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Yoshifumi Mizobuchi, Kenji Shouno, Kohei Nakajima, and Shinji Nagahiro

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Yoshihisa Murayama, Kazuhide Sakurama, Koichi Satoh, and Shinji Nagahiro

✓ The carotid artery (CA) dural ring is an important structure in aneurysm surgery of the paraclinoid region. The authors used three-dimensional computerized tomography (3D-CT) angiography to study the CA dural ring.

Three-dimensional computerized tomography angiography was performed in patients with cerebral aneurysms and other cerebrovascular diseases. The paraclinoid segment of the internal carotid artery (ICA) was examined by the shaded surface reconstruction method on targeted 3D-CT angiography. The concavity was recognized in the paraclinoid segment of the ICA. The relationship between the concavity and the dural ring was investigated with anatomical studies and surgical findings.

In anatomical studies, the concavity in the paraclinoid segment of the ICA on 3D-CT angiography coincided with the level of attachment of the dural ring. Using 3D-CT angiography, it is possible to identify the location of the dural ring in patients being considered for aneurysm surgery.

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Microvascular decompression for hemifacial spasm

Patterns of vascular compression in unsuccessfully operated patients

Shinji Nagahiro, Akira Takada, Yasuhiko Matsukado, and Yukitaka Ushio

✓ To determine the causative factors of unsuccessful microvascular decompression for hemifacial spasm, the follow-up results in 53 patients were assessed retrospectively. The mean follow-up period was 36 months. There were 32 patients who had compression of the seventh cranial nerve ventrocaudally by an anterior inferior cerebellar artery (AICA) or a posterior inferior cerebellar artery. Of these 32 patients, 30 (94%) had excellent postoperative results. Of 14 patients with more severe compression by the vertebral artery, nine (64%) had excellent results, three (21%) had good results, and two (14%) had poor results; in this group, three patients with excellent results experienced transient spasm recurrence. There were seven patients in whom the meatal branch of the AICA coursed between the seventh and eighth cranial nerves and compressed the dorsal aspect of the seventh nerve; this was usually associated with another artery compressing the ventral aspect of the nerve (“sandwich-type” compression). Of these seven patients, five (71%) had poor results including operative failure in one and recurrence of spasm in four. The authors conclude that the clinical outcome was closely related to the patterns of vascular compression.

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Ryoma Morigaki, Masaaki Uno, Atsuhiko Suzue, and Shinji Nagahiro

✓ In this paper the authors describe two patients with recurrent hemiparesis and limb shaking that gradually progressed to hemichorea. Cerebral angiography confirmed severe unilateral internal carotid artery stenosis (95%) contra-lateral to the hemichorea. The cerebral blood flow, assessed using N-isopropyl-p-(iodine-123) iodoamphetamine single-photon emission computed tomography (SPECT), disclosed markedly decreased vascular reserves in both patients. After carotid endarterectomy was performed, the hemichorea gradually subsided and SPECT confirmed increased cerebral perfusion. The results in these cases indicate that surgical revascularization is effective for hemichorea due to cerebral ischemia with reduced vascular reserve.

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Junichiro Satomi, A. Ammar Ghaibeh, Hiroki Moriguchi, and Shinji Nagahiro

OBJECT

The severity of clinical signs and symptoms of cranial dural arteriovenous fistulas (DAVFs) are well correlated with their pattern of venous drainage. Although the presence of cortical venous drainage can be considered a potential predictor of aggressive DAVF behaviors, such as intracranial hemorrhage or progressive neurological deficits due to venous congestion, accurate statistical analyses are currently not available. Using a decision tree data mining method, the authors aimed at clarifying the predictability of the future development of aggressive behaviors of DAVF and at identifying the main causative factors.

METHODS

Of 266 DAVF patients, 89 were eligible for analysis. Under observational management, 51 patients presented with intracranial hemorrhage/infarction during the follow-up period.

RESULTS

The authors created a decision tree able to assess the risk for the development of aggressive DAVF behavior. Evaluated by 10-fold cross-validation, the decision tree's accuracy, sensitivity, and specificity were 85.28%, 88.33%, and 80.83%, respectively. The tree shows that the main factor in symptomatic patients was the presence of cortical venous drainage. In its absence, the lesion location determined the risk of a DAVF developing aggressive behavior.

CONCLUSIONS

Decision tree analysis accurately predicts the future development of aggressive DAVF behavior.

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Shinji Nagahiro, Akira Takada, Satoshi Goto, Yutaka Kai, and Yukitaka Ushio

✓ Results in three patients with thrombosed giant aneurysms of the vertebral artery are reported. Each of the aneurysms presented as a mass lesion. On postcontrast computerized tomography and magnetic resonance imaging, each aneurysm demonstrated a patent lumen and intrathrombotic vascular channels. Two patients died and were autopsied, and the other patient was successfully treated. Pathological examination revealed that the aneurysms had staged clots, an open lumen, intrathrombotic channels with endothelial lining, and aneurysmal walls with intimal thickening. The authors suggest that the development of the intrathrombotic capillary channels may be an important factor in the growth of thrombosed giant aneurysm of the vertebral artery. Trapping of the aneurysm followed by aneurysmectomy appears to be the best treatment for this type of aneurysm.

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Shinji Nagahiro, Jun-ichiro Hamada, Yuji Sakamoto, and Yukitaka Ushio

✓ The authors assessed the reliability of magnetic resonance (MR) imaging contrast enhancement for the detection and follow-up evaluation of dissecting aneurysms of the vertebrobasilar circulation. Twenty consecutively admitted patients who underwent both gadolinium-enhanced MR imaging and conventional angiography were reviewed. Enhancement of the dissecting aneurysm was seen in all but one of the 20 patients, including 10 (71%) of 14 patients examined in the chronic phases, when the T1-hyperintensity signal that corresponded to the intramural hematoma was unrecognizable. The enhanced area corresponded to the “pearl sign” or aneurysm dilation noted on the comparable angiogram. On follow-up MR studies enhancement had spontaneously disappeared in four patients at a time when comparable vertebral angiograms revealed disappearance of the aneurysm dilation. The enhancement persisted in five of nine patients examined more than 24 weeks after symptom onset; in all five patients the aneurysm dilation remained on comparable angiograms. Dynamic MR studies showed rapid and remarkable enhancements with their peaks during the immediate dynamic phase after injection of the contrast material. The authors conclude that gadolinium-enhanced MR imaging is useful for the detection and follow-up evaluation of dissecting aneurysms of the vertebrobasilar circulation.

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Koichi Satoh, Junichiro Satomi, Norio Nakajima, Shunji Matsubara, and Shinji Nagahiro

Object. In this study the authors performed a retrospective analysis of five cases in which the patients (three women and two men) were treated for intracranial dural arteriovenous fistulas (AVFs) associated with cerebellar hemorrhage. On the basis of their findings, the authors evaluated the characteristics of this unusual symptom.

Methods. The dural AVFs were located in the right cavernous sinus in one patient, the left transverse—sigmoid sinus in three patients, and the right superior petrosal sinus (SPS) in one patient. All patients presented with severe headache and/or loss of consciousness. Computerized tomography scans revealed a small cerebellar hemorrhage near the fourth ventricle and hydrocephalus in four cases, and a massive hemispheric cerebellar hemorrhage in the remaining case. The four patients with small hemorrhages underwent ventriculostomy and endovascular treatment; all recovered. The patient suffering from a massive hemorrhage because of a dural AVF in the SPS was treated by suboccipital craniectomy, hematoma evacuation, and removal of the vascular anomaly. This patient remains in a persistent vegetative state. In four cases, results of angiography demonstrated retrograde leptomeningeal venous drainage through the SPS to the anastomotic lateral mesencephalic vein (ALMV) and/or to the vein of the lateral recess of the fourth ventricle (VLR4V). Retrograde leptomeningeal venous drainage to the ALMV and/or VLR4V was responsible for cerebellar hemorrhage in these cases.

Conclusions. Thus, it is important to consider dural AVF in cases in which there is even a small hemorrhage near the fourth ventricle accompanied by intraventricular perforation and a decreased level of consciousness.

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Jun-Ichiro Hamada, Shinji Nagahiro, Chikara Mimata, Takayuki Kaku, and Yukitaka Ushio

✓ Two techniques of revascularizing the posterior inferior cerebellar artery (PICA) during aneurysm surgery are presented. One involves transposition of the PICA to the vertebral artery proximal to the aneurysm using a superior temporal artery (STA) as a graft. This is used in cases in which the PICA has branched off from the wall of the giant vertebral artery aneurysm. The other technique involves end-to-end anastomosis of the PICA after excision of a giant distal PICA aneurysm located at the cranial loop near the roof of the fourth ventricle. The reconstructions of the PICA described here are surgical procedures designed to preserve normal blood flow in the PICA in patients treated for giant aneurysms involving that artery.

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Kazuhiko Bando, Koichi Satoh, Shunji Matsubara, Minoru Nakatani, and Shinji Nagahiro

✓ The authors report on a patient who underwent percutaneous transluminal angioplasty (PTA) for stenosis of the intracranial vertebral artery (VA). This 67-year-old man's dizziness while walking was caused by infarction of the left cerebellar peduncle. On angiograms, his left VA manifested 90% stenosis at the intracranial portion and his right VA ended at the posterior inferior cerebellar artery. Because single-photon emission computerized tomography (SPECT) showed low perfusion and poor perfusion reserve in the posterior circulation, the authors performed PTA of the left VA, which was only 35% dilated due to stenosis. Although the patient's postoperative course was uneventful, postoperative hemodynamic studies (SPECT and transcranial Doppler [TCD] ultrasonography) revealed the hyperperfusion phenomenon. A 100% increase of regional cerebral blood flow in the posterior circulation was demonstrated on SPECT studies and TCD ultrasonography revealed a doubling of blood flow velocity in the VA compared with preoperative values. Careful control of the patient's blood pressure resulted in resolution of the hyperperfusion phenomenon within 1 week post-PTA. Although hyperperfusion syndrome following carotid endarterectomy is not rare, it is seldom seen after reconstruction of the posterior circulation, and the possibility of its occurrence must be kept in mind when the posterior circulation is reconstructed.