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Published on: December 16, 2021
Evolution of a chronic dissecting aneurysm on magnetic resonance imaging in a pediatric patient
Long Chen1, Ivanna Yau, Gabrielle deVeber
1Division of Neuroradiology, Department of Medical Imaging, Toronto Western Hospital, University Health Network, Toronto;
Insights
Partially thrombosed aneurysms (PTAs) may develop from acute dissecting aneurysms. Serial imaging revealed blood layering within the aneurysm wall, indicating a potential new mechanism for PTA formation.
Area of Science:
- Neurology
- Vascular Imaging
- Pathology
Background:
- Partially thrombosed aneurysms (PTAs) present distinct clinical and imaging features compared to classic saccular aneurysms.
- Previous hypotheses suggest repeated intramural hemorrhages contribute to PTA formation.
- The pathological mechanisms underlying PTA development require further elucidation.
Purpose of the Study:
- To present a case of a partially thrombosed aneurysm evolving from an acute dissecting aneurysm.
- To illustrate the diagnostic utility of serial imaging in understanding PTA pathogenesis.
- To explore the potential role of dissection in PTA formation.
Main Methods:
- A case study of a 5-year-old boy with sudden onset hemiparesis.
- Initial magnetic resonance imaging (MRI) and conventional angiography to diagnose middle cerebral artery (MCA) dissection and infarction.
- Serial MRI studies to monitor the evolution of the dissection into a PTA.
Main Results:
- Initial imaging confirmed acute distal MCA dissection and a perforating vessel infarction.
- Serial MRI demonstrated progressive layering of blood within the MCA wall.
- The evolving dissection ultimately presented as a partially thrombosed aneurysm.
Conclusions:
- This case suggests that some PTAs may originate from repeated or chronic arterial dissections.
- Endothelial defects may allow blood to enter the vessel wall, contributing to PTA development.
- Understanding dissection-induced PTA formation can guide treatment strategies.
Abstract:
Clinical and imaging manifestations of the so-called partially thrombosed aneurysm (PTA) are different from those of the classic intracranial saccular aneurysm. Given some of their peculiar imaging features, it had been hypothesized that some PTAs occur due to repeated intramural hemorrhages. The authors present a case of PTA that evolved from an acute dissecting aneurysm as shown by serial imaging. A previously healthy 5-year-old boy had a sudden onset of left hemiparesis. Initial MRI sequences showed a perforating vessel infarction in the right basal ganglia area secondary to an acute distal middle cerebral artery (MCA) dissection as demonstrated on conventional angiography. Conservative management with close observation of this dissection was chosen, and serial MRI studies revealed layering of blood of various ages within the wall of an aneurysmal outpouching of the MCA, thereby leading to the imaging appearance of a PTA. The findings in this case indicate that some PTAs may be caused by repeated or chronic dissections, with blood entering the wall through an endothelial defect. Understanding the pathological mechanism underlying the formation of these aneurysms will help inform appropriate treatment strategies.
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