Angiographically negative subarachnoid hemorrhage
see also Non-aneurysmal subarachnoid hemorrhage.
“Spontaneous angiogram-negative subarachnoid hemorrhage” refers to a type of subarachnoid hemorrhage (SAH) that occurs without a detectable vascular abnormality on angiography. Subarachnoid hemorrhage is bleeding into the subarachnoid space, which is the space between the arachnoid membrane and the pia mater surrounding the brain.
In some cases of subarachnoid hemorrhage, the source of bleeding can be identified through cerebral angiography, a diagnostic imaging test that visualizes the blood vessels in the brain. However, when the angiogram is negative, it means that no vascular abnormality or aneurysm is apparent.
“Spontaneous” in this context means that the hemorrhage occurred without a clear external cause, such as trauma. Identifying the cause of spontaneous angiogram-negative subarachnoid hemorrhage can be challenging, and in some cases, the source of bleeding may remain unknown.
This condition is significant because subarachnoid hemorrhage can have serious consequences, and determining its cause is crucial for appropriate management and treatment decisions. Close monitoring and additional diagnostic tests may be necessary to identify potential underlying causes or contributing factors in cases of spontaneous angiogram-negative subarachnoid hemorrhage.
In approximately 15 % of cases, nor aneurysm or other vascular malformation can be identified by cerebral angiography as origin of the hemorrhage, and these are commonly defined as idiopathic subarachnoid hemorrhage SAH (ISAH). Because of the negative angiography, limited extension of the bleeding with prevalent prepontine pattern and the benign prognosis, the venous causes has been preferred rather than the arterial ones.
In the past, several possible explanations for idiopathic subarachnoid hemorrhage (ISAH) have been proposed; however, neuroimaging studies have never provided conclusive data about the structural cause of the bleeding 1).
Idiopathic subarachnoid hemorrhage is not clearly understood, and reasons suggested include the repair of a microaneurysm, the presence of vasospasm that prevents the aneurysm from filling up, the dissection of the basilary artery or other arteries, or bleeding from the perimesencephalic or other deep veins 2).
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 3).
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 4).
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 5).
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 6)
Outcome
Case series
Achrén et al. retrospectively reviewed all adult patients admitted to a neurosurgical intensive care unit during 2004-2018 due to spontaneous angiogram-negative SAH. The primary outcome was a dichotomized Glasgow Outcome Scale (GOS) at 3 months. They assessed factors that were associated with outcomes using multivariable logistic regression analysis.
Of the 108 patients included, 84% had a favorable outcome (GOS 4-5), and mortality was 5% within 1 year. The median age was 58 years, 51% were female, and 93% had a low-grade SAH (World Federation of Neurosurgical Societies grading I-III). The median number of angiograms performed per patient was two. Thirty percent of patients showed radiological signs of acute hydrocephalus, 28% were acutely treated with an external ventricular drain, 13% received active vasospasm treatment and 17% received a permanent shunt. In the multivariable logistic regression model, only acute hydrocephalus was associated with unfavorable outcomes (odds ratio = 4.05, 95% confidence interval = 1.05-15.73). Two patients had a new bleeding episode.
Subarachnoid hemorrhage complications such as hydrocephalus and vasospasm are common after angiographically negative subarachnoid hemorrhage. Still, most patients had a favorable outcome. Only acute hydrocephalus was associated with unfavorable outcomes. The high rate of SAH-related complications highlights the need for neurosurgical care in these patients 7)
Unclassified
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