Interhemispheric approach is a common route for aneurysmal surgery such as anterior communicating artery and distal anterior cerebral artery. During the procedure, preservation of the bridging vein is important. Until now, there has been no intraoperative monitoring system for the venous blood flow. We used microvascular Doppler sonography to monitor the venous blood flow velocity.
Eleven cases of anterior communicating artery aneurysm or distal anterior cerebral artery aneurysm. Venous blood flow velocity was measured at the following three different steps during the operation: before using the brain retractor, during the brain retraction with retractor, and after the operation. We used two different dissection techniques of the bridging vein according to the severity of adhesion between dura and bridging vein. In 6 cases, the bridging vein was dissected free for the whole length between the cortex and superior sagittal sinus (SSS group). In 5 cases, the vein was not dissected from the dura intentionally about 10 to 15 mm in length at its superior sagittal sinus side (dura group).
There is a strong tendency for venous blood flow velocity to decrease during the brain retraction in the SSS group. The blood flow velocity was well preserved in the dura group. Two out of 6 cases in the SSS group showed venous occlusion on postoperative angiography and they developed transient or permanent neurological deficit.
Our study revealed the importance of monitoring the venous blood flow velocity to minimize the postoperative complication due to venous circulation disturbance.

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Posterior tibial nerve somatosensory evoked potentials (SEPs) were monitored intraoperatively in 22 patients with anterior communicating artery (Acom) aneurysms and 3 patients with distal anterior cerebral artery (ACA) aneurysms. Changes in peak latency and amplitude of the early cortical potentials of SEPs were evaluated. In 14 cases without temporary occlusion, the SEPs did not change during the surgical course. In 11 patients with temporary occlusion of A1 segment for Acom aneursms, lasting from 3 to 44 minutes, 10 demonstrated variable changes of P37-N46 interpeak amplitude. In 1 case, SEP signals remained stable. The P37 and N46 peak latency were not prolonged more than 2 msec in all cases. Significant SEP changes (a decrease in P37-N46 amplitude more than 50% to baseline value) were found in 4 cases. In these cases, the temporary occlusion was used intermittently, and the occlusion time did not go over 10 minutes per occlusion. In 3 cases, the wave form of SEP recoved to the baseline after the release of temporary occlusion. However, 1 case where the SEP did not fully recover suffered from transient motor paresis of a unilateral lower extremity. Despite the large variability of territories of ACA, intraoperative posterior tibial nerve SEP monitoring was helpful in the operative management such as temporary vessel occlusion.

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With the further refinement of MRI for neuroimaging, cavernous angioma has become easier to diagnose. Its precise localization can also be assessed with this improved diagnostic modality.
Surgical intervention for cavernous angioma in the pons has been thought to be contraindicated. In recent years, however, reports of surgical treatment for it have increased in number. Some cavernous angiomas in the pons can now be operated on safely by evaluating the precise preoperative localization of the lesion and by using selective intraoperative monitoring.
We report a case of a cavernous angioma in the pons. The patient was operated on using an intraoperative monitoring that could show the location of the facial colliculus. This prevented injury of facial and abducens nerves.
The case was a 5 year-old girl who presented with a right facial palsy 4 days after a blunt injury to her face. An MRI disclosed a small hematoma in the pons of mixed intensity with a perifocal low signal and bulging to the IVth ventricle. Through an osteoplastic suboccipital craniotomy, the floor of the IVth ventricle was exposed. A brownish-discolored bulged region was seen on the right side of the floor with a displacement of the median sulcus to the left. An electromyogram (EMG) of the right M. orbicularis oris was elicited when it was stimulated at the upper half of the bulged region, indicating the right facial colliculus was located beneath the upper part of the bulged area. Through a 4 mm longitudinal incision at the lower half of the bulged area, cavernrus angioma was excised completely.
A conjugate deviation to the left was observed immediately after surgery for a few hours, probably because of transient impairment of the right paramedian pontine reticular formation (PPRF). Palsies of the right facial and the abducens nerves developed postoperatively, but completely resolved in 3 weeks.
The indicaion for cavernous angioma in the pons are when there are signs of a definite hemorrhage, signs of neurological deterioration, and the location is near the pial surface. Total excision must be carried out during surgery to prevent postoperative bleeding.

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Haemodynamic monitoring of cerebral blood flow during intravascular surgery is important to assess the effect of treatment in embolization for AVM and angioplasty for occlusive cerebrovascular disease. We measured the intravascular blood flow velocity with a Doppler micro-guidewire (FLOWIRE^®) during intravascular surgery in 17 patients (1 of AVM, 3 of dural AVM, 3 of cerebral aneurysm and 2 of other diseases), and compared the data with the transcranial Doppler sonography (TCD). Significant correlavion of flow velocity between TCD and FLOWIRE was seen in intracranial internal carotid artery (ICA) and middle cerebral artery. In cervical ICA, vertebral artery and basilar artery, flow velocities measured with TCD did not correlate with the data of FLOWIRE. Clinical applications of FLOWIRE include AVM embolization, cerebral angioplasty, checking flow after aneurysm embolization and outlining the operative criteria in occlusive cerebrovascular disease.

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We introduced multimonitoring system at aneurysmal surgery in our institute. Two channels of both direct cortical response (DCR) and local cerebral blood flow (l-CBF) were continuously monitored during temporary occlusion. These monitorings were useful to evaluate the ischemic change and its reversibility.
Flow velocity of the impotant vessels including small vessels about 0.5 mm in diameter was measured by microvascular Doppler sonography before and after the aneurysmal neck clipping.
Combining use of these monitoring systems can improve safety and accuracy during aneurysmal surgery.

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Clipping of aneurysm is generally performed as radical surgical therapy for ruptured cerebral aneurysm. In some cases, however, stenosis or occlusion of a parent artery or peripheral artery may occur because of clipping depending upon the shape of the aneurysm and the nature of the pedicle. For such aneurysms, aneurysm clipping is often attempted for angioplasty. For this purpose, the equipment and a system for intraoperative angioplasty are required, and these are not available in some medical facilities. On the other hand, the intraoperative Doppler method using a microprobe is adopted as a simple method, but this is convenient only for observing blood flow and has problems in reproducibility. Further, it is also disadvantageous in that blood flow changes before and after clipping cannot be continuously determined. In the present study, we used an ultrasonic probe with cuff to match the vascular diameter and continuously monitored blood flow velocity and blood flow volume before and after aneurysm clipping in the parent artery and peripheral artery to evaluate the validity of the clipping site. During cerebral aneurysm surgery, the region around the aneurysm was detached. To the arteries peripheral from aneurysm and also to the parent artery, if possible, ultrasonic probe with a cuff matching the outer diameter of the artery was attached, and blood flow velocity and blood flow volume were continuously monitored from immediately before clipping in order to evaluate the influence of clipping. The results of the study revealed that the present method is easy to perform and can quantitatively determine blood flow volume. In particular, it was found to be very useful for fusiform aneurysm or broad neck, which require clipping for angioplasty.

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During ruptured aneurysm surgery, local cortical blood flow (LCBF) was monitored with a thermonal diffusion flow probe. The probe was placed on the cortex of the area supplied by the middle cerebral artery and was covered with a small cottonoid sheet to avoid movement and prevent loose contact with the cortex.
Hemodynamic changes after temporary occlusion and opening of the parent vessels were observed.
At the time of LCBF measurements, many factors that can abnormally change the LCBF must be considered. Irrigation of the brain and inadequate contact between LCBF probe and brain surface easily produce abnormal LCBF.

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We reviewed the clinical characteristics of vertebrobasilar system dissecting aneurysms that presented SAH in 68 patients, including 20 in our institute and 48 from the literature. We especially focused on the incidence and time interval of rerupture in relation to the choice and timing of treatment. The overall rerupture rate including both 43 surgical and 25 non-surgical cases was 54.5% (37/68). Rerupture occurred in 20 of the 43 surgical cases, which included 19 preoperative attacks. Within 24 hours, rerupture occurred in 54.1% (20/37) and in 81.1% (30/37) within the first week. Many of the cases were surgically treated after one week from the onset. The outcome of rerupture was critical, the extent of morbidity and mortality in association with surgical therapy are relatively not serious. A delay in surgical treatment was reflected in the marked high incidence of rerupture. Our results showed that early surgical obliteration of the parent artery is the treatment of choice.

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We surgically treated 37 patients who had a tumor around the jugular foramen in our university over the past 8 years. The sigmoid sinus involved by the tumor was resected and occluded without reconstruction in 30 cases. Three to 8 years after the surgery, 4 patients were readmitted because of late complication secondary to sinus resection. Total sinus thrombosis was seen in 1 patient and dural arteriovenous fistula (AVF) of the affected lateral sinus in 3 patients. Pathological findings of the resected AVF and clinical course of the patients suggested strongly that these complications would be secondary retrograde extension of the thrombosis that occurred in the resected sinus rest.
To prevent late complications such as delayed retrograde thrombotic extension and chronic intracranial hypertension due to venous congestion after sigmoid sinus resection in the surgery for tumor around the jugular foramen, we performed sinus circulation reconstruction with vein graft bypass in 7 recent cases. The saphenous vein was used as a graft and the bypass was performed between the lateral sinus and jugular vein (3 cases) or the sigmoid sinus and jugular vein (4 cases). In 5 cases the patency of the graft vein was comfirmed on the follow-up angiography performed 3 months after the surgery.
Although because of the short follow-up periods we cannot say with certainty that the vein graft bypass after resection of the sigmoid sinus effectively prevents late complications we think that bypass with venous graft is a good strategy to prevent late complication after the sigmoid sinus resection.

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The distal aneurysms of posterior inferior cerebellar artery (PICA) are relatively uncommon, accounting for less than 0.5-3.0% of all aneurysms.
We clinically analyzed 63 cases of the distal aneurysm of PICA-7 cases we treated over the last 5 years at our institute and 56 cases reported in the literature. The most common CT findinges of these cases in subarachnoid hemorrhage with intraventricular hemorrhage in 27 cases (43%), complication of hydrocephalus in 21 cases (33.3%), vasospasm in 12 cases (19.0%), and arteriovenous malformation in 5 cases (7.9%). Fifty-four cases were surgically treated, and 9 cases were conservatively treated. In surgical treatment, direct neck clipping of the aneurysm was carried out in 38 cases, coating of the aneurysm in 6 cases, trapping in 3 cases, proximal ligation in 3 cases, wrapping in 2 cases, excision and end-to-end anastomosis in 2 cases. The outcome of these surgically treated cases shows good recovery in 43 cases, moderately disablities in 5 cases, and death in 6 cases. Based on these reports, surgical treatment is recommended. The characteristic CT finding of distal PICA aneurysm is intraventricular hemorrhage and there was no significant difference in the site of aneurysm. Vascular malformation is commonly seen with this aneurysm.

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