Complete spontaneous thrombosis in unruptured non-giant intracranial aneurysms: A case report and systematic review

Hemodynamics of thrombus formation in intracranial aneurysms: An in silico observational study

How prevalent is spontaneous thrombosis in a population containing all sizes of intracranial aneurysms? How can we calibrate computational models of thrombosis based on published data? How does spontaneous thrombosis differ in normo- and hypertensive subjects? We address the first question through a thorough analysis of published datasets that provide spontaneous thrombosis rates across different aneurysm characteristics. This analysis provides data for a subgroup of the general population of aneurysms, namely, those of large and giant size (>10 mm). Based on these observed spontaneous thrombosis rates, our computational modeling platform enables the first in silico observational study of spontaneous thrombosis prevalence across a broader set of aneurysm phenotypes. We generate 109 virtual patients and use a novel approach to calibrate two trigger thresholds: residence time and shear rate, thus addressing the second question. We then address the third question by utilizing this calibrated model to provide new insight into the effects of hypertension on spontaneous thrombosis. We demonstrate how a mechanistic thrombosis model calibrated on an intracranial aneurysm cohort can help estimate spontaneous thrombosis prevalence in a broader aneurysm population. This study is enabled through a fully automatic multi-scale modeling pipeline. We use the clinical spontaneous thrombosis data as an indirect population-level validation of a complex computational modeling framework. Furthermore, our framework allows exploration of the influence of hypertension in spontaneous thrombosis. This lays the foundation for in silico clinical trials of cerebrovascular devices in high-risk populations, e.g., assessing the performance of flow diverters in aneurysms for hypertensive patients.

A rare case of spontaneous thrombosis in saccular cerebral aneurysm in a patient with subarachnoid hemorrhage

Cerebral aneurysm is a known cause of spontaneous subarachnoid hemorrhage (SAH). Furthermore, this condition is often asymptomatic, but the occurrence of a rupture can lead to fatal complications. The incidence of spontaneous thrombosis in saccular aneurysm is rare, with an incidence rate of 1%-2%. The most common sites include the middle cerebral artery (MCA) (41%), posterior communicating artery (PCOMM) (15%), and posterior inferior cerebellar artery (PICA) (11%). A head computed tomography angiography (CTA) with contrast is a common diagnostic tool for detecting SAH in the temporoparietal area, hippocampal gyrus, and right fissure of Sylvie. In some cases, saccular aneurysm can be found in the segment bifurcation of the right middle cerebral artery. A cerebral angiography was carried out, specifically digital subtraction angiography, which revealed the presence of visible blister remnants of aneurysm in the form of spontaneous thrombosis. After 1 year, another angiography evaluation was performed to assess the condition of the patient. Furthermore, the results showed no evidence of recanalization and there were no new neurologic deficits. Although spontaneous thrombosis led to the healing of aneurysm in some cases, secondary recanalization remained a possibility. Therefore, it was essential to monitor any incidence of this complication. Precise knowledge of the mechanism of spontaneous thrombosis could lead to the development of new therapeutic approaches. Spontaneous thrombosis in cases of saccular aneurysm is a rare occurrence, which can provide temporary or permanent benefits to the patient. Therefore, periodic evaluation is required to assess the condition of the patient.

Interobserver reliability of computed tomography angiography in the assessment of ruptured intracranial aneurysm and impact on patient management

BACKGROUND

Aneurysmal subarachnoid hemorrhage is an emergency that can lead to a high mortality rate and many severe complications. It is critical to make a rapid radiological evaluation of ruptured intracranial aneurysms (RIAs) to determine the appropriate surgical treatment.

AIM

To assess the reliability of computed tomography angiography (CTA) in assessing different features of ruptured intracranial aneurysm and its impact on patient management.

METHODS

The final cohort of this study consisted of 146 patients with RIAs (75 male and 71 female) who underwent cerebral CTA. Their age ranged from 25 to 80, and the mean age ± SD was 57 ± 8.95 years. Two readers were asked to assess different features related to the aneurysm and perianeurysmal environment. Inter-observer agreement was measured using kappa statistics. Imaging data extracted from non-contrast computed tomography and CTA were considered to categorize the study population into two groups according to the recommended therapeutic approach.

RESULTS

The inter-observer agreement of both reviewers was excellent for the detection of aneurysms (K = 0.95, P = 0.001), aneurysm location (K = 0.98, P = 0.001), and (K = 0.98, P = 0.001), morphology (K = 0.92, P = 0.001) and margins (K = 0.95, P = 0.001). There was an excellent interobserver agreement for the measurement of aneurysm size (K = 0.89, P = 0.001), neck (K = 0.85, P = 0.001), and dome-to-neck ratio (K = 0.98, P = 0.001). There was an excellent inter-observer agreement for the detection of other aneurysm-related features such as thrombosis (K = 0.82, P = 0.001), calcification (K = 1.0, P = 0.001), bony landmark (K = 0.89, P = 0.001) and branch incorporation (K = 0.91, P = 0.001) as well as perianeurysmal findings including vasospasm (K = 0.91, P = 0.001), perianeurysmal cyst (K = 1.0, P = 0.001) and associated vascular lesions (K = 0.83, P = 0.001). Based on imaging features, 87 patients were recommended to have endovascular treatment, while surgery was recommended in 59 patients. 71.2% of the study population underwent the recommended therapy.

CONCLUSION

CTA is a reproducible promising diagnostic imaging modality for detecting and characterizing cerebral aneurysms.

A complete thrombotic large aneurysm at the nonbranching segment of the distal anterior cerebral artery mimicking a cavernous malformation: illustrative case

BACKGROUND

Thrombotic aneurysms at the nonbranching segment of the distal anterior cerebral artery (ACA) are extremely rare and difficult to differentiate from cavernous malformations by radiographic features alone.

OBSERVATIONS

Computed tomography and magnetic resonance imaging of a 30-year-old female patient with a chronic headache complaint revealed a 22-mm frontal lobe mass. The mass showed heterogeneous mixed intensity and hemosiderin deposits on magnetic resonance images. It was not visualized by conventional angiography, indicating that the mass and ACA/other vessels were not connected. The patient was preoperatively diagnosed with a cavernous malformation. However, during resection, the mass surface was white and smooth, different from a cavernous malformation. Although the mass was adherent to the pericallosal artery branch, no luminal continuity was observed. After detachment, the mass was completely resected. Pathological and immunohistochemical findings indicated a vessel wall and interior thrombus. The patient was rediagnosed with a thrombotic aneurysm at the distal ACA nonbranching segment and discharged 10 days postsurgery without neurological deficits.

LESSONS

Because radiographic findings of thrombotic aneurysm and cavernous malformation are similar, mass lesions in contact with major arteries should be differentiated as thrombotic aneurysms, even when the artery lumen appears disconnected from the mass.

De-novo formation of neighboring intracranial aneurysm after spontaneous thrombosis of a ruptured distal anterior cerebral artery aneurysm: A case report and review of the literature

Intracranial aneurysms arise in 1-2% of the population and usually present as hemorrhagic strokes. Spontaneous thrombosis of a ruptured intracranial aneurysm occurs in 1-3% and most commonly in giant aneurysms, with complete thrombosis in just 13-20% of the cases. Thrombosis of smaller aneurysms is rare. Here we present a case of a patient who presented with a ruptured intracranial aneurysm that subsequently thrombosed, discovering a neighboring de-novo aneurysm during follow-up. We hypothesized that after thrombosis, the hemodynamic characteristics that contributed to the formation of the first aneurysm were replicated.