Reinin Asato

Posterior Lobe of the Pituitary in Diabetes Insipidus: Mr Findings

The posterior lobe of the pituitary gland was evaluated by 1.5 T magnetic resonance (MR) in five cases of diabetes insipidus (DI), including one primary (idiopathic) and four secondary DI cases due to germinomas (two), teratoma (one), and histiocytosis χ (one). The normal posterior lobe displays high signal indistinguishable from fatty tissue on T1-weighted images (T1WI) (short T1 value). In all five DI cases the normal high signal of the posterior lobe was not detected in the pituitary fossa on T1WI. Hence, because of this characteristic finding, MR may greatly assist in the diagnosis of DI. We may speculate that the short T1 value of the posterior lobe is closely related to its functional integrity and may be due to the neurosecretory materials in the axons of the hypothalamohypophyseal tract.

Nuclear magnetic resonance abnormalities of the cerebral white matter in children with acute lymphoblastic leukemia and malignant lymphoma during and after central nervous system prophylactic treatment with intrathecal methotrexate

Background. A prospective study was conducted to test the feasibility of nuclear magnetic resonance (NMR) imaging in the early diagnosis of treatment‐induced leukoencephalopathy.

Anterior and Posterior Lobes of the Pituitary Gland; Assessment by 1.5 T MR Imaging

Pituitary glands of 60 normal volunteers (30 men 20–36 years old, and 30 women 18–42 years old) were studied by 1.5 T magnetic resonance (MR) imaging. The T1-weighted images (T1WI) [repetition time (TR) = 400 ms; echo time (TE) = 25 ms] were obtained in the coronal, sagittal, and axial planes. Proton density (PD)/T2-weighted images (PDW1/T2WI) (TR = 2,000 ms; TE = 25/100 ms) were obtained in the sagittal plane using 3 mm slice thickness. On T1WIs of all subjects the posterior part (PP) of the pituitary fossa showed the highest signal, which was indistinguishable from fatty tissue. This study reveals that this region of high signal intensity (PP) corresponds to the posterior lobe and not intrasellar fat because (a) its shape, size, and position are compatible with the posterior lobe; (b) its signal intensity differs from that of fatty tissue on PDWI and T2WI; (c) the absence of an intrinsic chemical shift artifact (CSA) characteristic of fat; and (d) due to CSA, a dorsum with fatty marrow is shifted relative to the PP (or may be made to merge with it). Regarding the differentiation of the two lobes of the pituitary gland on MR, the morphology of the anterior and posterior lobes was evaluated and great variation found. Appreciation of normal is particularly important in evaluating coronal images for small pituitary lesions.

Magnetic resonance imaging of neurohypophyseal germinomas

The authors reviewed magnetic resonance (MR) images in seven cases of germinoma in the hypothalamoneurohypophyseal axis (HNA). The intrasellar portions were clearly identified in six germinomas. Two small germinomas of these six were located only in the neurohypophysis. The major parts of the four large germinomas were located below the optic chiasm, and the large intrasellar portions were demonstrated. The remaining one small germinoma was localized from the pituitary stalk to the third ventricular floor. These findings strongly suggest that the primary site of germinomas in the HNA is the neurohypophysis. In the four large germinomas, the tumor shape was similar to that of pituitary adenoma. The authors believe that age (limited to first three decades), symptoms (diabetes insipidus), MR findings absence of normal hyperintense signal of the posterior pituitary on T1‐weighted (T1W1) images, and homogeneous hypointensity to the pons on T1W1 images/isointensity on T2‐weighted images are important in differential diagnosis.

Corpus callosum atrophy in amyotrophic lateral sclerosis

Recent studies have suggested widespread involvement of the cerebral regions other than the primary motor cortex in amyotrophic lateral sclerosis. To investigate atrophy of the corpus callosum as a measure of cerebral pathology, we studied 25 right-handed patients with sporadic amyotrophic lateral sclerosis using magnetic resonance imaging. Five patients had cognitive decline or emotional and personality changes. The ratios of mid-sagittal corpus callosum areas to the midline internal skull surface area on T1-weighted images were analysed. Compared with 25 age- and sex-matched right-handed control subjects, the patients had significantly decreased callosal/skull area ratio, with anterior predominance of the degree of atrophy. The patients with cognitive decline or psychiatric symptoms had substantial atrophy of the anterior fourth of the corpus callosum. These findings suggest that atrophy of the corpus callosum, especially in the anterior half, is present in amyotrophic lateral sclerosis, and that severe atrophy in the anterior fourth is associated with cognitive decline and psychiatric symptoms. Callosal atrophy may reflect the widespread distribution of pathological changes in the cerebral cortex, which are accentuated in the frontal cortex.

Primary spinal intramedullary malignant melanoma: case report

A rare case of primary spinal intramedullary malignant melanoma at the T6 level in a 31-year-old man is presented. The tumor was partially removed, and neuroaxis irradiation up to 50 Gy was then administered. Subsequently, systemic interferon beta (specific activity, 2.0 X 10(8) IU/mg protein) therapy (total dose, 2.2 X 10(7) units) was begun. At the completion of these therapies, immunohistochemical analysis with monoclonal antibodies against melanoma-associated antigens confirmed the presence of melanoma cells in the cerebrospinal fluid (CSF). Chemotherapy with intrathecal administration of dacarbazine (dimethyltriazenoimidazole carboxamide, DTIC) was then initiated, to avoid the dissemination of tumor cells by the CSF. Periodic cytological examination of CSF for melanoma cells revealed a marked reduction in the number of tumor cells. Pharmacokinetic study showed that the disappearance of DTIC from the CSF was biphasic, with an initial half-life of 30 minutes and a terminal half-life of 5 hours. Follow-up examination by MRI 1 year after the operation did not disclose any significant increase in size of the residual tumor. Neither recurrence nor metastasis was observed. The pertinent literature on spinal cord melanoma is reviewed, and the usefulness of MRI and intrathecal chemotherapy with DTIC is discussed.

White matter hyperintensities may correspond to areas of increased blood volume: correlative MR and PET observations.

A method for correlating positron emission tomography with magnetic resonance (MR) imaging enabled the authors to examine the high intensity white matter areas in T2-weighted images in patients with internal carotid artery occlusion. The high intensity areas showed increased cerebral blood volume compared with the ipsilateral and contralateral normal intensity white matter. This observation may have relevance in explaining some of the patchy white matter lesions seen in MR images.

Magnetic resonance imaging of the intracranial epidermoid

SummaryMagnetic resonance imaging (MRI) was performed in five cases of intracranial epidermoid. In three of the five patients, the lowdensity mass on the CT scans showed as low intensity on the T1 and high intensity on the T2 weighted images. In the two other patients, the masses with high or isodensity on CT showed as high intensity on the T1 weighted images and as high or low intensity on the T2 weighted images. Thus, the intensity of epidermoid on MRI correlated fairly well with the CT density, although the former was more variable. The variety of intensities on MRI reflects differences in the chemical composition of the components in the epidermoid tissue in addition to differences in the solid and liquid state of the tissue. An epidermoid could have similar MRI findings as an arachnoid cyst with regard to intensities but its irregular margin provides a useful guide for differentiation. As in other tumours, MRI is superior for evaluation of the size and the extent of the epidermoid as well as the displacement of important neurovascular structures.

MR imaging of a group I case of Hallervorden-Spatz disease.

Magnetic resonance (MR) imaging of a case of Hallervorden-Spatz disease (HSD) using a 1.5 T system is described. The patient showed progressive spastic diplegia with equinovarus deformity of the feet, dystonic postural movements, dysarthria, dysphagia, mental deterioration, optic nerve atrophy, and peripheral neuropathy. These clinical features were compatible with HSD. Symmetrical, decreased signal intensity was seen on both proton density weighted and T2-weighted spin echo images in the globus pallidus as well as in the substantia nigra (Group I). This MR finding suggests an increased iron deposition in these subcortical nuclei, which is characteristic of HSD. The characteristic MR imaging, together with the relevant clinical features, was considered to be useful for establishing the diagnosis of HSD.

Magnetic resonance imaging in relation to EEG epileptic foci in tuberous sclerosis

In 20 patients with tuberous sclerosis (TS), who were sequentially treated for epilepsy at our clinic, the high signal lesions in the cerebral cortex and subcortex detected on T2 weighted magnetic resonance imaging (MRI) were compared with the interictal EEG findings. In four cases who showed a unilateral distribution of the MRI lesions, there was a good correlation between the laterality of the affected lobes and the localization of the EEG epileptic foci. Thirteen cases with more than four affected lobes in both hemispheres also showed bilateral epileptic foci on EEG. The MRI lesions in the occipital lobes showed the best correlation with the EEG epileptic foci, while the worst correlation was seen in the frontal lobes. In addition, the cases with four or more affected lobes without laterality on MRI are more likely to show bilateral synchronization on EEG. The prognosis of epilepsy in these cases was found to be rather poor.