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Biomedical subjects

K Takemoto

Publications and source records attributed to K Takemoto.

167 records · Page 10Linked to original sources
PubMedDate not supplied

Displacement of the quadrigeminal plate in tumors of the fourth ventricle: MR appearance.

Magnetic resonance studies of 12 fourth ventricle tumors were reviewed. The relationship between the tumor and surrounding structures, such as the corpus medullare, the superior medullary velum, and the quadrigeminal plate, was assessed on midsagittal inversion recovery images. Two of the 12 tumors displaced the superior medullary velum superiorly. Seven of the 12 tumors displaced the corpus medullare posteriorly. The superior medullary velum was not recognized in 10 cases and the corpus medullare in 5. Ten of 12 quadrigeminal plates were displaced superoposteriorly due to focal enlargement of the cerebral aqueduct secondary to large intraventricular tumors. In the remaining two cases the tumor was not large enough to enlarge the cerebral aqueduct. The larger the tumor was, the more frequent was the displacement of the quadrigeminal plate. On T2-weighted images, CSF flow-void sign was seen around the tumor in 5 of 12 cases. We consider superoposterior displacement of the quadrigeminal plate to be a relatively constant and reliable sign accompanying fourth ventricle tumors.

Cerebral Aqueduct↗
PubMedDate not supplied

MR imaging of Wallerian degeneration in the brainstem: temporal relationships.

Degeneration of the myelin sheath and axon distal to the most proximal site of axonal interruption secondary to axonal disease has been called wallerian degeneration. On MR imaging, wallerian degeneration of the pyramidal tract can be observed as an abnormal signal intensity, showing prolonged T1 and T2 relaxation times that correspond to the corticospinal tract, with or without shrinkage of the ipsilateral cerebral peduncle and pons. Review of MR studies in 150 cases of supratentorial cerebrovascular accidents showed abnormal signal alterations in the ipsilateral brainstem in 33 of the cases. Abnormal intensity in the ipsilateral brainstem was seen as early as 5 weeks after the supratentorial ictus and was fully evident after 10 weeks in all 33 cases. Signal alterations were strongest at about 3-6 months when compared with alterations seen at 10 weeks or even 10 months after the ictus. Shrinkage of the ipsilateral brainstem appeared as early as 8 months and was demonstrated in all cases 13 months after the ictus. MR seems to be the most effective technique for early detection of wallerian degeneration and may provide insight into its pathophysiological and chemical changes.

Adult↗
PubMedDate not supplied

MR imaging of multiple sclerosis in the cervical cord.

This is a case of a 34-year-old woman with multiple sclerosis (MS) in whom an enlarged cervical spinal cord with long T1 and T2 relaxation times was demonstrated on MR images. This report seems to be the first description of MR imaging of MS with an enlarged spinal cord.

Adult↗
PubMedDate not supplied

Thin section CT of normal pituitary glands.

In order to better understand the CT appearance of the normal pituitary gland, we scrutinized the pituitary glands of 55 patients who had no clinical indication of pituitary abnormality. The superior surface of the pituitary gland was convex in 9 cases (16.4%), flat in 16 (29.1%), and concave in 30 (54.5%). All but one of the glands with upward convexity belonged to patients less than 40 years old. The height of the pituitary glands was from 2 mm to 7 mm in 48 (87.3%) and 7 mm to 9.1 mm in 7 (12.7%); all but one case was less than 40 years old. Although earlier reports have suggested the presence of a pituitary microadenoma when the gland has a convexity of its superior surface or is more than 7 mm in height, these findings can be seen in normal pituitary glands, particularly in younger individuals. Therefore, pituitary microadenoma should be diagnosed carefully in younger patients. The low density area frequently seen in the superior aspect of pituitary glands on axial scans was found to result from the concave superior surface of the gland. The pituitary stalk was off the midline in five patients (9%). Shifting of the pituitary stalk can be seen in the normal pituitary gland and is not always characteristic of microadenoma.

Adolescent↗