Toshiyuki Tsuboi

Surgical microanatomy of the anterior clinoid process for paraclinoid aneurysm surgery and efficient modification of extradural anterior clinoidectomy.

BACKGROUND Anatomic variations of the anterior clinoid process (ACP) should be recognized before clinoidectomy to ensure a safe approach. This study describes the incidence of caroticoclinoid foramen (CCF), interclinoid osseous bridge, and pneumatization of the ACP during extradural anterior clinoidectomy. The problems and technical issues encountered in such cases are described. METHODS Using multidetector-row computed tomography, 144 sides in 72 cases of paraclinoid aneurysm treated by extradural anterior clinoidectomy were analyzed preoperatively. RESULTS CCF, interclinoid osseous bridge, and pneumatization of the ACP were observed in 16.6%, 2.77%, and 27.7% of cases. Pneumatized patterns were divided into 3 groups according to route: pneumatization via the optic strut (in 74.1%), pneumatization via the anterior root (in 14.8%), and pneumatization via optic strut and anterior root (in 11.1%). CCF and interclinoid osseous bridge represent obstacles to complete extradural removal of the ACP. The ACP should not be moved even after drilling the lateral wall of the ACP, orbital roof, and optic strut, so an intradural approach is sometimes needed. A CCF warrants careful removal to open the distal dural ring. Awareness of the routes of pneumatization for the ACP should reduce the risk of tears in the paranasal mucosa. If tears arise in the mucosa, suturing and closure are needed to prevent liquorrhea. CONCLUSIONS Preoperative computed tomography is useful to detect variations in the anatomy around the ACP. When performing extradural anterior clinoidectomy in such anomalous cases, appropriate modifications are needed to ensure a safe approach.

Surgical Treatment of 127 Paraclinoid Aneurysms with Multifarious Strategy: Factors Related with Outcome.

BACKGROUND Few reports have been published discussing surgical outcomes of paraclinoid aneurysms using multifarious treatments such as high-flow bypass. MATERIAL AND METHODS We retrospectively analyzed findings from 127 consecutive patients (19 males, mean age at surgery: 56.8 years, range: 19-81 years) at our hospital. The size of aneurysms ranged from 2.7-43.2 mm (mean: 6.9 mm). Extradural anterior clinoidectomy was used to clip small aneurysms. As large or giant aneurysms required a longer temporal occlusion period and often could not undergo simple clipping, high-flow bypass with anterior clinoidectomy or cervical internal carotid ligation was performed to reduce aneurysm blood flow and induce thrombosis. We reviewed a postoperative modified Rankin Scale (mRS), radiographic outcomes, cerebral infarction, and visual disturbance. In addition, we analyzed factors relating to the outcomes and complications, with focus on the aneurysm size, location, and type of surgical treatment. RESULTS Good outcomes were achieved in all patients, as follows: mRS 0:100, mRS 1:16, mRS 2:11, and mRS 3-6:0. Among the 127 patients, complete exclusion of aneurysm was achieved in 119 cases (93.7%). Postoperative morbidity included ischemic lesions in 11 (8.6%) and visual disturbance in 24 (18.8%). Significant statistical differences were observed between ischemic complication and aneurysm size and location (P = 0.0001) and surgical treatment (P < 0.0001). CONCLUSION Surgical treatment of unruptured paraclinoid aneurysm has high efficacy with good outcomes and a high rate of complete exclusion. However, the rate of visual disturbance is relatively high. Careful surgical techniques and intraoperative monitoring are therefore required.

Risk factors for neurological worsening and symptomatic watershed infarction in internal carotid artery aneurysm treated by extracranial-intracranial bypass using radial artery graft.

OBJECT The revascularization technique, including bypass created using the external carotid artery (ECA), radial artery (RA), and M2 portion of middle cerebral artery (MCA), has remained indispensable for treatment of complex aneurysms. To date, it remains unknown whether diameters of the RA, superficial temporal artery (STA), and C2 portion of the internal carotid artery (ICA) and intraoperative MCA blood pressure have influences on the outcome and the symptomatic watershed infarction (WI). The aim of the present study was to evaluate the factors for the symptomatic WI and neurological worsening in patients treated by ECA-RA-M2 bypass for complex ICA aneurysm with therapeutic ICA occlusion. METHODS The authors measured the sizes of vessels (RA, C2, M2, and STA) and intraoperative MCA blood pressure (initial, after ICA occlusion, and after releasing the RA graft bypass) in 37 patients. Symptomatic WI was defined as presence of the following: postoperative new neurological deficits, WI on postoperative diffusion-weighted imaging, and ipsilateral cerebral blood flow reduction on SPECT. Neurological worsening was defined as the increase in 1 or more modified Rankin Scale scores. First, the authors performed receiver operating characteristic curve analysis for continuous variables and the binary end point of the symptomatic WI. The clinical, radiological, and physiological characteristics of patients with and without the symptomatic WI were compared using the log-rank test. Then, the authors compared the variables between patients with and without neurological worsening at discharge and at the 12-month follow-up examination or last hospital visit. RESULTS Symptomatic WI was observed in 2 (5.4%) patients. The mean MCA pressure after releasing the RA graft (< 55 mm Hg; p = 0.017), mean (MCA pressure after releasing the RA graft)/(initial MCA pressure) (< 0.70 mm Hg; p = 0.032), and mean cross-sectional area ratio ([RA/C2 diameter](2) < 0.40 mm [p < 0.0001] and [STA/C2 diameter](2) < 0.044 mm [p < 0.0001]) were related to the symptomatic WI. All preoperatively independent patients remained independent (modified Rankin Scale score < 3). After adjusting for age and sex, left operative side (p = 0.0090 and 0.038) and perforating artery ischemia (p = 0.0050 and 0.022) were related to neurological worsening at discharge (11 [29%] patients) and at the 12-month follow-up or last hospital visit (8 [22%] patients). CONCLUSIONS Results of the present study showed that the vessel diameter and intraoperative MCA pressure had impacts on the symptomatic WI and that operative side and perforating artery ischemia were related to neurological worsening in patients with complex ICA aneurysms treated by ECA-RA-M2 bypass.

Superficial temporal artery to proximal posterior cerebral artery bypass through the anterior temporal approach

Background: The superficial temporal artery (STA) to proximal posterior cerebral artery (PCA) (P2 segment) bypass is one of the most difficult procedures to perform because the proximal PCA is located deep and high within the ambient cistern. STA to proximal PCA bypass is usually performed through a subtemporal approach or posterior transpetrosal approach, and rarely through a transsylvian approach. The aim of this study was to describe the operative technique of STA to proximal PCA bypass through a modified transsylvian approach (anterior temporal approach). Methods: STA to proximal PCA bypass was performed through an anterior temporal approach in three patients with intracranial aneurysm. We describe the details of the surgical technique. Results: The STA was successfully anastomosed to the proximal PCA in all cases. One patient suffered hemiparesis and aphasia due to infarction in the anterior thalamoperforating artery territory. Conclusions: STA to proximal PCA bypass can be performed through an anterior temporal approach in selected patients. We recommend that every precaution, including complete hemostasis, placement of cellulose sponges beneath the recipient artery to elevate the site of the anastomosis, and placement of a continuous drainage tube at the bottom of the operative field to avoid blood contamination during the anastomosis, should be taken to shorten the temporary occlusion time.

Risk Factors for Low-Flow Related Ischemic Complications and Neurologic Worsening in Patients with Complex Internal Carotid Artery Aneurysm Treated by Extracranial to Intracranial High-Flow Bypass

BACKGROUND The revascularization technique has remained indispensable for complex aneurysms. However, risk factors for low-flow related ischemic complications (LRICs) and neurologic worsening (NW) have been less well documented. We evaluated the risk factors for LRICs and NW in 67 patients treated with extracranial to intracranial bypass graft using radial artery or saphenous vein graft for complex internal carotid artery (ICA) aneurysm with ICA occlusion. METHODS Intraoperative middle cerebral artery pressure (MCAP) by backup superficial temporal artery to middle cerebral artery bypass was measured. The MCAP ratio was the ratio of the MCAP after release of the graft bypass to the initial MCAP. LRICs were defined as new neurologic deficits and ipsilateral cerebral blood flow reduction in single-photon emission computed tomography. Early and late NW were defined as an increase in 1 or more modified Rankin Scale at discharge and at the 12-month follow-up examination. RESULTS During a median follow-up period of 13.3 months, LRICs were observed in 7 patients (10%). The Cox proportional hazards model showed that an MCAP ratio ≤0.80 was significantly related to LRICs. Multivariate logistic regression analysis revealed that perforating artery ischemia was significantly associated with early NW (n = 13, 19%) and late NW (n = 7, 13%). It also showed that LRICs were also significantly related to late NW. CONCLUSIONS The present study showed that regardless of the graft type, the MCAP ratio was associated with LRICs, which were related to late NW in patients with complex ICA aneurysms treated by extracranial to intracranial high-flow bypass graft.

Surgical Strategy for Complex Anterior Cerebral Artery Aneurysms: Retrospective Case Series and Literature Review.

OBJECTIVE Giant, or complex, aneurysms of the anterior cerebral artery (ACA) are rare, but their surgical treatment is important. The authors describe their experiences with bypasses for complex ACA aneurysms and discuss the new classification of ACA bypasses, the concept of using bypasses for insurance during the approach to the aneurysm, and simplifying the surgical algorithms for these complex ACA aneurysms. METHODS Over a 19-year period, 7 cases of complex ACA aneurysm were treated with bypasses and reviewed retrospectively. The bypasses were classified into 4 groups according to donor blood flow: internal carotid artery-ACA, external carotid artery-ACA, communicating bypass, and reconstruction bypass of the ipsilateral postcommunicating ACA. RESULTS The cases included 1 precommunicating aneurysm, 3 communicating aneurysms, 2 postcommunicating aneurysms, and 1 double aneurysm (communicating and postcommunicating). The types of bypass included 1 internal carotid artery-ACA, 6 communicating bypasses, 3 external carotid artery-ACAs, and 2 reconstruction bypass of the postcommunicating ACA. Postoperative modified Rankin Scale scores were 0 (6 cases) and 3 (1 case of a communicating aneurysm with complicated memory disturbance because of infarction). One case revealed asymptomatic infarction. CONCLUSIONS Surgical treatment of complex ACA aneurysms requires knowledge of a variety of bypass techniques. Although the type of bypass should be selected according to patient-specific anatomy and the neurosurgeons preference, the new classification of bypass-specified ACA aneurysms may alter the way surgeons think about ACA bypasses, and in combination with the concept of the protective bypass, can be used to establish a comprehensive algorithm for each type of complex ACA aneurysm.

Radical treatment for bilateral vertebral artery dissecting aneurysms by reconstruction of the vertebral artery

OBJECTIVE Bilateral vertebral artery dissecting aneurysms (VADAs) have a poor prognosis because progressive enlargement of the aneurysms compresses the brainstem or causes subarachnoid hemorrhage. The trapping of 1 vertebral artery (VA) places increased hemodynamic stress on the contralateral VA and may lead to enlargement and rupture. Therefore, management strategies are controversial. This study describes a radical treatment for bilateral VADAs using bypass surgery. METHODS Seven patients with bilateral VADAs were included. Three patients were treated by trapping of 1 VA via coiling or clipping at another hospital; the previously treated VA in 1 patient and the contralateral untreated VA in 2 patients subsequently enlarged. The other 4 patients presented without previous intervention and progressive enlargement of the aneurysms. RESULTS The post-coil embolization patients underwent V3-posterior cerebral artery (PCA) bypass and trapping. The other 4 patients underwent VA reconstruction via V3-V4 or V4-V4 bypass, with contralateral trapping on a separate day in 3 patients and observation in 1 patient. Perioperative complications included 1 case of cerebrospinal fluid leakage for which the patient required an additional operation, 1 case of dysphagia and facial palsy due to sigmoid sinus thrombosis, and 1 case of dysphagia. The long-term outcomes of these patients were favorable. CONCLUSIONS Patients with bilateral VADAs require treatment on both sides. If VA trapping is performed first, the treatment options for the other side are limited to V3-PCA bypass and trapping. This procedure is effective; however, it is also invasive and technically difficult. In cases of bilateral VADAs in which it is feasible to reconstruct 1 side, the best approach is to begin by reconstructing the VA that appears technically easiest, followed by trapping of the contralateral VADA. This strategy allows enough time to suture vessels because contralateral reverse flow is maintained.

An Effective Method of Frontal Sinus Reconstruction After Bifrontal Craniotomy: Experience with 103 Patients

BACKGROUND Bifrontal craniotomy is effective for the treatment of anterior skull base lesions. However, the frontal sinus (FS) is often opened during this surgery, and various postoperative complications may occur as a result of the open FS, including cerebrospinal fluid leakage and infection. We describe our procedure for maintaining the patency of the nasofrontal duct and direct suture of the exposed and violated FS mucosa. METHODS Bifrontal craniotomy with reconstruction of the FS was performed in 103 patients (68 women and 35 men; age range, 32-90 years; mean age, 62.6 years) for lesions including anterior cerebral artery aneurysm (100 cases), arteriovenous fistula (1 case), and meningioma (2 cases). After opening the FS, the mucosal membrane of the FS was dissected from the FS wall, and the orifice of the FS mucosa was closed with 7-0 monofilament running sutures. The nasofrontal duct was kept open by washing thoroughly to remove any bone dust and clot in the FS. The cavity of the FS was then packed with abdominal fat. RESULTS Postoperative cerebrospinal fluid leakage and mucocele formation did not occur in any patient. An intracranial infectious complication occurred in 1 patient (1.0%). CONCLUSIONS The present results indicate the effectiveness of our technique for the prevention of FS-related postoperative complications.

The anterior temporal approach for microsurgical thromboembolectomy of an acute proximal posterior cerebral artery occlusion.

BACKGROUND: In a short window of time, intravenous and intra-arterial thrombolysis is the first treatment option for patients with an acute ischemic stroke caused by the occlusion of one of the major brain vessels. Endovascular treatment techniques provide additional treatment options. In selected cases, high revascularization rates following microsurgical thromboembolectomy in the anterior circulation were reported. A technical note on successful thromboembolectomy of the proximal posterior cerebral artery has not yet been published. OBJECTIVE: To describe the technique of microsurgical thromboembolectomy of an acute proximal posterior cerebral artery occlusion and the brainstem perforators via the anterior temporal approach. METHODS: The authors present a technical report of a successful thromboembolectomy in the proximal posterior cerebral artery. The 64-year-old male patient had an acute partial P1 thromboembolic occlusion, with contraindications for intravenous recombinant tissue plasminogen activator. The patient underwent an urgent microsurgical thromboembolectomy after a frontotemporal craniotomy. RESULTS: The postoperative computerized tomography angiography showed complete recanalization of the P1 segment and its perforators, which were previously occluded. The early outcome after 1 month and 1 year follow-ups showed improvement from modified Rankin scale 4 to modified Rankin scale 1. CONCLUSION: Microsurgical thromboembolectomy can be an effective treatment option for proximal occlusion of the posterior cerebral artery in selected cases and experienced hands. Compared with endovascular treatment, direct visual control of brainstem perforators is possible. ABBREVIATIONS: ICG, indocyanine green mRS, modified Rankin scale P1, precommunicating segment of posterior cerebral artery PCA, posterior cerebral artery r-tPA, recombinant tissue plasminogen activator

Technical Description of the Medial and Lateral Anterior Temporal Approach for the Treatment of Complex Proximal Posterior Cerebral Artery Aneurysms.

BACKGROUND Posterior cerebral artery (PCA) aneurysms are often fusiform and associated with multiple intracranial aneurysms. A bypass procedure in combination with proximal occlusion or aneurysm trapping is considered to be effective for the treatment of patients with complex PCA aneurysms. Because of the deep, narrowed surgical corridor and the surrounding sensitive neuroanatomic structures, microsurgical procedures applied to the PCA are technically demanding. The authors present a technical report of a complex aneurysm formation located at the postcommunicating segment of the PCA (PCA-P2) treated via an anterior temporal approach. METHODS A 68-year-old woman had an unruptured PCA-P2 aneurysm formation, which was discovered incidentally. The fusiform aneurysm shape of the distal aneurysm aggravated direct microsurgical and endovascular treatment. After an individual case discussion, the patient underwent a microsurgical clipping of the proximal P2 segment aneurysm and the distal PCA-P2 segment aneurysm was treated by trapping after the application of a superficial temporal artery (STA) to PCA-P2 bypass using an anterior temporal approach. RESULTS Postoperative computed tomography angiography showed the exclusion of the proximal PCA-P2 aneurysm and an adequate flow from the STA to PCA-P2 bypass to the distal PCA segments. The patient showed a modified Rankin scale of 0 after follow-up at 1 and 3 months. CONCLUSIONS The anterior temporal approach is feasible for the microsurgical management of complex postcommunicating PCA aneurysms and the application of bypass procedures.