The author described treatment considerations for acute type intracranial arterial dissections (IADs) based on his experience of 229 clinical cases (SAH 115 and unruptured 114) and approximately 60 pathological cases. The primary mechanism of IADs is a sudden disruption of the internal elastic lamina (IEL) and the subsequent penetration of circulating blood into the media. Preceding headache prior to manifesting clinical symptoms suggests the IADs generation time. Depending on how deep into the vessel wall the dissection occurs, an aneurysm might develop, or if the dissection is pushed into the vessel lumen, then occlusion or narrowing of the vessel including the perforating arteries could occur with a resultant ischemia. The injured arterial wall is repaired with intima as a biological reaction. The neointima basically consists of newly synthesized smooth muscle cells and an extracelluar matrix, including rich collagen fibers. Specimens of chronic IAD showed a tough structure completely repaired by intima. In the author's experience, the rebleeding rate of the ruptured dissecting aneurysms markedly decreases 1 week after the SAH and the longest interval was 41 days. This clinical data corresponded well to the pathological healing process. IADs which are unruptured at diagnosis may be safe from bleeding after 2 months from their generation.

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Surgical outcomes of internal carotid artery dorsal (or anterior) wall aneurysms (ICDA) with subarachnoid hemorrhage (SAH) were assessed using the data from recent multi-institute surveys. The largest, nationwide study conducted by author and colleagues in 2004 disclosed that the outcomes of cases that underwent early surgery were significantly (p<0.02) worse than those with delayed surgery. In cases with dissecting type ICDA, which form 36.5% of the whole, the result was much worse, with an extremely high mortality rate of 36.3%. A study conducted in 2009 by the author to elucidate the surgical method which could bring better outcomes showed that, restricting to the focus institutes proficient in the surgical treatment of ICDA, there was no difference between outcomes in early and delayed surgery. High-flow bypass with trapping of the internal carotid artery (IC) was the method used most frequently and it brought better outcomes as well. Clipping on wrapping might be the second choice, but some cases exhibit postoperative rebleeding or regrowth of the dome. Regarding the mechanism producing dissecting or non-dissecting aneurysms exclusively at the same portion of the IC without any arterial branching, the author proposed the hypothesis whereby spontaneous disruption of the internal elastic lamina (IEL) of the IC wall can be the root cause of ordinary, dissecting or pseudo-type aneurysms.

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Large or giant aneurysms are very difficult to treat by endovascular therapy. Several modifications of standard intraaneurysmal embolization, such as balloon neck plasty and the double catheter technique, are sometimes very effective for large aneurysms but not for giant ones. Stent-assisted coil embolization is occasionally effective for large or giant wide neck aneurysms. The pipeline embolization device, a stent-like device with fine mesh, is reported to be an effective device for treating giant aneurysms which are thought to be difficult to treat by existing methods. Computational flow simulation is helpful for the prediction of treatment results, especially in parent artery occlusion. The technology mentioned above makes some difficult aneurysms treatable even large or giant aneurysms.

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The medical charts of 801 consecutive patients transferred to our critical care center over a 14-year interval (1994-2007) in poor neurological condition (World Federation of Neurological Surgeons; WFNS grade IV or V) after subarachnoid hemorrhage (SAH) were retrospectively analyzed. All patients were treated following a strict protocol. After initial neurological evaluation, patients were sedated, paralyzed, and underwent strict blood pressure control. For patients with WFNS grade IV and selected patients with grade V, aggressive ultra-early repair (mainly clipping for anterior circulation aneurysm, coiling for posterior circulation aneurysm) was initiated. In grade V patients with poor brainstem function or destruction of vital brain areas on CT, only comfort measures were offered. Compared to the former period (1994-2000), coiling was more frequently indicated in elderly patients and bypass surgery was more often applied in complex aneurysm cases in the latter period (2001-2007). Compared to the former period, the number of aggressively treated patients significantly increased (37.6% versus 28.8%) in the latter period. Outcome assessments performed at 3 months revealed a significant increase of favorable outcomes (Glasgow Outcome Scale; GR or MD) and a decreased mortality rate in those patients (34% versus 28%, and 43% versus 47%; respectively). The ratio of favorable outcome and morbidity in all admitted patients were also improved (12% versus 8%, and 79% versus 85%; respectively). Outcome was largely determined by the initial hemorrhage and subsequent development of intractable intracranial hypertension or cerebral infraction. Age was also found to be significantly correlated with outcome. There was no significant difference in outcomes by treatment modality (clip or coil). In the latter period, aneurismal location was not the predictor, but delayed ischemic neurological deficit (DIND) remained an important factor. In conclusion, the overall outcome of poor-grade SAH patients has recently improved owing to the expanding indication of aggressive treatment. Our policy does not lead to a large number of dependent survivors, even among elderly poor-grade patients. Adequate management of vasospasm is warranted to improve overall outcome of those patients.

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Digital subtraction angiography (DSA) has been the main technique used for the detection and characterization of intracranial aneurysms and still remains the gold standard. However, DSA is invasive and time consuming, and carries a risk of both neurological and non-neurological complications. In addition, DSA may increase the risk of rebleeding when examining acute stage subarachnoid hemorrhage. It has been demonstrated that three-dimensional (3D) CT can reliably detect intracranial aneurysms. Therefore, a review of the recent literature concerning the diagnostic values of 3D-CT for preoperative aneurysm assessment was performed. Employing even the most advanced technology, intraoperative findings are not always well or fully depicted before surgery. Among them, the vessel wall findings including arterioscrelosis, condition of the perforators, and the status of the aneurysm occlusion are critical to the surgical outcome. Therefore, the detection and management of these important intraoperative findings were also illustrated.

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In the treatment of cerebral aneurysm, both clipping and coiling are recognized as effective treatments. In Europe and America, clipping is often performed by neurosurgeons and coiling is often performed by neuroradiologists, and they say that coiling is the first choice after a report of ISAT. In Japan, clipping is done by neurosurgeons and coiling is often done by neuroendovascular therapists. Neurosurgeons are also neuroendovascular therapists, so in many hospital's neurosurgeons perform both clipping and coiling. However, in institutions with a high case load, specialization and sharing of roles, has been proceeding nowadays. I have experienced about five hundred cases of clipping and about nine hundred cases of coiling in the treatment of cerebral aneurysm. Recently, I have treated 30〜40 cases with clipping and 110〜120 cases with coiling as the main operator per year. Here I report the selection bias of these cases. As factors in order to decide take between clipping and coiling, there are several elements to consider: the size, shape and position of the aneurysm and patient characteristics (age, complications, severity when ruptured, request for treatment) etc. In fact, this is the result of decision as to which is more profitable. This report is based on my own experiences and I report the selection bias present when both clipping and coiling are done by one neurosurgeon who has plenty of cases.

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In a patient with a pressure programmable valve, a method to objectively evaluate shunt function is not yet established for when a shunt malfunction is doubted, and a symptom are not improved following changing back the pressure setting. The present study examined using the wave pattern data from conventional intracranial pressure (ICP) monitoring before and after shunt operations in 7 patients with idiopathic normal pressure hydrocephalus. All four cerebrospinal fluid (CSF) dynamics parameters: pulse amplitude, pressure fluctuations, ICP pressure rising rate, and CSF outflow resistance, decreased significantly, along with improved CSF circulation after the shunt surgery. Therefore, in vivo assessment of shunt function may be possible by evaluating these parameters.

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We report a case of intracranial schwannoma originating from the C_1 posterior root, detected incidentally by brain CT scan after traumatic examination. An 80-year-old. female fell down and suffered a head injury. She went to the nearest hospital by herself. Neurological examination showed no signs of injury. A CT scan revealed no traumatic changes, but a low-density mass from the posterior cranial fossa to upper cervical level. She was admitted to our hospital where MRI showed that the tumor extended from the C_2 level of the spinal cord to the vermis of the cerebellum. A whole body search, faild to show any abnormalities. We removed the tumor by posterior craniectomy and cervical laminectomy. In the operative views, the tumor was found to originate from the right C_1 posterior root. By cutting off the originating portion, the tumor was completely removed. The pathological diagnosis was schwannoma. The patient was discharged without any neurological deficits. To our knowledge, schwannomas of the cervical root are not necessarily rare, but a case evolving upward and found as an intracranial tumor with no symptomatic signs is uncommon.

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