Cerebral hemodynamics were studied in 3 patients with supratentorial arteriovenous malformations (AVMs). Cerebral blood flow (CBF) was measured by the methods using ¹²³I-IMP SPECT (IMP SPECT) and stable xenon CT (Xe-CT) before and after surgery. In addition, the cortical blood flow (CoBF) adjacent to AVMs was monitored during surgery using laser Doppler flowmetry. Preoperative CBF measurements were performed more than a month after stroke.
Case 1: A 48-year-old man developed disturbance of consciousness, right hemiparesis and motor dysphasia. Cerebral angiography disclosed a 3.5cm left frontal AVM fed by middle cerebral artery. In preoperative IMP SPECT and Xe-CT, hypoperfusion and low CBF were observed in the left frontoparietal region adjacent to the AVM. The CoBFs of the left frontal lobe were increased moderately during clipping of feeders and after excision of the AVM.
Case 2: A 51-year-old woman had vomiting and right hemiparesis. Angiography demonstrated a 2.0cm left parietal AVM. In preoperative CBF studies, neither hypoperfusion nor low CBF was seen in the areas surrounding the AVM. There were no alterations of CoBFs before and after excision.
Case 3: A 62-year-old man had a 5.0cm left frontoparietal AVM supplied by anterior and middle cerebral arteries. Preoperative CBF studies showed marked hypoperfusion and ischemia in the regions adjacent to as well as distant from the AVM. A large increase in CoBF up to two or three times the preexcision value was noted after total excision of the AVM. He developed the normal perfusion pressure breakthrough (NPPB) syndrome after operation. High dose barbiturate anesthesia combined with induced hypotension was maintained for 5 days and resulted in good outcome.
From reported clinical observations and hemodynamic data in this study, it is suggested that factors contributing to the development of NPPB syndrome include:(1) a large, high-flow AVM;(2) marked hypoperfusion and ischemia in the regions adjacent to as well as distant from an AVM;(3) low CoBF around an AVM; and (4) substantial increase in CoBF after AVM removal. Preoperative and intraoperative CBF measurements may be useful for perioperative management of a large, highflow AVM.

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We experienced three cases of newly developed aneurysms after clipping of an original aneurysmal neck. In all cases, newly developed aneurysms were founded on different arteries from the artery that had an original aneurysm.
In two cases, hypertension with arteriosclerotic change was noted. In one of two cases, multiple cerebral aneurysms were revealed by angiography.
In the other case, a new aneurysm was revealed at the bifurcation of middle cerebral artery after clipping of the contralateral middle cerebral artery aneurysm.
Many authors have reported the mechanisms of newly developed aneurysm. In their reports, existence of a mini-aneurysm that was not diagnosed by the initial angiography, arteriosclerotic change of the arterial wall due to hypertension, or damage of the arterial wall adjacent to the initial clip edge are insisted as causes of new aneurysm.
We would like to propose that hypertension and arteriosclerotic change of the arterial wall are the factors as the mechanism of newly developing aneurysm, and follow-up antiography should be recommended for patients with hypertension and arteriosclerotic change 5 to 6 years after clipping of the original aneurysm.

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Complications due to venous injury have been observed in the vein of Labbé or other bridging veins. In this paper, we present surgical techniques for the preservation of the sylvian vein when approaching skull base lesions.
Using the orbitofrontomalar approach with preserving the superficial sylvian vein, we approached 32 skull base lesions: nine aneurysms, four arteriovenous malformations and 19 skull base tumors.
The following surgical procedures were used;(1) Orbitofrontomalar approach a) Frontotemporal craniotomy b) Superolateral orbitotomy c) Removal of malar flap
(2) Combined epi- and subdural approach a) Removal of anterior clinoid process and optic strut, followed by unroofing of optic canal.
b) Dural incision along the sylvian fissure down to the cavernous sinus, opening of the dura of the superior orbital fissure and carotid fibrous ring, and finally cutting the falciform ligament and optic sheath.
c) The sphenoparietal sinus, superficial sylvian vein and internal carotid artery are mobilized. Thus, a sufficient operative field can be obtained.
With these procedures, we could approach skull base lesions while preserving the superficial sylvian vein without any complications.

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Several kinds of surgical approaches are proposed for the direct operation of a VA-PICA aneurysm, because it has a unique anatomical relationship, especially to the brainstem and the lower cranial nerves. But the surgical positioning for its operation has hardly been discussed. This paper describes the influences of the surgical positioning on the approach and the exposure of this aneurysm.
As the sitting position has a risk of air embolism, we have not used it as a routine. We have operated on 8 cases in the supine lateral position, 3 cases in the modified semilateral position and 4 cases in the modified semiprone position.
In the supine lateral position, the patient is first anesthetized in the supine position, the operating table on the cephalad is elevated ca. 20 degrees to reduce the intracranial venous pressure, the patient's shoulder on the operated side is elevated ca. 20 degrees, and his head is rotated toward the healthy side to a complete lateral position. His neck is flexed anteriorly and his vertex is pushed downwards to provide more space between the foramen magnum and the atlas.
In the modified semilateral position, the patient is first placed in the lateral position with his contralateral arm extended out from the table and lifted up from it. The patient's shoulder on the operated side, is let down ca. 50 degrees, his head is kept lateral. The slope of the operating table (head up), neck flexion and vertex down are undertaken in the same way as in the supine lateral position. As described, the contralateral arm is lifted with a splint-fixation.
In the modified semiprone position, the patient is anesthetized first on the other table, then turned round and moved to the operating table in the prone position. the patient's shoulder on the operated side is elevated ca. 40 degrees, his head is rotated toward the operated side to the lateral position. Other points are same as in the modified semilateral position. The only difference is that his contralateral arm is placed and fixed on his back.
The supine lateral position has a merit of not raising the intrathoracic pressure. But it does easily compress the jugular vein, resulting a rise of intacranial venous pressure, which may cause intraoperative venous bleeding and postoperative facial edema. In addition, this position has another major demerit. As the head is turned toward the non-operated side, the nuchal muscles become tense, interfering with sufficient opening of the operative field and adequate craniectomy to the lateral, making the far lateral approach difficult.
The modified semilateral or semiprone position has a tendency to raise the intrathoracic pressure, but it is within the range of easy control. The primary advantage of these positions is that the head is turned toward the operative side, which relaxes the nuchal muscles. We can therefore open the operative field sufficiently and extend the craniectomy laterally to enable the far lateral approach. We have an impression that, for the patients with short and thick neck, the modified semiprone position with the contralateral patient's arm placed and fixed on his back is better than the modified semilateral position with his contralateral arm lifted from the table.

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A case of surgically treated intracranial dissecting aneurysm involving left internal carotid artery (ICA) and middle cerebral artery (MCA) was described. This 62-year-old woman presented with cerebral infarction in the left MCA distribution. Cerebral arteriogram revealed a dissecting aneurysm with a finding of double lumen, extending from left intracranial ICA to M₁, which remained patent for 2 months. A silicone encircling hemostatic clip with mild encircling force was surgically applied to the whole lesion, attending selective thrombosis of pseudolumen with patent true lumen and prevention of further dissection. However, the true vascular lumen attenuated and the pseudolumen became dominant without further symptoms.

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A thalamic arteriovenous malformation (AVM) has a tendency to show frequent rebleeding and serious prognosis after initial bleeding. We reported a case with thalamic AVM which was removed through interhemispheric approach after preoperative embolization of the feeding arteries from the anterior choroidal artery (Acho A).
A 32-year-old female was admitted with semicomatose state and right hemiplegia. CT showed a left thalamic and intraventricular hemorrhage and, an emergency venticular drainage was performed. Angiography demonstrated a left thalamic AVM fed by the Acho A, perforators from P₁ of the posterior cerebral arteries and the left posterior choroidal arteries. After 44 days from the onset, a preoperative embolization of the feeder from the Acho A was performed with PVA particles (150-250μm) and 20% ethanol. On the following day, direct surgery was carried out through the interhemispheric transcallosal approach and the nidus of AVM located in the left thalamus was electrocoagulated, guided by intraoperative angiography without any deterioration in her neurological states.
It can be said that a thalamic AVM is relatively easy to resect through interhemispheric approach after preoperative embolization of the feeding arteries from the Acho A.

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Injuries to perforating arteries are one of the most frequent complications during aneurysmal surgery. Extreme care should be taken to avoid them. Out of 366 cases that underwent radical surgery for cerebral aneurysms, 33 were reviewed that had circulatory impairment of perforating artery (confirmed by CT scan). Of the 33 cases, 18 were internal carotid artery (the incidence was 14.2%), 2 middle cerebral artery (1.3%), 2 horizontal portion of anterior cerebral artery (40%), 6 anterior communicating artery (5.3%), and 5 basilar artery aneurysms (9.3%).
The causes of injury to perforating artery were as follows: insufficient identification of the perforator (9 cases), improper retraction of the brain or vessels (9 cases), temporary occlusion (5 cases), kinking or stenosis due to the clip (5 cases), premature rupture (2 cases), and others (3 cases). A neurological deficit remained in 39.3% of the cases; a particularly high incidence was noted in anterior thalamoperforating artery injuries, anterior choroidal artery injuries, and recurrent artery of Heubner injuries.
In order to reduce perforator injuries, we must manipulate carefully, approach by the minimal brain retraction method, avoid using temporary clipping, and identify perforating artery sufficiently (e. g. using endoscope).

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Embolization is used as a radical therapy, as well as an adjunctive therapy with surgery for cerebral arteriovenous malformations (AVM). Eight patients underwent endovascular embolization and then surgical resection for cerebral AVM. In two cases, although AVM was embolized completely on the digital subtraction angiographical (DSA) evaluation, slight arterial blood filling into the nidus of AVM was observed on the surgical exploration. Postoperative computerized tomography (CT) demonstrated extent infarction area which was seemed secondary to occlusion of feeding arterial trunk due to retrograde thrombosis from nidus, although new neurological deficits were not recognized because of infarction in the non-dominant temporal lobe. In three cases, embolization of AVM was partial, because catheterization into the all feeding arteries was difficult. But, in two cases who had AVM in the right temporal and in the left occipital lobe respectively, surgical removal of AVM was performed completely without excessive hemorrhage. In another case who had AVM in the corpus callosum, although AVM was smoothly removed, the patient died of postoperative pulmonary embolism. In three cases, AVM could not be embolized at all because of impossible catheterization into feeding arteries. Histological findings of removed AVM which was completely embolized angiographically demonstrated that embolus mainly existed in the nidus and draining veins, and existence of blood around the embolus in these vessels.
These histological findings and the our intraoperative obseravation of slight arterial blood inflow into the nidus in the angiographically complete embolized AVMs imply that AVM should be removed surgically, even if it is embolized sufficiently. We must not forget that angiographical complete embolization of AVMs may provoke infarction of the normal brain around them, although they can be removed surgically without difficulty by the embolization.

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The direct approach to a basilar artery aneurysm of lower position is one of the most difficult operations. The choice of approach should depend on the distance from an aneurysm to the posterior clinoid process and the clivus. Pterional approach is a common and easy procedure but aneurysm was hidden by the ipsilateral posterior clinoid process. Two patients with lower basilar artery aneurysm were operated upon via pterional approach.
Case 1: A 46-year-old female had a ruptured basilar bifurcation aneurysm and a non-ruptured right anterior inferior cerebellar artery (AICA) aneurysm. The right AICA aneurysm was located 10mm below the posterior clinoid process. Both aneurysms were clipped after partial removal of the posterior clinoid process via right pterional approach. Postoperatively, mild right hemiparesis developed due to the obstruction of right AICA by the clip.
Case 2: A 32-year-old male with a ruptured superior cerebellar artery (SCA) aneurysm. This aneurysm was located 10mm below the posterior clinoid process. Via left pterional approach, an aneurysm was clipped after removal of the posterior clinoid process and clivus. Postoperative course was uneventful and angiogram.showed successful clipping. In this maneuver, the posterior clinoid process and clivus should be drilled out widely, and if necessary, the tentorium should be incised. Another approach should be selected if aneurysm is located more than 10mm below the posterior clinoid process.

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A hundred and eight patients with unruptured aneurysms, who received surgical (78 patients) or medical treatments (30 patients) in Kanazawa University Hospital between 1976 and 1991, were studied with respect to their operative and follow-up results. Thirty-four were male and 74 were female. The age ranged from 13 to 84 years (mean, 56.2 years). Unruptured aneurysms were discovered incidentally in 40 cases, as one of multiple aneurysms in 32 cases with subarachnoid hemorrhage (SAH), and as symptomatic ones in 36 cases. The operative morbidity was 2.0% (a case in 49 cases, 1/49) with a small aneurysm (smaller than 10mm), 37.5% (3/8) with a large aneurysm (10-25mm in size), 19.0% (4/21) with a giant aneurysm (larger than 25mm), and 10.3% (8/78) in the total cases, respectively; the operative mortality, 0% (0/49), 12.5% (1/8), 19% (4/21), and 6.4% (5/78), respectively. The operative results were poor in the patients aged over 50 with a giant aneurysm and over 70 with a large one. Among 30 patients who were not operated on, nine patients (30.0%) experienced aneurysmal rupture between 4 months and 13 years (mean, 5.0 years). As regards the size of aneurysms, large ones most frequently ruptured. Untreated small ones of the multiple ones after subarachnoid hemorrhage also frequently ruptured. No giant ones ruptured in patients aged over 60. Among 15 patients who underwent palliative surgeries such as coating of aneurysm and parent artery ligation, two patients with a giant aneurysm died of aneurysmal rupture one year after surgery. The incidence of aneurysmal rupture exceeded the operative risk in the patients aged less than 70. These results show as follows: 1) unruptured small aneurysms, once discovered, should be operated on only when patients, even aged, have no risk factor such as a cerebral ischemic disease. 2) There might be indications for surgeries of giant aneurysms of patients aged less than 60 and of large ones of those less than 70, however, safer operative procedures need to be conducted. 3) Clipping is a radical surgery for aneurysms however, palliative surgeries such as aneurysmal trapping and parent artery occlusion combined with a bypass surgery might be preferable to clipping for (symptomatic) large and giant aneurysms.

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Aged patients were defined as those of 70 years or more of age.
In a consecutive series of 197 patients, who were operated on for ruptured anterior circulation aneurysm, 23 aged patients (12%) were analyzed in regards to the prognostic factors and outcome, as compared with 43 patients (22%) of 60 to 69 years of age (60's: 60 to 69 years of age).
The WFNS grading scale, CT grade of Fisher's and the site of ruptured aneurysm did not statistically differ in two groups. Hydrocephalus, requiring shunt operation, was significantly frequent (p<0.05) in the aged. Delayed ischemic neurological deficit occurred in 61% of the aged, and in 45% of the 60's, but this difference was statistically insignificant.
Postoperative sodium imbalance was observed in 74% of the aged and in 60% of the 60's, but this difference was statistically insignificant. The incidence of postoperative systemic complication was significantly high (p<0.02) in the aged, and cardiac complication, such as myocardial infarction and heart failure, was distinctive in the aged.
In serial measurement of mean hemispheric cerebral blood flow, reduced flow was persistently revealed in the aged, as compared with the 60's. The results of a long-term follow-up differ significantly (p<0.05) between two groups.
The outcome at 6 months after onset was significantly poor in the aged. Only 26% had good recovery in the aged, whereas 51% had good recovery in the 60's. This difference was statistically significant (p<0.05). None had good recovery in WFNS grade III and IV of the aged.
In conclusion, these results suggest that the poor outcome was due to high incidence of intracranial and systemic complications following acute stage operation, in addition to the poor brain plasticity in the aged. The aged patient, whose WFNS grade is I to II, achieved a reasonably good outcome and should be operated on in an acute stage.

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