PMC5609433_01
MRIs (a-d) and MRA (e) show right giant and left ICA aneurysms. Both on ASL with PLDs of 1.5 (f) and 2.5 s (g), the right aneurysm is depicted as hyperintense signal in the same configuration. ASL with PLD 1.5 s reveals decreased signal in the right MCA territory, and with 2.5 s improved. (h) Right CAG shows the contrast in the right aneurysm is stagnant at 4.5 s after injection. At 1.5 s, the trunks of the right MCA and ACA are barely visualized because of stagnation, and are opacified at 2.5 s. (i) Left CAG shows that the trunks of the left MCA and ACA are well opacified at 1.5 s
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Conventional MRI and MR angiography (MRA) revealed a giant right ICA aneurysm (diameter 30 mm) and a left ICA aneurysm (5 mm) [Figure 1a-e]. T1-weighted MRI (T1WI) showed a mixed iso-low-intensity area in the lumen of the right giant ICA aneurysm, although a flow artifact originating from the aneurysm was present [Figure 1c]. T2-weighted MRI (T2WI) revealed an iso-high-intensity area at the center of the aneurysm [Figure 1d]. In ASL-MRI with PLDs of 1.5 and 2.5 seconds, although the left aneurysm was not demonstrated, the right ICA aneurysm was depicted as a hyperintense signal area in nearly the same configuration [Figure 1f and g]. This area was large enough to extend to the axial level of the basal ganglia [Figure 1f and g], while the aneurysm was not seen at this level in conventional MRI [Figure 1b]. Hyperintensity circles were also noted in a concentric arrangement central to the right aneurysm [Figure 1f and g]. ASL-MRI with PLD 1.5 seconds demonstrated decreased signals in the right hemisphere, especially the right MCA territory [Figure 1f]. ASL-MRI with PLD 2.5 seconds showed improvement in this decreased area, although a slight right laterality was still present [Figure 1g]. Carotid angiography (CAG) at 1.5 and 2.5 seconds after contrast medium injection into the right and left ICA, respectively, clearly demonstrated the nonthrombosed giant aneurysm at the cavernous portion of the right ICA [Figure 1h] and the aneurysm at the cavernous portion of the left ICA [Figure 1i], respectively. ICA aneurysm was still stagnant [Figure 1h, right], while the contrast in the left aneurysm had completely disappeared [Figure 1i, right]. ACA were well opacified, and their peripheries had started to be visualized [Figure 1i, left]. In contrast, in the right CAG at 1.5 seconds, the trunks of the right MCA and ACA were barely visualized due to stagnation of the contrast in the giant aneurysm [Figure 1h, left]. At 2.5 seconds, the trunks and peripheries of the right MCA and ACA were opacified [Figure 1h, middle] but not fully visualized compared with the left [Figure 1i, middle].
PMC5609433_02
MRIs show gradual signal change in the right aneurysm, although the size is unchanged (a-f). The aneurysm is not demonstrable on MRA at postoperative (PO) 1 day (g), but reappears at PO 2 weeks and 2 months (h, i). The bypass is patent at PO 1 day and 2 weeks (g, h), but not at 2 months (i). Perioperative ASL (j-l) shows a gradual decrease in aneurysm size and improving ASL signals in the right MCA territory. Right common CAG at PO 5 days (m) shows part of the right MCA visualized at 2.5 and 3.5 s. Left CAG (n) reveals the trunk and periphery of the right MCA are visualized at 1.5 and 2.5 s
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T1WI depicted the aneurysm as homogenous and iso-low-intensity at PO 1 day [Figure 2a], iso-intensity surrounded by hyperintensity at PO 2 weeks [Figure 2b], and having an onion skin appearance with flow void signs at PO 2 months [Figure 2c]. In T2WI, the aneurysm was depicted as mixed iso-low-intensity with a low-intensity peripheral rim at PO 1 day [Figure 2d], mixed iso-hyperintensity at PO 2 weeks [Figure 2e], and having an onion skin appearance with flow void signs at PO 2 months [Figure 2f]. MRA did not demonstrate the aneurysm at PO 1 day [Figure 2g], but the reappearance of the aneurysm was noted at PO 2 weeks [Figure 2h] and 2 months [Figure 2i]. The STA-MCA bypass was patent at PO 1 day [Figure 2g] and 2 weeks [Figure 2h], but there was no visualization of the bypass at PO 2 months [Figure 2i]. ASL-MRI with a PLD of 1.5 seconds demonstrated a gradual decrease in the size of the aneurysm. At PO 1 day, the size of the ASL hyperintense signal area had markedly decreased in size compared with that shown by preoperative ASL-MRI, and the hyperintense signal area was not demonstrated at the level of the basal ganglia [Figure 2j]. ASL-MRI at PO 2 weeks [Figure 2k] and 2 months [Figure 2l] showed further size decreases of the aneurysm. At PO 1 day, ASL signals increased throughout both hemispheres compared with preoperative ASL-MRI [Figure 2j]. ASL signals on the right hemisphere were mostly improved, although there was still a slight laterality. At PO 2 weeks and 2 months, the increased ASL signals in both hemispheres showed gradual improvement, although the right side still showed slightly decreased ASL signals compared with the left side [Figure 2k and l]. Right common CAG (CCAG) demonstrated complete patency of the bypass, and part of the right MCA territory was visualized through this bypass at 2.5 and 3.5 seconds (equivalent to 1.5 and 2.5 seconds in CAG, respectively) [Figure 2m]. Through cross flow via the ACoA, left CAG revealed that the trunk of the right MCA was faintly visualized at 1.5 seconds, and the periphery of the right MCA was visualized at 2.5 seconds [Figure 2n].
PMC5609433_03
(a) Right common CAG at PO 1 year reveals no patency of the bypass. (b) The right MCA trunk and periphery are visualized at 1.5 and 2.5 s on left CAG. (c) Left vertebral angiography depicts right MCA periphery visualization at 2.5 s. MRIs (d-f) at PO 2 years reveal a marked size decrease of the right aneurysm. ASL shows the aneurysm as a tiny spot of low signal at 1.5 s (g) and iso at 2.5s (h). ASL with PLD 1.5 s shows the preoperative decreased ASL signals in the right MCA territory improving with slight laterality (g). ASL with PLD 2.5 s shows this laterality improving somewhat (h)
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At that time, right CCAG failed to reveal the patency of the bypass [Figure 3a]. Left CAG confirmed successful embolization of the left ICA aneurysm [Figure 3b]. At 2.5 seconds, left CAG [Figure 3b] and left VAG [Figure 3c] revealed visualization of the right MCA periphery, but right laterality was still present. The aneurysm was detected as a small hyperintensity surrounded by a low-intensity region in T1WI [Figure 3d] and a small low-intensity area surrounded by a hyperintensity in T2WI [Figure 3e]. MRA depicted the aneurysm as a small spot without any communication with the artery [Figure 3f]. ASL-MRI with dual PLDs demonstrated the aneurysm as a tiny spot of low-intensity signal at PLD 1.5 seconds [Figure 3g] and an iso-intense signal area at 2.5 seconds [Figure 3h]. Furthermore, preoperative decreased signals in the right hemisphere, especially in the right MCA territory, were markedly improved at PLD 1.5 seconds [Figure 3g]. Although there was a slight signal decrease in the right hemisphere, this laterality was somewhat improved at PLD 2.5 seconds [Figure 3h].