreatment of Spontaneous Subarachnoid Hemorrhage

A CTA-detected aneurysm does not by itself prove that the aneurysm caused the headache or that occult SAH occurred. Interpret a vascular lesion with the noncontrast CT, CSF findings when obtained, headache phenotype, and neuroradiologic review; incidental intracranial aneurysms can create downstream procedural decisions. accessdata fda+1accessdata fda[PDF] summary of safety and effectiveness data (ssed) - accessdata.fda.govAHA JournalsTreatment of Spontaneous Subarachnoid Hemorrhage

Proceed to digital subtraction angiography when noninvasive vascular imaging does not resolve the source in a patient with proven SAH or when neurovascular specialists require higher-resolution lesion characterization for treatment planning. Catheter angiography carries procedure-related risks including vessel dissection or perforation, embolic stroke, access-site bleeding, renal failure, and death, so reserve it for a result that will change management. accessdata fdaaccessdata fda[PDF] ESALIO - NeVa VS - accessdata.fda.gov

A confirmed SAH should prompt urgent source evaluation because rebleeding before aneurysm repair is a major preventable complication. A meta-analysis summarized in a clinical review found rebleeding in 7%-26% of patients, with a mean of 13%; risk was associated with proximity to the initial hemorrhage, higher blood pressure, worse neurologic grade, intraventricular or intracerebral hemorrhage, and larger aneurysm. AHA JournalsAHA JournalsTreatment of Spontaneous Subarachnoid Hemorrhage

Transfer or admit to a center with neurocritical care and an experienced aneurysm-treatment team when feasible. Care in centers with dedicated neurocritical care units, higher case volume, physician expertise in aneurysm treatment, expert nursing, and multidisciplinary teams is associated with lower mortality and greater likelihood of good functional outcome. AHA JournalsAHA Journals2023 Guideline for the Management of Patients With Aneurysmal Subarachnoid Hemorrhage: A Guideline From the American Heart Association/American Stroke Association | Stroke

In a patient with later neurologic deterioration after aneurysmal SAH, do not attribute the deficit automatically to vasospasm. Device-trial eligibility criteria for symptomatic vasospasm specifically excluded symptoms attributable to hydrocephalus, metabolic causes, or infection, illustrating the need to reassess these competing causes before escalating vasospasm-directed interventions. accessdata fdaaccessdata fda[PDF] ESALIO - NeVa VS - accessdata.fda.gov