Yoshihisa Oka

Ehime University, Matuyama, Ehime, Japan

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Publications (29)30.17 Total impact

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    ABSTRACT: We evaluated neuropsychological function before and after surgery in patients with unruptured cerebral aneurysms. Neuropsychological functions in 43 patients with unruptured cerebral aneurysms were evaluated before and 1 month after surgery. The neuropsychological examination included the Mini-Mental State examination, "Kana-hiroi" test, Kohs Block Design test, and Miyake's Memory test. Then, if scores of even a single test were decreased 1 month after surgery, the tests were performed again 5 months later. In 24 of the 43 subjects, cerebral blood flow (CBF) was measured before and 1 month after surgery by single-photon emission tomography. The outcome in all patients was evaluated as good according to the Glasgow Outcome Score (GOS). In 17 (40%) of the 43 patients, neuropsychological function had deteriorated 1 month after surgery. The most sensitive test applied was the Miyake's Memory test. Of 14 patients with neuropsychological deterioration 1 month after surgery, 6 showed complete recovery, 5 showed partial recovery, and 3 still showed cognitive deterioration 6 months after surgery. Patients over 65 years old, those with anterior communicating artery aneurysms, those operated by interhemispheric approach, or those with systemic diseases showed a greater tendency toward a decline in postoperative neuropsychological function than the other patients. The postoperative CBF and vascular response in the frontal lobe of affected-side was decreased in cases showing cognitive deterioration. These results suggested that the neuropsychological outcomes after surgery for unruptured cerebral aneurysms were not satisfactory.
    No preview · Article · May 2003 · Surgical Neurology
  • Yoshihisa Oka · Kazuhiko Sadamoto

    No preview · Article · Jan 2003 · No shinkei geka. Neurological surgery

  • No preview · Article · Jan 2003 · Surgery for Cerebral Stroke
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    ABSTRACT: Dynamic MR imaging provides hemodynamic information about normal and pathologic tissue of the brain. The purpose of our study was to evaluate the usefulness of dynamic MR imaging in the assessment of tumor vascularity and the tumor tissue blood flow of meningiomas. We studied 13 patients with meningiomas using dynamic spin-echo MR imaging. The histological subtypes of meningioma were confirmed by the examination of surgical specimens in all patients, and tumors were meningothelial in 9 cases, fibrous in 2, transitional in 1, and psammomatous in 1. Serial images were obtained every 18-24 sec for 8 minutes and 30 seconds after rapid injection of gadolinium diethylenetriaminepentaacetic acid. Different parameters (time to peak, maximum of signal intensity and the washout ratio) were calculated directly from signal intensity curves. As an indicator of tumor vascularity, microvessel density was counted based on immunohistochemically stained sections and tumor tissue blood flow was measured using an xenon-CT system. The maximum of signal intensity corresponded to the tumor vascularity. With dynamic MR imaging, the time intensity curves (TI curves) were divided into two patterns; type 1 had a steep increase with a peak and type 2 had a slow increase to a peak followed by plateau. The maximum of signal intensity measured from TI curve of dynamic MR imaging correlated significantly with microvessel density (R2 = 0.840, p < 0.0001). Linear regression revealed a significant positive relation between the washout ratio and the tumor tissue blood flow in group showed type 1 on TI curve (R2 = 0.961, p < 0.001). There was also a significant negative correlation between the time to peak and the tumor tissue blood flow (R2 = 0.792, p < 0.01). We suggest that dynamic MR imaging is useful for evaluating hemodynamics of meningiomas.
    No preview · Article · Jul 2002 · Nō to shinkei = Brain and nerve
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    ABSTRACT: The usefulness for evaluation of cerebral hemodynamics using time-resolved projection MRA was studied in normal volunteers and patients of cerebrovascular diseases. Six normal volunteers and ten patients with cerebrovascular occlusive diseases including 6 of IC occlusion and 4 of post EC/IC bypass surgery underwent time-resolved projection MRA on a 1.5 T clinical MRI system. Projection angiograms are acquired with 2 D-fast SPGR sequence with a time resolution of approximately one image per second, 40 images being acquired consecutively before and after bolus injection Gd-DTPA. And all images were calculated by complex subtraction from the background mask in a work station. In normal volunteers, the quality of images of time-resolved projection MRA was satisfactory. The arteries from internal carotid artery through M 2 segment of middle cerebral artery and all major venous systems were well portrayed. In 4 cases of IC occlusion who were assessed the collateral flow through the anterior communicating artery and posterior communicating artery, there were delayed to demonstrate the ipsilateral MCA. However, in 2 cases of IC occlusion that were assessed the collateral flow through leptomeningeal anastomosis, ipsilateral MCA and collateral circulation were not demonstrated. In all patients of post EC/IC bypass surgery, the patency of EC/IC bypass could be evaluated as properly with time-resolved projection MRA as 3 D-TOF MRA. Although the temporal and spatial resolutions are insufficient, time-resolved projection MRA was powerful non-invasive method to evaluate the cerebral hemodynamics via the basal communicating arteries in IC occlusion and identify the patency of EC/IC bypass.
    No preview · Article · Jun 2001 · Nō to shinkei = Brain and nerve

  • No preview · Conference Paper · Jun 2001
  • Y. Oka · K. Kohno · Y. Kumon · S. Sakaki · K. Sadamoto
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    ABSTRACT: A case is reported of a 48-year-old woman with a spinal subdural hematoma presented with severe back pain and sharp generalized headache. On admission, the patient presented with hypalgesia on her left leg but no motor weakness. Magnetic resonance (MR) images performed 5 days after admission, revealed a subdural mass extending anteriorly from Th10 to S1 level that was diffusely bright on T1- and T2-weighted images. These studies revealed an acute spinal subdural hematoma associated with spinal subarachnoid hemorrhage. Because the patient retained normal lower extremities function, it was decided not to evacuate the hematoma but to choose conservative management. Her clinical symptoms disappeared about 14 days after onset and spinal compression cleared in 1 month. However the patient was readmitted 3 months later and revealed paraparesis. MR images revealed a mass between the levels of Th6 to Th9 depicted as a low intensity signal on T1-weighted images and a high intensity signal on T2-weighted images. We diagnosed spinal arachnoid cyst induced by the spinal arachnoiditis following subdural hemorrhage associated with spinal subarachnoid hemorrhage. Subtotal cyst removal was insufficient, resulting in necessity of shunting of the cyst into the peritoneal cavity. Spontaneous acute spinal subdural hematoma is a rare spinal disease. Most of patients have been treated with surgical procedure, but in a few patients in whom neurological impairment is minimal, have been reported in which hematoma resolved spontaneously with conservative management. However, the careful observation may be needed using MR imaging if the subdural hematoma associated with spinal subarachnoid hemorrhage is expanded and large.
    No preview · Article · Jan 2001 · Japanese Journal of Neurosurgery
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    ABSTRACT: We report an adult onset patient with moyamoya disease showing acute progress after contralateral vascular reconstructive surgery. A 47-year-old female developed cerebral infarction in the left corona radiata. A magnetic resonance (MR) angiography and a cerebral angiogram revealed severe stenosis extending from the terminal portion of left internal carotid artery (ICA) to the M1 portion. The right ICA showed slight stenosis. We performed direct bypass surgery (STA-MCA anastomosis) on the affected left side. MR angiography 1 month after surgery revealed the progressive stenosis of the C1 portion of the right ICA. While measurement of cerebral blood flow (CBF) showed a slight impairment of vascular reactivity to acetazolamide loading in the region of the right MCA, we continued without vascular reconstructive surgery for the right side because there was no ischemic attack. The patient had a transient sensory disturbance of the left upper extremity 16 months after surgery. MR angiography and a cerebral angiogram revealed more progressive stenosis extending from the right ICA to the M1 portion. CBF study showed a low CBF at rest and a negative response to acetazolamide loading in the region of the right MCA. Direct bypass surgery was performed on the right hemisphere. Follow-up study revealed an increment of rest CBF and improvement of vascular reactivity. We underlined the necessity for careful postoperation observation of progressive contralateral arterial stenosis using MR angiography and CBF study in adult onset patients with moyamoya disease.
    No preview · Article · May 2000 · No shinkei geka. Neurological surgery
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    ABSTRACT: In comparison with 99mTc-ECD SPECT, the usefulness for evaluation of cerebral blood flow by the perfusion images using MRI with FAIR sequence was studied in ischemic stroke patients. Among 27 cases, 15 patients showed lacunar infarctions and 12 patients showed cortical infarctions determined by T2 weighted MR images. FAIR images were obtained as single images at the slice position running through the basal ganglia or corona radiata. The inversion times(TI) were varied, ranging from 800 to 1,400 msec. In 15 patients without definite low perfusions in the SPECT study, FAIR images showed sequentially proxymal arterial branches in early phase and distal arterial branches or capillary beds in the cortical tissues in a late phase as the TI was elongated. Nine of the 12 patients with low cerebral perfusions in the SPECT study showed perfusion defects in FAIR imaging. Five of the 12 patients with a small low cerebral perfusion area in the SPECT study showed a delay of the depiction of cortical arteries along with TI elongation. In 3 patients, ischemic lesions demonstrated by the SPECT study was not shown in the MRI study because of motion artifacts. In conclusion, FAIR imagings are considered to be useful in the evaluation of cerebral flow dynamics in the ischemic stroke patients.
    No preview · Article · Mar 2000 · Nō to shinkei = Brain and nerve
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    ABSTRACT: A 58-year-old female presented with right conjunctival chemosis and right abducens nerve paresis. Cerebral angiography demonstrated a right carotid-cavernous sinus fistula associated with persistent primitive trigeminal artery. The fistula was treated by introducing detachable coils through the transvenous approach, as the detachable balloon was not available. Follow-up angiography performed 14 days after the embolization revealed complete disappearance of the carotid-cavernous sinus fistula due to thrombosis, which was presumably accelerated by the coils. Transvenous coil embolization should be considered as an alternative treatment for high-flow carotid-cavernous sinus fistula, but only if transarterial balloon embolization is not successful or unavailable.
    No preview · Article · Feb 2000 · Neurologia medico-chirurgica
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    ABSTRACT: We investigated age-related changes in the visibility of intracranial arteries on magnetic resonance angiography (MRA) and the influence of risk factors for stroke. We studied 230 adult patients without specific neurological deficits. MRA was performed using the three-dimensional time-of-flight technique with a spoiled gradient-recalled acquisition sequence. We classified internal carotid artery (IC) and the horizontal (M1) and distal (beyond M2) middle cerebral segments into 4 grades. Linear regression revealed a significant negative relation between age and the quality of demonstration on MRA. For IC and M1, the score was significantly lower in subjects with risk factors than in those without. The distal MCA was poorly seen in patients without a history of hypertension or lacunar infarcts. A marked correlation was observed between visibility and age patients with no history of hypertension, diabetes mellitus and hyperlipidaemia. We suggest that atherosclerotic change and decline in flow velocity with normal ageing are factors leading to decreased visibility on MRA.
    No preview · Article · Dec 1999 · Neuroradiology
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    ABSTRACT: We examined the diagnostic use of isotropic diffusion-weighted (DW) MRI in 140 consecutive patients suspected of or diagnosed as having an ischaemic stroke. Isotropic DW imaging could demonstrate the lesion responsible for the clinical deficit in patients with multiple cerebral infarcts at an early stage, even small lesions without a perifocal oedema or mass effect. Accurate diagnosis by DW images may, however, be difficult about 2 weeks after the onset of stroke.
    No preview · Article · Nov 1999 · Neuroradiology
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    ABSTRACT: Endothelial nitric oxide synthase (eNOS) may play an important role in the regulation of tumor blood flow and vascular permeability. However, there have been no reports describing alterations of eNOS expression in relation to malignant progression in human astrocytic tumors. We immunohistochemically studied the relationship between eNOS expression in tumor vasculature and malignancy in supratentorial astrocytic tumors. Tissue samples were obtained from 12 patients with low-grade astrocytomas, 10 with anaplastic astrocytomas, and 17 with glioblastomas. Normal brain tissue samples were obtained from four patients with other brain diseases. Immunohistochemical staining was performed using the avidin-biotin complex method, with polyclonal anti-eNOS antibody, and the levels of eNOS expression in endothelial cells were evaluated as slight, moderate, or intense on the basis of eNOS immunoreactivity. The proliferative potential was assessed as the MIB-1 staining index for tumor cells. The expression of eNOS was slight in all specimens of normal brain tissue, slight in 7 and moderate in 5 specimens of low-grade astrocytoma, slight in 2, moderate in 6, and intense in 2 specimens of anaplastic astrocytoma, and moderate in 5 and intense in 12 specimens of glioblastoma. The MIB-1 staining index (mean+/-standard deviation) was 0.2+/-0.2% for normal specimens, 1.8+/-0.6% for low-grade astrocytomas, 9.6+/-6.9% for anaplastic astrocytomas, and 18.5+/-7.7% for glioblastomas. The MIB-1 staining indices for slight, moderate, and intense eNOS expression were 2.0+/-2.3%, 10.8+/-9.8%, and 16.9+/-7.7%, respectively. Expression of eNOS in tumor vessels was significantly correlated with histological grade and proliferative potential. These findings suggest that astrocytic tumor vessels possess higher activity for nitric oxide production than do normal vessels.
    No preview · Article · Aug 1999 · Neurosurgery
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    ABSTRACT: MR angiograms from 200 neurologically normal subjects aged 30 to 79 years were analyzed to assess the influence of aging and hypertension on the degree of the--visualization of the cerebral arteries. The degree of MR visualization of the cerebral arteries, including the IC, M 1, and distal MCA, was evaluated on a 4-degree scale. IC and M 1 differ in appearance. The MR gradings of each cerebral arteries showed a significant (p < 0.001) negative correlation with age. Hypertension, which is a risk factors for arteriosclerosis, significantly reduced MR grade. The degree of visualization of M 1 and the distal MCA decreased significantly with age in the normotensive group. Therefore, the decrease visualization of the cerebral arteries appears to involve not only cerebral arteriosclerosis but other factors associated with aging.
    No preview · Article · Apr 1999 · Nō to shinkei = Brain and nerve
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    ABSTRACT: Some adult patients with moyamoya disease have been treated successfully by indirect revascularization alone, although surgical indications and hemodynamic changes for these patients have not been fully explored. To examine surgical indications for this procedure, we studied the regional cerebral blood flow (rCBF) and angiographic findings in adult patients with moyamoya disease preoperatively and postoperatively. On 17 hemispheric sides of 12 adult patients with moyamoya disease treated surgically with a combination of various indirect procedures, mainly by encephaloduroarteriosynangiosis, we retrospectively evaluated changes in rCBF using xenon-133 single photon emission computed tomography, angiographic collateral formation, and clinical results. Preoperatively, the rCBF values in the cortices at the bypass site at rest and after acetazolamide loading were lower than normal. The rCBF values were significantly increased after revascularization, approaching normal, except for incomplete recovery of vascular reactivity. The extent of postoperative neovascularization from implanted tissues fed by the external carotid artery system was more developed, in parallel with the preoperative decrease in resting and loading rCBF values. One-third of the operated sides exhibiting both a low rCBF at rest and impaired vascular reactivity in the noninfarcted cortices achieved good revascularization over two-thirds of the middle cerebral artery territory, accompanied by rCBF improvement and moyamoya vessel regression. Enough potential for neovascularization in the noninfarcted cortices was indicated that the resting rCBF was lower than 50 ml/100 g per minute (below the normal value by 2 standard deviations) and did not increase more than that value after loading, even in a 40-year-old patient who presented with a hemorrhage. Clinically, 11 patients (92%) had good results at the 4-year follow-up, whereas 1 patient (8%) with unsatisfactory neovascularization and a lesser extent of moyamoya vessel reduction experienced rebleeding. We conclude that for the surgical treatment of adult patients with moyamoya disease, indirect procedures, mainly encephaloduroarteriosynangiosis, are recommended for patients with lower rCBF and no or negative vascular reactivity in the noninfarcted cortices, as well as for those who have no indication for the direct procedure. It is possible to determine these indications by a xenon-133 inhalation single photon emission computed tomographic study including an acetazolamide challenge test.
    No preview · Article · May 1998 · Neurosurgery
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    ABSTRACT: We conducted neuropsychological testing of 86 patients who had undergone operation for subarachnoid hemorrhage (SAH) due to ruptured aneurysm 6 months to 1.5 years after onset. All patients were assessed as Good Recovery according to the Glasgow Outcome Scale. The battery of neuropsychological tests consisted of the Mini Mental State Examination (MMS), Kohs's block design test, Paired associate learning test, and “Kanahiroi” test.All patients examined by MMS 1.5 years after SAH were normal. Visuoconstructional cognition examined by Kohs's block-design test was impaired in about 40% and long-term memory was impaired in 20-60%. Further, 30% of the patients had frontal dysfunction investigated by “Kanahiroi” test. Multivariate analysis proved significant harmful effects of the neurological grade on onset (Hunt & Kosnik grade) on “Kanahiroi” test and paired associate learning test.In a series of neuropsychological tests, the scores slightly improved by 1 year after SAH, whereas almost none of the patients exhibited improvement in test scores. These findings suggest that neurophycological deficits after SAH was permanent.
    No preview · Article · Jan 1998 · Surgery for Cerebral Stroke
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    ABSTRACT: Some types of carotid-ophthalmic artery aneurysms are still difficult to clip successfully because their exposure requires opening the cavernous sinus and/or retracting the optic nerve. It is useful to know the complications and to determine the type of aneurysm preoperatively for the management of carotid-ophthalmic artery aneurysms. The operative results in 15 patients with asymptomatic unruptured carotid-ophthalmic artery aneurysms were surveyed. The aneurysms were small in all the patients, and they underwent direct operation. Four patients presented with other ruptured aneurysms, four with other diseases (infarction, trauma, or pituitary adenoma), and seven were evaluated with magnetic resonance angiography for symptoms such as vertigo or headache. Among them, five had carotid cave aneurysms and one had paraclinoid aneurysm. Neck clipping was performed in 13 patients. Postoperatively, ipsilateral visual loss was encountered in one patient, and ipsilateral visual field defect was encountered in three patients. The visual field defect was lower nasal quadrant hemianopsia in two patients and lower hemianopsia in one patient. The cause of this complication was suspected to be retraction and/or the heat of the drill near the optic nerve. It seemed to be possible to distinguish the carotid cave or the paraclinoid aneurysm from the other carotid-ophthalmic aneurysms using carotid angiography preoperatively. When direct operation is performed for a carotid-ophthalmic artery aneurysm, care must be taken to avoid optic nerve injury caused by the retraction and/or the heat of the drill.
    No preview · Article · Dec 1997 · Surgical Neurology
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    ABSTRACT: Expansive laminoplasty of several types has been proposed for patients with cervical multisegmental stenotic myelopathy to reduce postlaminectomy complications. Its effectiveness has not been fully explored by evaluating long-term results and magnetic resonance imaging (MRI) findings before and after surgery. We conducted a 5-year follow-up study of 22 patients with cervical spondylotic myelopathy and/or ossification of the posterior longitudinal ligament surgically treated with expansive laminoplasty. The operative results were examined using the Japanese Orthopedic Association (JOA) disability scale, with reference to the findings of MRI, computed tomography, and radiography. Postoperative improvement was observed in 18 (81.8%) of the 22 patients. In 11 patients the percentage recovery of the JOA score was higher than 50% (average: 83.1%), while in the remaining 11 patients it was lower than 50% (average: 20.1%). Factors contributing to incomplete recovery appear to be related mainly to cord degeneration with atrophy (depicted as a T2-high intensity area) and to specific factors such as long symptom duration, age higher than 70 years, deterioration due to trauma, severe cord compression, radiculopathy, and kyphotic cervical curvature. In cervical myelopathy, patients with multisegmental stenosis, expansive laminoplasty can be expected to provide a favorable outcome by providing sufficient cord decompression and stabilization of the cervical spine, when the stenotic cervical canal is enlarged to the normal range (over 12 mm residual anteroposterior diameter and 200 mm2 residual canal area). The efficacy can be restricted by various factors, especially irreparable cord degeneration.
    No preview · Article · Sep 1997 · Surgical Neurology
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    ABSTRACT: We retrospectively studied 27 adult patients (male 9, female 18) with moyamoya disease, with and without vascular reconstructive surgery, with respect to angiographical finding, regional cerebral blood flow (rCBF) and long-term prognosis. Initial episodes involved intracranial hemorrhage in 20 cases (74%), ischemia in 6 cases and incidental detection in 1 case. Of 14 non-revascularization cases, 9 patients (64%) bled during 9 years follow-up. The recurrent bleeding rate in 10 cases of the hemorrhage type excluding aneurysm cases was calculated to be as high as 65% for 10 years. In the final outcome, 10 patients (71%) showed a poor prognosis including 5 who died due to rebleeding. The rCBF measured by 133Xe SPECT in the bilateral middle cerebral artery territory of 6 patients revealed 41±15 ml/100 g/min at rest and 48±18 ml/100 g/min after acetazolamide loading, indicating a percent increase of 20±22%. Thirteen cases were surgically treated on 22 hemispheric sides, by direct bypass (7 sides) and indirect bypass (15 sides) surgery. Postoperative angiogram demonstrated good neovascularization from the external carotid artery in 15 hemispheric sides (68%); all sides of direct procedure and half the sides of indirect procedure. Of these 15 sides, 14 sides (93%) showed reduction of moyamoya vessels fed by the internal carotid artery. Only 1 patient (8%) among 13 cases undergoing revascularization bled during 5-year follow-up and the other 12 patients returned to their previous jobs. The rCBF measured in the area fed from the bypass circuit in 18 hemispheres of 11 patients was preoperatively. 48±9 ml/100 g/min at rest and 53±15 ml/100 g/min after acetazolamide loading, indicating a percent increase of 8±17%. Postoperative study revealed the resting and loading rCBF significantly increased by around 30% to 60±6 and 70±9 ml/100 g/min, respectively, indicating a percent increase of 16±8%. Thus, vascular reconstructive surgery is recommended for adult patients with moyamoya disease, since the long-term prognosis of non-surgical cases is poor due to recurrent bleeding and surgery tends to inhibit recurrence of bleeding. The development of good collaterals from implanted external carotid artery can improve the cerebral blood flow and vascular reactivity at the bypass site leading to reduction of hemodynamic stress on basal moyamoya vessels. For this purpose, direct bypass surgery seems to be superior to indirect bypass surgery.
    No preview · Article · Jan 1997
  • K. Kohno · Y. Kawada · Y. Oka · S. Ohta · Y. Kumon · S. Sakaki
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    ABSTRACT: The authors report a child with moyamoya disease who repeated acute progression of major arterial stenosis on the contralateral side after two staged vascular reconstructive surgery. An 8-year-old boy had frequent transient ischemic attacks involving the left extremities starting at 1 years of age. Cerebral angiogram revealed right internal carotid artery (ICA) occlusion and typical moyamoya vessels in the right basal ganglia, while left anterior cerebral artery (ACA) and middle cerebral artery (MCA) showed only stenotic configurations without moyamoya vessels. Cerebral blood flow (CBF) measurement using 133Xe SPECT demonstrated low CBF and negative response to Diamox loading in the territories of the right MCA, ACA, part of the posterior cerebral artery (PCA) and the left ACA. We initially performed indirect reconstructive surgery on the affected right MCA and ACA territories, followed by cerebral infarct in the left frontal lobe 34 days after surgery due to the left ICA occlusion. One month later, we added left STA MCA anastomosis, followed again by cerebral infarct in the right occipital lobe 1 month after surgery due to right PCA occlusion. Thus, we underscore the necessity for careful postoperative observation of progressive major arterial stenosis using magnetic resonance angiography in pediatric patients with moyamoya disease undergoing indirect or direct reconstructive surgery of 1 hemisphere. In such patients, performing one staged extensive indirect reconstructive surgery may be prudent, covering whole areas where preoperative CBF measurement revealed low CBF at rest and impairment of vascular reactivity on Diamox loading.
    No preview · Article · Jan 1997