Interhemispheric Acute Subdural Hematoma Secondary to Falx Meningioma: A Case Report.

This report describes an unusual case of falx meningioma associated with acute subdural hematoma, which is a rare presentation. A 76-year-old woman presented with right-sided hemiparesis and a known falx meningioma that had rapidly increased in volume over the previous year. Computed tomography revealed interhemispheric and left-hemispheric acute subdural hematomas. Preoperative embolization and surgical tumor removal were performed to improve the symptoms, and pathological examination of the tumor revealed transitional meningioma (WHO Grade I). The patient's paresis symptoms improved postoperatively. This report provides valuable insights into the management and outcomes of falx meningioma with acute subdural hematoma, suggesting aggressive surgery to improve postoperative recovery.

A Case of Percutaneous Thrombectomy for Internal Carotid Artery Occlusion due to In-Stent Thrombosis Following Stent-Assisted Intra-Aneurysmal Embolization.

Objective: In-stent thrombosis (IST) is a known complication after stent-assisted coil (SAC) embolization. We report a case of mechanical thrombectomy using a stent retriever (SR) for IST and share our experience with this treatment to prevent a poor outcome in future cases. Case Presentation: The patient was a 62-year-old man. SAC embolization for an unruptured left internal carotid artery (ICA) aneurysm was performed. Three weeks after discharge, right hemiparesis and aphasia developed. Magnetic resonance imaging (MRI) demonstrated cerebral infarction in the left middle cerebral artery (MCA) territory and the left ICA was occluded. His relatives told us that the patient discontinued taking antiplatelet drugs. IST was diagnosed and emergency thrombectomy was performed. First, we tried to introduce an aspiration catheter or balloon catheter into the occluded lesion, but they were unable to be sufficiently inserted to the distal site. Therefore, we used a SR even though it carried a risk of friction on the deployed stent. The occluded artery was finally recanalized using the SR, but the stent became shortened. For the treatment strategy, sufficient medication (antithrombogenic agents and edaravone) should be administered first, followed by mechanical treatment. In mechanical treatment, thrombus fragmentation with a guidewire or balloon and aspiration should be attempted first. New aspiration catheters to carry the devices to the far distal site easily are now available. Conclusion: SRs cannot be utilized for thrombectomy with a stent. In emergency situations, careful consideration during troubleshooting rather than using a SR is needed.

[Corticospinal Tract Mapping by Calculating the Ratio of Subcortical to Cortical Stimulation Intensity:A Technical Note].

OBJECTIVE: Motor evoked potentials(MEPs)have been developed and utilized as safe surgical procedures. A correlation between the threshold intensity of direct stimulation MEPs and the distance of the corticospinal tract(CST)has been already established. However, MEPs are affected by anesthesia and patient-related conditions. Here, we describe a unique technique to avoid these effects. METHOD: When tumors developed in proximity to the CST, the transcortical MEP monitoring was done by placing grid electrodes on the primary motor cortex continuously while direct subcortical MEP mapping was conducted with a monopolar probe. The ratios of the subcortical to the transcortical stimulation intensity were calculated. The point at which the ratios reached 50% was defined as the surgical excision limit. DISCUSSION: MEPs are affected by anesthesia, paralysis, body temperature, and other factors. By measuring the ratio of the cortical stimulation intensity instead of the absolute value of the white matter stimulation intensity, various affecting factors can be avoided, and more accurate monitoring can become possible. CONCLUSION: By calculating the ratio of subcortical to cortical stimulation intensity, the corticospinal tract mapping is less likely to be influenced by the stimulation condition or facility setup, and this warrants further investigation.

Intraoperative Fluorescence Cerebral Angiography by Laser Surgical Microscopy: Comparison With Xenon Microscopy and Simultaneous Observation of Cerebral Blood Flow and Surrounding Structures.

BACKGROUND: Laser surgical microscopes should enable uniform illumination of the operative field, and require less luminous energy compared with existing xenon surgical microscopes. OBJECTIVE: To examine the utility of laser illumination in fluorescence cerebral angiography. METHODS: Fluorescein sodium (fluorescein) was used as a fluorescent dye. We first compared the clarity of cerebral blood flow images collected by fluorescence angiography between the laser illumination and xenon illumination methods. We then assessed use of the laser illuminator for simultaneous observation of blood flow and surrounding structures during fluorescence angiography. Furthermore, the study was designed to evaluate usefulness of the thus determined excitation light in clinical cases. RESULTS: Fluorescence angiography using blue light laser for excitation provided higher clarity and contrast blood flow images compared with using blue light generated from a xenon lamp. Further, illumination with excitation light consisting of a combination of 3 types of laser (higher level of blue light, no green light, and lower level of red light) enabled both blood flow and surrounding structures to be observed through the microscope directly by the surgeon. CONCLUSION: Laser-illuminated fluorescence angiography provides high clarity and contrast images of cerebral blood flow. Further, a laser providing strong blue light and weak red light for excitation light enables simultaneous visual observation of fluorescent blood flow and surrounding structures by the surgeon using a surgical microscope. Overall, these data suggest that laser surgical microscopes are useful for both ordinary operative manipulations and fluorescence angiography.

A Novel Intraoperative Laser Light Imaging System to Simultaneously Visualize Visible Light and Near-Infrared Fluorescence for Indocyanine Green Videoangiography.

BACKGROUND: Intraoperative indocyanine green videoangiography (ICG-VA) has been reported to be utilized in various cerebrovascular surgeries, wherein the blood flow is noticeably shown in white with a black background. ICG flow alone, but not other structures, can be observed using ICG-VA. We developed a novel high-resolution intraoperative imaging system using laser light source for simultaneously visualizing both visible light and near-infrared (NIR) fluorescence images of ICG-VA. METHODS: We used a novel system for 14 cerebrovascular cases. The operative field was illuminated via an operating microscope using a novel laser light source with four bands at 464 (blue), 532 (green), 640 (red), and 785 nm (NIR region). The observed light from the operative field was split using a beam splitter cube into visible (420- 660 nm) and NIR fluorescence emission light (832-900 nm). Images from the color video and NIR fluorescence emission windows were merged for visualization on a monitor screen simultaneously. Laser light was compared with xenon light, and both setups were tested for cerebrovascular surgeries. RESULTS: Laser light has numerous advantages over xenon light. The present setup clearly visualized the color operative field with enhanced blood flow. Complete clipping or incomplete clipping with neck remnant or remnant flow into an aneurysm was confirmed in aneurysm surgeries. Feeding arteries and draining veins were easily distinguished in case of arteriovenous malformation. CONCLUSIONS: Using the present setup, we can observe the color operative field and enhanced blood flow using ICG in real time. This setup could facilitate various cerebrovascular surgeries.

Utility and safety of a novel surgical microscope laser light source.

OBJECTIVE: Tissue injuries caused by the thermal effects of xenon light microscopes have previously been reported. Due to this, the development of a safe microscope light source became a necessity. A newly developed laser light source is evaluated regarding its effectiveness and safety as an alternative to conventional xenon light source. METHODS: We developed and tested a new laser light source for surgical microscopes. Four experiments were conducted to compare xenon and laser lights: 1) visual luminance comparison, 2) luminous and light chromaticity measurements, 3) examination and analysis of visual fatigue, and 4) comparison of focal temperature elevation due to light source illumination using porcine muscle samples. RESULTS: Results revealed that the laser light could be used at a lower illumination value than the xenon light (p < 0.01). There was no significant difference in visual fatigue status between the laser light and the xenon light. The laser light was superior to the xenon light regarding luminous intensity and color chromaticity. The focal temperature elevation of the muscle samples was significantly higher when irradiated with xenon light in vitro than with laser light (p < 0.01). CONCLUSION: The newly developed laser light source is more efficient and safer than a conventional xenon light source. It lacks harmful ultraviolet waves, has a longer lifespan, a lower focal temperature than that of other light sources, a wide range of brightness and color production, and improved safety for the user's vision. Further clinical trials are necessary to validate the impact of this new light source on the patient's outcome and prognosis.

Development of and Clinical Experience with a Simple Device for Performing Intraoperative Fluorescein Fluorescence Cerebral Angiography: Technical Notes.

To perform intraoperative fluorescence angiography (FAG) under a microscope without an integrated FAG function with reasonable cost and sufficient quality for evaluation, we made a small and easy to use device for fluorescein FAG (FAG filter). We investigated the practical use of this FAG filter during aneurysm surgery, revascularization surgery, and brain tumor surgery. The FAG filter consists of two types of filters: an excitatory filter and a barrier filter. The excitatory filter excludes all wavelengths except for blue light and the barrier filter passes long waves except for blue light. By adding this FAG filter to a microscope without an integrated FAG function, light from the microscope illuminating the surgical field becomes blue, which is blocked by the barrier filter. We put the FAG filter on the objective lens of the operating microscope correctly and fluorescein sodium was injected intravenously or intra-arterially. Fluorescence (green light) from vessels in the surgical field and the dyed tumor were clearly observed through the microscope and recorded by a memory device. This method was easy and could be performed in a short time (about 10 seconds). Blood flow of small vessels deep in the surgical field could be observed. Blood flow stagnation could be evaluated. However, images from this method were inferior to those obtained by currently commercially available microscopes with an integrated FAG function. In brain tumor surgery, a stained tumor on the brain surface could be observed using this method. FAG could be performed with a microscope without an integrated FAG function easily with only this FAG filter.

Development of a new high-resolution intraoperative imaging system (dual-image videoangiography, DIVA) to simultaneously visualize light and near-infrared fluorescence images of indocyanine green angiography.

BACKGROUND: Intraoperative indocyanine green videoangiography (ICG-VA) has been widely used in vascular surgery, where vessels are clearly shown as white on a black background. However, other structures cannot be observed during ICG-VA. We have developed a new, high-resolution intraoperative imaging system (dual-image VA [DIVA]) to simultaneously visualize both light and near-infrared (NIR) fluorescence images from ICG-VA, allowing observation of other structures. METHODS: The operative field was illuminated via an operating microscope by halogen and xenon lamps with a filter to eliminate wavelengths over 780 nm. In the camera unit, visible light was filtered to 400-700 nm and NIR fluorescence emission light was filtered to 800-900 nm using a special sensor unit with an optical filter. Light and NIR fluorescence images were simultaneously visualized on a single monitor. RESULTS: Our system clearly visualized the operative field together with fluorescence-enhanced blood flow. In aneurysm surgeries, we could confirm incomplete clipping with the neck remnant or with remnant flow into the aneurysm. In cases of arteriovenous malformation or arteriovenous fistula, feeding arteries and draining veins were easily distinguished. CONCLUSIONS: This system allows observation of the operative field and enhanced blood flow by ICG together in real time and may facilitate various types of neurovascular surgery.

Intra-arterial fluorescence angiography with injection of fluorescein sodium from the superficial temporal artery during aneurysm surgery: technical notes.

Intra-arterial fluorescence angiography from a catheter inserted into the external carotid artery (ECA) via the superficial temporal artery (STA) allowed us to satisfactorily evaluate cerebral arterial and venous blood flow. We report this novel method that allowed for repeated angiography within minutes with a low risk of complications due to catheter placement from the STA. The STA was secured at the edge of the standard skin incision during cerebral aneurysm surgery. A 3 Fr catheter was inserted approximately 5 cm to 10 cm into the STA. After manual injection of 5 ml of 20 times diluted 10% fluorescein sodium (fluorescein), fluorescein reached the intracranial internal carotid artery (ICA) through the common carotid artery or anastomoses between the ECA and ICA. Fluorescence emission from the cerebral arteries, capillaries, and veins was clearly observed through the microscope and results were recorded. Quick dye clearance makes it possible to reexamine within 1 minute. In addition, we made a graph of the fluorescence emission intensity in the arteries, capillaries, and veins using fluorescence analysis software. With intravenous fluorescence angiography, dye remains in the vessels for a long time. When repeated examinations are necessary, intervals of approximately 10 minutes are required. There were some cases we could not correctly evaluate with intravenous injection due to weak fluorescence emission. Fluorescence angiography with intra-arterial injection from a catheter inserted into the carotid artery or another major vessel, like conventional angiography, has a risk of procedure-related complications. We report our new method since it solved these problems and is useful.

Quantification of subarachnoid hemorrhage by three-dimensional computed tomography: correlation between hematoma volume and symptomatic vasospasm.

Subarachnoid hemorrhage (SAH) volume was measured by three-dimensional computed tomography (3D-CT) and the correlation examined between the SAH volume and the occurrence of symptomatic vasospasm (SVS). Experimental (in vitro) hematomas were made with blood obtained from 10 volunteers. The hematoma volume was determined by actual measurements and by 3D-CT using a CT number in the range of 40-80 Hounsfield units (HU) on days 1, 4, 7, 11, and 14. The coefficients on days 1 and 4 were relatively high and the correlation between measured and estimated volumes was significant on days 7, 11, and 14. 3D-CT was also performed in 50 patients with SAH at onset (day 0) and on days 1, 4, 7, and 14. The hematoma volume including the volume of normal structures was automatically calculated (V1). The volume of normal structures (V2) with CT numbers of 40-80 HU was calculated in another 50 patients without intracranial lesions as 12 ml. The total hematoma volume was defined as V1 minus mean V2. The mean SAH volume was 44, 36, 21, 11, and 8 ml on days 0, 1, 4, 7, and 14, respectively. The hematoma volumes were significantly larger in patients with SVS than in patients without SVS at all time points. The minimum hematoma volume in patients with SVS was 92, 76, 42, 24, and 12 ml on days 0, 1, 4, 7, and 14, respectively. This method allows the quantitative determination of SAH volume based on 3D-CT, and may be useful in clinical studies of cerebral vasospasm.

Utility and the limit of motor evoked potential monitoring for preventing complications in surgery for cerebral arteriovenous malformation.

OBJECTIVE: To evaluate the usefulness of motor evoked potential (MEP) monitoring and mapping in arteriovenous malformation surgery. METHODS: Intraoperative MEP monitoring was performed in 21 patients whose AVMs were located near the motor area or fed by arteries related to the corticospinal tract to detect blood flow insufficiency and/or direct injury to the corticospinal tract and/or to map the motor area. RESULTS: In 4 of 16 patients monitored for blood flow insufficiency, the MEP changed intraoperatively. In 2 patients, the changes were attributable to temporary occlusion of the feeding artery (anterior choroidal or lenticulostriate artery): 1 patient had a venous infarction around the internal capsule caused by thrombosis of the draining vein and the other bled intraoperatively from the nidus. In 17 patients, the MEP was monitored to rule out direct injury. In 1 patient, the MEP changed on coagulation of fragile vessels around the nidus in the precentral gyrus; it recovered after coagulation was discontinued. In 1 of 5 patients with MEP changes, the MEP did not recover; permanent hemiparesis developed in this patient because of venous infarction. In 1 of 11 patients subjected to MEP mapping of the motor area, we found translocation to the postcentral sulcus. CONCLUSION: In arteriovenous malformation surgery, MEP monitoring facilitates the detection of blood flow insufficiency and/or direct injury of the corticospinal tract and mapping of the motor area. It contributes to reducing the incidence of postoperative motor paresis.

Intraoperative monitoring of visual evoked potential: introduction of a clinically useful method.

OBJECT: To obtain a clinically useful method of intraoperative monitoring of visual evoked potentials (VEPs), the authors developed a new light-stimulating device and introduced electroretinography (ERG) to ascertain retinal light stimulation after induction of venous anesthesia. METHODS: The new stimulating device consists of 16 red light-emitting diodes embedded in a soft silicone disc to avoid deviation of the light axis after frontal scalp-flap reflection. After induction of venous anesthesia with propofol, the authors performed ERG and VEP recording in 100 patients (200 eyes) who were at intraoperative risk for visual impairment. RESULTS: Stable ERG and VEP recordings were obtained in 187 eyes. In 12 eyes, stable ERG data were recorded but VEPs could not be obtained, probably because all 12 eyes manifested severe preoperative visual dysfunction. The disappearance of ERG data and VEPs in the 13th eye after frontal scalp-flap reflection suggested technical failure attributable to deviation of the light axis. The criterion for amplitude changes was defined as a 50% increase or decrease in amplitude compared with the control level. In 1 of 187 eyes the authors observed an increase in intraoperative amplitude and postoperative visual function improvement. Of 169 eyes without amplitude changes, 17 manifested improved visual function postoperatively, 150 showed no change, and 2 worsened (1 patient with a temporal tumor developed a slight visual field defect in both eyes). Of 3 eyes with intraoperative VEP deterioration and subsequent recovery upon changing the operative maneuver, 1 improved and 2 exhibited no change. The VEP amplitude decreased without subsequent recovery to 50% of the control level in 14 eyes, and all of these developed various degrees of postoperative deterioration of visual function. CONCLUSIONS: With the strategy introduced here it is possible to record intraoperative VEPs in almost all patients except in those with severe visual dysfunction. In some patients, postoperative visual deterioration can be avoided or minimized by intraoperative VEP recording. All patients without an intraoperative decrease in the VEP amplitude were without severe postoperative deterioration in visual function, suggesting that intraoperative VEP monitoring may contribute to prevent postoperative visual dysfunction.

Separate demonstration of arterial- and venous-phase by 3D-CT angiography for brain tumors using 64-multidetector row CT: 3D-CT arteriography and 3D-CT venography.

We assessed the usefulness of the separate demonstration of the arterial- and venous phase on 3D-CT angiography (3D-CTA) using a 64-multidetector row CT (MDCT) scanner for the surgery of brain tumors. Nineteen patients with meningiomas (n=11), schwannomas, metastatic brain tumors (n=2 each), glioblastoma multiforme, malignant lymphoma, craniopharyngioma, and embryonal carcinoma (n=1 each) underwent scanning on a 64-MDCT scanner. After dynamic CT scanning to determine the scan timing for the arterial- and venous-phase, we individually scanned the arterial- and venous phase for 4 sec after injecting a nonionic contrast medium. Using the CT threshold setting and subtraction and cutting techniques, we produced individual 3D-CT images of the arteries, veins, tumors, and bones. The operators subjectively assessed the usefulness of these images in comparison with 3D-CTA. We separately demonstrated the arterial- and venous phase on 3D-CTA covering the entire head in all 19 cases. The 3D-CT arteriographs, 3D-CT venographs, and the fused 3D-CT images facilitated our understanding of the 3D anatomic relationship among the tumor, arteries, veins, and bony structures. In 14 of 19 cases our method provided the surgically valuable findings; the information on the anatomical relation between tumor and the surrounding arteries and veins (in 13 cases) the identification of anatomical course of the encased vessels (in one), and feeding arteries and draining veins (in one), and discrimination between the venous sinus and tumor (in one). The anatomical information yielded by our technique makes safer surgery possible. If more detailed information which 3D-CTA cannot provide is required, our method should be performed.

Evoked potentials elicited on the cerebellar cortex by electrical stimulation of the rat spinocerebellar tract.

BACKGROUND: In the current study, as a first step to develop a monitoring method of cerebellar functions, we tried to record evoked potentials on the cerebellar cortex by electrical stimulation of the rat SCT, which is located in the Inf-CPed. METHODS: The experimental study was performed on rats. Unilateral muscular contractions of quadriceps femoris muscle were elicited by electrical stimulation. The evoked potentials were recorded from the surface of the ipsilateral cerebellum and the contralateral primary sensory cortex. RESULTS: The highly reproducible potentials obtained from the ipsilateral cerebellar hemisphere were named SCEP. The SCEP exhibited one negative peak with a latency of 11.7 +/- 0.3 milliseconds (N(11)). Short-latency somatosensory evoked potential was recorded from the contralateral primary sensory cortex with a latency of 19.1 +/- 0.6 milliseconds. Coagulation of the ipsilateral Inf-CPed caused disappearance or marked reduction of the SCEP N(11), but it did not change the SSEP. On the other hand, sectioning of the ipsilateral dorsal column resulted in the disappearance of the SSEP, but it did not affect the SCEP N(11). CONCLUSIONS: Reproducible SCEP was recorded from the rat cerebellar hemisphere by electrical stimulation of the quadriceps femoris muscle. We posit that the SCEP differs from the SSEP, which ascends via the dorsal column, and that it is conducted by the dorsal SCT located in the Inf-CPed. Our results suggest that it may be possible to detect the dysfunction of the Inf-CPed electrophysiologically by using SCEP.

[Case of ruptured carotid-ophthalmic aneurysm splitting the optic nerve].

A rare case of ruptured carotid-ophthalmic aneurysm splitting the optic nerve was reported. A 52-year-old man presented with a sudden severe headache and bilateral visual deterioration. His right visual acuity was hand motion and the left was 2.0. His left visual field revealed a partial defect of the temporal visual field. Three-dimensional CT angiography revealed an ophthalmic aneurysm of 9 mm projecting superior-medially, The operation was performed to preserve the visual function as much as possible. The C2 portion aneurysm splitting the right optic nerve was visible. Before aneurysm clipping, the right anterior clinoid process and optic canal were drilled out to reduce the tension of the optic nerve. Intraoperative monitoring of visual evoked potential (VEP) under propofol anesthesia was performed to prevent further visual disturbance. Electroretinogram (ERG) was introduced to ascertain the arrival of the light stimulus at the retina even when the VEP could not be recorded. The right ERG was recorded, but the right VEP was flat. Both ERG and VEP were reproducible on the left side. Six months after the operation, the right visual acuity had improved to 0.08 and the visual field revealed nasal hemianopsia. The left visual acuity was unchanged while the visual field had improved to upper temporal quadrant hemianopsia. Various attempts to preserve the visual function were discussed.

Cerebral medulloepithelioma with long survival.

An 8-year-old boy presented with a rare cerebral medulloepithelioma manifesting as headache, nausea, and vomiting. Neuroimaging demonstrated a mass containing a cyst in the left frontal lobe. Gross total resection of the tumor with a 1-cm margin was performed under intraoperative monitoring. The histological diagnosis was medulloepithelioma. Stereotactic radiotherapy (total dose 20 Gy) was given to the brain up to 1 cm from the surgical margin. Follow-up neuroimaging 5 years later showed no signs of recurrence. He now attends junior high school, with normal mental and physiological development. Medulloepitheliomas are rare, highly malignant embryonal tumors of the central nervous system. Combined gross total tumor resection and radiotherapy are recommended to obtain the most favorable outcome.

Histologic study of arteriovenous shunts in the normal dura mater adjacent to the transverse sinus.

BACKGROUND: Although AV shunts are known to exist in the normal dura mater, their histologic appearance has not been examined in detail. Arteriovenous shunts in the normal dura mater adjacent to the transverse sinus, the most frequent site of DAVFs, were studied histologically. METHODS: Normal dura mater adjacent to the transverse sinus was obtained from 8 cadavers. Each specimen was cut into approximately 4-microm-thick serial sections; these were stained by the elastic Masson method and examined under a light microscope. RESULTS: Of the 8 specimens, 5 harbored a total of 6 AV shunts; no shunts were found in the other 3 specimens. The shunts, located in the supratentorial (n = 1) and infratentorial dura mater (n = 4) and in the tentorium cerebelli (n = 1), were classified into 2 types. In direct-type shunts, the artery connected directly to the vein; the diameter of these shunts ranged from 40 to 80 microm. In indirect-type shunts, the artery and vein were parallel and were indirectly connected by a shunt vessel, producing an H shape. The diameter of these shunt vessels ranged from 30 to 45 microm. All 6 shunts were connected to veins or the venous lake; none connected directly to the transverse sinus. CONCLUSIONS: The existence of direct- and indirect-type AV shunts in the normal dura mater was confirmed histologically. Both types exhibited the histologic features of DAVFs, suggesting that AV shunts in the normal dura mater might be involved in the etiology of DAVFs.

Blood flow disturbance in perforating arteries attributable to aneurysm surgery.

OBJECT: The object of this study was to investigate patients with cerebral infarction in the area of the perforating arteries after aneurysm surgery. METHODS: The authors studied the incidence of cerebral infarction in 1043 patients using computed tomography or magnetic resonance imaging and the affected perforating arteries, clinical symptoms, prognosis, and operative maneuvers resulting in blood flow disturbance. RESULTS: Among 46 patients (4.4%) with infarction, the affected perforating arteries were the anterior choroidal artery (AChA) in nine patients, lenticulostriate artery (LSA) in nine patients, hypothalamic artery in two patients, posterior thalamoperforating artery in five patients, perforating artery of the vertebral artery (VA) in three patients, anterior thalamoperforating artery in nine patients, and recurrent artery of Heubner in nine patients. Sequelae persisted in 21 (45.7%) of the 46 patients; 13 (28.3%) had transient symptoms and 12 (26.1%) were asymptomatic. Sequelae developed in all patients with infarctions in perforating arteries in the area of the AChA, hypothalamic artery, or perforating artery of the VA; in four of five patients with posterior thalamoperforating artery involvement; and in two of nine with LSA involvement. The symptoms of anterior thalamoperforating artery infarction or recurrent artery of Heubner infarction were mild and/or transient. The operative maneuvers leading to blood flow disturbance in perforating arteries were aneurysmal neck clipping in 21 patients, temporary occlusion of the parent artery in nine patients, direct injury in seven patients, retraction in five patients, and trapping of the parent artery in four patients. CONCLUSIONS: The patency of the perforating artery cannot be determined by intraoperative microscopic inspection. Intraoperative motor evoked potential monitoring contributed to the detection of blood flow disturbance in the territory of the AChA and LSA.

Confirmation of blood flow in perforating arteries using fluorescein cerebral angiography during aneurysm surgery.

OBJECT: The authors performed fluorescein cerebral angiography in patients after aneurysm clip placement to confirm the patency of the parent artery, perforating artery, and other arteries around the aneurysm. METHODS: Twenty-three patients who underwent aneurysm surgery were studied. Aneurysms were located in the internal carotid artery in 12 patients, middle cerebral artery in six, anterior cerebral artery in three, basilar artery bifurcation in one, and junction of the vertebral artery (VA) and posterior inferior cerebellar artery in one. After aneurysm clip placement, the target arteries were illuminated using a beam from a blue light-emitting diode atop a 7-mm diameter pencil-type probe. In all patients, after intravenous administration of 5 ml of 10% fluorescein sodium, fluorescence in the vessels was clearly observed through a microscope and recorded on videotape. RESULTS: The excellent image quality and spatial resolution of the fluorescein angiography procedure facilitated intraoperative real-time assessment of the patency of the perforating arteries and branches near the aneurysm, including: 12 posterior communicating arteries; 12 anterior choroidal arteries; four lenticulostriate arteries; three recurrent arteries of Heubner; three hypothalamic arteries; one ophthalmic artery; one perforating artery arising from the VA; and one posterior thalamoperforating artery. All 23 patients experienced an uneventful postoperative course without clinical symptoms of perforating artery occlusion. CONCLUSIONS: Because the fluorescein angiography procedure described here allows intraoperative confirmation of the patency of perforating arteries located deep inside the surgical field, it can be practically used for preventing unexpected cerebral infarction during aneurysm surgery.

High-frequency monopolar electrical stimulation of the rat cerebral cortex.

OBJECTIVE: Intraoperative monitoring of the motor-evoked potential has been widely used in patients undergoing neurosurgery. Direct stimulation of the brain with high-frequency monopolar stimulation (HFMS) is one of the most common methods to produce motor-evoked potential. We studied the influence of HFMS on the rat cerebral cortex. METHODS: We applied 1.5, 15, 30, 40, or 50 mA of HFMS to the rat sensorimotor cortex by a short sequence of five monopolar, monophasic, anodal rectangular 500-Hz pulses. We delivered one short five-pulse train 100 times every 5 seconds and examined pre- and post-stimulation electroencephalograms and histological changes at the stimulation site. RESULTS: We observed no spike waves after HFMS in any of the rats. There was no change in the power spectrum or frequency content in any of the rats exposed to HFMS. Histologically, there was significant swelling of the dendrites in rats sacrificed immediately after exposure to 40- and 50-mA stimulation; the 50-mA stimulation group also exhibited slight swelling of the mitochondria. These findings were not obtained in any of the rats sacrificed 30 days after stimulation. CONCLUSION: In rats exposed to a stimulation intensity of 30-mA or less, no morphological or electrophysiological changes were observed. However, the possibility that HFMS may affect neural tissue cannot be ruled out.