Surgery for lateral ventricular lesions requires precise knowledge of the anatomy of the lateral ventricle. The lateral ventricle has four parts; the anterior horn, body, trigone・posterior horn and inferior horn. The neural, arterial and venous structures in each part are reviewed. Various surgical approaches have been reported and considerations important in selecting one of these approaches are discussed according to the anatomical characteristics.

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Even a partial callosal disconnection can often cause various syndromes depending on the lesion site, as no callosal region remains completely free from function. Although most of these callosal symptoms fortunately will not affect the patients' everyday life or will disappear in a few weeks, some symptoms can and will seriously effect the patients. In particular, praxis and speech impairments may have a very much unfavorable effect on their everyday lives. This review will present the findings on the callosal disconnection syndrome and a related topography update.

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Surgical approaches to lesions arising within the body of the lateral ventricle are divided into the transcortical middle frontal gyrus approach and the anterior interhemispheric transcallosal approach. Although the transcallosal route minimizes direct injury to the cerebral cortex, the surgical field is relatively limited because of the parasagittal bridging veins and restriction of the callosal incision. In our series of giant central neurocytomas occupying the entire body of the lateral ventricle, the resection rate was equal regardless if either the transcortical or transcallosal approach was used. Serious surgical complications of lateral ventricle tumors are deep venous infarction and memory disturbance due to fornix injury. In operative procedures for lateral ventricle tumors, it is important to identify the choroid plexus first, and then reach the foramen of Monro to confirm the thalamostriate vein and anterior septal vein. Injury to the fornix and thalamostriate veins can be avoided with early identification of these important anatomical landmarks. If the tumor is attached firmly to the fornix, strategy of subtotal removal combined with stereotactic radiation therapy would be appropriate for central neurocytomas because their radiosensitivity is relatively high.

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We describe the various surgical approaches to the trigone of the lateral ventricle. There are four main approaches to those areas 1) a transcortical approach through the cerebral convexity, 2) a transcortical approach through the inferior surface of the temporal lobe, 3) an interhemispheric transcallosal or transcortical approach, and 4) a distal transsylvian approach. Many important structures such as the speech center area in the dominant cerebral hemisphere, visual pathways and high cognitive functions in the parieto-temporo-occipital lobes should be preserved during the surgical procedure. The high parietal lobe approach should be recommended in the dominant cerebral hemisphere. The stepwise procedures are demonstrated with a case of meningioma in the trigone of the left lateral ventricle. Knowledge of the microsurgical anatomy and an intraoperative neuronavigation system are helpful for safer and less invasive microsurgery.

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The prognosis for untreated partially thrombosed giant basilar tip aneurysms is not favorable. However, an optimal treatment for these aneurysms has not been established. Neck clipping carries a high risk of morbidity and mortality. In contrast, intra-aneurysmal coiling by endovascular approach is relatively safe, but has a high incidence of recurrence. Proximal parent artery occlusion, with bypass surgery if necessary, is effective in selected patients. We report on four patients treated via endovascular approach. Three patients, one of whom suffered subsequent subarachnoid hemorrhage, presented with mass effect, and one with intermittent headache. Two patients were treated with intra-aneurysmal coiling. One of these two suffered recurrent subarachnoid hemorrhage seven months later and died. In the other patient, recurrence of the aneurysm occurred six months later, and a 2nd coiling was performed. The remaining two patients were treated with intra-aneurysmal coiling followed by occlusion of both vertebral arteries. One of these two suffered respiratory disturbance and tetraparesis due to brainstem infarction. The other patient achieved good recovery despite brainstem infarction. Intra-aneurysmal coiling for partially thrombosed giant basilar tip aneurysms is ineffective, and additional treatment containing both vertebral artery occlusions will be required. Long-term follow-up is necessary to prove the efficacy of parent artery occlusion.

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Object: The authors report a retrospective analysis of treating 18 patients with symptomatic lumbar intraspinal extradural cysts from April 2003 to January 2008. Methods: Patient characteristics including age, sex, symptoms, and neuroimaging studies were reviewed. Surgical procedures, results, and pathological findings were then correlated with preoperative assessment. Results: Patients consisted of 14 men and 4 women with an average age of 68 years (range 41-90 years). The most common symptoms were painful radiculopathy (100%), back pain (83%), and neurogenic claudication (100%). The most commonly affected level was L_<4-5> (56%). Fourteen patients were surgically treated for symptomatic lumbosacral intraspinal extradural cyst. Four patients were treated with conservative therapy and experienced spontaneous resolution of their cyst. Conclusions: Lumbar intraspinal cysts can be a cause of lumbar radicular pain and intermittent claudication. Surgical removal of the cyst is a safe and effective treatment for symptomatic patients. However, spontaneous resolution of the cystic lesion can occur in some patients, so meticulous follow-up may play an important role in some cases.

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Although acute subdural intracapsular hematoma is one of the occational complications of burr hole surgery for chronic subdural hematoma, extracapsular bleeding is rare. We experienced a case of acute subdural extracapsular hematoma after burr hole surgery for chronic subdural hematoma. Acute subdural hematoma can be fatal in some cases and needs to be treated immediately. It should be borne in mind that acute subdural extracapsular hematoma can also occur after the burr hole surgery, especially in patients with the tearing apart of the dura-outer membrane, and that the surgical procedure needs to be performed carefully.

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