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N Hirabuki

Publications and source records attributed to N Hirabuki.

At least 37 records · Page 2Linked to original sources
PubMed1998

Transition of the craniocaudal velocity of the spinal cord: from cervical segment to lumbar enlargement.

RATIONALE AND OBJECTIVES: The authors investigate the craniocaudal velocity of the spinal cord over its full length by using magnetic resonance imaging. METHODS: A spin-echo pulse sequence with velocity encoding gradients was used to examine five normal volunteers. Oblique-axial phase images at nine levels, from cervical spinal cord to lumbar enlargement, were obtained with prospective electrocardiogram gating. Time-velocity curves were then generated for these levels. RESULTS: Every part of the spinal cord moves first caudally after the R-wave of the electrocardiogram, then cranially. When compared with the cranial levels, peak velocity tend to occur later and their values tend to be smaller at the more caudal levels. CONCLUSIONS: Craniocaudal velocity is transmitted from cervical segment to lumbar enlargement.

Adult↗
PubMed1998

Epidermoid tumor of the cerebellopontine angle: signal loss in the contralateral cistern.

We report a case of an epidermoid tumor of the right cerebellopontine angle (CPA) in which the contralateral CPA cistern showed abnormal, low signal intensity on T2-weighted fast spin-echo MR images. Diffusion-weighted images showed the epidermoid tumor of the right CPA extending to the prepontine cistern. The cause of the abnormal signal intensity was proved to be an artifactual signal loss due to cerebrospinal fluid flow by phase-contrast MR imaging.

Aged↗
PubMed1997

Craniocaudal motion velocity in the cervical spinal cord in degenerative disease as shown by MR imaging.

PURPOSE: To investigate, by means of MR phase imaging, the effects of compression on the velocity of craniocaudal motion in the spinal cord. MATERIAL AND METHODS: Spin-echo pulse sequences with velocity encoding gradients were used to examine 12 patients with cervical spondylosis and 6 normal volunteers. Oblique-axial phase images at 3 levels (cranial, middle and caudal), were obtained with prospective electrocardiogram gating. The middle level was set at the site where the spinal cord was most severely compressed, and the cranial and caudal sections were set where it was not compressed. Time-velocity curves were generated at these 3 levels and focal velocity change was correlated with motor function in the lower extremities. RESULTS AND CONCLUSION: The cord showed a higher motion velocity at the compression level than at noncompression levels. This paradoxical increase in velocity was observed in 7 out of 8 patients whose lower extremity motor function was impaired. Four patients with normal lower extremity motor function did not demonstrate this increase in velocity. An increase in motion velocity was therefore found to correlate with impaired lower extremity motor function.

Adult↗
PubMed1994

MR appearance of Virchow-Robin spaces along lenticulostriate arteries: spin-echo and two-dimensional fast low-angle shot imaging.

PURPOSE: To delineate the appearance of normal Virchow-Robin spaces on routine spin-echo images and demonstrate the lenticulostriate arteries within them with a flow-sensitive fast low-angle shot (FLASH) pulse sequence. METHODS: Seventy subjects, free of cerebrovascular diseases and other neurologic disorders, ranging in age from 1 to 75 years, were examined. On a 1.5-T MR system, axial spin-echo images of 5 mm thickness were obtained in all subjects. In 45 of 70 subjects axial two-dimensional FLASH images of 3 mm thickness were continuously imaged. RESULTS: On T1- and spin density-weighted images Virchow-Robin spaces were detected as small foci of cerebrospinal fluid intensity around the anterior commissure in all subjects (100%), and in the basal ganglia at the level of the foramen of Monro in 40 (57%). T2-weighted images equally showed Virchow-Robin spaces around the anterior commissure but were less sensitive than T1- and spin-density weighted images at the level of the foramen of Monro (14%). Virchow-Robin spaces identified on T2-weighted images should be isointense with cerebrospinal fluid. However, one or two spaces in 11 younger subjects were hypointense relative to adjacent brain tissue. On FLASH images most Virchow-Robin spaces identified on spin-echo images were delineated as high-intensity foci, corresponding to lenticulostriate arteries. CONCLUSIONS: Normal Virchow-Robin spaces along the lenticulostriate arteries are frequently detected on spin-echo images. Their appearance, affected by the flow of associated lenticulostriate arteries, varies from hyper- to hypointensity to brain tissue on T2-weighted images. The two-dimensional FLASH sequence can demonstrate the flow of the arteries, thereby helping confirm that these are truly Virchow-Robin spaces.

Adolescent↗
PubMed1994

MR imaging of middle cerebral artery stenosis and occlusion: value of MR angiography.

PURPOSE: To investigate the effectiveness of MR angiography in conjunction with spin-echo imaging for evaluating vascular patency in patients with middle cerebral artery (MCA) stenosis or occlusion. METHODS: Seven patients with MCA stenosis or occlusion, verified with contrast angiography in five and correlated with transcranial Doppler sonography in two, were examined using two-dimensional and/or three-dimensional time-of-flight MR angiographic techniques as well as conventional spin-echo imaging. RESULTS: Of the seven patients, six demonstrated basal ganglionic and/or cortical infarct in the MCA territory. Except one case with minimal stenosis immediately distal to the MCA origin, all six cases with either severe stenosis or occlusion of the main trunk of the MCA showed the absence of normal flow voids using spin-echo imaging in the sylvian fissure on the affected side. However, it was not possible to discriminate between stenosis and occlusion. Although different mechanisms (ie, flow-induced spin dephasing for the 2-D technique and progressive spin saturation for the 3-D technique) were predominantly responsible for the loss of signal through the area of stenosis, both the 2-D and 3-D MR angiograms clearly depicted the compromised flow of the MCA: a focal discontinuity with decreased vessel caliber corresponded to stenosis, and nonvisualization of distal MCA branches represented occlusion. CONCLUSION: Either 2-D or 3-D time-of-flight MR angiography is a useful adjunct to conventional parenchymal spin-echo imaging for evaluating vascular patency in patients with MCA stenosis or occlusion, although it is important to recognize that each technique has a different basis for the loss of signal through the area of stenosis.

Adult↗
PubMed1992

Follow-up MRI in dural arteriovenous malformations involving the cavernous sinus: emphasis on detection of venous thrombosis.

Six patients with a dural arteriovenous malformation (dural AVM) involving the cavernous sinus were followed up with magnetic resonance imaging in order to assess change in the lesions. Spin-echo (SE) imaging of three patients in whom the AVM appeared to have closed at least 1 month earlier (two of them spontaneously, and one after external carotid artery embolization) showed neither apparent flow void in the involved cavernous sinus nor evidence of venous thrombosis. SE images of the other three patients who had not been cured by external carotid artery embolization (two of whom were examined within a week of treatment), detected persisting arteriovenous shunts, including high-flow cortical venous drainage, seen as flow void. Two-dimensional time-of-flight MR angiography (2D TOF MRA) was performed simultaneously in three patients. Whereas shunting blood and the normal cavernous sinus were of high intensity, presumed thrombosed cavernous sinuses were isointense with stationary brain tissue. SE imaging can confirm the resolution of arteriovenous shunts, but poorly delineates very acute and chronic thrombosis of the draining veins. In contrast, 2D TOF MRA directly demonstrates flowing blood, permitting the diagnosis of venous thrombosis; it should be included in follow-up of a dural AVM involving the cavernous sinus when venous thrombosis is suspected.

Adult↗
PubMed1991

Nerve root avulsion of birth palsy: comparison of myelography with CT myelography and somatosensory evoked potential.

Findings at myelography and computed tomographic (CT) myelography were reviewed in 21 patients (22 limbs) with birth palsy; nerve root shadows were the focus of this study. Myelography demonstrated 51 completely avulsed roots (78%) and 14 incompletely avulsed roots (22%). A traumatic meningocele was detected at 38 roots on myelograms and 51 roots on CT myelograms. Thirteen avulsed roots (eight completely and five incompletely avulsed roots) (20%) were not associated with a meningocele. In nine patients who underwent brachial plexus exploration, myelographic findings were compared with root somatosensory evoked potential (SEP). SEP was not induced at 22 of 25 completely avulsed roots and was induced at all seven incompletely avulsed roots. Myelography and SEP were consistent in 29 of 32 roots (91%). It is concluded that myelography is indispensable for preoperative evaluation of cervical nerve root avulsion of birth palsy, because CT myelography is not sensitive to nerve root avulsion without a traumatic meningocele, and SEP cannot enable one to discriminate incomplete avulsion from intact roots.

Brachial Plexus↗
PubMed1990

[Myelography for nerve root avulsion in birth palsy].

Myelography and CT myelography (CTM) were reviewed in 18 cases of birth palsy with clinically suspected avulsion injury. Root-somatosensory evoked potential (root-SEP) was also reviewed for myelographic evaluation of the nerve root avulsion in birth palsy. Root-SEP is not induced in case of avulsed nerve roots, but is induced in case of both normal and incompletely avulsed roots. Myelography demonstrated 58 abnormal nerve roots in 18 cases (19 limbs); 45 (78%) complete and 13 (22%) incomplete nerve root avulsions. Each of complete and incomplete avulsions was defined as total absence and partial presence of rootlets on myelography, respectively. Traumatic meningoceles were detected at 46 roots (79%) on myelography and/or CTM; 35 roots on myelography and 45 roots on CTM. CTM could not detect only a very small meningocele at one root. At 11 roots CTM was superior to myelography in delineating a meningocele because CTM is sensitive to a poorly enhanced meningocele. CTM, however, could not diagnose nerve root avulsions so accurately as myelography, since myelography detected 12 (7 completely and 5 incompletely) avulsed roots without meningocele, whereas CTM could not delineate the nerve roots clearly. Thus, myelography is indispensable to evaluate nerve root avulsions without meningocele. Root-SEP was examined in 9 patients who underwent brachial plexus exploration. SEP was negative at 22/25 roots with complete avulsion and was positive at 7/7 roots with myelographically incomplete avulsion, regardless of presence or absence of any traumatic meningocele.(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗
PubMed1990

Computed tomographic findings of nasopharyngeal carcinoma with skull base and intracranial involvement.

Twenty-nine patients with nasopharyngeal carcinoma (NPC) with skull base or intracranial involvement were analyzed by high-resolution computed tomography (CT). We divided the path of the primary tumor spread into six directions from the nasopharynx. The most common direction of spread was the anterior region, and the second most common was the posterolateral region. Recently, high resolution CT has been used for the diagnosis of the nasopharynx. T-staging of NPC was made according to the International Union Against Cancer (UICC) TNM classification system, depending on clinical findings and conventional radiograph examinations (not including CT). CT images were valuable for detection of the primary tumor involvement of the skull base region in NPC. Furthermore, bone target CT images were better for searching for subtle bony changes. Therefore, we recommend that CT should be used in T-staging of NPC systematically. When CT is used as one of the staging criteria, some patients with NPC with subtle bony changes will be upstaged.

Adolescent↗
PubMed1990

Cranial metastasis from hepatocellular carcinoma.

We describe a case of cranial metastasis from an hepatocellular carcinoma studied by computed tomography and cerebral angiography. Although two similar cases have been reported, ours is the first that shows the angiographic findings so clearly and to present with neurological symptoms before primary disease was evident.

Adult↗
PubMed1990

External carotid artery embolization of dural arteriovenous malformations involving the cavernous sinus. Outcome and role of venous thrombosis.

Nine patients with dural arteriovenous malformations (AVMs) in the region of the cavernous sinus were treated by means of external carotid artery (ECA) embolization using polyvinyl alcohol. All AVMs received vascular supply from both the ECA and the internal carotid artery. Seven cases were clinically cured after embolization, while 2 cases with cortical venous drainage and high flow through the shunt were not completely cured. Venous thrombosis was observed in 5 cases before and in 9 after embolization. In 6 cases the drainage pattern changed owing to venous thrombosis. Complete thrombosis of the cavernous sinus was found on a follow-up angiography in 2 cases. Formation of venous thrombosis and occlusion of feeding arteries are crucial factors for success of ECA embolization. Dural AVMs with cortical venous drainage and high flow cannot be relieved by ECA embolization alone owing to difficulty in obtaining thrombosis of the veins.

Adult↗
PubMed1989

[Evaluation of CT myelography and conventional myelography for avulsion injury of nerve root--18 cases of birth palsy].

CT myelography (CTM) and conventional myelography were reviewed in 18 cases of birth palsy with clinically suspected avulsion injury. A traumatic meningocele was detected in 45 roots by CTM, and in 35 roots by myelography. CTM misinterpreted only one root with a very small meningocele. CTM was superior to myelography in delineating a traumatic meningocele, because CTM is sensitive to a poorly enhanced meningocele. On the other hand, CTM missed 9 avulsed roots without a meningocele. By myelography, these 9 roots were diagnosed as 6 roots of complete avulsion injury and 3 roots of incomplete avulsion. Myelography is indispensable in evaluating nerve root avulsion.

Child↗
PubMed1989

[Adverse reactions and intracranial contrast medium after myelography].

Correlation between adverse reactions and intracranial contrast media after myelography was studied. Myelography was carried out for 12 cases with metrizamide and 14 with iotrolan. In all patients, cranial CT scans were performed 18 approximately 22 hours after myelography. CT attenuation value of subarachnoid cistern was higher than the gray matter in 12 cases and lower in 14 cases. Six cases suffered from adverse reactions, but only 1 case belongs to the higher group. No correlation between adverse reactions and residual amount of contrast medium on CT was recognized.

Adult↗
PubMed1988

MR imaging of dural arteriovenous malformations with ocular signs.

Four patients with dural arteriovenous malformation (AVMs) draining into the cavernous sinus, who presented ophthalmic manifestations, were studied by magnetic resonance (MR) imaging. In all patients signal decrease in the involved cavernous sinus was demonstrated in coronal spin-echo (SE) imaging. It is attributable to rapid venous flow in the sinus, and this "high velocity signal loss" is a fairly pathognomonic finding in this condition. We stress the validity of MR imaging in the primary diagnosis of dural AVMs with ophthalmic symptoms.

Arteriovenous Malformations↗