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  • Author or Editor: Koji Iihara x
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Fredric B. Meyer

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Roberto C. Heros

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Susumu Miyamoto, Takeshi Funaki, Koji Iihara and Jun C. Takahashi

Object

The authors evaluated the efficacy of a new flow reduction strategy for giant partially thrombosed upper basilar artery (BA) aneurysms, for which proximal parent artery occlusion is not always effective.

Methods

Eight consecutive patients with severely symptomatic, partially thrombosed, giant upper BA aneurysms were treated with a tailored flow reduction strategy, or received conservative therapies. The flow reduction strategy comprised isolation of several branches from the upper BA at their origins with bypasses in addition to parent artery occlusion.

Results

The median follow-up period of all 8 patients was 15.0 months (range 4–31 months). In 6 patients treated with flow reduction, the mean decrease in residual blood lumen was −10.7 mm (95% CI −19.7 to −1.7 mm; p = 0.029) and the mean decrease in diameter of the aneurysms was −11.5 mm (95% CI −25.1 to 2.1 mm; p = 0.082). Complete or virtually complete thrombosis was achieved in all but 1 aneurysm (83%) and shrinkage was observed in 4 (67%). In those in whom complete or virtually complete thrombosis was achieved, significant shrinkage of the aneurysm was observed (mean decrease in diameter −14.8 mm; 95% CI −28.8 to −0.8 mm; p = 0.043). Improvement or stabilization of symptoms occurred in 67% of the patients who received flow reduction treatment. Both patients who received conservative treatment had unfavorable outcomes.

Conclusions

The flow reduction strategy is effective at promoting complete thrombosis of the aneurysm. This strategy can also induce shrinkage of the aneurysm if successful thrombosis is achieved. Although the neurological outcome of the treatment appears favorable considering its intractable nature, further study of the treatment is necessary to confirm its clinical efficacy and safety.

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Tomohito Hishikawa, Koji Iihara, Naoaki Yamada, Hatsue Ishibashi-Ueda and Susumu Miyamoto

Object

The aim of this study was to assess the histopathological differences between advanced atherosclerotic carotid artery (CA) plaques with signal hyperintensity on T1-weighted MR images and those without, focusing on necrotic core size and intraplaque hemorrhage (IPH).

Methods

Thirty-five patients scheduled for carotid endarterectomy underwent preoperative CA MR imaging using 3D inversion-recovery-based T1-weighted imaging (magnetization-prepared rapid acquisition gradient-echo [MPRAGE]). The signal intensity of the CA plaque on MPRAGE sequences was classified as “high” when the intensity was more than 200% that of adjacent muscle. A total of 96 axial MR images obtained in 35 patients were compared with corresponding histological sections from 36 excised specimens. The area of the necrotic core in histological sections was compared between specimens with and without high signal intensity on MPRAGE sequences. The IPH was histopathologically graded according to the size of the area positive for glycophorin A as revealed by immunohistochemical staining. The difference between plaques with and without high signal intensity was investigated with respect to the degree of IPH. The relationship of the severity of IPH to size of the necrotic core was also evaluated.

Results

The area of the necrotic core in plaques with high signal intensity on MPRAGE sequences was significantly larger than that in plaques without high signal intensity (median 51.2% [interquartile range 43.3–66.8%] vs 49.0% [33.2–57.6%], p = 0.029). Carotid artery plaques with high signal intensity had significantly more severe IPH than plaques with lower signal intensity (p < 0.0001). The severity of IPH was significantly associated with the size of the necrotic core (p < 0.0001).

Conclusions

Atherosclerotic CA plaques with high signal intensity on MPRAGE sequences had large necrotic cores with IPH in patients with high-grade stenosis; MPRAGE is useful for the evaluation of CA plaque progression.

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Jun C. Takahashi, Nobuyuki Sakai, Koji Iihara, Hideki Sakai, Toshio Higashi, Shuji Kogure, Ayumi Taniguchi, Hatsue I. Ueda and Izumi Nagata

✓ Polyarteritis nodosa (PAN) is a rare systemic necrotizing arteritis that involves small- and medium-sized arteries in various organs. Although aneurysm formation in visceral arteries is a typical finding in PAN, intracranial aneurysms are much less common, and only a few cases of aneurysm rupture associated with this disease have been documented. In this paper, the authors report on a ruptured PAN aneurysm of the anterior cerebral artery; the lesion was trapped and resected. On histological examination, extensive fibrinoid necrosis and an inflammatory infiltration of leukocytes were seen in the aneurysm wall. To the authors' knowledge this is the first report of subarachnoid hemorrhage from a histologically confirmed PAN aneurysm.

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Hiroyuki Hao, Koji Iihara, Hatsue Ishibashi-Ueda, Fumio Saito and Seiichi Hirota

Object

Preoperative clinical risk classification of carotid artery (CA) stenosis anticipates the outcome of CA intervention. A higher incidence of neurological morbidity was noted after CA stenting (CAS) in patients with medical risks than in those without risks. However, little is known about the correlation between clinical risks and plaque composition. The purpose of this study was to characterize the CA plaque histology in 3 groups of patients who were classified based on clinical risks for carotid endarterectomy (CEA). Furthermore, the authors examined whether the plaque with high embolic potential after CA intervention, particularly CAS, could be predicted based on clinical risks for CEA.

Methods

Patients were divided into 4 groups, according to the CEA risk classification system, and 3 groups with more than 10 cases were enrolled in this study as follows: absence of all angiographic, medical, and neurological risks (Grade I, 27 cases); presence of medical risk, but no neurological risk (Grade III, 31 cases); and presence of neurological risk (Grade IV, 17 cases). Histopathological characteristics of CA plaques, including fibrous cap thickness, plaque disruption, thrombus formation, intraplaque hemorrhage (IPH), and adipophilin expression were examined without information regarding clinical status.

Results

Plaques in patients in Grades III and IV demonstrated a thin fibrous cap and enhanced IPH, compared with those in Grade I. Plaques in patients in Grade IV showed more adipophilin-expressing macrophages in the fibrous cap than in those of the other groups.

Conclusions

Plaques in Grades III and IV patients were characterized by thin fibrous cap atheroma with IPH. Adipophilin-positive macrophage infiltration in the fibrous cap might be correlated with instability in neurological status. The plaque morphology in patients with medical and neurological risks needs to be examined carefully with the aid of imaging modalities. In plaques demonstrating a thin fibrous cap and IPH, the CAS procedure should be avoided and CEA should be performed instead.

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Koji Iihara, Masakazu Okawa, Tomohito Hishikawa, Naoaki Yamada, Kazuhito Fukushima, Hidehiro Iida and Susumu Miyamoto

The authors report a rare case of slowly progressive neuronal death associated with postischemic hyperperfusion in cortical laminar necrosis after radial artery/external carotid artery–middle cerebral artery bypass graft surgery for an intracavernous carotid artery aneurysm. Under barbiturate protection, a 69-year-old man underwent high-flow bypass surgery combined with carotid artery sacrifice for a symptomatic intracavernous aneurysm. The patient became restless postoperatively, and this restlessness peaked on postoperative Day (POD) 7. Diffusion-weighted and FLAIR MR images obtained on PODs 1 and 7 revealed subtle cortical hyperintensity in the temporal cortex subjected to temporary occlusion. On POD 13, 123I-iomazenil (123I-IMZ) SPECT clearly showed increased distribution on the early image and mildly decreased binding on the delayed image with count ratios of the affected–unaffected corresponding regions of interest of 1.23 and 0.84, respectively, suggesting postischemic hyperperfusion. This was consistent with the finding on 123I-iodoamphetamine SPECT. Of note, neuronal density in the affected cortex on the delayed 123I-IMZ image further decreased to the affected/unaffected ratio of 0.44 on POD 55 during the subacute stage when characteristic cortical hyperintensity on T1-weighted MR imaging, typical of cortical laminar necrosis, was emerging. The affected cortex showed marked atrophy 8 months after the operation despite complete neurological recovery. This report illustrates, for the first time, dynamic neuroradiological correlations between slowly progressive neuronal death shown by 123I-IMZ SPECT and cortical laminar necrosis on MR imaging in human stroke.

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Eika Hamano, Hiroharu Kataoka, Naomi Morita, Daisuke Maruyama, Tetsu Satow, Koji Iihara and Jun C. Takahashi

OBJECTIVE

Transient neurological symptoms are frequently observed during the early postoperative period after direct bypass surgery for moyamoya disease. Abnormal signal changes in the cerebral cortex can be seen in postoperative MR images. The purpose of this study was to reveal the radiological features of the “cortical hyperintensity belt (CHB) sign” in postoperative FLAIR images and to verify its relationship to transient neurological events (TNEs) and regional cerebral blood flow (rCBF).

METHODS

A total of 141 hemispheres in 107 consecutive patients with moyamoya disease who had undergone direct bypass surgery were analyzed. In all cases, FLAIR images were obtained during postoperative days (PODs) 1–3 and during the chronic period (3.2 ± 1.13 months after surgery). The CHB sign was defined as an intraparenchymal high-intensity signal within the cortex of the surgically treated hemisphere with no infarction or hemorrhage present. The territory of the middle cerebral artery was divided into anterior and posterior parts, with the extent of the CHB sign in each part scored as 0 for none; 1 for presence in less than half of the part; and 2 for presence in more than half of the part. The sum of these scores provided the CHB score (0–4). TNEs were defined as reversible neurological deficits detected both objectively and subjectively. The rCBF was measured with SPECT using N-isopropyl-p-[123I]iodoamphetamine before surgery and during PODs 1–3. The rCBF increase ratio was calculated by comparing the pre- and postoperative count activity.

RESULTS

Cortical hyperintensity belt signs were detected in 112 cases (79.4%) and all disappeared during the chronic period. Although all bypass grafts were anastomosed to the anterior part of the middle cerebral artery territory, CHB signs were much more pronounced in the posterior part (p < 0.0001). TNEs were observed in 86 cases (61.0%). Patients with TNEs showed significantly higher CHB scores than those without (2.31 ± 0.13 vs 1.24 ± 0.16, p < 0.0001). The CHB score, on the other hand, showed no relationship with the rCBF increase ratio (p = 0.775). In addition, the rCBF increase ratio did not differ between those patients with TNEs and those without (1.15 ± 0.033 vs 1.16 ± 0.037, p = 0.978).

CONCLUSIONS

The findings strongly suggest that the presence of the CHB sign during PODs 1–3 can be a predictor of TNEs after bypass surgery for moyamoya disease. On the other hand, presence of this sign appears to have no direct relationship with the postoperative local hyperperfusion phenomenon. Vasogenic edema can be hypothesized as the pathophysiology of the CHB sign, because the sign was transient and never accompanied by infarction in the present series.

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Koji Iihara, Nobuyuki Sakai, Kenichi Murao, Hideki Sakai, Toshio Higashi, Shuji Kogure, Jun C. Takahashi and Izumi Nagata

Object. The authors present a retrospective analysis of their experience in the treatment of vertebral artery (VA) dissecting aneurysms and propose a management strategy for such aneurysms, with special emphasis on the most formidable VA dissecting aneurysms, which involve the origin of the posterior inferior cerebellar artery (PICA).

Methods. Since 1998, 18 patients with VA dissecting aneurysms, 11 of whom presented with subarachnoid hemorrhage (SAH), have been treated by endovascular surgery at the authors' institution. Obliteration of the entire segment of the dissected site with coils (internal trapping) was performed for aneurysms without involvement of the origin of the PICA (12 cases; among these the treatment-related morbidity rate was 16.7%). The treatment strategy applied to PICA-involved VA dissecting aneurysms presenting with SAH (three cases) included proximal occlusion of the parent artery followed by internal trapping of the aneurysm (one case), proximal occlusion of the parent artery followed by occipital artery (OA)—PICA bypass (one case), and two-staged internal trapping of the aneurysm involving double PICAs (one case). For PICA-involved VA dissecting aneurysms that were not associated with SAH at presentation (three cases), OA—PICA bypass was performed and followed by internal trapping of the aneurysm (two cases). In the remaining case in which a fetal-type posterior communicating artery was present, internal trapping was performed following successful balloon test occlusion (BTO). Overall, there was no sign of infarction in the PICA territory, despite complete occlusion of aneurysms involving the PICA. There was no recurrent bleeding or ischemic symptoms during the follow-up periods. The overall treatment-related morbidity rate for the VA dissecting aneurysms involving the PICA was 16.7%.

Conclusions. Dissecting VA aneurysms that do not involve the PICA can be safely treated by internal trapping. For those lesions that do involve the PICA, a decision-making algorithm is advocated to maximize the efficacy of the treatment as well as to minimize the risks of treatment-related morbidity based on BTO.

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Koji Iihara, Kenichi Murao, Nobuyuki Sakai, Akio Soeda, Hatsue Ishibashi-Ueda, Chikao Yutani, Naoaki Yamada and Izumi Nagata

✓ A 58-year-old woman harboring a partially thrombosed giant aneurysm of the vertebral artery (VA) presented with lower cranial nerve palsies and cerebellar ataxia. The authors initially attempted to reduce the mass effect by obliterating the lumen of the aneurysm as well as by trapping of the parent artery with coils. Although there was no angiographically demonstrated evidence of filling, the aneurysm continued to enlarge. Magnetic resonance imaging revealed a marked enhancement around the packed coils close to the neck of the aneurysm. Aneurysmectomy and removal of the coils were performed and resulted in an almost complete cure of the patient's symptoms. Interestingly, at the time of resection, a marked development of vasa vasorum on the occluded VA and the neck of the aneurysm was noted. When the occluded VA was cut, there was blood oozing through the coils packed within its lumen on the side where the aneurysm lay. Histological examination showed the presence of inflammatory cells and neovascularization of a partially organized thrombus around the packed coils in both the aneurysm and occluded VA. The proliferation of vasa vasorum was also recognized histologically. This unique case provides insight into the growth mechanisms of a partially thrombosed giant aneurysm after an apparently complete occlusion by endovascular treatment, especially the role of vaso vasorum on the occluded parent artery in the dynamic process of neovascularization in the incomplete organization of thrombus around the packed coils.