Outcome of brain check up in 782 healthy subjects

Monday, 7 July /997 clearly imaged. However, 29 (74.4%) of the associated unruptured cerebral aneurysms were prospectively diagnosed by 3D-CTA. Conclusion: Three-dimensional CTA was less invasive than conventional angiography, and could be performed safely and rapidly even in patients immediately after the onset of subarachnoid hemorrhage. It was suggested that 3D·CTA facilitates accurate diagnosis of ruptured cerebral aneurysm.

IP-2-2091

CT angiography in isolated third nerve palsy

E. Teasdale, R.M. McFadzean, M. Bain, M. Hussain, J. Fatukasi. Instituteof

Neurological Sciences, Glasgow, United Kingdom Introduction: Any patient with a third neNe palsy may have an aneurysm as the cause. Angiography is the gold standard but potentially hazardous and expensive. We have previously demonstrated a dynamic CT angiography technique which can accurately diagnosis an aneurysm causing third nerve palsy in a prospective study comparing CT angiography with intra-arterial angiography. An assessment of the routine use of this technique in 100 consecutive patients is reported. Current Study: CT angiography was used as the first investigation in 100 consecutive patients with isolated third nerve palsy and angiography performed only as a pre surgical procedure or if specifically requested by the clinician. The patients not having angiography were followed carefully for a mean of 9 months. Results: 53 of the 100 patients had a pupil sparing third nerve palsy. Dynamic CT angiography was negative in 72, abnormal in 28: 18 showing one or more aneurysm and 10 a non-aneurysmal vascular abnormality. Conventional angiography performed on 23 patients confirmed the CT aneurysm in 14, the non-aneurysmal abnormality in 6 and confirmed no abnormality in 3. The 77 patients without angiography were followed for a period of 9 months. 5 died within one month of the examination due to malignant meningitis (3) infective meningitis and septicaemia (1) and congestive cardiac failure with severe diabetes and hypertension (1). Of the remaining 72, 44 underwent complete recovery, 23 incomplete recovery and 4 remained unchanged. Of these 4, 1 developed posterior scleritis. 1 an infiltrative orbital tumour, 1 dysthyroid eye disease and the other was a very poorly controlled diabetic. In no patient was an aneurysm subsequently diagnosed. Conclusion: Screening patients with non invasive CT angiography allowed detection of a causative aneurysm in 18% of patients with isolated third nerve palsy (previously 3to 5%). CT angiography is a reliable, accurate, safe and cost effective out patient examination and should be the investigation of choice for any patient with third nerve palsy.

IP-2-210 I depicting Efficacy of MR angiographic source images on the topography of cerebral aneurysms S. Nagasawa, J. Deguch, Y. Tada, M. Kawanishi, 1. Ohta, E. Tsuda 1.

Department of Neurosurgery, Osaka Medical College, Osaka, Japan, 1 Soseikai GeneralHospital, Kyoto, Japan Introduction: This study evaluated the specific usefulness of magnetic resonance (MR) angiographic source images on preoperative depiction of surgical topography around cerebral aneurysms. Methods: Conventional and MR angiograms were retrospectively reviewed in 20, 20 and 40 patients with internal carotid artery (ICA), anterior communicating artery (AcomA) and middle cerebral artery (MCA) aneurysms, respectively. By comparing the topography based on these angiograms to that confirmed during surgery, we evaluated the specific information provided by MR angiography that was beneficial during surgery. Results: The source images were useful in 20% of the cases with ICA aneurysms and 25% with AcomA aneurysms, visualizing aneurysmal domes in the gyrus rectus or temporal lobe, and aneurysmal adhesion to the optic nerve or chiasma. They demonstrated that in 55% of the cases with MCA aneurysms the M1 segment was visualized between the aneurysmal neck and the insular surface from the postero-lateral perspective. These aneurysms were successfully clipped via the distal approach after definite proximal control of the M1 segment. Discussion and Conclusions: MR angiographic source images have a distinguishing feature in defining cerebral tissue-vascular relationship and they are useful for the surgical planning for cerebral aneurysm.

I P-2-211 I Spontaneous rupture of an cerebral aneurysm during angiography. Physical considerations

M. Lorenz, B. Haubitz 1, G. Stamm 2, E. Rickels, M. Samii. Neuro-Chirurgische

Klinik, 1 Neuroradiofogie, 2 DiagnostischeRadiologie, Medizinische Hochschule Hannover, 0-30623 Hannover, Germany Introduction: An angiographically induced rupture of a cerebral aneurysm is a rare complication. With the help of an illustrative example some physical

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considerations about the pressure-relationships during the inflow of contrast medium (CM) into the intemal carotid artery (ICA) are made. Patient: Three hours after spontaneous subarachnoid hemorrhage (SAH) and a Hunt and Hess-score of IV a 37 year old female underwent a digital subtraction angiography (endotracheal anesthesia, transfemoral 5-F-catheter, autornatical injection of 8 ml Ultravist" within 1.5 sec). Within a second series, an ICA-aneurysm ruptured at the onset of CM-flow having an inflow into the basal cisterns and the side-ventricle. The patient died SUbsequently as an result of the severe SAH. Physical Considerations: The normal flow in the leA is about 5 mils. An inflow of eM leads to an abrupt increase of the volume load. A doubled flow-rate will result in a pressure increase of up to 40% by estimating an increase of the diameter of the vessel of 10% (law of Hagen-Poisseuille). The pressure-impulse will be conducted by the bloodflow. The increased pressure leads to increased tension in the wall of the vessel (law of Laplace) and potentially the wall of the aneurysm as well. Discussion: Any repeated SAH may worsen the prognosis of the disease. An angiography carries such a risk. Therefore, efforts have to be made to reduce the dangers in diagnostic procedures. Technically, options may be an improved flow-profile of the CM input, or avoidance of injection simultaneous with the systolic peak pressure. Clinically, a rupture is less likely to happen after day 1 of SAH, and a reduction of the number of series may lower the risks. On the other hand, an optimal presentation will help in planning of the surgical strategy.

IP-2-212I

Evaluation of vasospasm with three-dimensional CT angiography in patients with subarachnoid hemorrhage

Hiroaki Okabe, Ikuzo Iguchi, Akira Kito, Hisatake Yoshihara. Department of

Neurosurgery, Ohgaki MunicipalHospital, Ohgaki, Japan Introduction: Three-dimensional CT angiography (3D-CTA) was performed immediately after the onset of aneurysmal subarachnoid hemorrhage, during the vasospastic phase and during the chronic phase. The vascular diameter of the circle of Willis was investigated in order to assess whether vasospasm can be evaluated by 3D-CTA. Methods: Subjects were 32 patients treated by clipping of ruptured aneurysm during the acute phase. Initial 3D-CTA was performed within 3 days after the onset of subarachnoid hemorrhage, the second 3D-CTA was performed 8 to 10 days after onset, and the third 3D-CTA was performed more than 1 month after onset. All imaging was performed under the same conditions, using a Toshiba X force spiral CT scanner. Contrast medium (100 ml) was injected at a rate of 2 ml/second. A helical scan was initiated 20 seconds after injection was started, with a slice thickness of 2 mm and a table movement rate of 2 mm/second. After the images were rearranged at a rearrangement pitch of 1 mm, thresholds of 120 HU or more were processed to obtain three-dimensional images. Results: There was some influence of clip artifact in identifying the vessels. The limit of the vascular diameter that can be identified is approximately 1 mm. There was a positive correlation between the vascular diameter evaluated on the initial 3D-eTA and that measured on preoperative angiography. Normalization of the vascular diameter was observed on 3D-CTA during the chronic phase. In 23 patients without neurological symptoms or with transient neurological symptoms, during the vasospastic phase the diameters of the right At, left A1, right M1 and left M1 were decreased to 63.1%, 61.4%, 88.8% and 84.8% of the values on initial 3D-CTA, respectively. However, in 9 patients with serious neurological symptoms (inclUding 1 patient in a vegetative state and 2 deaths), during the vasospastic phase the diameters of the right A1, left A1, right M1 and left M1 were decreased to 9.8%, 28.2%, 50.0% and 50.2% of the values on the initial 3D-CTA, respectively. Conclusion: Three-dimensional CTA was less invasive than angiography, and Willis' arterial ring could be safely observed during the acute phase. It was suggested that the functional prognosis can be predicted by observing the vascular diameter on 3D-CTA during the acute phase.

IP-2-213I

Outcome of brain check up in 782 healthy subjects

Takahiko Metozaki, Takashi Koyama. Department of Neurosurgery,

Nishinomiya City CentralHospital, Nishinomiya, Japan Introduction: The purpose of brain check up is to detect asymptomatic intracranial lesions such as a cerebral aneurysm, brain tumor, cerebral infarction, and white matter lesion by noninvasive method. We performed MR imaging and MR angiography in healthy SUbjectsusing a 1.5 Testa MR apparatus. Method: Between Aug 1993 and Ju11996, 782 healthy subjects were examined with a 1.5 Tesla MR unit (Signa Advantage). There were 453 men and 329 women, ranging in age from 17to 82 years. The scan comprised T1 weighted, and T2 weighted images and MR angiography which included 3 D time of flight (TOF) and 3 0 phase contrast methods (PC). If we suspected the presence of a cerebral aneurysm, MR angiography was repeated, or conventional cerebral angiography was done, and recently 3 D-CT.

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Result: BrainCheckUp for healthysubjectsdisclosed8 cerebralaneurysms, 2 brain tumors (2 meningiomas), 7 vascular malformations (3 cavemous angiomas, 3 venous angiomas, 1 AVM), 35 cerebral infarctions (except for etat crible), and 45 white matter lesions (Leuko-araosis, unidentified bright object, periventricularhigh intensityarea etc). - Conclusion: We conclude that Brain Check Up for healthy subjects using MR- images and MR angiography is a safe and useful examination for detecting asymptomatic intracranial lesions. There are, however, some limitations in detecting small cerebral aneurysms.

IP-2-214 ! Three-dimensional angio-CT (30-MPVR). Effectiveness in vascular anatomy for meningioma patients G. Rocchi, P. Missori, E. Rastelli, M. Dazzl. Neurotraumatology, University of Rome "La Sapienza", Rome, Italy, Neuroradiology II, University of Rome"La Sapienza ~ Rome, Italy Introduction: The most common method for studying cerebral vessels in neurosurgical patients is cerebral angiography. Nowadays however, tomographic scannerswith higher resolution and the application of three-dimensional techniques are able to provide images of vasal structures comparable to those supplied by angiography. Material: Twelve patientswith intracranial meningioma underwent CT scanning of the skull before neurosurgical operationfor this lesion. Method: General Electric Sytec Plus scanner. Bolus of hydrosoluble non-ionic iodate contrast medium at 30% concentration, t cc per kg. Scanning technique: 1 mm thickness, 1 mm slice spacing, 120 Kilovolt, 100 or 130 milliamperes according to the individual patient. Average performance time, 6-8 minutes. The images obtained were transferred to another consolle, GE Advantages Windows, programmed for 3-D reconstruction MPVR. Results: None of the patients had an adVerse reaction to contrastmedium. In all cases the vascular structureswere imaged, directlyor indirectly related to the meningioma. Radiological findings compatible with dislocation or compression of the vessels, were always clearly defined. Slrnultaneous definition of the meningioma and vasal structures, together with the possibility of three-dimensional assessmentof the borders and distances, made precise planning of the neurosurgical operation possible. Conclusions: Three-dimensional angio-CT (3D-MPVR) is an effective means of studying the relationship between the vascular structures and the meningioma before operation. Its rapid perlormance, lack of risks, low cost and high image qualitymake this methodfrequentlysuperiorto cerebral angiography in patients with intracranialmeningiomas.

IP-2-215 I Interhemispheric approach to the corpus callosum:

Preoperative assessment of the midline entry corridor by magnetic resonance venography (MRV)

Francesco M. Salpietro, Marcello Longo, Cetty Alafaci, Domenico D'Avella, Francesco Tomasello. Depts. of Neurosurgery and Radiological Sciences (ML), University of Messina, Messina, Italy The optimal entry corridor to the corpus callosum should not compromise neurological functions through direct manipulation of eloquent cortical structures. Brain relaxation, patient positioning and careful preoperative identification of paramedian veins draining into the superior sagittal sinus are of paramount importance to avoid postoperativeneurological deficits by excessiveretraction or venous infarction. Most often there are two or three large veins that serve the medial hemisphere but there is no clear rule on Which may be sacrificed to create an adequatecorridor. The line of approachshouldavoid these veins as suchas possible, providing a large enough space for a 3 em retractor blade. If the needed corridor to reach the tumour is crossed by a bridging vein a careful microsurgical dissection of arachnoid and strippingof the vein from the cortical surface can reduce tension allowing, with a correct positioning of the head of the patient,the hemisphere to fall away from the falx creatinga greater access to the interhemispheric region. The preoperativeidentification, by magnetic resonance venography, allows the surgeon to evaluatein a threedimensional fashion the best corridorto reach a given tumour and to plan a well argumented surgical strategy also when a combined approach is needed.

Monday, 7 July 1997

IP-2-216I

Usefulness of three-dimensional imaging for operation in patients with hemifacial spasm and trigeminal neuralgia

Shinsuke Ohta 1 , Yoshiaki Kumon 1, Hirooki Tohdoh " Hideaki Watanabe 1 , Masahiro Sakanaka 2 , Saburo Sakaki I . 1 Department of Neurosurgery, 2 Department of Anatomy, Ehime UniversitySchoolof Medicine, chime, Japan Introduction: In patients with hemifacial spasm and trigeminal neuralgia, preoperative detection of the relationship betweenthe blood vesselsand the cranial nervesinvolved is essential. Methods: We studied the causative vessels in 22 patients with hemifacial spasmand 6 patientswith trigeminal neuralgiaby meansof magneticresonance (MR) imaging with spoiled gradient recaned acquisition in the steady state (SPGR). MR angiography, and tnree-dimenslonal (3-D) imaging reconstructed from the data of SPGR MR imaging by the surface rendering method at a workstation. Results: In all patients, the preoperative SPGR MR images demonstrated that the causativevessels compressed or were in contact with the root exit or root entry zone (REZ) of the facial or trigeminal nerve. These causativevessels were identified by inspection of the MR angiographicand 3-D images.The 3-D imagesprovided clearinformation as to the anatomicalrelationship betweenthe causative vessels and the REZ of these nerves. These findings were corroborated by the intraoperative findings. The symptoms were completely relieved after surgery in 20 of the patients with hemifacial spasm and in all 6 patients with trigeminal neuralgia. In all patients sufficient decompression was depicted on the postoperative SPGR MR images at the causative vessels and the REZ of the nerve. Conclusion: SPGRMRimages, MR angiographyand 3-0 images are useful for the identification of the causative vessels in patients with hemifacial spasm or trigeminal neuralgia. The 3-0 images are particularty useful for the simulation planning of the operative procedure.

IP-2-217 I Study of the vestibular aquaduct by CT scan:

A landmark for labyrinthine preservation in acoustic neurinoma surgery

R.L. Silveira,S. Gusmao, G. Cabral, U. Tazinaffo, R. Piva. Hospital Madre Teresa, Belo Horizonte, Brazil Introduction: The external aperture of the vestibular aquaduct was evaluated by CT scans of the temporalbones as a landmark to help in the preservation of the labyrinthby the retrosigmoid transmeatal approach. Material and Methods: The external aperture of the vestibular aquaduct was studied in 50 high-resolution bone window CT scans. We performed measurements between the extemal apertureand the porus and comparedit to the length of the internal auditory canal. By using a line of sight that avoided the labyrinth, we calculated a safety angle to expose the lateral meatal end. Results: The external apertureof the vestibular aquaductwas visualized in 89 (89%) of the temporal bones. The distance of the meatal lip to the extemal apertureof the vestibular aquaductwas never shorter than the distance of the meatallip to the lateralmeatusend. This landmarkofferedan appropriateangle to avoid the postero-medial part of the labyrinth. Conclusions: The external aperture of the vestibular aquaduct can be identified by high-resolution CT scans of the temporal bones and it can help the preservation of the labyrinthby the retrosigmoidtransmeatal approach. One can estimate the amount of this wall that can be drilled without entering the labyrinth.

IP-2-218 ! lateral Anatomical aspects of posterior fossa affecting suboccipital approach evaluated by bone-window CT Iwao Yamakami, Junichi Ono, Akira Yamaura. Dept. of Neurosurgery, Chiba University, Chiba, Japan Evaluating bone-window CT of 40 patients who underwent tumor removal by lateralsuboccipital approach (LSOA), we investigated three anatomical aspects of the posteriorfossa and discussedtheir effects on the LSOA.The anatomical aspects are 1) intemal occipital crest (IOC), 2) the posterior surfaceof petrous bone, 3) "petrous angle". 1)The lOGoften protrudedprofoundlyintothe posterior fossa. The height of 10C from the inner table of the occipital bone was 10 ± 3 mm (max: 17 mm, min: 3 mm). 2) The conveXity of the posterior surface of the petrousbone was evaluated by the "porus angle'; made by the anterior and posterior halvesof the posteriorsurfaceof petrousbone. The "porus angle" was 28 ± 13° (max: 61°, min: 0°).3) The "petrous angle", betweenthe cranial sagittal lineand the posteriorsurfaceof petrousbone, was 62 ± 6° (max:75°, min: 46°). In the LSOA, a prominent 10C may cause cerebellar contusion due to brain retraction . This surgicalcomplication should be avoided by a large SUboccipital craniotomy resecting the prominent 10C. A large "porus angle" may make it difficultto get a view of the petroclival region. These three anatomical aspects