Angiographically negative subarachnoid hemorrhage

see also Non-aneurysmal subarachnoid hemorrhage.

Repeat angiogram is probably not necessary in patients with perimesencephalic subarachnoid hemorrhage and they tend to have better outcomes. Classic-SAH pattern of bleed is associated with fair chances of the underlying pathology and a repeat angiogram is recommended in these cases and they have a poorer outcome 1).

The overall incidence of true aneurysms in patients with angiographically negative subarachnoid hemorrhage is low (2.9%). Initial bleeding pattern strongly correlates with diagnostic yield and clinical outcome. The diffuse bleeding pattern is associated with significantly higher diagnostic yield, more in-hospital complications, and worse clinical outcomes. Patients with initial imaging characteristics other than diffuse pattern SAH developed few disease-related complications, with the majority of in-hospital adverse events treatment related 2).

Standard magnetic resonance imaging (MRI) rarely identifies the cause of hemorrhage in patients with an angiogram-negative, non perimesencephalic subarachnoid hemorrhage (SAH). Yet up to 10 % of these patients have recurrent hemorrhage

Vessel wall-MRI showed abnormalities in seven patients with angiogram-negative SAH. These findings did not alter patient management, but the findings may be useful for other physicians who choose to perform vessel wall-MRI in this patient population 3).

The basal vein of Rosenthal (BVR) variant is a potential origin of bleeding in angiogram-negative subarachnoid hemorrhage (AN-SAH). perimesencephalic angiographically negative subarachnoid hemorrhage patients have a higher rate and degree of BVR variants compared with patients with non-perimesencephalic subarachnoid hemorrhage . Those AN-SAH patients with bilateral normal BVRs are more likely to be of arterial origin and are at risk of suffering from rebleeding and a poor outcome 4)

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Kumar R, Das KK, Sahu RK, Sharma P, Mehrotra A, Srivastava AK, Sahu RN, Jaiswal AK, Behari S. Angio negative spontaneous subarachnoid hemorrhage: Is repeat angiogram required in all cases? Surg Neurol Int. 2014 Aug 7;5:125. doi: 10.4103/2152-7806.138367. PMID: 25140284; PMCID: PMC4135542.
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Fang Y, Shao A, Wang X, Lu J, Wu H, Ren R, Huang Y, Lenahan C, Xu J, Chen S, Zhang J. Deep venous drainage variant rate and degree may be higher in patients with perimesencephalic than in non-perimesencephalic angiogram-negative subarachnoid hemorrhage. Eur Radiol. 2021 Mar;31(3):1290-1299. doi: 10.1007/s00330-020-07242-5. Epub 2020 Sep 11. Erratum in: Eur Radiol. 2020 Dec 23;: PMID: 32918092.
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