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Biomedical subjects

A Hakuba

Publications and source records attributed to A Hakuba.

136 records · Page 8Linked to original sources
PubMedDate not supplied

MR imaging of dural AV fistulas at the cavernous sinus.

The magnetic resonance appearance of dural arteriovenous fistulas (AVFs) at the cavernous sinus (CS) was studied in six angiographically verified cases. Magnetic resonance clearly demonstrated shunted blood as an area of signal void both in the CS and in the superior ophthalmic vein. The relationship between shunted blood, internal carotid artery, and extraocular nerves, as well as proptosis, enlargement of the extraocular muscles, and bulging of the lateral wall of the CS were also depicted in the images. Normal venous flow in the involved CS was shown as a low signal area that enhanced after gadolinium administration. Magnetic resonance is useful for screening and follow-up examinations of dural AVFs at the CS. It is essentially a noninvasive procedure that may be repeated and obviates the need for follow-up angiography. However, it should be noted that a signal void in the CS sometimes represents normal venous flow. A definite diagnosis should rely on angiography, which is essential for therapeutic planning.

Aged↗
PubMedDate not supplied

PET for diagnosis of malignant lymphoma of the scalp: comparison of [11C]methyl-L-methionine and [18F]fluoro-2-deoxyglucose.

A 43-year-old woman was admitted with a tumor mass in her forehead. Two months previously, a lump in her breast had been diagnosed as mastopathy. Palpation revealed an elastically hard immobile tumor mass in her forehead. MRI detected a tumoral lesion of generally uniform contrast involving frontal subcutaneous, cranial, and intracranial regions. PET demonstrated more intensive and wider accumulation of [11C]methyl-L-methionine (Met) than of [18F]fluoro-2-deoxyglucose (FDG). Biopsy of the forehead mass was performed, which was diagnosed as B-cell-type malignant lymphoma. The tumor mass in the forehead then shrank spontaneously, as confirmed by palpation and MRI. The tumor mass in the left breast was totally extirpated and histologically diagnosed as B-cell-type malignant lymphoma, like the tumor mass in the forehead. Postoperatively, chemotherapy (VEPA) was performed. Although FDG accumulation had not been detected, postchemotherapy PET demonstrated slight Met accumulation, suggesting the presence of a residual tumor. PET served well to detect the lesion and evaluate therapeutic efficacy in malignant lymphoma. Met-PET was more sensitive to malignant lymphoma than FDG-PET.

Adult↗
PubMedDate not supplied

Pathogenesis of encephaloschisis in retinoic-acid-treated hamster embryos I: a morphometric study of the craniofacial structures.

The severity of the developmental disorders of the paraxial mesoderm and neuroectoderm must objectively be compared to determine which of the two structures is more deeply involved in the pathogenesis of encephaloschisis. In the present study, hamster fetuses were obtained from dams that had been treated with retinoic acid, and divided into two groups: fetuses with encephaloschisis and those without apparent external malformations in the cranium and face. Mid-sagittal serial sections of the head were prepared, histologically processed, and utilized for the reconstruction of the profile of the head structures. Using this reconstructed profile, we measured the length of the skull base bone structures (basisphenoid and basiocciput), which develop from the paraxial mesoderm, brain structures (mesencephalon and metencephalon), which develop from the neuroectoderm, and facial bone structures (nasal septum and hard palate), which develop from cephalic neural crest cells. The measured length of each structure was compared between the treated and control groups. It was found that treatment with retinoic acid resulted in significantly (P < 0.05) shortened lengths of the skull base bone structures both in fetuses with encephaloschisis and those without apparent external malformations in the cranium and face. In the brain structure of fetuses without encephaloschisis, as well as in the facial bone structures, however, this shortness was not observed. These results suggest that developmental disorders in the paraxial mesoderm may play an important role in the pathogenesis of encephaloschisis.

Animals↗
PubMedDate not supplied

A hypothesis of epiarachnoidal growth of vestibular schwannoma at the cerebello-pontine angle: surgical importance.

AIMS: The purpose of this study is to clarify the rearrangement of the arachnoid membrane on the vestibular schwannoma during its growth in relation to adjacent neurovascular structures for a better understanding of dissecting plane of arachnoid during surgery. METHODS: Arachnoid membrane over the tumour was investigated during surgery with suboccipital transmeatal approach in twenty-six tumours. All microsurgical procedures were recorded with a video and reviewed. The tumour growth was classified into five stages depending upon the tumour diameter in the cerebello-pontine (CP) angle: Stage 1; purely intracanalicular (2 cases), Stage 2; less than 5 mm (2 cases), Stage 3; > or = 5 and <15 mm (8 cases), Stage 4; > or = 15 and <25 mm (9 cases) and Stage 5; > or = 25 mm (5 cases). Rearrangement of the arachnoid on the tumour was conceptualised throughout all stages. RESULTS: All tumours of Stage 1 and 2 were entirely located in the subarachnoid space of the cerebello-pontine cistern without arachnoidal rearrangement, while all tumours of Stages 3 to 5 were enveloped, in the CP angle, with invaginated arachnoid membrane consisting of cerebello-pontine cistern except two surfaces; the medial pole and the tumour surface under the facial and cochlear nerves near the porus. CONCLUSION: The tumour originates subarachnoidally within the internal auditory meatus (IAM) and grows epiarachnoidally in the CP angle. Rearrangement of the arachnoid begins with its adhesion on the medial pole of the tumour along the porus, resulting in the arachnoidal invagination into the cerebello-pontine cistern with further growing of the tumour.

Adult↗
PubMedDate not supplied

MR imaging: possibility of tissue characterization of brain tumors using T1 and T2 values.

To evaluate the usefulness of T1 and T2 values for tissue characterization of brain tumors, 37 histologically confirmed brain tumors were examined with a 0.5-T superconductive MR system. With spin-echo and inversion-recovery imaging sequences, computed T1 and T2 images were reconstructed, and T1 and T2 values of the tumors were calculated. Relaxation rates (1/T1 and 1/T2), T1/T2 ratios, and malignancy indexes, which were originally designed for gastrointestinal tumors, were also calculated. Values of all these parameters were so wide-ranged that it was impossible to characterize the tumor tissue types.

Adenoma↗
PubMedDate not supplied

MR imaging of brainstem hemorrhage.

To determine the chronologic changes in the MR appearance of brainstem hemorrhage and to evaluate the clinical efficacy of MR imaging, 15 patients were examined with a 0.5-T MR scanner with inversion-recovery (IR) and T2-weighted spin-echo (SE) images. In the acute stage (up to the sixth day), hematomas were hypo- or isointense on IR images and isointense and then hypointense on SE images. In the subacute stages (the seventh day to 2 months), hematomas changed from hypo- or isointensity to hyperintensity centripetally on IR images and to hyperintensity on SE images. Parenchymal reactions were hypointense first on SE images and then on IR images. In the chronic stage (over 2 months), hematomas "disappeared" and the parenchyma was hypointense on both IR and SE images. The superior clinical efficacy of MR imaging relative to CT for the detection of hemorrhage was obvious except in the acute stage, when hematomas had an intensity similar to that of the adjacent brainstem, and the patients usually were in serious condition.

Adult↗
PubMedDate not supplied

MR imaging of blood flows in the cavernous sinus.

To evaluate blood flows in the cavernous sinus (CS), seven normal CSs and a postmortem CS were evaluated using T1-weighted spin echo sequences. After the noncontrast study, contrast study with Gd-DTPA was performed in all cases except the postmortem one. In the normal CSs, arterial flows of the intracavernous carotid artery (ICA) were disclosed as no-signal areas in the noncontrast study and were not enhanced with Gd-DTPA. Most venous flows in the CS were seen as low-intensity areas in the noncontrast study and were markedly enhanced with Gd-DTPA. However, these low-intensity areas were heterogeneous in intensity and several were higher and lower in intensity compared with most venous spaces. In the postmortem case, the CS showed homogeneous low intensity due to the stasis of blood flow. It was thought that the heterogeneous appearance of venous spaces in the normal CSs was due to flow-related phenomena. This heterogeneous pattern of signal intensity suggested the distribution of flow velocities. MR demonstrated both arterial and venous flows, and this was facilitated by Gd-DTPA. MR is a promising modality for the demonstration of blood flows in the CS.

Adult↗