The development of endovascular surgery has drastically changed the treatment of cerebral aneurysm and occlusive cerebrovascular disease. In particular, many cerebral aneurysms are occluded by coil placement using endovascular techniques. Consequently, complicated cerebral aneurysms that can not be safely treated by endovascular techniques and require cerebral revascularization for their treatment are becoming the main candidates for surgery. In other words, cerebral revascularization techniques are becoming an indispensable requirement for the treatment of cerebral aneurysms. In addition, the evidence of the favorable effects of bypass surgery to prevent cerebral ischemic events has promoted extracranial-intracranial bypass surgery. The author reviews the present and future of cerebral revascularization surgery. In particular, the new technological developments including intra-operative flow measurement and intra-operative fluorescent angiography are introduced. Moreover, contemporary information on the neuroradiological diagnosis of hyper-perfusion syndrome is described.

View full abstract

Here the authors reviewed current indications and technical standards for superficial temporal artery-middle cerebral artery (STA-MCA) bypass. STA-MCA bypass is one of the most fundamental techniques for cerebrovascular surgery. Main indications are a recently symptomatic carotid or middle cerebral artery occlusive disease with misery perfusion (stage II ischemia) proven by positron emission tomography (PET) or single photon emission computed tomography (SPECT) corresponding to the inclusion criteria of the Japanese EOIC Bypass Trial (JET) Study. STA-MCA bypass is also indicated for flow alteration or as an isolation strategy for complex aneurysm surgery. Microsurgical training in the animal lab is a key step for successful surgery especially for younger neurosurgeons.

View full abstract

The surgical anatomy for an occipital artery to posterior inferior cerebellar artery anastomosis and for exposing the V3 portion of the vertebral artery will be decribed in detail. The anatomical course of the occipital artery is complicated because it traverses multiple layers. The occipital artery runs in the subcutaneous layer in the upper area of the superior nuchal line, and then runs between the splenius capitis and semispinalis capitis muscle below the superior nuchal line. Each suboccipital muscle in the superficial layer should be identified and must then be detached from the superior nuchal line and mastoid bone in order to dissect and to expose the occipital artery. The V3 portion of the vertebral artery can be a source for suboccipital revascularization, and the V3 portion can be secured before the craniotomy as a proximal control in the early stage of a vertebro-basilar artery aneurismaloperation. It is not easy to expose the V3 segment without bleeding from the vertebral venous plexus surrounding the V3 portion, because a lot of venous channels exist on the surface of the V3 segment of vertebral artery. The technical points will be also described in opening the venous plexus without bleeding.

View full abstract

Cerebral hyperperfusion that is well above the metabolic demands of the brain tissue may develop following superficial temporal artery-middle cerebral artery bypass surgery. Impairment of cerebrovascular autoregulation due to chronic cerebral ischemia causes the phenomenon. Cerebral hyperperfusion syndrome and cognitive impairment are complications of cerebral hyperperfusion. The incidence of cerebral hyperperfusion syndrome and intracerebral hemorrhage following arterial bypass surgery are 5% and 1%, respectively. In particular, the incidence in adult moyamoya disease is considerably high (40%). Preoperative dilation of cerebrovascular resistance vessels that can be measured by SPECT can be used to predict the development of postoperative hyperperfusion. Strictly controlling the patient's blood pressure early after surgery can help prevent the development of postoperative hyperperfusion.

View full abstract

OBJECTIVE: Extracranial-to-intracranial(EC-IC)bypasses are established techniques for treating complex aneurysms, cerebrovascular insufficiency, and moyamoya disease. Intracranial-to-intracranial (IC-IC) bypasses that are entirely intracranial and do not rely on the extracranial circulation are less established alternatives for revascularization. A consecutive clinical experience with IC-IC bypass applied to aneurysm therapy is reviewed. METHODS: During a 9.75 year period, 64 bypasses were performed for complex aneurysms, including 25 IC-IC bypasses : in situ bypasses in 7 patients, reanastomosis in 9 patients, reimplantation in 5 patients, and intracranial bypasses using grafts in 4 patients. RESULTS: In situ bypasses consisted of 4 PICA-PICA bypasses, 2 A3-A3 ACA bypasses, and one ATA-MCA bypass. Aneurysm excision with reanastomosis of the parent artery was performed for 5 MCA aneurysms and 4 PICA aneurysms. Two PICAs were reimplanted onto vertebral arteries I one pericallosal artery was reimplanted onto a callosomarginal artery; one M2 MCA trunk was reimplanted onto another M2 MCA trunk; and one MCA bifurcation was reconstructed with a double reimplantation technique. Intracranial bypasses included two petrous-to-supraclinoid ICA bypasses using saphenous vein grafts; one vertebral artery-to-superior cerebellar artery bypass using a radial artery graft; and one ACA-to-pericallosal artery bypass using a radial artery graft, with reimplantation of the callosomarginal artery. Postoperative angiography confirmed graft patency in 23 patients (92%) and complete aneurysm occlusion in all cases. By Glasgow Outcome Scale scores, good outcomes were observed in 22 patients (88% GOS 5 or 4). CONCLUSION: IC-IC bypasses are appealing because they are entirely intracranial, are less vulnerable to injury or occlusion, do not require harvesting an extracranial artery, and use donor and recipient arteries with diameters that are well matched. When grafts are needed, radial arteries are well suited. These bypasses often require end-to-end or side-to-side anastomoses not normally used with traditional EC-IC bypasses. When appropriate, an IC-IC bypass can be a safe and effective treatment for complex intracranial aneurysms.

View full abstract

Experience with dissection of the temporal bone is essential for training in skull base surgery, but only a limited number of neurosurgical residents have the chance of cadaver dissection. We propose a modification of a commercially available prototype three-dimensional (3D) temporal bone model to include artificial dura mater, venous sinuses, and cranial nerves for such surgical training. The base 3D temporal bone model incorporates surface details and the inner ear structures and air cells. We added dural sinuses and dura mater made from silicone, cranial nerves made from rubber fibers, and internal carotid artery made from rubber tubes to the model. Anterior and posterior petrosectomy were performed on this model using a high speed drill and ultrasonic bone curette under an operating microscope. The modified 3D temporal bone model provided good experience with the complicated three-dimensional anatomy. The model could be dissected, and the dural sinuses and dura mater preserved by the egg-shell peeling technique in almost the same way as real temporal bone. The modified 3D temporal bone model provides a good educational tool for training in skull base surgery.

View full abstract

The authors describe a 60-year-old female patient in whom profound ischemia due to temporary occlusion of the internal carotid artery (ICA) was clearly detected during surgery for complex ICA aneurysms by motor evoked potential (MEP). Repeated temporary occlusion of the ICA shortened the latency of MEP amplitude reduction and enhanced its degree. Reopening of the ICA immediately recovered MEP amplitude. Somatosensory evoked potential (SEP) did not show any significant change throughout the surgery. After surgery, she developed transient hemiparesis, which was closely related to transient.reduction of MEP amplitude during surgery. Although blood flow threshold and mechanism for MEP amplitude reduction have not been clarified, the findings strongly suggest that MEP monitoring can also be a sensitive, reliable modality during temporary parent artery occlusion.

View full abstract

Antiplatelet, endovascular therapy or open surgery are all treatment options for subclavian steal syndrome. We reported two patients with subclavian artery occlusion who suffered subclavian steal syndrome and underwent carotid-subclavian bypass. A 65-year-old male and a 60-year-old male had recurrent symptoms related to verte-brobasilar insufficiency. The patients successfully underwent carotid-subclavian bypass grafting with a saphenous vein graft. Their postoperative courses were uneventful and no further symptoms developed after surgery.

View full abstract