What is the initial management for a patient with angiogram (Angio) negative subarachnoid hemorrhage (SAH)?

Initial Management of Angiogram-Negative Subarachnoid Hemorrhage

For patients with angiogram-negative SAH, you should repeat catheter angiography (DSA) with 3D rotational imaging, initiate nimodipine 60 mg every 4 hours for 21 days, maintain euvolemia, control blood pressure to systolic <160 mmHg, and monitor closely for hydrocephalus and delayed cerebral ischemia. 1

Repeat Vascular Imaging Strategy

Patients with SAH and negative initial noninvasive vascular imaging (CTA) must undergo catheter angiography (DSA) with 3D rotational angiography, as this is the gold standard. 1 The initial CTA may miss small aneurysms, particularly those <3 mm in size, which have only 61% sensitivity on CTA but >98% sensitivity on DSA. 1, 2

Timing and Pattern-Based Approach

• If the initial DSA is negative and the bleeding pattern is diffuse (non-perimesencephalic), repeat DSA should be performed at 1-2 weeks, as delayed angiography detects aneurysms in 14% of initially negative cases with diffuse patterns. 1, 3

• For perimesencephalic bleeding patterns (blood centered around the midbrain with no extension into lateral sylvian fissures or interhemispheric fissure), a single negative DSA may be sufficient, as these patients have excellent prognosis and structural causes are exceedingly rare. 1, 3

• For cortical/sulcal SAH patterns, obtain brain and cervical spine MRI with gradient echo sequences to evaluate for cerebral amyloid angiopathy (CAA), reversible cerebral vasoconstriction syndrome (RCVS), posterior reversible encephalopathy syndrome (PRES), cortical vein thrombosis, or vascular malformations. 4 These etiologies account for over 50% of sulcal SAH cases and require specific MRI sequences for detection. 4

Pharmacological Management

Administer oral nimodipine 60 mg (two 30 mg capsules) every 4 hours immediately upon diagnosis and continue for 21 consecutive days, starting within 96 hours of hemorrhage onset. 1, 5, 6 This improves neurological outcomes even in angiogram-negative SAH, though the mechanism is neuroprotection rather than vasospasm prevention. 1, 6

• If the patient cannot swallow, extract capsule contents with an 18-gauge needle into an oral syringe labeled "Not for IV Use" and administer via nasogastric tube followed by 30 mL normal saline flush. 6
• Never administer nimodipine intravenously—this causes life-threatening hypotension. 6

Blood Pressure Management

Maintain systolic blood pressure <160 mmHg using titratable intravenous agents to balance rebleeding risk against cerebral perfusion. 1, 5, 2 Even in angiogram-negative SAH, blood pressure control is critical as occult vascular lesions may still be present. 1

• Avoid aggressive blood pressure reduction that could compromise cerebral perfusion, particularly if intracranial pressure is elevated. 2
• Use short-acting agents (nicardipine, clevidipine, labetalol) that allow rapid titration. 5

Monitoring for Complications

Hydrocephalus

Monitor closely for acute hydrocephalus, which occurs in approximately 29% of angiogram-negative SAH patients. 3, 7 Place an external ventricular drain (EVD) urgently if hydrocephalus is symptomatic (decreased level of consciousness, clinical deterioration). 1

• Approximately 23% of patients with angiogram-negative SAH who require EVD will subsequently need ventriculoperitoneal shunt placement. 7

Delayed Cerebral Ischemia

Delayed cerebral ischemia occurs in 7-10% of angiogram-negative SAH patients, lower than aneurysmal SAH but still clinically significant. 3, 7

• Maintain euvolemia—avoid both hypovolemia and prophylactic hypervolemia, as triple-H therapy is no longer recommended. 1, 5
• If delayed cerebral ischemia develops, induce hypertension unless baseline blood pressure is already elevated or cardiac status precludes it. 1

Prognosis and Pattern-Specific Outcomes

Overall prognosis for angiogram-negative SAH is favorable, with 72-91% achieving good functional outcome (mRS 0-2). 3, 7 However, outcomes vary significantly by bleeding pattern:

• Perimesencephalic pattern: Excellent prognosis with minimal complications, most adverse events are treatment-related rather than disease-related. 3
• Diffuse pattern: Higher complication rates (more hydrocephalus, vasospasm), worse outcomes, and 12% chance of identifying structural cause on repeat imaging. 3
• Cortical/sulcal pattern: Requires evaluation for CAA, RCVS, or other specific etiologies that may require distinct management. 4

Critical Pitfalls to Avoid

• Do not stop at negative CTA alone—catheter angiography is mandatory as CTA misses small aneurysms. 1
• Do not assume all angiogram-negative SAH is benign—diffuse patterns warrant repeat angiography and have worse outcomes. 3
• Do not use prophylactic hypervolemia—maintain euvolemia only. 1
• Do not continue imaging beyond 6 weeks from ictus if initial workup (including repeat DSA and MRI) is negative, as diagnostic yield becomes negligible and rebleeding is not expected. 7