Spontaneous disappearance of an intracranial small unruptured aneurysm on magnetic resonance angiography: Report of two cases

Abstract

Spontaneous radiographic disappearance of cerebral aneurysms is often observed under special conditions such as giant aneurysms. However, spontaneous disappearance of an unruptured and nongiant intracranial saccular aneurysms is rare. We describe two cases of this rare vascular phenomenon. The first patient is a 64-year-old female diagnosed with a small unruptured aneurysm arising from the distal anterior cerebral artery. Spontaneous disappearance of the aneurysm on magnetic resonance angiography (MRA) was observed 5 years after the initial diagnosis. Continuous imaging surveillance also revealed spontaneous reappearance of the aneurysm 2 years later. The second patient is a 57-year-old female harboring a small unruptured saccular aneurysm arising from the M1–M2 bifurcation of the middle cerebral artery. The aneurysm showed spontaneous disappearance on MRA 13 years after the initial diagnosis. These cases provide a new insight into this natural dynamic process even in cases of a small unruptured intracranial saccular aneurysm.

Disappearance of a small unruptured intracranial aneurysm: A case report and brief literature review

“…All the cases showed either a reduction in size or complete disappearance on formal angiography, MRA, or CTA without any intervention. Although >50% of the cases noted complete disappearance, 11,13–15 one of the reported cases noted recurrence 2 years after documented disappearance 11 and two cases (including our patient) only had a partial reduction in size. 12 Given the unknown pathophysiology that led to the disappearance of these aneurysms and the documented possibility of recurrence at the same location, observation and follow-up should continue even in patients with small and unruptured aneurysms given the risk of recanalization and possibility of growth or rupture.…”

“…9,10 Changes in hemodynamic flow are thought to lead to spontaneous regression of aneurysms, if shear forces on the vessel wall no longer maintain intra-aneurysm blood flow and allow for stasis. 11,12…”

“…Literature review reveals, to the best our knowledge, only six 11–15 reported cases of disappearance of a small unruptured intracranial aneurysm (Table 1). As with our patient, all aneurysms documented were <5 mm.…”

“…9,10 Changes in hemodynamic flow are thought to lead to spontaneous regression of aneurysms, if shear forces on the vessel wall no longer maintain intra-aneurysm blood flow and allow for stasis. 11,12 Literature review reveals, to the best our knowledge, only six [11][12][13][14][15] reported cases of disappearance of a small unruptured intracranial aneurysm (Table 1). As with our patient, all aneurysms documented were <5 mm.…”

“…15,16 The proposed etiology of small, unruptured aneurysm disappearance is thought to be linked to spontaneous thrombosis, as it is with giant aneurysms, although the factors that encourage thrombosis in these small sacs are less understood. 11,12 Small aneurysms have less potential for stasis, although this is increased in aneurysms with large diameters and narrow necks. Since unruptured aneurysms are not subjected to the endothelial injury associated with rupture, other factors must trigger the coagulation process.…”