H Ohnishi

Nara Medical University, Nara-shi, Nara, Japan

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Publications (69)98.18 Total impact

  • S Okuno, H Touho, H Ohnishi, J Karasawa
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    ABSTRACT: Acute subdural hematomas caused by meningiomas have been rarely encountered. Pathophysiologic mechanisms and clinical considerations in these patients have not been sufficiently explored. We addressed the possible mechanism of spontaneous hemorrhage in our case and briefly discuss the optimal treatment. This case of falx meningioma presenting as an acute subdural hematoma in a 78-year-old woman is described. On initial computed tomography (CT), an enhancing tumor of the falx appeared to be the cause of hemorrhage. Only faint contrast staining in the periphery of the tumor was seen on right external carotid arteriograms, with no evidence of other vascular supply. Extravasation of contrast material during the procedure occurred suddenly and was successfully treated by endovascular embolization using a microcatheter. The hematoma was emergently evacuated with gross total removal of the tumor. Pathologic examination confirmed a transitional meningioma with abundant hyalinized structures. Disruption of a thin-walled vessel adjacent to the tumor capsule was assumed to be the site of hemorrhage. The longstanding ischemia of the tumor was considered to have produced the deposition of hyalin in the tissue, which changed the hemodynamics within the tumor, producing vascular stress leading to rupture. The prognosis of patients with meningiomas complicated by acute subdural hematoma is generally poor, with mortality reported in approximately one-half of such patients. Surgical exploration is the most effective treatment and should be conducted before irreversible brain damage has occurred.
    Surgical Neurology 09/1999; 52(2):180-4. · 1.67 Impact Factor
  • S Okuno, H Touho, H Ohnishi, J Karasawa
    Acta Neurochirurgica 02/1998; 140(6):629-30. · 1.55 Impact Factor
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    ABSTRACT: The surgical management of extensive skull base neoplasms, which often extend to both the sub- and epidural spaces, is still a great challenge with considerable risk. The authors report 12 cases in which a two-stage operation was performed for such nonmalignant tumours. The series consisted of four cavernous sinus meningiomas, one sphenoid-ridge meningioma, one cerebello-pontine angle meningioma, three pituitary adenomas, two chordomas, and one fibroma. Our operative strategy involved removal of the epidural part of the tumour and extensive skull base reforming during the first stage. After approximately one month, the second stage operation was performed by removing the residual subdural parts and the affected dura, which were less vascular, with dural plasty and subsequent spinal drainage. No complications such as cerebrospinal fluid (CSF) leakage or infection were observed. During the long-term follow-up (1.4 to 4.6 years, with a mean of 2.7 years), tumour recurrence was observed in a single case. In conclusion, the major advantages of this procedure were as follows: [1] improvement of the total removal rate, [2] prevention of postoperative CSF leak and infection, [3] residual tumours were avascular, necrotic, and dwindling, and also shifted outwards resulting in less adhesions to the brain. Although it may counter the trend toward less invasive procedures, the two-staged skull base surgery warrants serious consideration as an option for the management of patients with such extensive cranial base tumours.
    Acta Neurochirurgica 02/1998; 140(9):891-8. · 1.55 Impact Factor
  • S Okuno, H Touho, H Ohnishi, J Karasawa
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    ABSTRACT: Cases of cervical infarction with clearly documented evidence of the underlying aetiology and associated neuroradiological abnormalities have not been frequently reported. A rare case of cervical infarction caused by midvertebral artery occlusion due to spondylotic degeneration of the spine is described. The most probable aetiological factor affecting this disease entity, and the usefulness of magnetic resonance imaging in the detection of this rare lesion, are briefly discussed.
    Acta Neurochirurgica 02/1998; 140(9):981-5. · 1.55 Impact Factor
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    ABSTRACT: Carotid rete mirabile is a physiological vascular network between the external carotid and internal carotid systems present in some vertebrate species, but rarely observed in humans. We describe a 17-year-old girl with rete mirabile who presented with subarachnoid hemorrhage. Angiography disclosed the bilateral internal carotid arteries (ICAs) ended at the cavernous portion, and abnormal arterial networks visualized via the ICAs and the external carotid arteries in the paracavernous region. The distal ICAs were visualized via the abnormal arterial networks. After 18 years of follow-up she is leading a normal life without neurological problems. Rete mirabile in humans may present with hemorrhage or ischemic symptoms, but the prognosis appears to be good.
    Neurologia medico-chirurgica 03/1997; 37(2):188-92. · 0.49 Impact Factor
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    ABSTRACT: The clinical application of intraoperative motor-evoked potentials (MEPs) has been hampered by their sensitivity to anesthetics. Recently, to overcome anesthetic-induced depression of myogenic MEPs, multiple stimulus setups with a paired or a train of pulses for stimulation of the motor cortex were reported. However, the effects of anesthetics on MEPs induced by these stimulation techniques are unknown. Bipolar electrical stimulation of the left motor cortex was carried out in 15 rats anesthetized with thiopental while the compound muscle action potentials were recorded from the contralateral hind limb. After recording of the MEP in response to the single-shock stimulation of the motor cortex, paired pulses (double pulses) or a train of three pulses (triple pulses) with an interstimulus interval of each pulse at 0.3, 0.5, 1.0, 1.5, and 2.0 ms were applied. After control MEP recording, isoflurane was administered at a concentration of 0.25 minimum alveolar anesthetic concentration (MAC), 0.5 MAC, 0.75 MAC, and 1.0 MAC, and the effects of isoflurane on the MEPs induced by single, double, and triple pulses were evaluated. In all animals, distinct baseline MEPs were recorded. During the administration of 0.25 MAC and 0.5 MAC isoflurane, MEPs induced by stimulation with a single pulse could be recorded in 87% and 33% of animals, respectively, and MEP amplitude was significantly reduced in a dose-dependent manner. During the administration of 0.75 MAC isoflurane, MEPs after single-pulse stimulation could not be recorded in any animals. By stimulating with paired or triple pulses, the success rate of MEP recording and MEP amplitude significantly increased compared with those after single pulse before and during the administration of isoflurane. Both the success rate of MEP recording and MEP amplitude after double- and triple-pulse stimulation decreased significantly in a dose-dependent manner during the administration of isoflurane. Application of double or triple stimulation of the motor cortex increases the success rate of MEP recording and its amplitude during isoflurane anesthesia in rats. However, these responses are suppressed by isoflurane in a dose-dependent manner.
    Anesthesiology 12/1996; 85(5):1176-83. · 5.16 Impact Factor
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    ABSTRACT: After temporal craniotomy, pseudoankylosis of the mandible can cause difficult airway management during subsequent anesthesia. However, postcraniotomy changes in maximal mouth opening and the incidence of limited mouth opening have not been characterized. Ninety-two adult patients who underwent elective craniotomy were divided into three groups: Group A (n = 28) included patients who underwent parietal, occipital, or frontal craniotomy without incision of the temporalis muscles; Group B (n = 25) included patients who underwent temporal craniotomy; and Group C (n = 39) included patients who underwent frontotemporal craniotomy. Maximal mouth opening (interincisor gap) and the frequency of limited mouth opening (maximum mouth opening < or = 2.5 cm) were evaluated before operation and 3 days, 1 wk, 2 wk, 1 mo, and 3 mo after operation. The three groups did not differ with respect to age, sex, body weight, height, operative time, anesthetic time, or maximum mouth opening before operation. The postoperative reduction in maximal mouth opening was significantly greater in Group C than in Group B. In Group C, the incidence of limited mouth opening was 33.3% and 20.5% 2 wk and 1 mo after operation, respectively; however, limited mouth opening resolved within 3 mo in most patients. Supratentorial craniotomies separated by short intervals can increase the risk of limiting the mandibular opening, which may result in a difficult intubation. Careful preoperative assessment of the airway is mandatory if patients have previously undergone temporal or frontotemporal craniotomy.
    Anesthesia & Analgesia 10/1996; 83(4):731-4. · 3.30 Impact Factor
  • H Touho, J Karasawa, H Ohnishi, S Ueda
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    ABSTRACT: Selective angiography of the vertebral arteries has not been performed in rabbit models. We used a tracker-10 microcatheter for selective vertebral artery angiography. Five Japanese male rabbits weighing 2.0 to 2.5 kg were used. The right femoral artery was identified and an 18-gauge Teflon catheter was introduced into the iliac artery. A Tracker-10 microcatheter was introduced through the 18-gauge Teflon catheter into the right vertebral artery under fluoroscopic guidance. Selective angiograms of the right vertebral artery were obtained using a bolus injection of 0.1 mL of iopamidol in all five rabbits. Selective vertebral artery angiograms could be obtained via the transfemoral route with the use of Tracker-10, and intraarterial selective administration of vasodilators will be achieved using our technique.
    Surgical Neurology 08/1996; 46(1):84-6. · 1.67 Impact Factor
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    ABSTRACT: We monitored myogenic motor evoked potentials (MEPS) during intracranial surgery in 21 patients anesthetized with nitrous oxide in oxygen, fentanyl, and 0.75-1.5 minimum alveolar anesthetic concentration (MAC) isoflurane (n = 11) or sevoflurane (n = 10). The exposed motor cortex was stimulated with a single or train-of-five rectangular pulses at a high frequency (500 Hz), while the compound muscle action potentials (CMAPS) were recorded from the abductor pollicis brevis muscle. Neuromuscular block was monitored by recording the CMAPs from the abductor pollicis brevis muscle in response to electrical stimulation of the median nerve at the wrist (M-response). Stimulation of the motor cortex with a single pulse elicited MEPs in none of the patients, while stimulation with a train-of-five rectangular pulses at high frequency elicited MEPs in all patients. The relationship between MEP amplitude and the level of neuromuscular block induced by vecuronium infusion was evaluated in seven patients. For comparison of the individual measurements, the MEP amplitude at a M-response amplitude of 100% was calculated by means of the individual regression curve as 100% of MEP amplitude. There was a linear correlation between percent MEP amplitude and percent M-response amplitude (r = 0.81; P < 0.01). Intraoperative monitoring of MEP could be performed at a M-response amplitude above 90 % of the baseline value in 10 patients and at a M-response amplitude of 20%-50% of the baseline value in 11 patients. During monitoring of the 21 patients, MEPs did not change in 18 patients and disappeared in two patients. In the remaining patient, MEP amplitudes were attenuated to approximately 10% of the baseline value and recovered after cessation of surgical manipulation. In the two patients in whom MEPs disappeared, motor paresis developed postoperatively. We conclude that 1) intraoperative myogenic MEP monitoring is feasible during isoflurane or sevoflurane anesthesia if stimulation is performed with a short train of rectangular pulses, and 2) that electromyographic monitoring of neuromuscular block is useful to assess intraoperative MEP changes under partial neuromuscular block.
    Anesthesia & Analgesia 04/1996; 82(3):593-9. · 3.30 Impact Factor
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    ABSTRACT: To determine preoperative predictors of blood pressure reduction following dural opening during surgical evacuation of hematoma, we retrospectively assessed preoperative variables including clinical profile, hemodynamic parameters, neurological findings, and computed tomography (CT) scan results in 56 patients with traumatic acute subdural hematoma (ASDH). Patients were divided into two groups according to the degree of changes in mean arterial pressure (MAP) in response to dural opening. Group A (n = 18) had a MAP reduction > 20%, and group B (n = 38) had a MAP change within +/- 20% of baseline values (5 min before opening the dura). Significant relationships were found between MAP reductions > 20% and Glasgow coma scale (GCS) scores, abnormalities of the mesencephalic cistern on CT scan, pupillary abnormalities, and degree of midline shift. Low GCS score, absence of the mesencephalic cistern on CT scan, and bilaterally dilated pupils were particularly strong predictors of this amount of blood pressure reduction. The clinical outcomes of patients with MAP reduction > 20% following dural opening during surgery were significantly poorer than those of patients without this amount of blood pressure reduction. Our findings suggest that blood pressure reduction following opening of the dura in patients undergoing surgical evacuation of hematoma for traumatic ASDH may be predicted by careful preoperative assessment of neurological and CT scan findings.
    Journal of Neurosurgical Anesthesiology 04/1996; 8(2):117-22. · 1.67 Impact Factor
  • H Touho, J Karasawa, H Ohnishi
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    ABSTRACT: The results of long-term follow-up studies of cerebral perfusion and vasodilatory capacity following administration of acetazolamide after serial vascular reconstructions in 25 patients with childhood moyamoya disease are reported. Cerebral perfusion was measured with 99mTc-hexamethylpropyleneamine oxime single-photon emission CT before and after IV administration of 10 mg/kg acetazolamide, which was performed both before and after vascular reconstruction by superficial temporal artery-middle cerebral artery anastomosis and encephalomyosynangiosis (first and second operations) and/or omental transplantation to the brain (third operation). Follow-up periods ranged between 12 and 24 months (mean +/- SD, 18.5 +/- 3.2 months) after the first operation. Repetitive transient ischemic attacks disappeared completely after serial vascular reconstructions in all patients. Before the first operation, cerebral perfusion in the territory of the middle cerebral artery on the side of initial operation was 83.9 +/- 4.7% and was significantly lower than that in the contralateral side (88.3 +/- 4.9%, n = 25; P < .0001, paired t test). Vasodilatory capacity on the side of the first operation was -18.4 +/- 2.5% and that on the contralateral side -14.4 +/- 2.1%. The former value was significantly lower than the latter value (n = 25; P < .0001, paired t test). After the first operation, cerebral perfusion and vasodilatory capacity on the side of initial operation were markedly improved, to 87.8 +/- 4.5% and -14.7 +/- 2.7%, respectively (n = 25; P < .0001, both cases, paired t test). Before the second operation, cerebral perfusion and vasodilatory capacity on the side of the second operation were 76.6 +/- 4.1% and -20.1 +/- 1.9%, respectively, and significantly lower than those before the first operation (n = 25; P < .0001, both cases, paired t test). Eight patients subsequently required bifrontal omental transplantation for repetitive paraparetic transient ischemic attacks after the second operation; they had low cerebral perfusion and vasodilatory capacity bilaterally in the territories of the anterior cerebral arteries (72.4 +/- 2.7% and -18.6 +/- 1.7%, respectively). After omental transplantation, both were significantly increased, to 81.9 +/- 3.4% and -11.8 +/- 1.9%, respectively (n = 25; P < .0001, both cases, paired t test). Hemodynamic compromise existed in patients with childhood moyamoya disease and was a major cause of development of ischemic symptoms. Regions in which hemodynamic compromise was present could be determined by measuring regional cerebral perfusion and vasodilatory capacity.
    Stroke 03/1996; 27(2):282-9. · 6.16 Impact Factor
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    ABSTRACT: The feasibility and usefulness of intraoperative electromyographic monitoring of the oculomotor nerve (CN III), trochlear nerve (CN IV), and abducens nerve (CN IV) were evaluated under conditions of partial neuromuscular blockade in 21 patients undergoing skill base surgery. Intracranial electrical stimulation of each nerve was performed, and compound muscle action potentials (CMAPs) were reconded from the inferior or superior rectus muscle, the superior oblique muscle, and the lateral rectus muscle for monitoring of CN III, IV, and VI, respectively. Partial neuromuscular blockade was achieved by controlled infusion of vecuronium titrated to eliminate about 90% of the twitch response of the abductor pollicis brevis to electrical stimulation of the median nerve. A total of 30 cranial nerves were stimulated intraoperatively. Of these, 29 were successfully monitored (19 CN III, 6 CN IV, 4 CN VI). A relationship was found between intraoperative findings of cranial nerve monitoring, such as disappearance of response and increase in latency and stimulus threshold during manipulation of a lesion, and the presence of postoperative nerve deficits. We conclude that intraoperative electromyographic monitoring of ocular motor nerves is feasible during partial neuromuscular blockade, and that partial neuromuscular blockade does not affect the relationship between findings of intraoperative monitoring and postoperative nerve function.
    Skull Base 02/1996; 6(1):9-15.
  • H Touho, H Ohnishi, J Karasawa
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    ABSTRACT: An ultra-thin-walled 4-French catheter was used for angiography and as a guiding catheter for the Tracker-18 microcatheter in patients with intracranial dural arteriovenous fistulas (AVFs), spinal dural AVFs, spinal epidural AVF, meningioma, and acute embolic occlusion of major cerebral vessels. The 4-French guiding catheter was introduced through the transfemoral or transbrachial route. The guiding catheter and the guidewire were advanced to the aortic arch and then turned over just above the aortic valves, and finally the catheter was introduced into the external carotid artery or vertebral artery when the transbrachial approach was selected. Images of the intracranial vessels and spinal dural branches obtained were excellent in all cases. The Tracker-18 could smoothly be advanced to the target artery through the 4-French catheter in all patients. Endovascular treatment with the Tracker-18 can be performed using an ultra-thin 4-French guiding catheter, and safely via the transbrachial route.
    Neurologia medico-chirurgica 11/1995; 35(10):759-64. · 0.49 Impact Factor
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    ABSTRACT: A new technique using intravascular ultrasound has been used for diagnosis of coronary artery in order to obtain intravascular echo images. In this study, an intracisternally positioned ultrasound catheter was introduced obtaining serial echo images of the first segment (MI) of the middle cerebral artery in order to detect cerebral vasospasm following subarachnoid hemorrhage (SAH). Thirteen patients were admitted to Osaka Neurological Institute with SAH due to ruptured intracranial aneurysm. All patients underwent surgical neck clipping on the day of admission. In each patient, an 8 Fr. ultrasound imaging catheter (Cardiovascular Imaging Systems, Inc. (CVIS), Sunnyvale, CA) was detained intracisternally adjacent to the M1 segment following neck clipping of the aneurysm and placement of cisternal drainage(s) in the prepontine and/or distal portion of the Sylvian fissure. In order to detain the mirro device near the M1 segment, the tip of a 2.0 cm cisternal drainage tube (SILASCON, E-3L-12, Kaneka Medix Co, Osaka, Japan) was attached to the tip of the intravascular ultrasound catheter with 3-0 silk suture. The tip was placed in the prechiasmal cistern. Angiographic evidence of delayed vasospasm was obtained for three (23.1%) of the 13 patients. In one (33.3%) of the three patients who had angiographic evidence of vasospasm (25% stenosis), decrease in the inner diameter of the M1 segment was detected on the echo images, but in the other two (66.7%), no such decrease was noted on echo images. Angiographically identified vasospasm in the latter patients was associated with only 10% stenosis. Intracisternally positioned ultrasound catheter can be used for intermittent measurement of the diameter of a target artery for detection of cerebral vasospasm after SAH.
    Surgical Neurology 11/1995; 44(4):319-25. · 1.67 Impact Factor
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    ABSTRACT: Superficial temporal artery (STA)-superior cerebellar artery (SCA) anastomosis, and STA-posterior cerebral artery (PCA) anastomosis are considered suitable as surgical procedures for the treatment of patients with significant stenosis or occlusion in the rostral portion of the basilar artery and patients with significant stenosis or occlusion of the posterior cerebral artery, respectively. However, several authors have reported frequent and serious complications of these surgical procedures, including temporal lobe retraction edema and hematoma. In this study, we introduce a new surgical revascularization using an occipital interhemispheric transtentorial approach for the treatment of severe stenosis of the rostral portion of the basilar artery. A 47-year-old man with hypertension noted the sudden onset of nuchal pain followed by vertigo, diplopia, drunken gait, and motor weakness on his right side. Angiography performed on the day of the onset disclosed severe stenosis of the basilar artery. The stenotic portion extended just distal to the anterior-inferior cerebellar artery (AICA) to just proximal to the SCA, and in addition, a pseudolumen was visualized just distal to the left AICA. The patient underwent right occipital artery (OA) to left PCA anastomosis with interposition of the STA using an occipital interhemispheric transtentorial approach. Marked improvement in dysarthria, diplopia, ataxia gait, and visual disturbance were noted and he was able to walk without aid 3 days after operation. A postoperative angiogram of the right OA obtained 25 days after operation demonstrated visualization of the left PCA via the anastomosed OA and STA graft. OA-PCA anastomosis with interposition of STA graft using an occipital interhemispheric transtentorial approach can be substituted for STA-SCA anastomosis and STA-PCA anastomosis for treatment of stenosis/occlusion of the rostral portion of the basilar artery.
    Surgical Neurology 10/1995; 44(3):245-9; discussion 249-50. · 1.67 Impact Factor
  • Anesthesiology 09/1995; 83(2):434-5. · 5.16 Impact Factor
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    ABSTRACT: We report our experience with anesthetic care for six patients with pseudoankylosis of the mandible following neurosurgical procedures, four of whom required fiberoptically guided intubation for anesthesia. We suggest that the development of operative approaches and reconstruction techniques in skull base surgery may increase the risk of difficult airway due to limitation of mouth opening.
    Journal of Neurosurgical Anesthesiology 08/1995; 7(3):183-6. · 1.67 Impact Factor
  • H Touho, J Karasawa, H Ohnishi, S Ueda
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    ABSTRACT: This preliminary study investigated local hemodynamic changes in intramedullary spinal arteriovenous malformation (AVM) before and after embolization. 99mTcO4- was injected into the anterior spinal artery feeding the AVM via a Tracker-10 or MAGIC microcatheter. Time-dependent radioisotope images were sequentially obtained in the anteroposterior plane every 0.2 sec before and just after embolization. Local mean transit time (MTT) was then calculated for both the nidus and draining vein and compared before and after embolization. Prior to embolization, MTTs in the nidus and in the draining vein were 1.84 +/- 0.62 (mean +/- SD) and 2.80 +/- 0.69 sec for the five patients, respectively. MTTs in both the nidus and the draining vein were significantly prolonged after embolization to 3.32 +/- 1.14 and 4.90 +/- 0.93 sec, respectively (p < 0.02 and p < 0.005, respectively). In vivo measurements of local hemodynamic changes in the spinal cord during the treatment of spinal AVMs could be achieved. This method may allow investigation of the hemodynamic mechanisms which induce ischemic symptoms in patients with spinal AVM.
    Neurologia medico-chirurgica 07/1995; 35(7):445-9. · 0.49 Impact Factor
  • H Touho, T Monobe, H Ohnishi, J Karasawa
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    ABSTRACT: BACKGROUND Perimedullary arteriovenous fistulas (AVFs) are abnormal vascular connections between medullary arteries and veins without an intervening nidus. It is thought to be difficult to treat Type II AVFs which have multiple feeding branches. We performed intraoperative transvenous embolization to treat Type II AVFs. CASE REPORT A 30-year-old man with Type II perimedullary arteriovenous fistulas (AVFs), present at the level of the L-1 vertebral body, underwent surgical and endovascular treatment. The patient displayed slight motor weakness (4/5) and slight hypesthesia in the right lower extremity. Angiograms demonstrated that an anterior spinal artery and posterior spinal arteries were feeding arteries for the perimedullary AVFs. The patient underwent surgical occlusion of the fistulas three times. Fistulas present on the dorsal surface of the spinal cord were occluded with hemoclips, while those located on the ventral and ventolateral aspect of the spinal cord were occluded transvenously with isobuthyl-2-cyanoacrylate (IBCA) during surgery. Total occlusion of the perimedullary AVFs was achieved with these procedures, and no change was noted postsurgically in the patient's symptoms. CONCLUSIONS In summary, Type II perimedullary AVFs are sometimes difficult to treat using either embolization or open surgery. In such cases, both open surgery and intraoperative transvenous embolization should be performed in order to obtain occlusion of multiple fistulas.
    Surgical Neurology 06/1995; 43(5):491-6. · 1.67 Impact Factor
  • H Touho, J Karasawa, H Ohnishi
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    ABSTRACT: The haemodynamic mechanisms responsible for the appearance of paraparetic transient ischaemic attacks in ten patients with childhood moyamoya disease who subsequently underwent bifrontal omental transplantation were investigated. Cerebral perfusion (CP) was measured with 99mTc-hexamethylene-propyleneamine oxime single photon computed tomography prior to and after administration of acetazolamide. Cerebral perfusion was obtained by dividing radioisotope uptake per pixel in regions of interest by that in cerebellum. Haemodynamic reserve was defined as [CP after acetazolamide--CP before acetazolamide]/CP before acetazolamide x 100. Amounts of CP in the anterior portion of the frontal lobe and in the paracentral lobule were 0.70 +/- 0.04 and 0.74 +/- 0.03, respectively, before appearance of the transient ischaemic attacks. The latter was significantly higher than the former (p < 0.0001). Haemodynamic reserves were -11.1 +/- 2.8 and -9.6 +/- 3.0, respectively, at that time. These two parameters were significantly decreased just after paraparetic transient ischaemic attacks and two parameters in the paracentral lobule were more decreased than those in the anterior portion of the frontal lobe. But these increased again after bifrontal omental transplantation in these two regions. In summary, the watershed region was located anterior to the paracentral lobule before appearance of the transient ischaemic attacks, and widened and moved backward to include the paracentral lobule just before their appearance.
    Neurological Research 06/1995; 17(3):162-8. · 1.18 Impact Factor